Indigenous Microbial Communities Research Articles

Indene, indane and naphthalene in a mixture with BTEX affect aerobic compound biodegradation kinetics and indigenous microbial community development

BTEX (benzene, toluene, ethylbenzene, xylene) are common pollutants often found in former gasworks sites together with some other contaminants like indene, indane and naphthalene (Ie, Ia, N). This study aimed to evaluate the inhibitory or stimulative substrate interactions between BTEX, and Ie, Ia, N during aerobic biodegradation. For this, batch bottles, containing originally anaerobic subsurface sediments, groundwater and indigenous microorganisms from a contaminated former gasworks site, were spiked with various substrate combinations (BTEX, BTEXIe, BTEXIa, BTEXN, BTEXIeIa, BTEXIeN, BTEXIaN, BTEXIeIaN). Subsequently concentrations were monitored over time. For the BTEXIeIaN mixture, initial concentrations were between 1 and 5 mg L-1, and all compounds were completely degraded by the microbial consortia within 39 days of incubation. The experimental data were fitted to a first order kinetic degradation model for interpretation of inhibition/stimulation between the compounds. Results showed that indene, indane, and naphthalene inhibited the degradation of benzene, toluene, ethylbenzene, o-xylene, with benzene being the most affected. M/p-xylene is the only compound whose biodegradation is stimulated by the presence of indene and indane (individually or mixed) but inhibited by the presence of naphthalene. 16S rRNA amplicon sequencing revealed differentiation in the microbial communities within the batches with different substrate mixtures, especially within the two microbial groups Micrococcaceae and Commamonaceae. Indene had more effect on the BTEX microbial community than indane or naphthalene and the presence of indene increased the relative abundance of Micrococcaceae family. In conclusion, co-presence of various pollutants leads to differentiation in degradation processes as well as in microbial community development. This sheds some light on the underlying reasons for that organic compounds present in mixtures in the subsurface of former gasworks sites are either recalcitrant or subjective towards biodegradation, and this understanding helps to further improve the bioremediation of such sites.

Responses of Petroleum Contamination at Different Sites to Soil Physicochemical Properties and Indigenous Microbial Communities

Responses of Petroleum Contamination at Different Sites to Soil Physicochemical Properties and Indigenous Microbial Communities

Microbial communities succession post to polymer flood demonstrate a role in enhanced oil recovery.

The role of indigenous microbial communities in residual oil extraction following a recovery process is not well understood. This study investigated the dynamics of resident microbial communities in oil-field simulating sand pack bioreactors after the polymer flooding stage resumed with waterflooding and explored their contribution to the oil extraction process. The microbial community succession was studied through high-throughput sequencing of 16S rRNA genes. The results revealed alternating dominance of minority populations, including Dietzia sps., Acinetobacter sps., Soehngenia sps., and Paracoccus sps., in each bioreactor following the flooding process. Additionally, the post-polymer waterflooding stage led to higher oil recovery, with hydroxyethylcellulose, tragacanth gum, and partially hydrolyzed polyacrylamide polymer-treated bioreactors yielding additional recovery of 4.36%, 5.39%, and 3.90% residual oil in place, respectively. The dominant microbial communities were previously reported to synthesize biosurfactants and emulsifiers, as well as degrade and utilize hydrocarbons, indicating their role in aiding the recovery process. However, the correlation analysis of the most abundant taxa showed that some species were more positively correlated with the oil recovery process, while others acted as competitors for the carbon source. The study also found that higher biomass favored the plugging of high permeability zones in the reservoir, facilitating the dislodging of crude oil in new channels. In conclusion, this study suggests that microbial populations significantly shift upon polymer treatment and contribute synergistically to the oil recovery process depending on the characteristics of the polymers injected. KEY POINTS: • Post-polymer flooded microbial ecology shows unique indigenous microbial consortia. • Injected polymers are observed to act as enrichment substrates by resident communities. • The first study to show successive oil recovery stage post-polymer flood without external influence.

