Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2013
The ethnic tribes of NorthEastern region of India are known to prepare and consume traditionally ... more The ethnic tribes of NorthEastern region of India are known to prepare and consume traditionally fermented soybean food as a part of their dietary components, thereby providing the basic components of diet with diverse characteristics of nutrition, flavour, palatability and texture. These tribes adopt their own ethnic method of fermentation resulting in unique taste and flavour. In the present study, different types of ethnically fermented soybean foods of NorthEast India were analyzed for their physico-chemical properties and molecular characterization of associated bacteria was performed. The fermented soybean products were found to be slightly alkaline with high protein content. The pH of all the samples ranged from 7.1 to 8.2. Protein content was seen highest in hawaijar and titratable acidity in Aakhone. The samples had very less percentage of titratable acidity and hydrophobicity. The microbiological analysis showed that all the samples had high aerobic mesophilic count and low yeast and mold count. The predominant bacteria, in all the products, were found to be lactic acid bacteria and species of Bacillus and Staphylococcus. The lactic acid bacteria present in the samples belonged to the genera Lactococcus, Lactobacillus, Enterococcus, Vagococcus and Weissella.
Tuberculosis is a most important human disease in its global prevalence. It is caused by tubercle... more Tuberculosis is a most important human disease in its global prevalence. It is caused by tubercle bacilli. Among the various methods for diagnosis of pulmonary tuberculosis, bacteriological methods are more important. Standard Ziehl-Neelsen method of staining is most reliable for this. But due to some operational disadvantages in the Ziehl-Neelsen method, many other methods were also discovered. In this research work two such techniques that is Modified Ziehl-Neelsen method where a boiling water bath is used as a source of heating and cold staining method where heating is completely eliminated and instead of which duration of exposure to carbol-fuchsin stain prolonged to 10 minutes were compared with conventional Ziehl-Neelsen method. For these 145 sputum samples having the symptoms of tuberculosis were collected and each of these samples were stained by three above mentioned methods. The results were analyzed by Mc Nemar's chi-square test and kappa statistics. It was observed that Cold-staining method is more appropriate than that of the Modified Ziehl-Neelsen method. Additionally due to some advantages in cold staining method it is more reliable and safer than that of the standard Ziehl-Neelsen method in field conditions.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2013
Three metal tolerant Serratia spp. isolates from sediments of pre-mined uranium ore deposit of Do... more Three metal tolerant Serratia spp. isolates from sediments of pre-mined uranium ore deposit of Domiasiat, Meghalaya, India were characterized using morphological, biochemical and molecular methods. 16S rRNA gene analysis of the isolates identified one of the isolates (DB-10) as Serratia nematodiphila with 99.33 % pairwise similarity whereas remaining two isolates (DB-11 and DB-15) showed similarity with Serratia marcescens subsp. sakuensis with similarity of 98.78 and 99.54 % respectively. Randomly amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) studies of the isolates revealed genetic diversity among them. The isolates were found to tolerate all the five tested metals namely, uranium, cadmium, copper, zinc and lead and also could resist nine commonly used antibiotics namely, ampicillin, kanamycin, chloramphenicol, erythromycin, gentamicin, aztreonam, tetracycline, imipenem and ciprofloxin. All the three isolates were found to be superior in tolerance and resistance to the reference strain S. marcescens ATCC13880. The isolates showed high efficiency of uranium (VI) removal ranging from 90 to 92 % (21.4-21.9 mg/L) and from 65 to 70 % (309.4-333.2 mg/L) when challenged with 100 lM (23.8 mg/L) and 2 mM (476 mg/L) uranyl nitrate solutions respectively within 1 h of incubation.
Himalayan range of India was screened for root fungal endophytes. This plant is distributed in th... more Himalayan range of India was screened for root fungal endophytes. This plant is distributed in the wild habitats and in the traditionally preserved 'Sacred Groves' of Meghalaya in Eastern India, which is of late getting over-exploited for its medicinal value. Isolation of endophytes in water agar plates yielded a unique fungus that had similar morphological characteristics with the members of the genus Talaromyces. Scanning and transmission electron microscopic studies of the fungus revealed its surface morphological features, close association and extensive colonization of plant root tissues. Molecular characterization using fungal specific 18S rRNA primers showed that the fungus shared a 98% homology with Penicillium verruculosum (Genbank accession number AF510496). The isolate investigated is likely to be a novel endophytic strain of P. verruculosum which has evolved a very close symbiotic association with the host plant roots. The fungal endophyte characterized is being explored as an early colonizer in the establishment of seedlings and successful micropropagation of the plant.
The genus Mahonia belongs to one of the primitive groups of plant family Berberidaceae. A number ... more The genus Mahonia belongs to one of the primitive groups of plant family Berberidaceae. A number of species from this genus are widely used in traditional and folk medicine systems in different parts of the world. Mahonia manipurensis crude alkaloid extract was obtained from the stem bark by extracting from 80% of methanol extract. In vitro antibacterial activity of the alkaloid extract was screened against five different pathogenic bacteria of clinical origin including two species of gram-negative and three species of gram-positive bacteria. Using agar well diffusion method, growth inhibition was observed in four of the five tested pathogens at two different concentrations (5 and 2.5 mg/ml). The result indicates that the alkaloid extract exhibited significant antibacterial activity. Similar antimicrobial activity was also reported from other species of this genus by previous workers. Minimum inhibitory concentration (MIC) was also determined using agar dilution method, following two-fold serial dilution and observed that the lowest value was exhibited by Bacillus cereus and Enterococcus faecalis each corresponding to 256 µg/ml concentration.
