Bacterial Succession Research Articles

The Succession of the Cellulolytic Microbial Community from the Soil during Oat Straw Decomposition.

The process of straw decomposition is dynamic and is accompanied by the succession of the microbial decomposing community, which is driven by poorly understood interactions between microorganisms. Soil is a complex ecological niche, and the soil microbiome can serve as a source of potentially active cellulolytic microorganisms. Here, we performed an experiment on the de novo colonization of oat straw by the soil microbial community by placing nylon bags with sterilized oat straw in the pots filled with chernozem soil and incubating them for 6 months. The aim was to investigate the changes in decomposer microbiota during this process using conventional sequencing techniques. The bacterial succession during straw decomposition occurred in three phases: the early phase (first month) was characterized by high microbial activity and low diversity, the middle phase (second to third month) was characterized by low activity and low diversity, and the late phase (fourth to sixth months) was characterized by low activity and high diversity. Analysis of amplicon sequencing data revealed three groups of co-changing phylotypes corresponding to these phases. The early active phase was abundant in the cellulolytic members from Pseudomonadota, Bacteroidota, Bacillota, and Actinobacteriota for bacteria and Ascomycota for fungi, and most of the primary phylotypes were gone by the end of the phase. The second intermediate phase was marked by the set of phylotypes from the same phyla persisting in the community. In the mature community of the late phase, apart from the core phylotypes, non-cellulolytic members from Bdellovibrionota, Myxococcota, Chloroflexota, and Thermoproteota appeared. Full metagenome sequencing of the microbial community from the end of the middle phase confirmed that major bacterial and fungal members of this consortium had genes of glycoside hydrolases (GH) connected to cellulose and chitin degradation. The real-time analysis of the selection of these genes showed that their representation varied between phases, and this occurred under the influence of the host, and not the GH family factor. Our findings demonstrate that soil microbial community may act as an efficient source of cellulolytic microorganisms and that colonization of the cellulolytic substrate occurs in several phases, each characterized by its own taxonomic and functional profile.

Succession of Bacteria Attached to Microplastics After Transferring from a Mariculture Area to a Seagrass Meadow.

Microplastics have been recognized as a novel niche for bacteria. However, studies have characterized the plastisphere microbial community in situ without exploring the microbial changes after transferring to other ecosystems. Here we focus on bacterial succession on typical microplastics (polypropylene and expanded polystyrene) and natural substrates (wood) after transferring from mariculture area to seagrass meadows system. Using high-throughput sequencing of 16S rRNA, we found that alpha diversity significantly reduced after transferring and microplastics especially PP had significant separations on PCoA plots at different succession stages. The abundance and metabolic pathways of potential pathogen-associated microorganisms are significantly decreased. The relative abundance of xenobiotics biodegradation pathways was significantly lower and of energy metabolism pathways was significantly higher by comparing before and after transferring. Main environmental factors affecting microbial communities changed from nutrient characteristics to basic physicochemical properties after transferring. The succession times of the microbial communities of the three materials were different.

Quality improvement of fermented chili pepper by inoculation of Pediococcus ethanolidurans M1117: Insight into relevance of bacterial community succession and metabolic profile

Pediococcus species have been found as the dominant microorganism in a low temperature fermented Sichuan paocai, whereas their role in quality formation remains unclear. In this work, the chili pepper fermented with P. ethanolidurans M1117 (PFP) was compared with that fermented spontaneously (SFP). We noticed that inoculation of P. ethanolidurans M1117 can decrease salinity, pH, nitrite and capsaicinoids, protect pepper's color and texture, and increase sourness and sweetness. Metabolomic analysis showed that esters and terpenes which are the main aroma compounds in PFP group were more plentiful than those in SFP. Furthermore, correlation analysis between microbiota and flavors demonstrated that most metabolites in glycolysis/gluconeogenesis, citrate cycle and biosynthesis of terpenoids and steroids were positively correlated with P. ethanolidurans, which probably played a vital role in the formation of special flavor and taste. These findings suggested that inoculation of P. ethanolidurans M1117 can enhance the sensory quality of fermented chili pepper, and the strain is expected to be a starter for Sichuan pickle fermentation.