Low-temperature corn straw-degrading bacterial agent and moisture effects on indigenous microbes

While the in situ return of corn straw can improve soil fertility and farmland ecology, additional bacterial agents are required in low-temperature areas of northern China to accelerate straw degradation. Moisture is an important factor affecting microbial activity; however, owing to a lack of bacterial agents adapted to low-temperature complex soil environments, the effects of soil moisture on the interaction between exogenous bacterial agents and indigenous soil microorganisms remain unclear. To this end, we explored the effect of the compound bacterial agent CFF constructed using Pseudomonas putida and Acinetobacter lwoffii, developed to degrade corn straw in low-temperature soils (15 °C), on indigenous bacterial and fungal communities under dry (10% moisture content), slightly wet (20%), and wet (30%) soil-moisture conditions. The results showed that CFF application significantly affected the α-diversity of bacterial communities and changed both bacterial and fungal community structures, enhancing the correlation between microbial communities and soil-moisture content. CFF application also changed the network structure and the species of key microbial taxa, promoting more linkages among microbial genera. Notably, with an increase in soil moisture, CFF enhanced the rate of corn straw degradation by inducing positive interactions between bacterial and fungal genera and enriching straw degradation-related microbial taxa. Overall, our study demonstrates the alteration of indigenous microbial communities using bacterial agents (CFF) to overcome the limitations of indigenous microorganisms for in situ straw-return agriculture in low-temperature areas.Key points• Low-temperature and variable moisture conditions (10–30%) were compared• Soil microbial network structure and linkages between genera were altered• CFF improves straw degradation via positive interactions between soil microbes

Monitoring of an Applied Beneficial Trichoderma Strain in Root-Associated Soil of Field-Grown Maize by MALDI-TOF MS.

The persistence of beneficial microorganisms in the rhizosphere or surrounding soil following their application is a prerequisite for the effective interaction with the plant or indigenous microbial communities in the respective habitats. The goal of the study was to analyze the establishment and persistence of the applied beneficial Trichoderma harzianum (OMG16) strain in the maize root-associated soil depending on agricultural practice (soil management practice, N-fertilizer intensity) in a field experiment. A rapid identification of the inoculated strain OMG16 is essential for its monitoring. We used a culture-based approach coupled to matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis for the rapid identification of the inoculated Trichoderma strain as part of the beneficial microbe consortium (BMc). We isolated 428 fungal isolates from eight treatments of the field experiment. Forty eight percent of the isolated fungi equivalent to 205 fungal isolates were identified as Trichoderma, of which 87% (=179 isolates) were obtained from the fields inoculated with BMc. Gene sequence analysis showed a high similarity of the MALDI-TOF MS-identified Trichoderma, with that of the inoculated Trichoderma harzianum OMG16 confirming the re-isolation of the added beneficial fungus. This study highlighted the use of MALDI-TOF MS analysis as a quick, cost-effective detection and efficient monitoring tool for microbial-based bioinoculants in the field.

Degradation of crude oil by the microbial populations of Lagos and Ologe lagoon waters