Crude metabolite extracts derived from the culture broths of endophytic fungi of five ethnopharma... more Crude metabolite extracts derived from the culture broths of endophytic fungi of five ethnopharmacologically important plant species used by the ethnic tribes of the hill state of Meghalaya in NorthEast India were screened for the presence of toxins and secondary metabolites using agar plug paper chromatography, thin layer chromatography (TLC) and liquid chromatography-mass spectroscopy (LC-MS). The endophytic fungal isolates were found to produce a wide range of toxins, growth hormones and antibiotics upon searching in a fungal mycotoxin database. Relatedness among the fungal isolates was determined based upon their extra-cellular metabolite production pattern. The endophytic fungal isolates in the present study showed a wide range of metabolomic diversity and can be explored as potential microbial cell factories for production of a diverse range of biomolecules. Taxonomic relatedness of the endophytes based upon the snapshots of their secretomes, presented a contrasting picture in relation to their morphological identity. Rapid metabolome analysis of endophytic fungi using analytical techniques like LC-MS coupled with mass related search in fungal specific metabolite databases is bound to increase our insights about fungal chemo-taxonomy as a whole and bio-prospection of useful fungal metabolites in particular.
Sacred groves' represents a traditional effort to conserve biodiversity. They are rich patches of... more Sacred groves' represents a traditional effort to conserve biodiversity. They are rich patches of undisturbed forests and serve as a natural habitat for many endemic, rare, primitive and economically valuable organisms representing a micro-level biodiversity hotspots. In this study, Bacillus spp. and related genera characterized from native soils of the pristine sacred groves of Meghalaya, India revealed dominance of Bacillus, Paenibacillus, Lysinibacillus and Viridibacillus. All the isolates exhibited good plant growth promoting traits when screened for traits like phosphate solubilization, 1-aminocyclopropane-1carboxylate deaminase and catalase activity, production of auxin, siderophores, hydrogen cyanide and ammonia. Bacteria native to the pristine niche of sacred groves showed better plant growth promoting activities as compared to isolates from disturbed forest as well as type strains implicating the importance of sacred groves and their potential role in microbial diversity conservation.
In the present investigation, Tungrymbai, an ethnic fermented soybean food of the ethnic tribes o... more In the present investigation, Tungrymbai, an ethnic fermented soybean food of the ethnic tribes of Meghalaya, India was analyzed for the proximate microbial and chemical changes occurring in the fermented product due to preparation method. Among the aerobic mesophilic forms, lactic acid bacteria (LAB), Enterobacteriaceae, spore formers, yeast and fungal counts; the microbial loads of spore forming bacteria count were not affected in the post-cooked Tungrymbai as compared to other counts. The pH and total titratable acidity were higher in the pre-cooked Tungrymbai while moisture content was higher in the post-cooked sample. The microbes that were prevalent in both the pre-cooked and post-cooked fermented samples were Bacillus subtilis, Enterococcus durans, Vagococcus lutrae, Staphylococcus equorum and Saccharomyces sp. However, probiotic bacteria like Lactobacillus were not detected in post-cooked samples indicating that the preparation method significantly altered the composition of...
Background: Acinetobacter baumannii has emerged as an important nosocomial pathogen, its ability ... more Background: Acinetobacter baumannii has emerged as an important nosocomial pathogen, its ability to acquire resistance to carbapenems and aminoglycosides, has complicated their treatment regimen. The present study investigates the prevalence and diversity of aminoglycoside-modifying enzymes and 16S methyltransferases in A. baumannii isolates recovered from patients admitted in Intensive Care Unit (ICU) of a tertiary referral hospital in Northeastern India. Materials and Methods: We investigated the high-level aminoglycoside-resistance (HLAR) (gentamicin and amikacin minimum inhibitory concentration ≥ 512 μg/ml) among 164 multidrug-resistant A. baumannii obtained from ICU. Genes encoding aminoglycoside-modifying enzymes, 16S methyltransferase and coexisting beta-lactamases were amplified. Horizontal transferability, plasmid stability and elimination assays were performed. Clonality and sequence types were evaluated by repetitive extragenic palindromic-polymerase chain reaction and multilocus sequence typing (MLST) respectively. Results: A total of 130 (79.2%) isolates were found to exhibit HLAR, with acquired aminoglycoside-resistance genes in 109 (83.8%) isolates along with coexisting extended-spectrum beta-lactamases and metallo-beta-lactamases. Genes aph (3') I, aph (3') VIa and armA were predominant and horizontally transferable. Plasmids were eliminated with single sodium dodecyl sulphate treatment. Seventeen haplotypes were found responsible for the infection. MLST revealed circulation of ST583 and ST188 in ICU. Conclusions: This study reveals the presence of aminoglycoside-resistance genes in combination with blaCTXM and blaNDM, which are highly stable and not frequently reported from this geographical region. Further, the study could predict limited treatment option and need for formulating infection control strategy.
A library of biologically important heterocycles, viz. pyrazolyl pyrimidine-triones, bis(heterocy... more A library of biologically important heterocycles, viz. pyrazolyl pyrimidine-triones, bis(heterocyclyl)methanes were successfully synthesised by the condensation of barbituric acid, pyrazolone with an aldehyde and dimedone/4-hydoxy coumarin with various substituted aldehydes in aqueous medium at room temperature catalysed by nickel nanoparticles which proved to be an efficient magnetically recyclable catalyst. The method is simple, eco-friendly and gave excellent yields of the products without taking recourse to column chromatographic separation procedures. Computational method was employed to elucidate the selective formation of uncyclised product in reaction course. The biological activity of the synthesized compounds were investigated and the results demonstrated profound antibacterial activity.
