Papers by Shalini Rajkumar
PLOS ONE, 2015
The mode of succinate mediated repression of mineral phosphate solubilization and the role of rep... more The mode of succinate mediated repression of mineral phosphate solubilization and the role of repressor in suppressing phosphate solubilization phenotype of two free-living nitrogen fixing Klebsiella pneumoniae strains was studied. Organic acid mediated mineral phosphate solubilization phenotype of oxalic acid producing Klebsiella pneumoniae SM6 and SM11 were transcriptionally repressed by IclR in presence of succinate as carbon source. Oxalic acid production and expression of genes of the glyoxylate shunt (aceBAK) was found only in glucose but not in succinate- and glucose+succinate-grown cells. IclR, repressor of aceBAK operon, was inactivated using an allelic exchange system resulting in derepressed mineral phosphate solubilization phenotype through constitutive expression of the glyoxylate shunt. Insertional inactivation of iclR resulted in increased activity of the glyoxylate shunt enzymes even in succinate-grown cells. An augmented phosphate solubilization up to 54 and 59% soluble phosphate release was attained in glucose+succinate-grown SM6Δ and SM11Δ strains respectively, compared to glucose-grown cells, whereas phosphate solubilization was absent or negligible in wildtype cells grown in glucose+succinate. Both wildtype and iclR deletion strains showed similar indole-3-acetic acid production. Wheat seeds inoculated with wildtype SM6 and SM11 improved both root and shoot length by 1.2 fold. However, iclR deletion SM6Δ and SM11Δ strains increased root and shoot length by 1.5 and 1.4 folds, respectively, compared to uninoculated controls. The repressor inactivated phosphate solubilizers better served the purpose of constitutive phosphate solubilization in pot experiments, where presence of other carbon sources (e.g., succinate) might repress mineral phosphate solubilization phenotype of wildtype strains.
The fates of Pseudomonas striata (P-27) and its mutant were compared in the rhizosphere of soybea... more The fates of Pseudomonas striata (P-27) and its mutant were compared in the rhizosphere of soybean at different fertilizer level. Three lacZ tagged mutant strains designated as superior, inferior and homologous to parent with respect to P-solubilization (T-80, T-128, T-125) and IAA production (T-49, T-57, T-87) were selected for establishment studies. The comparison of mutants for their ability to survive and establish in soybean rhizosphere revealed, a linear decline of the population with plant growth period. Individual pot experiments were conducted with superior strains to study the influence of level of fertilizer on phosphobacterial population in rhizosphere and crop growth. It is concluded that inoculation of P. striata strain increases the population of phosphobacteria and growth parameters of soybean irrespective of the level of fertilizer. The application of fertilizer beyond 50% of the recommended dose was found to be relatively unresponsive.
... Varsha Nenwani, Pratima Doshi, Tithi Saha and Shalini Rajkumar* ... Despite the existence of ... more ... Varsha Nenwani, Pratima Doshi, Tithi Saha and Shalini Rajkumar* ... Despite the existence of phytase-positive soil organisms, which may account for 30 - 50% of total soil microbial flora, phytate remains the most recalcitrant pool of organic phosphorus in soils (Ognalaga et al ...
Indian Journal of Biotechnology
Medicinal plants are the most important source of life saving drugs for the majority of the world... more Medicinal plants are the most important source of life saving drugs for the majority of the world's population. Plant secondary metabolites are economically important as drugs, fragrances, pigments, food additives and pesticides. The biotechnological tools are important to select, multiply, improve and analyze medicinal plants. In-vitro production of secondary metabolites in plant cell suspension cultures has been reported from various medicinal plants and bioreactors are the key step towards commercial production of secondary metabolites by plant biotechnology. Genetic transformation is a powerful tool for enhancing the productivity of novel secondary metabolites; especially by Agrobacterium tumefacians . Combinatorial biosynthesis is another approach in the generation of novel natural products and for the production of rare and expensive natural products. DNA profiling techniques like DNA microarrays serve as suitable high throughput tools for the simultaneous analysis of mult...