Introduction: hydrocarbon contamination of surface waters as a result of anthropogenic activity poses threat to ecosystems and counter their beneficial uses. Some indigenous microbial communities have the potential to purify such waters unaided. Aims: To show the biodegradative potential of microbial communities in Lagos and Ologe Lagoons during minimal pollution with crude oil. Materials and Methods: The total heterotrophic bacteria and hydrocarbon utilising bacterial and fungal populations were estimated from Lagos and Ologe lagoon water samples contaminated with 1% crude oil over 42-day incubation period by plate count and vapour-phase transfer techniques. Residual hydrocarbons were determined by Gas chromatography. Results: The predominant bacterial genera identified from the lagoons include Enterobacter, Klebsiella and Proteus, while Escherichia, and Morganella. Aspergillus and Mucor were the predominant fungal genera in both waters. The hydrocarbon degradation rate in the Lagos Island microcosm was 65.391±0.370 mg/l/d, degradation rate constant 0.05±0.01 /d, half-life 9.559±0.093 /d and percentage degradation of 95.315 ± 0.134. Corresponding values in the Ologe water were 61.190± 8.542 mg/l/d, 8.725 ±0.389 /d, 0.055±0.003/d and 96.345±0.488 respectively. There was almost complete disappearance of the various fractions of the oil in the two samples. The microbial communities from both lagoons effectively utilised majority of the hydrocarbon fractions after 42 days where 66.890±1.075 and 100±000 were recorded for benzene, toluene had 100±000 percent degradation, anthracene 96.755±0.119 and 99.726±0.026, and pristane had 91.674±0.222 and 99.943±0.015 while phytane had 96.44±0.058 and 99.670±0.104 respectively. Conclusion: Efficient biodegradation of moderate contamination crude oil could be achieved by indigenous microbial flora present in Lagos and Ologe lagoon waters.

Response characteristics of indigenous microbial community in polycyclic aromatic hydrocarbons (PAHs) contaminated aquifers under polyethylene microplastics stress: A microcosmic experimental study

To understand the response characteristics of indigenous microbial community in PAH-contaminated aquifers to the coexistence of microplastics. In this paper, we constructed a groundwater microecosystem using lithologic media collected from the field and subjected it to the stress of a polyethylene microplastics (PE-MPs) concentration gradient. By conducting adsorption experiments and 16S rRNA sequencing, we revealed the growth, structure, metabolism, and resistance mechanisms of the indigenous microbial community in the aquifer lithologic media exposed to varying levels of co-stress from PE-MPs and phenanthrene. Our findings suggest that the adsorption capacity of aquifer lithologic media for phenanthrene is significantly weaker than that of PE-MPs. Additionally, our observations indicated that small particle lithologic media had a greater adsorption capacity for phenanthrene than large particle lithologic media. The presence of PE-MPs was found to increase both the abundance and diversity of microbial communities, although the relationship was not linear with the content of PE-MPs. When exposed to the combined stress of PE-MPs and phenanthrene, the relative abundance of Proteobacteria decreased while that of Bacteroidetes increased. Several genera belonging to Proteobacteria (Aeromonas, Desulfovibrio, Klebsiella, Pantoea, and Microvirgula) and Bacteroidetes (Macellibacteroides and Bacteroides) occupied a central position in the microbial community interaction network and showed significant correlations with other genera. Furthermore, an increase in the proportion of genera capable of degrading various refractory organics was observed. The presence of PE-MPs increased the phenanthrene content in the aquifer lithologic media, thereby intensifying the inhibitory effect on indigenous microbial community in this environment. Despite an increase in the phenanthrene content of aquifer lithologic media due to the presence of PE-MPs, indigenous microbial community in this environment exhibited resistance to the combined inhibition of PE-MPs and phenanthrene through a series of resistance mechanisms. These mechanisms included strengthening the N-cycle process, enhancing metabolic capacity for phenanthrene, improving perception, response, and adaptation to changes in the external environment or intracellular state, modifying the transmembrane transport of the cell membrane to the substrate, and regulating life processes.

Natural polysaccharide polymer network for sustained nutrient release to stimulate the activity of aromatic hydrocarbon-degrading indigenous microflora present in groundwater