The present study attempted to evaluate the antimicrobial and antioxidant activity of fungal endo... more The present study attempted to evaluate the antimicrobial and antioxidant activity of fungal endophytes associated with Centella asiatica and Murraya koengii , the ethnomedicinal plants used in traditional practices. Two endophytic fungi Aspergillus oryzae CeR1 and Colletotrichum gloeosporioides MKL1 were isolated from C. asiatica and M. koengii respectively which were characterized morphologically and by using rDNA-internal transcribed spacer. The total antioxidant power and free radical scavenging activity of the fungal extracts was estimated using the total phenolic content and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay along with the flavonoids and alkaloids content. The DPPH free radical assay showed that the ethanolic extract of endophytic fungi Aspergillus oryzae CeR1 had higher radical scavenging activity than Colletotrichum gloeosporioides MKL1. Antimicrobial activity of fungal extract tested against three bacterial strain namely, Staphylococcus aureus MTCC 96, Streptococcus pyogenes MTCC1925, Enteroccocus faecalis MTCC2729 and one fungal strain Candida albicans MTCC183 showed inhibition of growth of test organisms except Staphylococcus aureus MTCC96.
A vast diversity of microbes including macrofungi remain untapped for valuable bioactivities incl... more A vast diversity of microbes including macrofungi remain untapped for valuable bioactivities including antimicrobial activity. Searching wild sources may bring novel natural products with antimicrobial properties that can provide protection against infectious diseases. The present study was designed to identify the diverse forms of mushrooms being used as an ethnomycological source of food and medicine by the tribes of Meghalaya, India, and microscopically study the structures of mushrooms along with observing their antimicrobial effects on pathogens. Fruiting bodies of mushrooms were viewed morphologically and microscopically, and were identified using molecular markers. The dried aerial parts of the fruiting bodies were extracted with methanol and screened for their antimicrobial activity using 2,3,-triphenyl tetrazolium chloride against two Gram-negative and two Gram-positive bacteria. The average diameter of the inhibitory zone induced by fungal extracts ranged from 9 mm to 22 mm for Gram-negative and from 16 mm to 24 mm for Gram-positive bacteria, indicating that this dietary source is a good antimicrobial agent. Mushroom structures were examined using optical microscopy, while the deformities on the pathogens inflicted by mushroom extracts were visualized using scanning electron microscopy, which showed accumulation and formation of biofilm in Gram-positive and shrinkage with cavity formation in Gram-negative bacteria.
Most cases of bacterial resistance towards antibiotics, encourage various efforts to gain new sou... more Most cases of bacterial resistance towards antibiotics, encourage various efforts to gain new sources of antibiotics. Endophyte bacteria is a micoorganism has important role as the producer of bioactive compounds. Endophyte bacteria from Curcuma longa with antimicrobial and antioxidant activities have not been studied yet. Curcuma longa has been utilized as the main ingridients of traditional herbal medicines (jamu). The objective of this research was to investigate the antimicrobial and antioxidant activity of endophyte bacteria associated with Curcuma longa rhizome. Based on morphological characteristics of bacterial colonies, eight endophyte bacteria was isolates from Curcuma longa rhizome. Screening of endophyte isolate has antimicrobial activity was done using agar well diffusion method. The culture supernatant of each endophyte isolate was dropped on agar well against pathogenic bacteria Salmonella enterica ser. Typhi, Staphylococcus aureus and yeast Candida albicans. Three endophyte isolates K 3 , K 2 and M 1b showed antimicrobial activity against pathogenic bacteria and yeast. Isolate K 3 showed strong antimicrobial activity againts C. albicans and S. aureus, however isolate K 2 and isolate M 1b showed antimicrobial activity againts Salmonella enterica ser. Typhi and S. aureus, respectively. Those endophyte bacteria also had antioxidant activity shown by scavenging ability toward DPPH radical with consecutive percentage of isolate K 3 (72.3 %), K 2 (51.3 %) and M 1b (64.6 %). Isolate K 3 showed the highest antimicrobial and antioxidant activity. Based on biochemical characteristics using Microbact 24E kit, isolate K 3 was identified as Paenibacilus alvei and isolate K 2 as Enterobacter agglomerans.
The caves of Meghalaya in India are some of the longest caves in the subcontinent that have so fa... more The caves of Meghalaya in India are some of the longest caves in the subcontinent that have so far received negligible attention of geomicrobiologists. The present work was undertaken to discover and explore bacterial biofilms of various textures and colors from five caves of Meghalaya in NorthEast India. There are no previous specific scientific investigations from three of the studied caves. Thirty-two different culturable bacterial species belonging to sixteen different genera were characterized. Based on molecular identification, the isolates were related to nearest taxa, with the majority belonging to Bacillus and Pseudomonas. The study also indicated the capabilities of the isolated microbial strains to precipitate calcite, providing evidence for biotic processes involved in the formation of natural speleothems. SEM studies revealed an array of crystal polymorphs generated in vitro by the isolated bacteria similar to the microscopic observations of speleothems. The EDX spectrum showed that the precipitated crystals were predominately composed of calcium carbonate. The results endorse the hypothesis that the isolated chemoheterotrophic bacterial species contribute to the process of cave-speleothem formation in a hypogean environment.