Indian journal of pharmaceutical sciences, 2013
The research work reported in this paper is extension of our previous findings related to interca... more The research work reported in this paper is extension of our previous findings related to intercalation of procainamide hydrochloride, an antiarrythmia drug in interlayer gallery of Na(+)-clay (montmorillonite). The microcomposite particles prepared from procainamide-montmorillonite hybrid and poly L-lactide were characterised by scanning electron microscope and atomic force microscopy analysis. In vitro drug release study in simulated intestinal fluid showed controlled release pattern up to ~72 h and significant reduction in the drug release in gastric environment. In vivo pharmacokinetics and biodistribution in rats showed that the plasma/tissue drug levels were within therapeutic window as compared with free drug. The data from toxicity biomarker estimations and clinical biochemistry/haematological parameters showed significant reduction in drug toxicity when formulated in montmorillonite/poly L-lactide as compared with free drug, which is of considerable value in achieving impro...
We report here, the preparation and characterization of polyacrylamide/Na+‐MMT (Montmorillonite) ... more We report here, the preparation and characterization of polyacrylamide/Na+‐MMT (Montmorillonite) composite hydrogels and its application as anticancer drug carrier reservoir. The X‐ray diffraction patterns, thermal and spectroscopic analyses indicate that the acrylamide and MMT has been successfully conglomerated to form composite gels. The degree of swelling was higher in composite hydrogels as compared to pristine hydrogel; and the hydrophilic MMT improved the water absorbing properties of composite hydrogels. The mode of water transport in the composite hydrogels was partially through a swollen polymeric matrix and water filling in clay layers of the composite hydrogels. In vitro drug release study demonstrated the controlled release pattern. In vitro cytotoxicity of drug loaded composite hydrogel was evaluated in MCF‐7 and Hela cells by MTT assay. In vivo pharmacokinetics, biodistribution, toxicity biomarkers and total serum protein analysis were also investigated after single oral administration of drug in rats.
Colloids and surfaces. B, Biointerfaces, 2014
This work reports intercalation of a sparingly soluble antibiotic (ciprofloxacin) into layered na... more This work reports intercalation of a sparingly soluble antibiotic (ciprofloxacin) into layered nanostructure silicate, montmorillonite (MMT) and its reaction with bone derived polypeptide, gelatin that yields three-dimensional composite hydrogel. Drug intercalation results in changes in MMT layered space and drug loaded MMT and gelatin creates 3D morphology with biodegradable composite hydrogels. These changes can be correlated with electrostatic interactions between the drug, MMT and the gelatin polypeptides as confirmed by X-ray diffraction patterns, thermal, spectroscopic analyses, computational modeling and 3D morphology revealed by SEM and TEM analysis. No significant changes in structural and functional properties of drug was found after intercalation in MMT layers and composite hydrogels. In vitro drug release profiles showed controlled release up to 150h. The drug loaded composite hydrogels were tested on lung cancer cells (A549) by MTT assay. The results of in vitro cell mi...
Bacteria in Agrobiology: Crop Ecosystems, 2011
... M. Saraf (*) Department of Microbiology, Gujarat University, Ahmedabad 380009, Gujarat, India... more ... M. Saraf (*) Department of Microbiology, Gujarat University, Ahmedabad 380009, Gujarat, India e-mail: [email protected] S. Rajkumar and T. Saha ... that act as nitrogen-fixing and phosphate-solubilizing bacteria have indicated increased yields in the rice crop (Sudha et al. ...
