This review summarizes the recent papers published about the microbial communities under the conditions of persistent heavy metals around the world. Many microbial communities’ study has demonstrated ...intense changes in the community composition, and microbial diversity caused by heavy metals, environmental pollution as well as adaptation processes allowing survival of microbes in metal-polluted ecosystems. The effect of heavy metals such as Cu, Pb, Hg, Ni, Cd, Zn, and As on soil microbial communities in mediated soil are reviewed. The different sensitivity measurement, toxicity of metals, relative toxicity is discussed. In recent years, industrial activities have a significant influence on the environment. Especially, heavy metals such as Hg, Cr, Pb, Mn, and As, have induced seriously affected the soil microbial communities, cause diseases and even death of organisms through contaminated soils, although heavy metals in trace amounts are beneficial even significant to organisms. The effect of heavy metals on soil microbial communities is still poorly understood. That how microbial communities respond to environmental changes is a key issue in ecology. In the future further work needed to understand the microbial community under persistent heavy metals, their effects, how to reduce and decrease the microbial diversity, and resistance of specific bacterial species to heavy metals.
•To highlights the variation and succession of microbial communities.•Study has demonstrated intense changes in the community composition, and microbial diversity caused by heavy metals.•The environmental pollution as well as adaptation processes allowing survival of microbes in metal-polluted ecosystems.•Microbial communities under the conditions of persistent heavy metal.
Plastic pollution is a major global concern with several million microplastic particles entering every day freshwater ecosystems via wastewater discharge. Microplastic particles stimulate biofilm ...formation (plastisphere) throughout the water column and have the potential to affect microbial community structure if they accumulate in pelagic waters, especially enhancing the proliferation of biohazardous bacteria. To test this scenario, we simulated the inflow of treated wastewater into a temperate lake using a continuous culture system with a gradient of concentration of microplastic particles. We followed the effect of microplastics on the microbial community structure and on the occurrence of integrase 1 (int1), a marker associated with mobile genetic elements known as a proxy for anthropogenic effects on the spread of antimicrobial resistance genes. The abundance of int1 increased in the plastisphere with increasing microplastic particle concentration, but not in the water surrounding the microplastic particles. Likewise, the microbial community on microplastic was more similar to the original wastewater community with increasing microplastic concentrations. Our results show that microplastic particles indeed promote persistence of typical indicators of microbial anthropogenic pollution in natural waters, and substantiate that their removal from treated wastewater should be prioritised.
Display omitted
•Increasing microplastic concentrations lead to a higher frequency integrase 1.•Bacterial community pattern on microplastic resembles freshwater and waste water.•Similarity of bacterial community to waste water increases with increasing microplastic.
Increasing microplastic concentrations allow the persistence of integrase 1 on the plastic pollutants.
Soil management is fundamental to all agricultural systems and fertilization practices have contributed substantially to the impressive increases in food production. Despite the pivotal role of soil ...microorganisms in agro-ecosystems, we still have a limited understanding of the complex response of the soil microbiota to organic and mineral fertilization in the very long-term. Here, we report the effects of different fertilization regimes (mineral, organic and combined mineral and organic fertilization), carried out for more than a century, on the structure and activity of the soil microbiome. Organic matter content, nutrient concentrations, and microbial biomass carbon were significantly increased by mineral, and even more strongly by organic fertilization. Pyrosequencing revealed significant differences between the structures of bacterial and fungal soil communities associated to each fertilization regime. Organic fertilization increased bacterial diversity, and stimulated microbial groups (Firmicutes, Proteobacteria, and Zygomycota) that are known to prefer nutrient-rich environments, and that are involved in the degradation of complex organic compounds. In contrast, soils not receiving manure harbored distinct microbial communities enriched in oligotrophic organisms adapted to nutrient-limited environments, as Acidobacteria. The fertilization regime also affected the relative abundances of plant beneficial and detrimental microbial taxa, which may influence productivity and stability of the agroecosystem. As expected, the activity of microbial exoenzymes involved in carbon, nitrogen, and phosphorous mineralization were enhanced by both types of fertilization. However, in contrast to comparable studies, the highest chitinase and phosphatase activities were observed in the solely mineral fertilized soil. Interestingly, these two enzymes showed also a particular high biomass-specific activities and a strong negative relation with soil pH. As many soil parameters are known to change slowly, the particularity of unchanged fertilization treatments since 1902 allows a profound assessment of linkages between management and abiotic as well as biotic soil parameters. Our study revealed that pH and TOC were the majors, while nitrogen and phosphorous pools were minors, drivers for structure and activity of the soil microbial community. Due to the long-term treatments studied, our findings likely represent permanent and stable, rather than transient, responses of soil microbial communities to fertilization.