The study of lithic microbial communities, inhabiting rock substrates has been gathering momentum... more The study of lithic microbial communities, inhabiting rock substrates has been gathering momentum due to a growing attention of their wide importance as model systems in ecological studies and for their community structure. It is generally accepted that the success of cultivation-based technique is primarily based on suitable culture medium for isolation. The media available for enumeration and recovery of endolithic bacteria are mainly specific to particular type of rock which may not be suitable to isolate endolithic bacterial community from diverse lithobiontic niches. In this study, a new unoptimized medium was formulated, designated LM10 (unoptimized) for enumeration and recovery of endolithic bacteria by addition and/or omission of media components to the basal medium R2G, which was selected after experimental evaluation of five different existing media. The endolithic bacterial count in LM10 medium (unoptimized) was significantly higher than the R2G medium (t=-12.57, p<0.0001). The culture and nutritional parameters associated with unoptimized LM10 medium were optimized using statistical approach to maximize the recovery and enumeration of endolithic bacteria. The first phase of the study comprised of a Plackett-Burman (PB) design experiment conducted to screen thirteen medium components and two culture parameters as variables with effect on bacterial enumeration and recovery. Out of these, Yeast extract, Casein hydrolysate, Glucose, Starch and Sodium thiosulphate were found to be significantly affecting the bacterial count (p<0.05) based on PB design. On keeping rest of the media components and culture conditions at fixed value as per the PB design analyses (p>0.05 and coefficients), further optimization was carried out for significant factors using Box-Behnken design (BBD) of response surface methodology (RSM). Optimized media components obtained by BBD were Yeast extract, Casein hydrolysate, Glucose and Starch in 0.05g/l each and Sodium thiosulphate in 0.047g/l concentrations. The composition of optimized LM10 medium formulated (per litre) is 0.05g Yeast extract, 0.05g Casein hydrolysate, 0.05g Glucose, 0.05g Starch, 0.01g K2HPO4, 0.02g Sodium pyruvate, 0.2g MgSO4, 0.001g FeSO4·7H2O, 0.285g NH4Cl, 0.039g CaCl2·2H2O, 0.047g Na2S2O3·5H2O, 0.002g NaHCO3 and 11g Gellan gum (pH=7.4). Validation of optimized LM10 medium using nine different rock samples from Meghalaya clearly indicated that optimized LM10 medium was better suited for higher recovery and enumeration of endolithic bacteria under both aerobic and anaerobic conditions.
Arthrobacter sp. KMSZP6 isolated from a pristine uranium ore deposit at Domiasiat located in Nort... more Arthrobacter sp. KMSZP6 isolated from a pristine uranium ore deposit at Domiasiat located in NorthEast India exhibited noteworthy tolerance for cesium (Cs) and strontium (Sr). The strain displayed a high minimum inhibitory concentration (MIC) of 400 mM for CsCl and for SrCl 2. Flow cytometric analysis employing membrane integrity indicators like propidium iodide (PI) and thiazole orange (TO) indicated a greater sensitivity of Arthrobacter cells to cesium than to strontium. On being challenged with 75 mM of Cs, the cells sequestered 9612 mg Cs g −1 dry weight of cells in 12 h. On being challenged with 75 mM of Sr, the cells sequestered 9989 mg Sr g −1 dry weight of cells in 18 h. Heat killed cells exhibited limited Cs and Sr binding as compared to live cells highlighting the importance of cell viability for optimal binding. The association of the metals with Arthrobacter sp. KMSZP6 was further substantiated by Field Emission-Scanning Electron Microscopy (FE-SEM) coupled with Energy dispersive X-ray (EDX) spectroscopy. This organism tolerated up to 1 kGy 60 Co-gamma rays without loss of survival. The present report highlights the superior tolerance and binding capacity of the KMSZP6 strain for cesium and strontium over other earlier reported strains and reveals its potential for bioremediation of nuclear waste.
The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia e... more The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia esculenta was investigated for removal of Cu(2+), Fe(2+) and As(5+) from simulated coal mine wastewater. SSAB was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyser. Adsorption isotherm indicated monolayer adsorption which fitted best in Langmuir isotherm model. Thermodynamic study suggested the removal process to be exothermic, feasible and spontaneous in nature. Adsorption of Fe(2+), Cu(2+) and As(5+) on to SSAB was found to be governed by pseudo-second order kinetic model. Efficacy of SSAB in terms of metal desorption, regeneration and reusability for multiple cycles was studied. Regeneration of metal desorbed SSAB with 1 N sodium hydroxide maintained its effectiveness towards multiple metal adsorption cycles. Cost estimation of SSAB production substantiated its cost effectiveness as compared to commercially availa...
Pasteurella multocida is an important veterinary pathogen causing infections in animals and birds... more Pasteurella multocida is an important veterinary pathogen causing infections in animals and birds. Nowadays, different reports have described the severity of infections, increasing resistance of micro-organisms to antibiotics, and the contribution of ethnoveterinary practices towards the treatment of various ailments of animals. The aim of the present study was to investigate the antibacterial efficacy of the ethanolic extracts of endophytic fungi against P. multocida Capsular Type A strains. A total of six endophytic fungi were isolated from two tropical ethnoveterinary plants: Garcinia xanthochymus H. and Polygonum chinense L. The ethanolic extracts of the endophytic fungi were subjected to in vitro antimicrobial activity by the well diffusion method. Besides, we evaluated the treatment of mice with the potent fungal extract and observed the effects in different organs under electron microscopy. Our results showed that four fungi had antimicrobial activity against the selected pathogen. The best antibacterial activity was showed by the extract of the endophytic fungi, Glomerella magna isolated from G. xanthochymus, with a minimum inhibitory concentration of 46.9 µg/mL and minimum bactericidal concentration of 750 µg/mL. Treatment of mice with the potent fungal extract caused a considerable inhibitory effect on the pathogen growth in vital organs, results that was also confirmed by histopathological studies made by scanning electron microscopy. The present findings indicated that the endophytic fungi G. magna has the potential to provide an effective treatment against infections caused by Pasteurella multocida. However, the isolation of bioactive components needs further investigation.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2013
The ethnic tribes of NorthEastern region of India are known to prepare and consume traditionally ... more The ethnic tribes of NorthEastern region of India are known to prepare and consume traditionally fermented soybean food as a part of their dietary components, thereby providing the basic components of diet with diverse characteristics of nutrition, flavour, palatability and texture. These tribes adopt their own ethnic method of fermentation resulting in unique taste and flavour. In the present study, different types of ethnically fermented soybean foods of NorthEast India were analyzed for their physico-chemical properties and molecular characterization of associated bacteria was performed. The fermented soybean products were found to be slightly alkaline with high protein content. The pH of all the samples ranged from 7.1 to 8.2. Protein content was seen highest in hawaijar and titratable acidity in Aakhone. The samples had very less percentage of titratable acidity and hydrophobicity. The microbiological analysis showed that all the samples had high aerobic mesophilic count and low yeast and mold count. The predominant bacteria, in all the products, were found to be lactic acid bacteria and species of Bacillus and Staphylococcus. The lactic acid bacteria present in the samples belonged to the genera Lactococcus, Lactobacillus, Enterococcus, Vagococcus and Weissella.