Study on the Ecological Succession of Microbial Communities During Hot Composting of Livestock Manure

Abstract There have been various environmental issues in the treatment and resource utilisation of solid waste of livestock and poultry industry in Gansu Province. Thus, in this study, manure of cattle, pig, and chicken from farms near the Lanzhou University of Technology in Lanzhou City, Gansu Province were selected as raw materials for composting using 10 % corn stalk as a leavening agent for aerobic static composting. This study focused on bacterial, fungal, and actinomycetes community succession during livestock manure composting and the underlying microbial degradation mechanism. The results demonstrated that during livestock manure composting, the number of the above-mentioned types of microbes was all positively correlated with the temperature of the compost piles. In the initial stage of composting, the number of microbes increased as the temperature increased, and reached the peaks at the highest temperature, after which, their numbers decreased with the decrease in temperature. At the end of composting, in the cattle, pig, and chicken manure compost piles, the number of bacteria were respectively (3.1 ±1.0) · 109 CFU·g−1 d.w., (4.4 ±1.0) · 109 CFU·g−1 d.w. and (6.7 ±1.8) · 109 CFU·g−1 d.w., respectively, those of fungi were (8.6 ±1.2) · 104 CFU·g−1 d.w., (7.2 ±1.6) · 104 CFU·g−1 d.w. and (8.0 ±2.8) · 104 CFU·g−1 d.w., respectively, while those of actinomycetes were (8.8 ±2.2) · 106 CFU·g−1 d.w., (9.5 ±2.1) · 106 CFU·g−1 d.w. and (6.32 ±0.98) · 106 CFU·g−1 d.w., respectively.

Effect of growth stage on Italian ryegrass (Lolium multiflorum Lam.) silage fermentation from microbiological perspective

BackgroundItalian ryegrass is a temperate climate crop, which is widely cultivated in the winter fallow paddy fields of subtropical China. The utilization efficiency of Italian ryegrass depends greatly on its growth stage at harvest. Previous studies have reported the optimum stage for harvesting various forage to balance their quality and quantity. However, when considering the practice condition, such as rainy or unavailability of harvest equipment, the harvest stage of forage cannot always be implemented according to the production schedules. Thus, to characterize the effect of growth stage on the silage fermentation profile, bacterial community construction and metabolisms of carbohydrates and amino acids, Italian ryegrass were naturally ensiled at the filling stage (FSN) and the dough stage (DSN), respectively. After ensiling for 1, 3, 7, 15, 30, and 60 days, triplicate silos were opened for sampling.ResultsThe growth of Italian ryegrass increased the pH, dry matter, neutral, and acid detergent fiber contents, but decreased buffering capacity, crude protein and water-soluble carbohydrates contents, and the epiphytic microbiota of Italian ryegrass harvested at the filling stage was simpler than that harvested at the dough stage. During ensiling, FSN had lower pH and higher organic acid content than DSN. The bacterial succession rate in FSN was also faster than DSN, which showed that Lactobacillus becomes the dominant genus in the early stage of ensiling. The predicted metabolisms revealed that carbohydrate and amino acid metabolisms were the two main metabolisms in silage fermentation. When compared with epiphytic microbiota, ensiling enhanced carbohydrate metabolism and diminished amino acid metabolism. The difference of these two metabolisms between FSN and DSN was obvious at the early stage of ensiling.ConclusionsGrowth stage affected the chemical and microbial composition of Italian ryegrass, so as to the fermentation profile, bacterial community and its metabolisms intensity. Italian ryegrass harvested at the filling stage was prone to ferment. The complexity of epiphytic microbiota made Italian ryegrass harvested at the dough stage more difficult to ferment.Graphical

Nutritional additives dominance in driving the bacterial communities succession and bioremediation of hydrocarbon and heavy metal contaminated soil microcosms