Renewable H2 production from a plentiful biomass, waste activated sludge (WAS), can be achieved by fermentation, but the yields are low. The use of a microbial electrolysis cell (MEC) can increase ...the H2 production yields to several times that of fermentation. We have proved that the enhancement of H2 production was due to the ability of MECs to use a wider range of organic matter in WAS than in fermentation. To support this result strongly, we here investigated the microbial community structures of WAS and anode biofilms in WAS-fed MECs. A pyrosequencing analysis based on the bacterial 16S rRNA gene showed that dominant populations in MECs were more diverse than those in WAS (inoculum and substrate) after enrichment, and there was a clear distinction between MECs and WAS in microbial community structure. Diverse acid-producing bacteria and exoelectrogens (predominance of Geobacter) were detected in MECs but they were only rarely found in WAS. It has been reported that these acid-producing bacteria can ferment various sugars and amines with acetate, propionate, and butyrate as their major by-products. This was consistent with our chemical analyses. Detected exoelectrogens are known to use these organic acids (mainly acetate) and certain sugars to directly produce current for H2 generation at the cathodes in the MECs. Using quantitative real-time PCR, we demonstrated that a consistent feed of alkaline-pretreated WAS containing large amounts of acetate led to a predominance of acetoclastic methanogens, while hydrogenotrophic methanogens were abundant in MECs fed both raw and alkaline-pretreated WAS. Syntrophic interactions between phylogenetically diverse microbial populations in anodophilic biofilms were found to drive the efficient cascade utilization of organic matter in WAS.
Display omitted
► Pyrosequencing reveals microbial communities in MECs fed waste activated sludge. ► Microbial populations in MECs are more diverse than those in waste activated sludge. ► Syntrophic interactions drive MEC cascade utilization of various organic materials. ► QPCR is used to quantify bacteria, Archaea, and methanogens in the microbial community. ► Predominance of hydrogenotrophic or acetoclastic methanogens depends on substrate.
Terrestrial ecosystems worldwide are receiving increasing amounts of biologically reactive nitrogen (N) as a consequence of anthropogenic activities. This intended or unintended fertilization can ...have a wide‐range of impacts on biotic communities and hence on soil respiration. Reduction in below‐ground carbon (C) allocation induced by high N availability has been assumed to be a major mechanism determining the effects of N enrichment on soil respiration. In addition to increasing available N, however, N enrichment causes soil acidification, which may also affect root and microbial activities. The relative importance of increased N availability vs. soil acidification on soil respiration in natural ecosystems experiencing N enrichment is unclear. We conducted a 12‐year N enrichment experiment and a 4‐year complementary acid addition experiment in a semi‐arid Inner Mongolian grassland. We found that N enrichment had contrasting effects on root and microbial respiration. N enrichment significantly increased root biomass, root N content and specific root respiration, thereby promoting root respiration. In contrast, N enrichment significantly suppressed microbial respiration likely by reducing total microbial biomass and changing the microbial community composition. The effect on root activities was due to both soil acidity and increased available N, while the effect on microbes primarily stemmed from soil acidity, which was further confirmed by results from the acid addition experiment. Our results indicate that soil acidification exerts a greater control than soil N availability on soil respiration in grasslands experiencing long‐term N enrichment. These findings suggest that N‐induced soil acidification should be included in predicting terrestrial ecosystem C balance under future N deposition scenarios.
Heavy metal pollution of paddy fields is of increasing concern due to the huge losses in rice yield that occur every year. Therefore, it is important to understand the microecological and ...physicochemical changes to paddy soil under varying cadmium (Cd) pollution levels. Here, we explore the bacterial community response to cadmium contamination of agricultural paddy soil. Our results reveal that high cadmium level sites displayed lower diversity indices than low cadmium level groups. In addition, total and available cadmium exhibited significant negative correlations with diversity indices. The dominant phyla that were observed in the paddy soil samples included Proteobacteria, Chloroflexi, Acidobacteria, Actinobacteria, Gemmatimonadetes, Verrucomicrobia, Thaumarchaeota, Firmicutes, and Nitrospirae. The results suggest that Actinobacteria are tolerant to cadmium, whereas Proteobacteria, Verrucomicrobia, and Nitrospirae are sensitive. According to the results of pCoA, bacterial communities were differentiated across cadmium pollution levels, suggesting that the active members of the microbial communities under cadmium stress were different from those in the control soils. In addition, Mantel tests showed that the overall bacterial community structure significantly correlated with total pH, available phosphorus (AP), organic matter (OM), total cadmium (TCd), and available cadmium (ACd).