Aromatic hydrocarbons (AHs) are known to contaminate groundwater with low indigenous microorganism populations and limited nutrient substrates for degradation reactions, resulting in weak natural remediation abilities of groundwater ecosystems. In this study, we aimed to utilize the principles of AH degradation by microorganisms to identify effective nutrients and optimize nutrient substrate allocation through actual surveys of AH-contaminated sites and microcosm experiments. Building on this, using biostimulation and controlled-release technology, we developed a natural polysaccharide-based encapsulated targeted bionutrient (SA-H-CS) that is characterized by easy uptake, good stability, controllable slow-release migration, and longevity to stimulate indigenous microflora in groundwater to efficiently degrade AHs. Results showed that SA-H-CS is a simple overall dispersion system, and nutrient components diffuse readily through the polymer network. The crosslinking of SA and CS resulted in a more compact structure of the synthesized SA-H-CS, effectively encapsulating the nutrient components and extending their active duration to >20 days. SA-H-CS improved the degradation efficiency of AHs and prompted microorganisms to maintain a high degradation rate (i.e., above 80 %) even in the presence of high concentrations of AHs, particularly naphthalene and O-xylene. Under SA-H-CS stimulation, microorganisms grew rapidly, and the diversity and total number of species of microflora increased significantly, with a notable increase in the proportion of Actinobacteria in the microbial community primarily due to the increased abundance of Arthrobacter, Rhodococcus, and Microbacterium, which are capable of degrading AHs. Concurrently, there was a notable enhancement in the metabolic function of the indigenous microbial communities responsible for AH degradation. SA-H-CS injection facilitated the delivery of nutrient components into the underground environment, improved the conversion ability of inorganic electron donors/receptors in the indigenous microbial community system, and strengthened the co-metabolism mechanism among microorganisms, achieving the goal of efficient AH degradation.

Enrichment of rare methanogenic Archaea shows their important ecological role in natural high-CO2 terrestrial subsurface environments.

Long-term stability of underground CO2 storage is partially affected by microbial activity but our knowledge of these effects is limited, mainly due to a lack of sites. A consistently high flux of mantle-derived CO2 makes the Eger Rift in the Czech Republic a natural analogue to underground CO2 storage. The Eger Rift is a seismically active region and H2 is produced abiotically during earthquakes, providing energy to indigenous microbial communities. To investigate the response of a microbial ecosystem to high levels of CO2 and H2, we enriched microorganisms from samples from a 239.5 m long drill core from the Eger Rift. Microbial abundance, diversity and community structure were assessed using qPCR and 16S rRNA gene sequencing. Enrichment cultures were set up with minimal mineral media and H2/CO2 headspace to simulate a seismically active period with elevated H2. Methane headspace concentrations in the enrichments indicated that active methanogens were almost exclusively restricted to enrichment cultures from Miocene lacustrine deposits (50-60 m), for which we observed the most significant growth. Taxonomic assessment showed microbial communities in these enrichments to be less diverse than those with little or no growth. Active enrichments were especially abundant in methanogens of the taxa Methanobacterium and Methanosphaerula. Concurrent to the emergence of methanogenic archaea, we also observed sulfate reducers with the metabolic ability to utilize H2 and CO2, specifically the genus Desulfosporosinus, which were able to outcompete methanogens in several enrichments. Low microbial abundance and a diverse non-CO2 driven microbial community, similar to that in drill core samples, also reflect the inactivity in these cultures. Significant growth of sulfate reducing and methanogenic microbial taxa, which make up only a small fraction of the total microbial community, emphasize the need to account for rare biosphere taxa when assessing the metabolic potential of microbial subsurface populations. The observation that CO2 and H2-utilizing microorganisms could only be enriched from a narrow depth interval suggests that factors such as sediment heterogeneity may also be important. This study provides new insight on subsurface microbes under the influence of high CO2 concentrations, similar to those found in CCS sites.