Soil quality and microbial diversity are essential to the health of ecosystems. However, it is unclear how the use of eco-friendly natural additives can improve the quality and microbial diversity of contaminated soils. Herein, we used high-throughput 16 S rDNA amplicon Illumina sequencing to evaluate the stimulation and development of microbial diversity and concomitant bioremediation in hydrocarbon (HC) and heavy metal (HM)-rich waste disposal site soil when treated with meat and bone meal (MBM), cyclodextrin (Cdx), and MBM and cyclodextrin mixture (Cdx MBM) over a period of 3 months. Results showed that natural additive treatments significantly increased the soil bacterial diversity (higher Shannon index, Simpson index and evenness) in a time-dependent manner, with Cdx eliciting the greatest enhancement. The two additives influenced the bacterial community succession patterns differently. MBM, while it enhanced the enrichment of specific genera Chitinophaga and Terrimonas, did not significantly alter the total bacterial community. In contrast, Cdx or Cdx MBM promoted a profound change of the bacteria community over time, with the enrichment of the genera Parvibaculum, Arenimonas and unclassified Actinobacteria. These results provide evidence on the involvement of the two natural additives in coupling HC and HM bioremediation and bacterial community perturbations, and thus illustrates their potential application in ecologically sound bioremediation technologies for contaminated soils.

Appraising co-composting efficiency of biodegradable plastic bags and food wastes: Assessment microplastics morphology, greenhouse gas emissions, and changes in microbial community

Biodegradable plastic bags (BPBs) to collect food waste and microplastics (MPs) produced from their biodegradation have received considerable scientific attention recently. Therefore, the current study was carried out to assess the co-composting efficiency of biodegradable plastic bags (polylactic acid (PLA) + polybutylene terephthalate (PBAT) + ST20 and PLA + PBAT+MD25) and food waste. The variations in greenhouse gas (GHG) emissions, microbial community and compost fertility were likewise assessed. Compared with the control, PLA + PBAT+ST20 and PLA + PBAT+MD25 both accelerated organic matter degradation and increased temperature. Moreover, PLA + PBAT+ST20 aggravated CH4 and CO2 emissions by 12.10 % and 11.01 %, respectively. PLA + PBAT+MD25 decreased CH4 and CO2 emissions by 5.50 % and 9.12 %, respectively. Meanwhile, compared with PLA + PBAT+ST20, the combined effect of plasticizer and inorganic additive in PLA + PBAT+MD25, reduced the NO3−-N contents, seed germination index (GI) and compost maturity. Furthermore, adding BPBs changed the richness and diversity of the bacterial community (Firmicutes, Proteobacteria and Bacteroidetes). Likewise, redundancy analysis (RDA) showed that the co-compost system of BPBs and food waste accelerated significantly bacterial community succession from Firmicutes and Bacteroidetes at the initial stage to Proteobacteria and Actinobacteria at the mature stage, increased co-compost temperature to over 64 °C and extended thermophilic composting phase, and promoted the degradation of MPs. Additionally, according to structural equation model quantification results, the inorganic additive of PLA + PBAT+MD25 had more serious toxicity to microorganisms and had significantly adverse effects on GI through CO2-C (λ = −0.415, p < 0.05) and NO3−-N (λ = −0.558, p < 0.001), thus reduced compost fertility and quality. The results also indicated that the BPBs with ST20 as an additive could be more suitable for industrial composting than the BPBs with MD25 as an additive. This study provided a vital basis for understanding the potential environmental and human health risks of the MPs' generated by the degradation of BPBs in compost.

Correlation between bacterial diversity and flavor substances in Longgang soy sauce.

Longgang soy sauce is one of the traditional fermented condiments in China, but its bacterial community succession and its unique flavor development during the fermentation process are not well-investigated. This study evaluated the bacterial diversity, flavor changes, and their correlation during the fermentation of Longgang soy sauce. The results showed that Weissella was the dominant bacterial genus in the fermentation stage of sauce fermented grains. In the first 31 days of the moromi fermentation stage, a variety of bacterial genera such as Weissella, Halomonas, Bacteroides, Pseudomonas, and Tetragenococcus were the dominant bacteria. Our results showed that these bacteria have a significantly positive correlation with phenylethyl alcohol, ethyl acetate, and 3-methyl-1-butanol. As the fermentation progressed, a flora structure with Halomonas as the main bacterial genus was formed. This genus exhibited a significantly positive and positive correlation with 1-octanol, ethyl palmitate, heptanol, and 2-nonanol, which are the unique flavor components of Longgang soy sauce.

