Soil Microbial Ecology

This study assessed the heavy metals concentrations in municipal solid wastes at Eldoret Mwenderi dumpsites located at the shores of river Sosiani within the Lake Victoria Basin, Kenya. Concentrations of the three heavy metals analysed (lead, arsenic and cadmium) in water and leachate were higher than the WHO acceptable standards. Lead concentrations in solid wastes were slightly above East African acceptable standards but well above the US EPA compost standards. The wastes dumped in this site are not sorted and the dumpsite lacks a leachate collection and removal system. Lack of composite liners at the bottom and side of the dumpsite allow leachates to move into the ground water around the dumpsite. These metals are a potential threat to Lake Victoria and regular monitoring of ground and surface water of the surrounding area should be done to detect any heavy metals escaping the dumpsite.

The effects of 55 pesticides (27 fungicides, 26 herbicides and 2 insecticides) on 25 Rhizobium strains were studied in laboratory tests. Fungicides, especially captan, fuberidazole, HPMTS and tilt were the most toxic preparations. Eleven preparations were not toxic, among them were benomyl, quintozene and thiophanate-methyl. The herbicides and insecti-cides tested were found to inhibit the growth of rhizobia to a lesser extent than the fungicides.

Investigations on arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungi are limited in trees of subtropical forests compared to other terrestrial ecosystems. We assessed the seasonal dynamics of endorhizal fungal symbioses in four dominant tree species (Alnus nepalensis, Castanopsis hystrix, Emblica officinalis, Schima wallichii) in two plantation forest stands of Northeastern India, a biodiversity hotspot part of the Indo-Burma region. All tree species examined had a dual association of AM and DSE fungi and such fungal symbioses are reported for the first time in A. nepalensis, C. hystrix and S. wallichii. Intermediate-type AM morphology was common in three tree species, while Paris-type AM morphology was found in S. wallichii. Colonization of AM and DSE fungi varied significantly across tree species and seasons. A total of 18 AM fungal spore morphotypes were isolated from the air-dried natural rhizosphere soils and trap culture experiments. Spore density of AM fungi was highest in summer, whereas AM col-onization in roots was highest during the rainy season. In contrast, root colonization with DSE fungi was highest during summer, except for E. officinalis. A significant negative correlation occurred between certain AM fungal and soil variables. In contrast, DSE fungal measures were not correlated to any of the soil properties examined. Correlation analysis indicated a certain degree of competition between AM and DSE fungi. Occurrence of AM and DSE fungal associations in economically important indigenous tree species indicates the possibility of utilizing them in future conservation programs.

Soil is a complex ecosystem comprised of several and mutually interacting components, both abiotic (organo-mineral associations) and biotic (microbial and pedofaunal populations and plants), where a single parameter depends on other factors and affects the same and other factors, so that a network of influences among organisms coexists with the reciprocal actions between organisms and their environment. Therefore, it is difficult to undoubtedly determine what is the cause and what the effect within relationships between factors and processes. Soil is commonly studied through the evaluation and measurement of single parameters (e.g. the content of soil organic matter (SOM), microbial biomass, enzyme activities, pH, etc.), events (e.g. soil erosion, compaction, etc.) and processes (e.g. soil respiration, carbon fluxes, nitrification/denitrification, etc.), often carried out in laboratory conditions in order to limit the number of factors acting within the ecosystem under study, but missing the information about the global soil environment that way. In the last decade, several scientists have proposed and suggested the need for a holistic approach to soil ecosystems in different contexts. Recently, we have applied a sensing system developed in the last decades and capable of analysing complex mixtures of gases and volatiles (odours or aromas) in atmospheres, namely called electronic nose (EN). Typically, ENs are devices consisting of an array of differentially and partially specific, despite selective, sensors upon diverse coatings of sensitive films, i.e. interacting with single analytes of the same chemical class, despite not highly specific for a single substance, only, but showing also lower extent of cross-selectivity towards compounds of other chemical classes. ENs can be used in the classifications of odours by processing the collected responses of all sensors in the array through pattern recognition analyses, in order to obtain a chemical fingerprint (olfactory fingerprint) typical of the analysed air sample. Due to these features, we decided to apply such a sensing technology to the analyses of soil atmospheres, because several processes in soil, both abiotic and biotic, result in gas and/or volatile production and the dynamics of such releases may also be affected by several additional environmental factors, such as soil moisture, temperature, gas exchange rates with outer atmosphere, adsorption/desorption processes, etc. Then, the analysis of soil atmosphere may provide information about global soil conditions (e.g. soil quality and health), according to a holistic approach, where several factors are contemporarily taken into account. At the same time, the use of such a technology, if adequately trained on purpose, can supply information about a single or a pool of processes sharing similar features, which occur in soil over a certain period of time and mostly affecting soil atmosphere. According to these premises and hypotheses, we demonstrated that EN is an useful technology to measure soil microbial activity, through its correlation to specific metabolic activities occurring in soil (i.e. global and specific respiration and some enzyme activities), but also soil microbial biomass. On the basis of such evidences, we also were able to use this technology to assess the quality and health conditions of soil ecosystems in terms of metabolic indices previously identified, according to some metabolic parameters and biomass quantification of microbial populations. In other studies, we also applied EN technology, despite using a different set of sensors in the array, to analyse the atmosphere of soil ecosystems in order to assess their environmental conditions after contamination with polycyclic aromatic hydrocarbons (PAHs) (i.e. semivolatile - SVOCs - organic pollutants). In this case, EN technology resulted capable of distinguishing between contaminated and uncontaminated soils, according to the differences in a list of substances, occurring in the atmospheres of differently treated soils, which were identified through SPME-GC/MS analyses and then suggested to be responsible for the different classification. Analysing the EN responses, it was also possible to follow the degradation process of pollutants by resident microbial populations over time, on the basis of the contemporary decrease of contaminant and the increased release of CO2. Then, we suggest that EN technology may be usefully employed in the analyses of soil ecosystems in order to both supply information about global soil environment, according to the holistic approach, and about specific processes occurring therein. Furthermore, since EN technology resulted to be effective and successful in detecting processes in soil, in both natural and perturbed conditions, involving microbial populations, which are commonly considered as the most sensitive and responsive to soil environmental modifications, we suggest it might be reasonably employed in analyses concerning the assessment of soil quality and health. Consequently, such a technology may also be used to study several processes involving soil ecosystems, such as soil management practices, soil restoration, soil contamination and remediation, soil fertility, etc.