The grape string theory is inspired by Mortierella and Trichocladium species that promote soil aggregation more than indigenous microorganisms

Soil aggregates are the core physically distinct units that are embedded in the complex soil matrix. The roles of saprophytic fungi in soil aggregation and their relevant mechanism is not fully understood. Here, a microcosm was conducted to study the roles of two saprophytic fungi on soil aggregation. The plant growth promoting fungi Mortierella (K1) and Chaetomium (F1) were selected as representative species. After the original aggregates were destroyed using a 100 mesh sieve, the sterilized soil was placed in a petri dish, and the fungal strains were inoculated after sterile water was added to bring the soil to 60 % of the maximum field water capacity. The treatments contained a negative control that was not inoculated and single inoculated F1 and K1, as well as their combined inoculation. Non-sterilized soil as a positive control. All the soils were cultured in the dark for 45 days at 20 °C and followed by aggregate grading. Biological aggregates and abiotic soil fragments were clearly distinguished using scanning electron microscopy. The mysterious nature of the effective entanglements of fungal hyphae to soil particles and the special gossamer in the pores within aggregates have been clearly uncovered. Both fungi can effectively promote the formation of macroaggregates and the accumulation of organic carbon and nitrogen in the macroaggregates. The extracellular polymeric substance (EPS) uronic acid produced by both fungi has a significant positive effect on soil aggregation, but the impact of EPS-humic acid and EPS-protein is a nondeterministic process that occurs during the 45 days of incubation. The results of separating aggregates showed that the driving effect of a single fungus on soil aggregation was stronger than that of complex indigenous microbial communities. Therefore, the theory of grape cluster-like aggregates was proposed. Grape-like microaggregates (<0.25 mm) and abiotic soil fragments can further form a grape cluster composed of large aggregates (>1 mm) owing to the adherence and entanglement of filamentous hypha. Compared with diverse and competitive microbial communities, fungi of the same or similar species are conducive to mutual attraction and linkage between hyphae, which more strongly promote soil aggregation. Our research provides direct evidence that saprophytic fungi promote soil aggregation, and highlights a new theory of aggregate formation that will contribute to a better understanding of the mechanisms that regulate soil aggregation.

N/S element transformation modulating lithospheric microbial communities by single-species manipulation

BackgroundThe lithospheric microbiome plays a vital role in global biogeochemical cycling, yet their mutual modulation mechanisms remain largely uncharted. Petroleum reservoirs are important lithosphere ecosystems that provide desirable resources for understanding microbial roles in element cycling. However, the strategy and mechanism of modulating indigenous microbial communities for the optimization of community structures and functions are underexplored, despite its significance in energy recovery and environmental remediation.ResultsHere we proposed a novel selective stimulation of indigenous functional microbes by driving nitrogen and sulfur cycling in petroleum reservoirs using injections of an exogenous heterocycle-degrading strain of Pseudomonas. We defined such bacteria capable of removing and releasing organically bound sulfur and nitrogen from heterocycles as “bioredox triggers”. High-throughput 16S rRNA amplicon sequencing, metagenomic, and gene transcription-level analyses of extensive production water and sandstone core samples spanning the whole oil production process clarified the microbiome dynamics following the intervention. These efforts demonstrated the feasibility of in situ N/S element release and electron acceptor generation during heterocycle degradation, shifting microbiome structures and functions and increasing phylogenetic diversity and genera engaged in sulfur and nitrogen cycling, such as Desulfovibrio, Shewanella, and Sulfurospirillum. The metabolic potentials of sulfur- and nitrogen-cycling processes, particularly dissimilatory sulfate reduction and dissimilatory nitrate reduction, were elevated in reservoir microbiomes. The relative expression of genes involved in sulfate reduction (dsrA, dsrB) and nitrate reduction (napA) was upregulated by 85, 28, and 22 folds, respectively. Field trials showed significant improvements in oil properties, with a decline in asphaltenes and aromatics, hetero-element contents, and viscosity, hence facilitating the effective exploitation of heavy oil.ConclusionsThe interactions between microbiomes and element cycling elucidated in this study will contribute to a better understanding of microbial metabolic involvement in, and response to, biogeochemical processes in the lithosphere. The presented findings demonstrated the immense potential of our microbial modulation strategy for green and enhanced heavy oil recovery.7ucoPBoC4m39tpZT7x_42NVideo Graphical

The effects of adding exogenous lignocellulose degrading bacteria during straw incorporation in cold regions on degradation characteristics and soil indigenous bacteria communities.