Effects of the Marinating Process on the Quality Characteristics and Bacterial Community of Leisure Dried Tofu

Leisure dried tofu (LD-tofu) was prepared using two different marinating processes: the repeated heating method (RHM) and the vacuum pulse method (VPM). The quality characteristics and bacterial community succession of LD-tofu and the marinade were evaluated. The results showed that the nutrients in LD-tofu were easily dissolved into the marinade during the marinating process, while the protein and moisture content of RHM LD-tofu changed most dramatically. With the increase in marinade recycling times, the springiness, chewiness and hardness of VPM LD-tofu increased significantly. The total viable count (TVC) of the VPM LD-tofu decreased from the initial value of 4.41 lg cfu/g to 2.51-2.67 lg cfu/g as a result of the marinating process, which had a significant inhibitory effect. Additionally, 26, 167 and 356 communities in the LD-tofu and marinade were detected at the phylum, family and genus levels, respectively. Pearson correlation analysis showed that Pseudomonadaceae, Thermaceae and Lactobacillaceae were closely related to the quality characteristics of LD-tofu, whereas Caulobacteriaceae, Bacillaceae and Enterobacteriae were closely related to the marinade. The present work provides a theoretical basis for the screening of functional strains and quality control in LD-tofu and marinade.

Biochar as smart organic catalyst to regulate bacterial dynamics during food waste composting

The impact of wheat straw biochar (WSB) on bacterial dynamics succession during food waste (FW) composting was analyzed. Six treatments [0(T1), 2.5(T2), 5 (T3), 7.5 (T4), 10 (T5), and 15 %(T6)] dry weight WSB were used with FW and saw dust for composting. At the highest thermal peak at 59 ℃ in T6, the pH varied from 4.5 to 7.3, and electrical conductivity among the treatments varied from 1.2 to 2.0 mScm1. Firmicutes (25–97 %), Proteobacteria (8–45 %), and Bacteroidota (5–50 %) were among the dominate phyla of the treatments. Whereas, Bacillus (5–85 %), Limoslactobacillus (2–40 %), and Sphingobacterium (2–32 %) were highest among the identified genus in treatments but surprisingly Bacteroides was in greater abundance in the control treatments. Moreover, heatmap constructed with 35 various genera in all the treatments showed that Gammaproteobacterial genera contributed in large proportion after 42 days in T6. Additionally, a dynamic shift from Lactobacillus fermentum to higher abundance of Bacillus thermoamylovorans was reported on 42 days of FW composting. Biochar 15 % amendment can improve FW composting by influencing bacterial dynamics.

Effects of Cr Stress on Bacterial Community Structure and Composition in Rhizosphere Soil of Iris tectorum under Different Cultivation Modes

With the rapid development of industry, Cr has become one of the major heavy metal pollutants in soil, severely impacting soil microecology, among which rhizosphere microorganisms can improve the soil microenvironment to promote plant growth. However, how rhizosphere bacterial communities respond to Cr stress under different cultivation modes remains to be further studied. Therefore, in this study, a greenhouse pot experiment combined with 16S rRNA high-throughput sequencing technology was used to study the effects of Cr stress at 200 mg kg−1 on the bacterial community structure and diversity in the rhizosphere soil of Iris tectorum under different cultivation modes. The results showed that the rhizosphere bacterial community diversity index (Shannon and Simpson) and abundance index (Ace and Chao) increased significantly with wetland plant diversity under Cr stress. Moreover, the bacterial community changed by 20.1% due to the addition of Cr, further leading to a 15.9% decrease in the common species of the bacterial community, among which Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteriota accounted for more than 74.8% of the total sequence. However, with the increase in plant diversity, the abundance of rhizosphere-dominant bacteria and plant growth-promoting bacteria communities increased significantly. Meanwhile, the symbiotic network analysis found that under the two cultivation modes, the synergistic effect between the dominant bacteria was significantly enhanced, and the soil microenvironment was improved. In addition, through redundancy analysis, it was found that C, N, and P nutrients in uncontaminated soil were the main driving factors of bacterial community succession in the rhizosphere of I. tectorum, and Cr content in contaminated soil was the main driving factor of bacterial community succession in I. tectorum rhizosphere. In summary, the results of this study will provide a basis for the response of the rhizosphere bacterial community to Cr and the interaction between wetland plants and rhizosphere bacteria in the heavy metal restoration of wetland plants under different cultivation modes.