Tuberculosis is a most important human disease in its global prevalence. It is caused by tubercle... more Tuberculosis is a most important human disease in its global prevalence. It is caused by tubercle bacilli. Among the various methods for diagnosis of pulmonary tuberculosis, bacteriological methods are more important. Standard Ziehl-Neelsen method of staining is most reliable for this. But due to some operational disadvantages in the Ziehl-Neelsen method, many other methods were also discovered. In this research work two such techniques that is Modified Ziehl-Neelsen method where a boiling water bath is used as a source of heating and cold staining method where heating is completely eliminated and instead of which duration of exposure to carbol-fuchsin stain prolonged to 10 minutes were compared with conventional Ziehl-Neelsen method. For these 145 sputum samples having the symptoms of tuberculosis were collected and each of these samples were stained by three above mentioned methods. The results were analyzed by Mc Nemar's chi-square test and kappa statistics. It was observed that Cold-staining method is more appropriate than that of the Modified Ziehl-Neelsen method. Additionally due to some advantages in cold staining method it is more reliable and safer than that of the standard Ziehl-Neelsen method in field conditions.
Proceedings of the National Academy of Sciences, India Section B: Biological Sciences, 2013
Three metal tolerant Serratia spp. isolates from sediments of pre-mined uranium ore deposit of Do... more Three metal tolerant Serratia spp. isolates from sediments of pre-mined uranium ore deposit of Domiasiat, Meghalaya, India were characterized using morphological, biochemical and molecular methods. 16S rRNA gene analysis of the isolates identified one of the isolates (DB-10) as Serratia nematodiphila with 99.33 % pairwise similarity whereas remaining two isolates (DB-11 and DB-15) showed similarity with Serratia marcescens subsp. sakuensis with similarity of 98.78 and 99.54 % respectively. Randomly amplified polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus sequence-based PCR (ERIC-PCR) studies of the isolates revealed genetic diversity among them. The isolates were found to tolerate all the five tested metals namely, uranium, cadmium, copper, zinc and lead and also could resist nine commonly used antibiotics namely, ampicillin, kanamycin, chloramphenicol, erythromycin, gentamicin, aztreonam, tetracycline, imipenem and ciprofloxin. All the three isolates were found to be superior in tolerance and resistance to the reference strain S. marcescens ATCC13880. The isolates showed high efficiency of uranium (VI) removal ranging from 90 to 92 % (21.4-21.9 mg/L) and from 65 to 70 % (309.4-333.2 mg/L) when challenged with 100 lM (23.8 mg/L) and 2 mM (476 mg/L) uranyl nitrate solutions respectively within 1 h of incubation.
Himalayan range of India was screened for root fungal endophytes. This plant is distributed in th... more Himalayan range of India was screened for root fungal endophytes. This plant is distributed in the wild habitats and in the traditionally preserved 'Sacred Groves' of Meghalaya in Eastern India, which is of late getting over-exploited for its medicinal value. Isolation of endophytes in water agar plates yielded a unique fungus that had similar morphological characteristics with the members of the genus Talaromyces. Scanning and transmission electron microscopic studies of the fungus revealed its surface morphological features, close association and extensive colonization of plant root tissues. Molecular characterization using fungal specific 18S rRNA primers showed that the fungus shared a 98% homology with Penicillium verruculosum (Genbank accession number AF510496). The isolate investigated is likely to be a novel endophytic strain of P. verruculosum which has evolved a very close symbiotic association with the host plant roots. The fungal endophyte characterized is being explored as an early colonizer in the establishment of seedlings and successful micropropagation of the plant.
The genus Mahonia belongs to one of the primitive groups of plant family Berberidaceae. A number ... more The genus Mahonia belongs to one of the primitive groups of plant family Berberidaceae. A number of species from this genus are widely used in traditional and folk medicine systems in different parts of the world. Mahonia manipurensis crude alkaloid extract was obtained from the stem bark by extracting from 80% of methanol extract. In vitro antibacterial activity of the alkaloid extract was screened against five different pathogenic bacteria of clinical origin including two species of gram-negative and three species of gram-positive bacteria. Using agar well diffusion method, growth inhibition was observed in four of the five tested pathogens at two different concentrations (5 and 2.5 mg/ml). The result indicates that the alkaloid extract exhibited significant antibacterial activity. Similar antimicrobial activity was also reported from other species of this genus by previous workers. Minimum inhibitory concentration (MIC) was also determined using agar dilution method, following two-fold serial dilution and observed that the lowest value was exhibited by Bacillus cereus and Enterococcus faecalis each corresponding to 256 µg/ml concentration.