•Bacterial community in high Cd level groups displayed lower alpha diversity indices•TCd and ACd exhibited significant negative correlations with alpha diversity indices•Bacterial communities change significantly across cadmium pollution levels•The bacterial community was significantly correlated with pH, AP, OM, TCd and ACd
This work was conducted to assess the influence of a compost-born multifunctional thermophilic microbial consortium (CTMC) on the physico-chemical parameters, organic matter (OM) transformation and ...dynamic succession of microbial communities in dairy manure-sugarcane leaves co-composting. The results revealed that CTMC inoculation not only improved the bio-degradation of OM and lignocellulose but also distinctly enhanced the aromaticity and stability degrees of dissolved organic matter and humic substance (HS). Additionally, the complexity and diversity of bacterial and fungal community increased after inoculation. Redundancy analysis indicated that the microbial communities compositions and the physico-chemical parameters interacted with each other in humification process. The dominated bacterial and fungal species related to lignocellulose degradation and humification process were also detected. Accordingly, this research could put forward a possible optimized inoculation strategy to enhance the mineralization of organic carbon, accelerate the lignocellulose degradation and promote the humification process in solid organic waste composting.
Display omitted
•CTMC agent induced on the organic matter convert into humic substance.•The stronger aromaticity and stability of DOM and HS was obtained in CPT.•Identify CTMC effects on the succession of microbial communities were proposed.•Key factors accounting for microbial communities dynamics were studied by RDA.
Conventional agriculture still relies on the general use of agrochemicals (herbicides, fungicides and insecticides) to control various pests (weeds, fungal pathogens and insects), to ensure the yield ...of crop and to feed a constantly growing population. The generalized use of pesticides in agriculture leads to the contamination of soil and other connected environmental resources. The persistence of pesticide residues in soil is identified as a major threat for in-soil living organisms that are supporting an important number of ecosystem services. Although authorities released pesticides on the market only after their careful and thorough evaluation, the risk assessment for in-soil living organisms is unsatisfactory, particularly for microorganisms for which pesticide toxicity is solely considered by one global test measuring N mineralization. Recently, European Food Safety Authority (EFSA) underlined the lack of standardized methods to assess pesticide ecotoxicological effects on soil microorganisms. Within this context, there is an obvious need to develop innovative microbial markers sensitive to pesticide exposure. Biomarkers that reveal direct effects of pesticides on microorganisms are often viewed as the panacea. Such biomarkers can only be developed for pesticides having a mode of action inhibiting a specific enzyme not only found in the targeted organisms but also in microorganisms which are considered as “non-target organisms” by current regulations. This review explores possible ways of innovation to develop such biomarkers for herbicides. We scanned the herbicide classification by considering the mode of action, the targeted enzyme and the ecotoxicological effects of each class of active substance in order to identify those that can be tracked using sensitive microbial markers.
Display omitted
•Herbicide mode of action is depicted according to the HRAC classification.•Numerous herbicides target an enzyme found in plants and in microorganisms.•Possible effects of herbicides on soil microbial communities are described.•Targeted microbial enzymes are suggested to be used as exposure biomarkers.
Resource acquisition and growth yield are fundamental microbial traits that affect biogeochemical processes and have consequences for ecosystem functioning. However, there is a lack of empirical ...observations linking these traits. Using a landscape-scale survey of temperate near-neutral pH soils, we show tradeoffs in key community-level parameters linked to these traits. Increased investment into extracellular enzymes estimated using specific potential enzyme activity was associated with reduced growth yield obtained using carbon use efficiency measures from stable isotope tracing. Reduction in growth yield was linked more to carbon than nitrogen acquisition highlighting smaller stoichiometric than energetic constraints on community metabolism in examined soils.
•Evidence for tradeoff in microbial resource acquisition and growth yield traits.•Growth yield patterns linked more to carbon than nitrogen enzyme activity.•Smaller stoichiometric than energetic constraints on community metabolism.•Community-aggregated trait tradeoffs have consequences for soil carbon cycling.
PDF