Valorizing kitchen waste to produce value-added fertilizer by thermophilic semi-continuous composting followed by static stacking: Performance and bacterial community succession analysis

To explore an effective decentralized kitchen waste (KW) treatment system, the performance and bacterial community succession of thermophilic semi-continuous composting (TSC) of KW followed by static stacking (SS) was studied. A daily feeding ratio of 10% ensured stable performance of TSC using an integrated automatic reactor; the efficiencies of organic matter degradation and seed germination index (GI) reached 80.88% and 78.51%, respectively. SS for seven days further promoted the quality of the compost by improving the GI to 91.58%. Alpha- and beta-diversity analyses revealed significant differences between the bacterial communities of TSC and SS. Firmicutes, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Myxococcota were dominant during the TSC of KW, whereas the members of Proteobacteria and Bacteroidetes responsible for product maturity rapidly proliferated during the subsequent SS and ultimately dominated the compost with Firmicutes and Actinobacteria. These results provide new perspectives for decentralized KW treatment using TSC for practical applications.

Functional insights into succession in a phyllospheric microbial community across a full period of aquatic plant litter decomposition

Phyllosphere microbes are essential in the mediation of plant–soil biogeochemical recycling during the decomposition of plant litter in wetland ecosystems. However, there are few studies into microbial community succession in phyllosphere microbial communities in wetlands, and their functional attributes across a full period of wetland plant litter decomposition remain unclear. Here, we collected leaf samples of Typha latifolia var. orientalis (C. Presl.) Rohrb., an emergent wetland plant, during various stages of decomposition (growing, standing, lodging, and submerging stages) to investigate fungal and bacterial assemblage succession in the phyllosphere. We then parsed these assemblages into specific fungal trophic modes and bacterial phenotypes. Over the litter decomposition period, both fungal and bacterial assemblages underwent distinct succession, with generally increasing alpha diversity, and the proportion of litter microbes originating from sediments increased with decomposition. Saprotrophic and pathotrophic fungi dominated the fungal assemblage in the early stages of decomposition, but their dominance was replaced by undefined fungi as decomposition progressed. Relative abundances of both pathotrophic fungi and potentially pathogenic bacteria increased from the growing to the standing stage, implying that there was a turning point in assemblage composition shortly after plant leaf death. Gram-positive and gram-negative bacteria had opposite trends in their relative abundances over successive decomposition stages. When plant litter entered the water, bacteria tolerant of oxidative stress gradually decreased in abundance, but anaerobic bacteria abundance increased. We also aimed to determine the relationships between predicted microbial functional traits and leaf litter physicochemical attributes. Lignin and N content were the predominant predictors of decomposer fungal trophic modes and bacterial phenotypes. These findings provide evidence that the complex litter decomposition seen in wetlands is accompanied by a dynamic cross-kingdom succession of phyllospheric microbial communities, coupled with distinct changes in the phenotypes of the microbes present. Insights into phyllospheric microbial functional traits have implications for better elucidating the plant litter cycle for wetland plants.