Low temperature is one of the bottleneck factors that limits the degradation of straw during rice straw incorporation. Determining strategies to promote the efficient degradation of straw in cold regions has become a highly active research area. This study was to investigate the effect of rice straw incorporation by adding exogenous lignocellulose decomposition microbial consortiums at different soil depths in cold regions. The results showed that the lignocellulose was degraded the most efficiently during straw incorporation, which was in deep soil with the full addition of a high-temperature bacterial system. The composite bacterial systems changed the indigenous soil microbial community structure and diminished the effect of straw incorporation on soil pH, it also significantly increased rice yield and effectively enhanced the functional abundance of soil microorganisms. The predominant bacteria SJA-15, Gemmatimonadaceae, and Bradyrhizobium promoted straw degradation. The concentration of bacterial system and the depth of soil had significantly positive correlations on lignocellulose degradation. These results provide new insights and a theoretical basis for the changes in the soil microbial community and the application of lignocellulose-degrading composite microbial systems with straw incorporation in cold regions.

Linking DOM characteristics to microbial community: The potential role of DOM mineralization for arsenic release in shallow groundwater

Dissolved organic matter (DOM) play critical roles in arsenic (As) biotransformation in groundwater, but its compositional characteristics and interactions with indigenous microbial communities remain unclear. In this study, DOM signatures coupled with taxonomy and functions of microbial community were characterized in As-enriched groundwater by excitation-emission matrix, Fourier transform ion cyclotron resonance mass spectrometry and metagenomic sequencing. Results showed that As concentrations were significantly positively correlated with DOM humification (r = 0.707, p < 0.01) and the most dominant humic acid-like DOM components (r = 0.789, p < 0.01). Molecular characterization further demonstrated high DOM oxidation degree, with the prevalence of unsaturated oxygen-low aromatics, nitrogen (N1/N2)-containing compounds and unique CHO molecules in high As groundwater. These DOM properties were consistent with microbial composition and functional potentials. Both taxonomy and binning analyses demonstrated the dominance of Pseudomonas stutzeri, Microbacterium and Sphingobium xenophagum in As-enriched groundwater which possessed abundant As-reducing gene, with organic carbon degrading genes capable of labile to recalcitrant compounds degradation and high potentials of organic nitrogen mineralization to generate ammonium. Besides, most assembled bins in high As groundwater presented strong fermentation potentials which could facilitate carbon utilization by heterotrophic microbes. This study provides better insight into the potential role of DOM mineralization for As release in groundwater system.

Rapid Biodegradation of the Organophosphorus Insecticide Acephate by a Novel Strain Burkholderia sp. A11 and Its Impact on the Structure of the Indigenous Microbial Community.

The acephate-degrading microbes that are currently available are not optimal. In this study, Burkholderia sp. A11, an efficient degrader of acephate, presented an acephate-removal efficiency of 83.36% within 56 h (100 mg·L-1). The A11 strain has a broad substrate tolerance and presents a good removal effect in the concentration range 10-1600 mg·L-1. Six metabolites from the degradation of acephate were identified, among which the main products were methamidophos, acetamide, acetic acid, methanethiol, and dimethyl disulfide. The main degradation pathways involved include amide bond breaking and phosphate bond hydrolysis. Moreover, strain A11 successfully colonized and substantially accelerated acephate degradation in different soils, degrading over 90% of acephate (50-200 mg·kg-1) within 120 h. 16S rDNA sequencing results further confirmed that the strain A11 gradually occupied a dominant position in the soil microbial communities, causing slight changes in the diversity and composition of the indigenous soil microbial community structure.

Electrokinetic-Enhanced Bioremediation of Trichloroethylene-Contaminated Low-Permeability Soils: Mechanistic Insight from Spatio-Temporal Variations of Indigenous Microbial Community and Biodehalogenation Activity.