Microbiology, 2014
The application of plant-growth-promoting rhizobacteria (PGPR) at field scale has been hindered b... more The application of plant-growth-promoting rhizobacteria (PGPR) at field scale has been hindered by an inadequate understanding of the mechanisms that enhance plant growth, rhizosphere incompetence and the inability of bacterial strains to thrive in different soil types and environmental conditions. Actinobacteria with their sporulation, nutrient cycling, root colonization, bio-control and other plant-growth-promoting activities could be potential field bio-inoculants. We report the isolation of five rhizospheric and two root endophytic actinobacteria from Triticum aestivum (wheat) plants. The cultures exhibited plant-growth-promoting activities, namely phosphate solubilization (1916 mg l(-1)), phytase (0.68 U ml(-1)), chitinase (6.2 U ml(-1)), indole-3-acetic acid (136.5 mg l(-1)) and siderophore (47.4 mg l(-1)) production, as well as utilizing all the rhizospheric sugars under test. Malate (50-55 mmol l(-1)) was estimated in the culture supernatant of the highest phosphate solublizer, Streptomyces mhcr0816. The mechanism of malate overproduction was studied by gene expression and assays of key glyoxalate cycle enzymes - isocitrate dehydrogenase (IDH), isocitrate lyase (ICL) and malate synthase (MS). The significant increase in gene expression (ICL fourfold, MS sixfold) and enzyme activity (ICL fourfold, MS tenfold) of ICL and MS during stationary phase resulted in malate production as indicated by lowered pH (2.9) and HPLC analysis (retention time 13.1 min). Similarly, the secondary metabolites for chitinase-independent biocontrol activity of Streptomyces mhcr0817, as identified by GC-MS and (1)H-NMR spectra, were isoforms of pyrrole derivatives. The inoculation of actinobacterial isolate mhce0811 in T. aestivum (wheat) significantly improved plant growth, biomass (33%) and mineral (Fe, Mn, P) content in non-axenic conditions. Thus the actinobacterial isolates reported here were efficient PGPR possessing significant antifungal activity and may have potential field applications.
Journal of Applied Microbiology, 2012
To evaluate the plant growth promotion (PGP) potential and soil enzyme production under solid sta... more To evaluate the plant growth promotion (PGP) potential and soil enzyme production under solid state fermentation (SSF) by most abundant Streptomyces spp. isolated from the wheat rhizosphere and to evaluate their effect on plant growth parameters. Actinomycetes were isolated from wheat rhizosphere and screened for PGP activities. Three actinomycete isolates having significantly higher PGP activities (Streptomyces rochei IDWR19, Streptomyces carpinensis IDWR53, Streptomyces thermolilacinus IDWR81) were selected. The soil enzymes production potential of these isolates using soil extract and wheat straw under ssf was assessed. Utilization of soil extract as a fermentation medium for soil enzyme production by Actinomycetes has been reported first time in this study. Maximum chitinase (S. rochei IDWR19 12·2 U mg(-1) protein) and phytase activity (S. carpinensis IDWR53 5·2 U mg(-1) protein) was produced on 7th day of incubation, whereas maximum alkaline protease (S. rochei IDWR19 3·2 U mg(-1) protein) was produced on 6th day of incubation. For cellulase (S. rochei IDWR19 7·4 U mg(-1) protein) and invertase (S. carpinensis IDWR53 451 U mg(-1) protein) maximum activity was observed on 4th as well as 5th day of incubation. On the basis of PGP activity and enzyme production, two actinomycete isolates (S. rochei IDWR19 and S. thermolilacinus IDRWR81) were selected for plant growth experiment. An increase of 12·2 and 24·5% in shoot length of plants inoculated with S. rochei IDWR19 and S. thermolilacinus IDWR81 was observed, respectively. A similar increase in biomass of 1·8- and 2·3-fold was also recorded for the two isolates, respectively. It could be concluded that Streptomyces sp. with high PGP activities and soil enzyme production capability significantly improved growth and development of wheat cv. The abundant Actinomycetes obtained in this study (S. rochei IDWR19 and S. thermolilacinus IDWR81) are rhizosphere competent and effective strains.