Hazard reduction and persistence of risk of antibiotic resistance during thermophilic composting of animal waste

Animal production contributes substantially to the dissemination of antibiotic resistance genes (ARGs) in the environment. Thermophilic composting is cost-effective for reducing hazards in animal wastes. However, ARGs can still persist in composts and the mechanism remains largely unclear. In the present study, metagenomics and real-time quantitative PCR were employed to assess the dynamics of ARGs, especially those of high risk to human health, their host species and pathogenicity of the bacterial community during thermophilic composting of chicken manure. The results showed that thermophilic composting was effective at reducing the majority of the spreading risk of antibiotic resistance by 1) eliminating more than half of allARGs that accounted for 80% of the total abundance, 2) reducing the number and abundance of high-risk ARGs significantly, and 3) removing the ARG hosts and the pathogenicity of the bacterial community substantially. The attenuation of ARGs was primarily driven by the bacterial community succession. However, the abundance of some ARGs, especially those associated with plasmids, rebounded during the cooling phase, likely caused by horizontal gene transfer. Our research reveals that minimising the horizontal transfer of plasmid-associated ARGs during the cooling phase of thermophilic composting is crucial for a more effective reduction of the hazards associated with the spread of antibiotic resistance.

Decades of weathering improves coal waste biogeochemical properties by altering dissolved organic matter and microbial communities: A case‐study of a coal waste pile

AbstractThe spatial heterogeneity of vegetation cover in coal waste pile suggests that the geochemical and biological properties of coal waste are spatially heterogeneous, which contributes to vegetation colonization on tailings. However, whether and how altering the organic matter components and microbial community of coal waste via weathering affects biogeochemical characteristics and vegetation establishment mechanisms remain unclear. Thus, we explored the characterization of dissolved organic matter in coal waste and its biogeochemical implications. Our results highlight coal waste as primary succession for bacterial communities and provide new insights into the bacterial community assembly response to dissolved organic matter and geochemical properties at such sites. Biogeochemical parameters including pH, EC, nutrients, particle size, and enzymatic activities were affected differently by organic components. The electrical conductivity (EC) decreased after decades of natural weathering, whereas pH, moisture, available N and P, urease, phosphatase, soluble microbial byproduct‐like material, humic acid‐like organics, bacterial diversity, and richness increased significantly. Further taxonomical and co‐occurrence network analyses indicated that the primary succession of bacterial communities was strongly influenced by biogenically formed organic components, particle size, and available nutrients. Our results revealed that the humic‐like components facilitated the improved biogeochemical properties and succession of composition and structure of the bacterial community. It demonstrated that weathering‐induced organic matter degradation trigger biogeochemical property improvement and bacterial community succession, and further facilitate the transformation of coal waste into a plant growth substrate. Our results provide a reference for engineering and application practice of utilization and in‐situ remediation ecological reconstruction in coal waste deposits.

Polyethylene mulching film degrading bacteria within the plastisphere: Co-culture of plastic degrading strains screened by bacterial community succession.

As an ecological niche close to the polymer, microorganisms in the plastisphere possess the advantage of degrading plastics. This study aims to investigate the bacterial community succession and obtain degrading bacteria in the plastisphere, as well as identify the most efficient degradation combination by co-culture of multiple strains. The findings demonstrate the alpha-diversity indices of the plastisphere bacterial community are significantly lower, and the community structure is regularly and significantly altered. With the time of culture, the plastisphere community composition alters regularly, and the hydrocarbon-degrading genera become the core members. Functional prediction of community reveals the potential for Xenobiotics Biodegradation and Metabolism of plastisphere, and the apparent variations detections of polyethylene mulching film (PMF) indicating the PMF degrading ability of plastisphere. Besides, three PMF-degrading bacterial strains, Rhodopseudomonas sp. P1 (P), Rhodanobacter sp. Rs (R) and Microbacterium sp. M1 (M), are screened for co-culture with PMF degrading strain Bacillus aryabhattai 5-3 (B). By considering bacterial growth, biofilm adhesion, and apparent degradation of different samples, RB (R. sp. Rs + B. aryabhattai 5-3) is ultimately selected as the best PMF degradation combination. This study provides a new possibility for plastisphere-related research from the perspective of mitigating plastic pollution on agricultural land.