Crude metabolite extracts derived from the culture broths of endophytic fungi of five ethnopharma... more Crude metabolite extracts derived from the culture broths of endophytic fungi of five ethnopharmacologically important plant species used by the ethnic tribes of the hill state of Meghalaya in NorthEast India were screened for the presence of toxins and secondary metabolites using agar plug paper chromatography, thin layer chromatography (TLC) and liquid chromatography-mass spectroscopy (LC-MS). The endophytic fungal isolates were found to produce a wide range of toxins, growth hormones and antibiotics upon searching in a fungal mycotoxin database. Relatedness among the fungal isolates was determined based upon their extra-cellular metabolite production pattern. The endophytic fungal isolates in the present study showed a wide range of metabolomic diversity and can be explored as potential microbial cell factories for production of a diverse range of biomolecules. Taxonomic relatedness of the endophytes based upon the snapshots of their secretomes, presented a contrasting picture in relation to their morphological identity. Rapid metabolome analysis of endophytic fungi using analytical techniques like LC-MS coupled with mass related search in fungal specific metabolite databases is bound to increase our insights about fungal chemo-taxonomy as a whole and bio-prospection of useful fungal metabolites in particular.
Sacred groves' represents a traditional effort to conserve biodiversity. They are rich patches of... more Sacred groves' represents a traditional effort to conserve biodiversity. They are rich patches of undisturbed forests and serve as a natural habitat for many endemic, rare, primitive and economically valuable organisms representing a micro-level biodiversity hotspots. In this study, Bacillus spp. and related genera characterized from native soils of the pristine sacred groves of Meghalaya, India revealed dominance of Bacillus, Paenibacillus, Lysinibacillus and Viridibacillus. All the isolates exhibited good plant growth promoting traits when screened for traits like phosphate solubilization, 1-aminocyclopropane-1carboxylate deaminase and catalase activity, production of auxin, siderophores, hydrogen cyanide and ammonia. Bacteria native to the pristine niche of sacred groves showed better plant growth promoting activities as compared to isolates from disturbed forest as well as type strains implicating the importance of sacred groves and their potential role in microbial diversity conservation.
In the present investigation, Tungrymbai, an ethnic fermented soybean food of the ethnic tribes o... more In the present investigation, Tungrymbai, an ethnic fermented soybean food of the ethnic tribes of Meghalaya, India was analyzed for the proximate microbial and chemical changes occurring in the fermented product due to preparation method. Among the aerobic mesophilic forms, lactic acid bacteria (LAB), Enterobacteriaceae, spore formers, yeast and fungal counts; the microbial loads of spore forming bacteria count were not affected in the post-cooked Tungrymbai as compared to other counts. The pH and total titratable acidity were higher in the pre-cooked Tungrymbai while moisture content was higher in the post-cooked sample. The microbes that were prevalent in both the pre-cooked and post-cooked fermented samples were Bacillus subtilis, Enterococcus durans, Vagococcus lutrae, Staphylococcus equorum and Saccharomyces sp. However, probiotic bacteria like Lactobacillus were not detected in post-cooked samples indicating that the preparation method significantly altered the composition of...
Background: Acinetobacter baumannii has emerged as an important nosocomial pathogen, its ability ... more Background: Acinetobacter baumannii has emerged as an important nosocomial pathogen, its ability to acquire resistance to carbapenems and aminoglycosides, has complicated their treatment regimen. The present study investigates the prevalence and diversity of aminoglycoside-modifying enzymes and 16S methyltransferases in A. baumannii isolates recovered from patients admitted in Intensive Care Unit (ICU) of a tertiary referral hospital in Northeastern India. Materials and Methods: We investigated the high-level aminoglycoside-resistance (HLAR) (gentamicin and amikacin minimum inhibitory concentration ≥ 512 μg/ml) among 164 multidrug-resistant A. baumannii obtained from ICU. Genes encoding aminoglycoside-modifying enzymes, 16S methyltransferase and coexisting beta-lactamases were amplified. Horizontal transferability, plasmid stability and elimination assays were performed. Clonality and sequence types were evaluated by repetitive extragenic palindromic-polymerase chain reaction and multilocus sequence typing (MLST) respectively. Results: A total of 130 (79.2%) isolates were found to exhibit HLAR, with acquired aminoglycoside-resistance genes in 109 (83.8%) isolates along with coexisting extended-spectrum beta-lactamases and metallo-beta-lactamases. Genes aph (3') I, aph (3') VIa and armA were predominant and horizontally transferable. Plasmids were eliminated with single sodium dodecyl sulphate treatment. Seventeen haplotypes were found responsible for the infection. MLST revealed circulation of ST583 and ST188 in ICU. Conclusions: This study reveals the presence of aminoglycoside-resistance genes in combination with blaCTXM and blaNDM, which are highly stable and not frequently reported from this geographical region. Further, the study could predict limited treatment option and need for formulating infection control strategy.
A library of biologically important heterocycles, viz. pyrazolyl pyrimidine-triones, bis(heterocy... more A library of biologically important heterocycles, viz. pyrazolyl pyrimidine-triones, bis(heterocyclyl)methanes were successfully synthesised by the condensation of barbituric acid, pyrazolone with an aldehyde and dimedone/4-hydoxy coumarin with various substituted aldehydes in aqueous medium at room temperature catalysed by nickel nanoparticles which proved to be an efficient magnetically recyclable catalyst. The method is simple, eco-friendly and gave excellent yields of the products without taking recourse to column chromatographic separation procedures. Computational method was employed to elucidate the selective formation of uncyclised product in reaction course. The biological activity of the synthesized compounds were investigated and the results demonstrated profound antibacterial activity.