European Journal of Pharmaceutics and Biopharmaceutics, 2012
We report here the intercalation of 5-fluorouracil (5-FU), an anticancer drug in interlayer galle... more We report here the intercalation of 5-fluorouracil (5-FU), an anticancer drug in interlayer gallery of Na + clay (Montmorillonite, MMT), with the assistance of biopolymer (chitosan, CS). The X-ray diffraction patterns, thermal and spectroscopic analyses indicated the drug intercalation into the clay interlayer space in support of CS and stabilized in the longitudinal monolayer by electrostatic interaction. In vitro drug release showed controlled release pattern. The genotoxic effect of drug was in vitro evaluated in human lymphocyte cell culture by comet assay, and results indicated significant reduction in DNA damage when drug was intercalated with clay and formulated in composites. The results of in vitro cell viability assay in cancer cells pointed at decreased toxicity of drug when encapsulated in Na + -clay plates than the pristine drug. In vivo pharmacokinetics, biodistribution, hepatotoxicity markers, e.g., SGPT and SGOT, and liver/ testicular histology in rats showed plasma/tissue drug levels were within therapeutic window as compared to pristine drug. Therefore, drug-clay hybrid and composites can be of considerable value in chemotherapy of cancer with reduced side effects.
European Journal of Pharmaceutical Sciences, 2012
This work evaluates intercalation of tamoxifen (Tmx) in interlayer gallery of Na(+)-MMT (Montmori... more This work evaluates intercalation of tamoxifen (Tmx) in interlayer gallery of Na(+)-MMT (Montmorillonite, MMT) (Tmx-MMT), which is further compounded with poly-(ε-caprolactone) (PCL) (Tmx-MMT/PCL, MPs), for oral chemotherapy of breast cancer. The X-ray diffraction patterns, thermal and spectroscopic analyses indicated the intercalation of Tmx into the MMT interlayer that stabilized in the longitudinal monolayer mode by electrostatic interaction. No significant change in structural and functional properties of Tmx was found in the MMT layers. In vitro study of drug release profiles showed controlled release pattern. The genotoxic effect of drug was in vitro evaluated in human lymphocyte cell culture by comet assay, and results indicated moderate reduction in DNA damage when pristine Tmx was intercalated with MMT and formulated in composites. The Tmx-MMT hybrid efficacy was also confirmed on HeLa and A549 cancer cells by in vitro cell viability assay. In vivo pharmacokinetics (PK) of formulated Tmx in rats was examined and the results showed that plasma Tmx levels were within therapeutic window as compared to pristine Tmx. Therefore, Tmx-MMT hybrid and microcomposite particles (MPs) can be of considerable value in chemotherapy of malignant neoplastic disease with reduced side effects. This study clearly indicated that MMT not only plays a role as a delivery matrix for drug, but also facilitates significant increase in the delivery proficiency.
Colloids and Surfaces B: Biointerfaces, 2013
Intercalation of 6-mercaptopurine (6-MP), an antineoplastic drug in interlayer gallery of Na + -c... more Intercalation of 6-mercaptopurine (6-MP), an antineoplastic drug in interlayer gallery of Na + -clay (MMT) was further entrapped in poly (l-lactide) matrix to form microcomposite spheres (MPs) in order to reduce the cell toxicity and enhance in vitro release and pharmacokinetic proficiency. The drug-clay hybrid was fabricated via intercalation by ion-exchange method to form MPs from hybrid. In vitro drug release showed controlled pattern, fitted to kinetic models suggested controlled exchange and partial diffusion through swollen matrix of clay inter layered gallery. The in vitro efficacy of formulated composites drug was tested in Human neuroblastoma cell line (IMR32) by various cell cytotoxic and oxidative stress marker indices. In vivo pharmacokinetics suggested that the intensity of formulated drug level in plasma was within remedial borders as compared to free drug. These clay based composites therefore have great potential of becoming a new dosage form of 6-MP.
Archives of Microbiology, 2013
Two strains of Klebsiella (SM6 and SM11) were isolated from rhizospheric soil that solubilized mi... more Two strains of Klebsiella (SM6 and SM11) were isolated from rhizospheric soil that solubilized mineral phosphate by secretion of oxalic acid from glucose. Activities of enzymes for periplasmic glucose oxidation (glucose dehydrogenase) and glyoxylate shunt (isocitrate lyase and glyoxylate oxidase) responsible for oxalic acid production were estimated. In presence of succinate, phosphate solubilization was completely inhibited, and the enzymes glucose dehydrogenase and glyoxylate oxidase were repressed. Significant activity of isocitrate lyase, the key enzyme for carbon flux through glyoxylate shunt and oxalic acid production during growth on glucose suggested that it could be inducible in nature, and its inhibition by succinate appeared to be similar to catabolite repression.