Dynamics of cellulose decomposition activity of chernozems in steppe zone Zauralskogo Plateau are investigated (on example of reserve "Arkaim" in Chelyabinsk region). As objects of studies were the soils with natural vegetation as well as unploughed soils. The observations carried out during last 10 years after introduction reserved mode. The purpose of the observations was to study natural reconstruction of soil microbial proper-ties after stopping the agricultural treatment. According to the forecast it-negralny indicator of soil biological activity - cellulase activity - reservoir analysis will approach the virgin by 2045, 57 years after the cessation of agricultural use in the form of plowing.

Microbial communities from two field-scale swine wastewater treatment plants (WWTPs) were assessed by pyrosequencing analyses of bacterial and archaeal 16S ribosomal DNA (rDNA) fragments. Effluent samples from secondary (anaerobic covered lagoons and upflow anaerobic sludge blanket [UASB]) and tertiary treatment systems (open-pond natural attenuation lagoon and air-sparged nitrification-denitrification tank followed by alkaline phosphorus precipitation process) were analyzed. A total of 56,807 and 48,859 highquality reads were obtained from bacterial and archaeal libraries, respectively. Dominant bacterial communities were associated with the phylum Firmicutes, Bacteroidetes, Proteobacteria, or Actinobacteria. Bacteria and archaea diversity were highest in UASB effluent sample. Escherichia, Lactobacillus, Bacteroides, and/or Prevotella were used as indicators of putative pathogen reduction throughout the WWTPs. Satisfactory pathogen reduction was observed after the open-pond natural attenuation lagoon but not after the airsparged nitrification/denitrification followed by alkaline phosphorus precipitation treatment processes. Among the archaeal communities, 80 % of the reads was related to hydrogenotrophic methanogens Methanospirillum. Enrichment of hydrogenotrophic methanogens detected in effluent samples from the anaerobic covered lagoons and UASB suggested that CO 2 reduction with H 2 was the dominant methanogenic pathway in these systems. Overall, the results served to improve our current understanding of major microbial communities' changes downgradient from the pen and throughout swine WWTP as a result of different treatment processes.

The combination of high tides, strong winds and low pressure between the 5th and 7th of December 2013 caused a devastating storm surge that reached the North Norfolk coast (fig. 1a). Tides along parts of the North Norfolk coast reached higher levels than the devastating floods of 1953. Natural and man made sea defences were breached (fig. 1c, 2a) and large areas of the coastal ecosystem were flooded (fig. 2b) . This coastline is a mosaic of natural and semi-natural habitats and farmland, supporting significant wildlife populations, protecting the coastline against erosion and are widely used for recreation. The extent and duration of the impacts is still unclear and uncertain.