The present study attempted to evaluate the antimicrobial and antioxidant activity of fungal endo... more The present study attempted to evaluate the antimicrobial and antioxidant activity of fungal endophytes associated with Centella asiatica and Murraya koengii , the ethnomedicinal plants used in traditional practices. Two endophytic fungi Aspergillus oryzae CeR1 and Colletotrichum gloeosporioides MKL1 were isolated from C. asiatica and M. koengii respectively which were characterized morphologically and by using rDNA-internal transcribed spacer. The total antioxidant power and free radical scavenging activity of the fungal extracts was estimated using the total phenolic content and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay along with the flavonoids and alkaloids content. The DPPH free radical assay showed that the ethanolic extract of endophytic fungi Aspergillus oryzae CeR1 had higher radical scavenging activity than Colletotrichum gloeosporioides MKL1. Antimicrobial activity of fungal extract tested against three bacterial strain namely, Staphylococcus aureus MTCC 96, Streptococcus pyogenes MTCC1925, Enteroccocus faecalis MTCC2729 and one fungal strain Candida albicans MTCC183 showed inhibition of growth of test organisms except Staphylococcus aureus MTCC96.
A vast diversity of microbes including macrofungi remain untapped for valuable bioactivities incl... more A vast diversity of microbes including macrofungi remain untapped for valuable bioactivities including antimicrobial activity. Searching wild sources may bring novel natural products with antimicrobial properties that can provide protection against infectious diseases. The present study was designed to identify the diverse forms of mushrooms being used as an ethnomycological source of food and medicine by the tribes of Meghalaya, India, and microscopically study the structures of mushrooms along with observing their antimicrobial effects on pathogens. Fruiting bodies of mushrooms were viewed morphologically and microscopically, and were identified using molecular markers. The dried aerial parts of the fruiting bodies were extracted with methanol and screened for their antimicrobial activity using 2,3,-triphenyl tetrazolium chloride against two Gram-negative and two Gram-positive bacteria. The average diameter of the inhibitory zone induced by fungal extracts ranged from 9 mm to 22 mm for Gram-negative and from 16 mm to 24 mm for Gram-positive bacteria, indicating that this dietary source is a good antimicrobial agent. Mushroom structures were examined using optical microscopy, while the deformities on the pathogens inflicted by mushroom extracts were visualized using scanning electron microscopy, which showed accumulation and formation of biofilm in Gram-positive and shrinkage with cavity formation in Gram-negative bacteria.
Most cases of bacterial resistance towards antibiotics, encourage various efforts to gain new sou... more Most cases of bacterial resistance towards antibiotics, encourage various efforts to gain new sources of antibiotics. Endophyte bacteria is a micoorganism has important role as the producer of bioactive compounds. Endophyte bacteria from Curcuma longa with antimicrobial and antioxidant activities have not been studied yet. Curcuma longa has been utilized as the main ingridients of traditional herbal medicines (jamu). The objective of this research was to investigate the antimicrobial and antioxidant activity of endophyte bacteria associated with Curcuma longa rhizome. Based on morphological characteristics of bacterial colonies, eight endophyte bacteria was isolates from Curcuma longa rhizome. Screening of endophyte isolate has antimicrobial activity was done using agar well diffusion method. The culture supernatant of each endophyte isolate was dropped on agar well against pathogenic bacteria Salmonella enterica ser. Typhi, Staphylococcus aureus and yeast Candida albicans. Three endophyte isolates K 3 , K 2 and M 1b showed antimicrobial activity against pathogenic bacteria and yeast. Isolate K 3 showed strong antimicrobial activity againts C. albicans and S. aureus, however isolate K 2 and isolate M 1b showed antimicrobial activity againts Salmonella enterica ser. Typhi and S. aureus, respectively. Those endophyte bacteria also had antioxidant activity shown by scavenging ability toward DPPH radical with consecutive percentage of isolate K 3 (72.3 %), K 2 (51.3 %) and M 1b (64.6 %). Isolate K 3 showed the highest antimicrobial and antioxidant activity. Based on biochemical characteristics using Microbact 24E kit, isolate K 3 was identified as Paenibacilus alvei and isolate K 2 as Enterobacter agglomerans.
The caves of Meghalaya in India are some of the longest caves in the subcontinent that have so fa... more The caves of Meghalaya in India are some of the longest caves in the subcontinent that have so far received negligible attention of geomicrobiologists. The present work was undertaken to discover and explore bacterial biofilms of various textures and colors from five caves of Meghalaya in NorthEast India. There are no previous specific scientific investigations from three of the studied caves. Thirty-two different culturable bacterial species belonging to sixteen different genera were characterized. Based on molecular identification, the isolates were related to nearest taxa, with the majority belonging to Bacillus and Pseudomonas. The study also indicated the capabilities of the isolated microbial strains to precipitate calcite, providing evidence for biotic processes involved in the formation of natural speleothems. SEM studies revealed an array of crystal polymorphs generated in vitro by the isolated bacteria similar to the microscopic observations of speleothems. The EDX spectrum showed that the precipitated crystals were predominately composed of calcium carbonate. The results endorse the hypothesis that the isolated chemoheterotrophic bacterial species contribute to the process of cave-speleothem formation in a hypogean environment.