Applied Microbiology and Biotechnology, 2006
This paper reports the successful isolation and characterization of a new phenol-degrading bacter... more This paper reports the successful isolation and characterization of a new phenol-degrading bacterium, strain EDP3, from activated sludge. Strain EDP3 is a nonmotile, strictly aerobic, Gram-negative, and short-rod or coccobacillary bacterium, which occurs singly, in pairs, or in clusters. 16S rRNA gene sequence analysis revealed that strain EDP3 belonged to the gamma group of Proteobacteria, with a 97.0% identity to 16S rRNA gene sequences of Acinetobacter calcoaceticus. Strain EDP3 could aerobically grow on a number of aromatic compounds, such as phenol, sodium benzoate, p-hydroxybenzoate, phenylacetate, benzene, ethylbenzene, benzylalcohol, and so on. In particular, it could mineralize up to 1,000 mg l(-1) phenol at room temperature (25 degrees C). The growth kinetics of strain EDP3 on phenol as a sole carbon and energy source at 25 degrees C can be described using the Haldane equation. It has a maximal specific growth rate (mu(max)) of 0.28 h(-1), a half-saturation constant (K(S)) of 1,167.1 mg l(-1), and a substrate inhibition constant (Ki) of 58.5 mg l(-1). Values of yield coefficient (Y(X/S)) are between 0.4 and 0.6 mg dry cell (mg phenol)(-1). Strain EDP3 has high tolerance to the toxicity of phenol (up to 1,000 mg l(-1)). It therefore could be an excellent candidate for the biotreatment of high-strength phenol-containing industrial wastewaters and for the in situ bioremediation of phenol-contaminated soils.
The fates of Pseudomonas striata (P-27) and its mutant were compared in the rhizosphere of soybea... more The fates of Pseudomonas striata (P-27) and its mutant were compared in the rhizosphere of soybean at different fertilizer level. Three lacZ tagged mutant strains designated as superior, inferior and homologous to parent with respect to P-solubilization (T-80, T-128, T-125) and IAA production (T-49, T-57, T-87) were selected for establishment studies. The comparison of mutants for their ability to survive and establish in soybean rhizosphere revealed, a linear decline of the population with plant growth period. Individual pot experiments were conducted with superior strains to study the influence of level of fertilizer on phosphobacterial population in rhizosphere and crop growth. It is concluded that inoculation of P. striata strain increases the population of phosphobacteria and growth parameters of soybean irrespective of the level of fertilizer. The application of fertilizer beyond 50% of the recommended dose was found to be relatively unresponsive.
Journal of Yeast and …, 2010
... Varsha Nenwani, Pratima Doshi, Tithi Saha and Shalini Rajkumar* ... Despite the existence of ... more ... Varsha Nenwani, Pratima Doshi, Tithi Saha and Shalini Rajkumar* ... Despite the existence of phytase-positive soil organisms, which may account for 30 - 50% of total soil microbial flora, phytate remains the most recalcitrant pool of organic phosphorus in soils (Ognalaga et al ...
Legumes develop symbiotic relationships with Rhizobium by a complex exchange of signals. Despite ... more Legumes develop symbiotic relationships with Rhizobium by a complex exchange of signals. Despite the high specificity between symbiotic partners, the presence of non-rhizobial bacteria in root nodules has been reported. To investigate how these rhizobacteria enter root nodules, fluorescently tagged Pseudomonas fluorescens and Klebsiella pneumoniae were co-inoculated with host-nodulating Ensifer adhaerens to Vigna radiata seedlings and root hair infection was monitored using confocal microscopy at 5 days post inoculation. Pseudomonas fluorescens and K. pneumoniae invaded the root hair only when co-inoculated with E. adhaerens. Recovery of inoculated tagged strains and confirmation through CLSM and 16S rRNA gene sequencing confirmed that the test rhizobacteria occupied nodules. We hereby report with the help of confocal microscopy that rhizobacteria migrate along the length of host-nodulating rhizobial strain and become localized in root nodules. We further report isolation of eight non-rhizobial bacterial genera, predominantly Bacillus spp. and Paenibacillus spp., from nodules of field-grown V. radiata.