Electrokinetic-enhanced bioremediation (EK-Bio), particularly bioaugmentation with injection of biodehalogenation functional microbes such as Dehalococcoides, has been documented to be effective in treating a low-permeability subsurface matrix contaminated with chlorinated ethenes. However, the spatio-temporal variations of indigenous microbial community and biodehalogenation activity of the background matrix, a fundamental aspect for understanding EK-Bio, remain unclear. To fill this gap, we investigated the variation of trichloroethylene (TCE) biodehalogenation activity in response to indigenous microbial community succession in EK-Bio by both column and batch experiments. For a 195 day EK-Bio column (∼1 V/cm, electrolyte circulation, lactate addition), biodehalogenation activity occurred first near the cathode (<60 days) and then spread to the anode (>90 days), which was controlled by electron acceptor (i.e., Fe(III)) competition and microbe succession. Amplicon sequencing and metagenome analysis revealed that iron-reducing bacteria (Geobacter, Anaeromyxobacter, Geothrix) were enriched within initial 60 d and were gradually replaced by organohalide-respiring bacteria (versatile Geobacter and obligate Dehalobacter) afterward. Iron-reducing bacteria required an initial long time to consume the competitive electron acceptors so that an appropriate reductive condition could be developed for the enrichment of organohalide-respiring bacteria and the enhancement of TCE biodehalogenation activity.

Spatial-vertical variations of energetic compounds and microbial community response in soils from an ammunition demolition site in China

Ammunition-related activities have caused severe energetic compound (EC) contamination and pose serious risks to ecosystems. However, little is known regarding the spatial-vertical variations of ECs or their migration in soils at ammunition demolition sites. Although the toxic effect of some ECs to microorganisms have been reported through laboratory simulations, the responses of indigenous microbial communities to ammunition demolition activities are unclear. In this study, the spatial-vertical variations of ECs in 117 topsoil samples and three soil profiles from a typical ammunition demolition site in China were studied. Heavy contamination of ECs was concentrated in the top soils of the work platforms, and ECs were also detected in the surrounding area and nearby farmland. ECs showed different migration characteristics in the 0–100 cm soil layer of the different soil profiles. Demolition activities and surface runoff play critical roles in the spatial-vertical variations and migration of ECs. These findings suggest that ECs are able to migrate from the topsoil to the subsoil and from the core demolition area to further ecosystems. The work platforms exhibited lower microbial diversity and different microbiota compositions compared to the surrounding areas and farmlands. Using the random forest analysis, pH and 1,3,5-trinitrobenzene (TNB) were characterized as the most important factors affecting microbial diversity. Network analysis revealed that Desulfosporosinus was highly sensitive to ECs and may be a unique indicator of EC contamination. These findings provide key information in understanding EC migration characteristics in soils and the potential threats to indigenous soil microorganisms in ammunition demolition sites.

Biostimulation of jarosite and iron oxide-bearing mine waste enhances subsequent metal recovery.

Novel resource recovery technologies are required for metals-bearing hazardous wastes in order to achieve circular economy outcomes and industrial symbiosis. Iron oxide and co-occurring hydroxysulphate-bearing wastes are globally abundant and often contain other elements of value. This work addresses the biostimulation of indigenous microbial communities within an iron oxide/ hydroxysulphate-bearing waste and its effect on the subsequent recoverability of metals by hydrochloric, sulphuric, citric acids, and EDTA. Laboratory-scale flow-through column reactors were used to examine the effect of using glycerol (10% w/w) to stimulate the in situ microbial community in an iron oxide/ hydroxysulphate-bearing mine waste. The effects on the evolution of leachate chemistry, changes in microbiological community, and subsequent hydrometallurgical extractability of metals were studied. Results demonstrated increased leachability and selectivity of Pb, Cu, and Zn relative to iron after biostimulation with a total of 0.027kg of glycerol per kg of waste. Biostimulation, which can be readily applied in situ, potentially opens new routes to metal recovery from globally abundant waste streams that contain jarosite and iron oxides.