Bacterial succession in an abandoned circum-neutral opencast coal mine in India

Context Abandoned mines provide an ideal opportunity to study the succession of microbial communities, which is crucial for the development and stability of the soil. Aims We examined the diversity and temporal succession of the microbial community in an abandoned coal mine. Methods We investigated soil geochemical parameters and microbial succession using high-throughput 16S rRNA gene amplicon sequences over a 4-year period in a derelict opencast circum-neutral coal mine in Tasra colliery, Jharkhand, India. Results Soil pH (4.46–6.13), organic carbon (0.86–4.53%), available nitrogen (0.001–0.003%) and total cultivable heterotrophic microbial load increased, and concentrations of chloride (24 865–15 067 ppm), sulfate (26 417–417 ppm) and heavy metals reduced over the period of 4 years. The 16S rRNA gene sequences identified Proteobacteria as the dominant phylum across samples except for the fourth year, where Actinobacteria was predominant. Chlorobi, WPS-2 and Spirochaetes were exclusively identified in the first year. Twelve phyla present in the first year were completely absent by the end. In the fourth year, an abundance of nitrogen-fixing members such as Burkholderiales, Rhizobiales, Roseiflexales and Actinomycetales was noted and semi-quantitative PCR suggested that nitrogenases were predominately vanadium dependent (relative to molybdenum). Gradual shifts from purportedly chemolithotrophic to heterotrophic metabolic strategies were also observed. Conclusion This work establishes that soil improvement in abandoned coal mines involves the dynamic interplay of physicochemical parameters and shifts in microbial communities and dominant metabolic guilds. This knowledge can be used to plan and monitor remediation measures in such sites.

Insights into the influence on 2,4,6-trichlorophenol microbial reductive dechlorination process by exposure to microplastics

As a newly emerging pollutant, the adverse effects of ubiquitous microplastic on ecosystems and living have attracted increasing attention, however, the microplastic intervention influencing anaerobic biotransformation behaviors of chlorinated aromatics remains poorly understood. Here, the significantly altered 2,4,6-trichlorophenol microbial reductive dechlorination activities were found by single- and multi-exposure to microplastics. Single contact with five different types of microplastics showed diverse dechlorination performance, that PET was the most promoted ( k T of 0.037 h -1 ) and PP was the largest inhibited ( k T of 0.01 h -1 ) compared to control ( k T of 0.023 h -1 ). The microplastic size was negatively correlated with dechlorination activities, with 1.8~1.9 times decreased k T as the particle size decreased from 1000μm to 75μm. The higher the concentration, the more promoted effects by PET and the more inhibited effects by PP on dechlorination performance, with the respective k T of 0.052 h -1 and 0.006 h -1 under 2.0 g/L condition. Bio-enrichment on hydrophilic surfaces of microplastics (e.g. PET) was speculated to be responsible for the favored dechlorination activity, while adsorption of chlorophenols posed little influence. However, the overall inhibited 2,4,6-TCP dechlorination performance was found under all conditions by extending exposure cycles. The obvious bacterial succession that the abundance of some absolute anaerobic fermentator ( Dysgonomonas ) or dechlorinator ( Desulfitobacterium ) was greatly decreased, while, some facultative anaerobic genera ( Comamonas , Pseudomonas ) that held microplastic degradation potential were enriched. The increased positive correlations among networks were found and the more simplified molecule network as the size of microplastics became larger. The study provided significant theoretical support for understanding anaerobic biotransformation process of CAs influenced by the microplastic intervention. • Altered microbial reductive dechlorination activities by microplastic intervention • PET mostly promoted and PP largest inhibited the dechlorination by single contact • Microplastic size was negatively correlated with the dechlorination activities • Serious inhibited dechlorination performance was found by multi-cycle exposure • Obvious population succession and increased positive correlations of eco-networks

Total petroleum hydrocarbons and influencing factors in co-composting of rural sewage sludge and organic solid wastes