This work evaluates cationic intercalation of Capecitabine (Xeloda), an antineoplastic agent in i... more This work evaluates cationic intercalation of Capecitabine (Xeloda), an antineoplastic agent in interlayer
gallery of Na+-MMT, which was further compounded with Poly (L-Lactide) to form microcomposite
spheres, for oral chemotherapy of breast cancer. The XRD, TGA, SEM, TEM and FT-IR analysis indicated
the CAP intercalated in interlayer of MMT and stabilized in the longitudinal monolayer mode by electrostatic
interface. No significant alteration in fundamental active properties of CAP was found in the MMT
efficacy and data from in vitro study showed controlled drug release pattern >72 h. The efficacy of CAPMMT
hybrid/MPs was also confirmed on Human neuroblastoma cell line (IMR32) by in vitro cell culture
experiments evaluating cell cytotoxic and oxidative stress marker indices which showed that intercalated
drug and MPs, were as effective as pristine drug. In vivo pharmacokinetics of CAP-MMT hybrids in rats
was examined and plasma CAP levels were evaluated. Our findings suggest that CAP-MMT hybrids and
MPs can be of considerable value in chemotherapy of malignant neoplastic disease with reduced side
effects and clearly demonstrated that MMT not only plays a role as a delivery matrix for drug but also
facilitates significant increase in the delivery proficiency.
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Papers by Shalini Rajkumar
gallery of Na+-MMT, which was further compounded with Poly (L-Lactide) to form microcomposite
spheres, for oral chemotherapy of breast cancer. The XRD, TGA, SEM, TEM and FT-IR analysis indicated
the CAP intercalated in interlayer of MMT and stabilized in the longitudinal monolayer mode by electrostatic
interface. No significant alteration in fundamental active properties of CAP was found in the MMT
efficacy and data from in vitro study showed controlled drug release pattern >72 h. The efficacy of CAPMMT
hybrid/MPs was also confirmed on Human neuroblastoma cell line (IMR32) by in vitro cell culture
experiments evaluating cell cytotoxic and oxidative stress marker indices which showed that intercalated
drug and MPs, were as effective as pristine drug. In vivo pharmacokinetics of CAP-MMT hybrids in rats
was examined and plasma CAP levels were evaluated. Our findings suggest that CAP-MMT hybrids and
MPs can be of considerable value in chemotherapy of malignant neoplastic disease with reduced side
effects and clearly demonstrated that MMT not only plays a role as a delivery matrix for drug but also
facilitates significant increase in the delivery proficiency.
gallery of Na+-MMT, which was further compounded with Poly (L-Lactide) to form microcomposite
spheres, for oral chemotherapy of breast cancer. The XRD, TGA, SEM, TEM and FT-IR analysis indicated
the CAP intercalated in interlayer of MMT and stabilized in the longitudinal monolayer mode by electrostatic
interface. No significant alteration in fundamental active properties of CAP was found in the MMT
efficacy and data from in vitro study showed controlled drug release pattern >72 h. The efficacy of CAPMMT
hybrid/MPs was also confirmed on Human neuroblastoma cell line (IMR32) by in vitro cell culture
experiments evaluating cell cytotoxic and oxidative stress marker indices which showed that intercalated
drug and MPs, were as effective as pristine drug. In vivo pharmacokinetics of CAP-MMT hybrids in rats
was examined and plasma CAP levels were evaluated. Our findings suggest that CAP-MMT hybrids and
MPs can be of considerable value in chemotherapy of malignant neoplastic disease with reduced side
effects and clearly demonstrated that MMT not only plays a role as a delivery matrix for drug but also
facilitates significant increase in the delivery proficiency.