Bioaugmentation of the green alga to enhance biogas production in an anaerobic hollow-fiber membrane bioreactor

Anaerobic membrane reactors (AnMBRs) offer an alternative wastewater treatment system, presenting both reclamation of value through biogas production, and efficient treatment of recalcitrant contaminants such as antibiotics from wastewater. The effects of bioaugmentation with the green alga Haematococcus pluvialis on anaerobic treatment of pharmaceutical wastewaters, alleviating membrane biofouling, biogas production and impact on the indigenous microbial communities were evaluated using AnMBRs. The outputs of the bioreactor experiments revealed that bioaugmentation strategies with the green alga increased removal of chemical oxygen demand by 12% and delayed membrane fouling by 25% and increased biogas production by 40%. Furthermore, bioaugmentation with the green alga led to a significant change in relative abundance of archaea and the main methanogenesis pathway shifted from Methanothermobacter to Methanosaeta, accompanied by their respective syntrophic bacteria.

The impact of novel azotobacter Bacillus sp. T28 combined sea buckthorn pomace on microbial community structure in paddy soil

Nitrogen (N) fertilizer application is an essential part of agricultural production in order to improve rice yields. However, long-term irrational application and low utilization of N fertilizer have caused a series of environmental problems. Biofertilizer is considered an effective alternative to N fertilizer. In this study, the effect of biofertilizer made of diazotrophic bacteria Bacillus sp. T28 combined with sea buckthorn pomace on the soil N changes and microbial community structure was conducted. Compared to CK, NO3−-N content decreased 33.1%–43.8% and the rate of N2O release decreased 8–26 times under different fertilizer treatments during incubation of 0–7 days. On the contrary, NH4+-N in T28 with or without sea buckthorn pomace treatments increased by 56.5–118.8% during incubation of 7–14 days. The results indicated that this biofertilizer reduced the environmental risk associated with the accumulation of NO3−-N in paddy soil and the release of N2O to the atmosphere and maintained the soil available N supply capacity. Besides, applying Bacillus T28 with sea buckthorn pomace increased the abundance of soil N functional genes such as nifH, narG, nirS, nirK, and nosZ. The 13C-PLFAs results demonstrated that this biofertilizer improves soil microbial community diversity, nutrient turnover rate and ecosystem stability by altering soil pH and total carbon (TC). In conclusion, Bacillus sp. T28 combined with sea buckthorn pomace regulated the indigenous soil microbial community structure and mitigated the environmental risk of conventional N fertilization in agroecosystems.

Indigenous microbial community governs the survival of Escherichia coli O157:H7 in constructed wetlands

The survival pattern of Escherichia coli O157:H7 (E. coli O157:H7) and its regulatory factors in natural environments have been widely studied. However, there is little information about the survival of E. coli O157:H7 in artificial environments, especially in wastewater treatment facilities. In this study, a contamination experiment was performed to explore the survival pattern of E. coli O157:H7 and its central control factors in two constructed wetlands (CWs) under different hydraulic loading rates (HLRs). The results showed that the survival time of E. coli O157:H7 was longer in the CW under the higher HLR. Substrate ammonium nitrogen and available phosphorus were the main factors that influenced the survival of E. coli O157:H7 in CWs. Despite the minimal effect of microbial α-diversity, some keystone taxa, such as Aeromonas, Selenomonas, and Paramecium, governed the survival of E. coli O157:H7. In addition, the prokaryotic community had a more significant impact on the survival of E. coli O157:H7 than the eukaryotic community. The biotic properties had a more substantial direct power on the survival of E. coli O157:H7 than the abiotic factors in CWs. Collectively, this study comprehensively disclosed the survival pattern of E. coli O157:H7 in CWs, which is an essential addition to the environmental behavior of E. coli O157:H7, providing a theoretical basis for the prevention and control of biological contamination in wastewater treatment processes.