Co-composting is an efficient strategy for collaborative disposal of multiple organic wastes in rural areas. In this study, we explored the co-composting of rural sewage sludge and other organic solid wastes (corn stalks and kitchen waste), with a focus on the variation of total petroleum hydrocarbons (TPH) during this process. 12% corn-derived biochar was applied in the composting (BC), with no additives applied as the control treatment (CK). The TPH contents of piles after composting ranged from 0.70 to 0.74 mg/g, with overall removal efficiencies of 35.6% and 61.1% for CK and BC, respectively. The results indicate that the addition of 12% biochar increased the rate of TPH degradation and accelerated the degradation process. 16s rDNA high-throughput sequencing was applied to investigate the biodiversity and bacterial community succession during the composting process. Diverse bacterial communities with TPH degradation functions were observed in the composting process, including Acinetobacter, Flavobacterium, Paenibacillus, Pseudomonas, and Bacillus spp. These functional bacteria synergistically degraded TPH, with cooperative behavior dominating during composting. Biochar amendment enhanced the microbial activity and effectively promoted the biodegradation of TPH. The physicochemical properties of the compost piles, including environmental factors (pH and temperature), nutrients (nitrogen, phosphorus, potassium), and humic substances produced in composting (humic acids and fulvic acids), directly and indirectly affected the variation in TPH contents. In conclusion, this work illustrates the variation in TPH content and associated influencing factors during co-composting of rural organic solid wastes, providing valuable guidance toward the further optimization of rural organic waste management.

Diurnal Variation of Epiphytic Microbiota: an Unignorable Factor Affecting the Anaerobic Fermentation Characteristics of Sorghum-Sudangrass Hybrid Silage.

Forage epiphytic microbiota exhibits pronounced changes in composition and function throughout the day. However, the effects of these changes on silage fermentation are rarely explored. Here, we transplanted the epiphytic microbiota of sorghum-sudangrass hybrid (SSG) harvested at 7:00h (AM), 12:00h (M), and 17:00h (PM) to sterilized SSG to evaluate the effects of diurnal variation of epiphytic microbiota on fermentation characteristics. During fermentation, remarkable differences in bacterial community successions were observed between silages inoculated with AM and M microbiota. Compared to AM microbiota, M microbiota inoculation increased the proportions of Pantoea dispersa, Leuconostoc lactis, Enterobacter, and Klebsiella variicola, whereas it decreased the proportions of Weissella cibaria and Lactobacillus plantarum during fermentation. This led to the most rapid pH declines and organic acid production in AM silage and the slowest in M silage. Both M and PM microbiota affected the bacterial cooccurrence patterns, indicated by decreased complexity and stability in the community structures of M and PM silages compared to that of AM silage. The predicted functions indicated that some key carbohydrate metabolism pathways related to lactic acid synthesis were downregulated, while some competing pathways (ascorbate and aldarate metabolism and C5-branched dibasic acid metabolism) were upregulated in M silage compared to AM silage after 3days of fermentation. Correlation analysis revealed positive correlations between competing pathways and enterobacterial species. The current study highlights the importance of diurnal variation of epiphytic microbiota in affecting the silage bacterial community, potentially providing an effective strategy to improve silage quality by optimizing harvest time. IMPORTANCE Ensiling is a way to preserve wet biomass for animal and bioenergy production worldwide. The fermentation quality of silage is largely dependent on the epiphytic microbiota of the material. Plant epiphytic microbiota exhibit diurnal changes in composition and function. However, the effects of these changes on silage fermentation are rarely explored. The results presented here demonstrated that diurnal variation of epiphytic microbiota could affect the fermentation characteristics and bacterial community during SSG fermentation. Marked bacterial community differences were observed between AM and M silages during the initial 3days of fermentation. The dominance rate of Lactobacillus plantarum was highest in AM silage, whereas enterobacterial species were more abundant in M silage. The predicted function revealed downregulated lactic acid synthesis pathways and upregulated competing pathways in M silage compared to those in AM silage. This study provides clues for technological-parameter optimization of the fermentation process by the selection of harvest time.