The study of lithic microbial communities, inhabiting rock substrates has been gathering momentum... more The study of lithic microbial communities, inhabiting rock substrates has been gathering momentum due to a growing attention of their wide importance as model systems in ecological studies and for their community structure. It is generally accepted that the success of cultivation-based technique is primarily based on suitable culture medium for isolation. The media available for enumeration and recovery of endolithic bacteria are mainly specific to particular type of rock which may not be suitable to isolate endolithic bacterial community from diverse lithobiontic niches. In this study, a new unoptimized medium was formulated, designated LM10 (unoptimized) for enumeration and recovery of endolithic bacteria by addition and/or omission of media components to the basal medium R2G, which was selected after experimental evaluation of five different existing media. The endolithic bacterial count in LM10 medium (unoptimized) was significantly higher than the R2G medium (t=-12.57, p<0.0001). The culture and nutritional parameters associated with unoptimized LM10 medium were optimized using statistical approach to maximize the recovery and enumeration of endolithic bacteria. The first phase of the study comprised of a Plackett-Burman (PB) design experiment conducted to screen thirteen medium components and two culture parameters as variables with effect on bacterial enumeration and recovery. Out of these, Yeast extract, Casein hydrolysate, Glucose, Starch and Sodium thiosulphate were found to be significantly affecting the bacterial count (p<0.05) based on PB design. On keeping rest of the media components and culture conditions at fixed value as per the PB design analyses (p>0.05 and coefficients), further optimization was carried out for significant factors using Box-Behnken design (BBD) of response surface methodology (RSM). Optimized media components obtained by BBD were Yeast extract, Casein hydrolysate, Glucose and Starch in 0.05g/l each and Sodium thiosulphate in 0.047g/l concentrations. The composition of optimized LM10 medium formulated (per litre) is 0.05g Yeast extract, 0.05g Casein hydrolysate, 0.05g Glucose, 0.05g Starch, 0.01g K2HPO4, 0.02g Sodium pyruvate, 0.2g MgSO4, 0.001g FeSO4·7H2O, 0.285g NH4Cl, 0.039g CaCl2·2H2O, 0.047g Na2S2O3·5H2O, 0.002g NaHCO3 and 11g Gellan gum (pH=7.4). Validation of optimized LM10 medium using nine different rock samples from Meghalaya clearly indicated that optimized LM10 medium was better suited for higher recovery and enumeration of endolithic bacteria under both aerobic and anaerobic conditions.
Arthrobacter sp. KMSZP6 isolated from a pristine uranium ore deposit at Domiasiat located in Nort... more Arthrobacter sp. KMSZP6 isolated from a pristine uranium ore deposit at Domiasiat located in NorthEast India exhibited noteworthy tolerance for cesium (Cs) and strontium (Sr). The strain displayed a high minimum inhibitory concentration (MIC) of 400 mM for CsCl and for SrCl 2. Flow cytometric analysis employing membrane integrity indicators like propidium iodide (PI) and thiazole orange (TO) indicated a greater sensitivity of Arthrobacter cells to cesium than to strontium. On being challenged with 75 mM of Cs, the cells sequestered 9612 mg Cs g −1 dry weight of cells in 12 h. On being challenged with 75 mM of Sr, the cells sequestered 9989 mg Sr g −1 dry weight of cells in 18 h. Heat killed cells exhibited limited Cs and Sr binding as compared to live cells highlighting the importance of cell viability for optimal binding. The association of the metals with Arthrobacter sp. KMSZP6 was further substantiated by Field Emission-Scanning Electron Microscopy (FE-SEM) coupled with Energy dispersive X-ray (EDX) spectroscopy. This organism tolerated up to 1 kGy 60 Co-gamma rays without loss of survival. The present report highlights the superior tolerance and binding capacity of the KMSZP6 strain for cesium and strontium over other earlier reported strains and reveals its potential for bioremediation of nuclear waste.
The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia e... more The adsorptive capability of superheated steam activated biochar (SSAB) produced from Colocasia esculenta was investigated for removal of Cu(2+), Fe(2+) and As(5+) from simulated coal mine wastewater. SSAB was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analyser. Adsorption isotherm indicated monolayer adsorption which fitted best in Langmuir isotherm model. Thermodynamic study suggested the removal process to be exothermic, feasible and spontaneous in nature. Adsorption of Fe(2+), Cu(2+) and As(5+) on to SSAB was found to be governed by pseudo-second order kinetic model. Efficacy of SSAB in terms of metal desorption, regeneration and reusability for multiple cycles was studied. Regeneration of metal desorbed SSAB with 1 N sodium hydroxide maintained its effectiveness towards multiple metal adsorption cycles. Cost estimation of SSAB production substantiated its cost effectiveness as compared to commercially availa...
Pasteurella multocida is an important veterinary pathogen causing infections in animals and birds... more Pasteurella multocida is an important veterinary pathogen causing infections in animals and birds. Nowadays, different reports have described the severity of infections, increasing resistance of micro-organisms to antibiotics, and the contribution of ethnoveterinary practices towards the treatment of various ailments of animals. The aim of the present study was to investigate the antibacterial efficacy of the ethanolic extracts of endophytic fungi against P. multocida Capsular Type A strains. A total of six endophytic fungi were isolated from two tropical ethnoveterinary plants: Garcinia xanthochymus H. and Polygonum chinense L. The ethanolic extracts of the endophytic fungi were subjected to in vitro antimicrobial activity by the well diffusion method. Besides, we evaluated the treatment of mice with the potent fungal extract and observed the effects in different organs under electron microscopy. Our results showed that four fungi had antimicrobial activity against the selected pathogen. The best antibacterial activity was showed by the extract of the endophytic fungi, Glomerella magna isolated from G. xanthochymus, with a minimum inhibitory concentration of 46.9 µg/mL and minimum bactericidal concentration of 750 µg/mL. Treatment of mice with the potent fungal extract caused a considerable inhibitory effect on the pathogen growth in vital organs, results that was also confirmed by histopathological studies made by scanning electron microscopy. The present findings indicated that the endophytic fungi G. magna has the potential to provide an effective treatment against infections caused by Pasteurella multocida. However, the isolation of bioactive components needs further investigation.
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Papers by Santaram Joshi