This study investigated the control of dissolved organic matter (DOM) molecular compositions by microbial community shifts under temperature regulation (range from 5 to 35 °C), using riverine DOM and in situ microorganisms as examples. The functioning of different microbial metabolisms, including the utilization and generation processes, was comprehensively analyzed. Though the overall quantity of DOM was less temperature-affected, more molecules were identified at moderate temperatures (e.g., 15 and 25 °C) and their accumulated mass peak intensities increased with the temperature. The results were ascribed to 1) the microbial production of macromolecular (m/z > 600) CHO, CHON, and CHONS species was stimulated at higher temperatures; 2) the microorganisms consumed more DOM molecules at both higher and lower temperatures; and 3) the simultaneously decreased utilization and increased generation of recalcitrant CHO and CHON molecules with m/z < 600 at higher temperatures. The strong correlations among the temperature, community structures, and DOM chemodiversity suggested that temperature promoted the community evenness to increase the DOM generation. In addition, the higher temperature decreased the abundance of microorganisms that utilized more recalcitrant molecules and produced fewer new molecules (e.g., Proteobacteria, Acinetobacter, and Erythrobacter) while increased others that functioned the opposite (e.g., Verrucomicrobia, Bacteroidetes, and Flavobacterium) to increase the DOM production. The constructed temperature-community-DOM chemistry relationship deepened the molecular-level understanding of DOM variations and provided implications for the warming future.

Effluent is often treated with ozone before being discharged into a natural water environment. This process will change the interaction between effluent organic matter and pollutants in aquatic environment. The impact of ozonation on complexation between dissolved organic matter in such wastewater and sulfadimidine often found in natural water was studied in laboratory experiments using four types of real wastewater. Ozonation was found to decrease the proportion of organic matter with a molecular weight greater than 5 kDa as well as protein-like, fulvic-like and humic-like components, but except the proportion of hydrophilic components. The aromaticity of the dissolved organic matter was also reduced after ozonation. The complexation of tryptophan and tyrosine with sulfadimidine mainly depends on their hydrophobicity and large molecular weight. Ozonation of fulvic and humic acid tends to produce small and medium molecular weight hydrophilics. The complexation of humic and fulvic acids with sulfadimidine was enhanced by ozonation. Dissolved organic matter, with or without oxidation, were found to weaken sulfadimidine’s inhibition of microbial growth, especially for Aeromonas and Acinetobacter species. This finding will expand our understanding about the impact of advanced treatment processes on the dissolved organic matters’ properties in effluent.

Understanding the composition and assembly mechanism of waterborne pathogen is essential for preventing the pathogenic infection and protecting the human health. Here, based on 16S rRNA sequencing, we investigated the composition and spatial variation of potentially pathogenic bacteria from different sections of the Pearl River, the most important source of water for human in Southern China. The results showed that the potential pathogen communities consisted of 6 phyla and 64 genera, covering 11 categories of potential pathogens mainly involving animal parasites or symbionts (AniP), human pathogens all (HumPA), and intracellular parasites (IntCelP). Proteobacteria (75.87%) and Chlamydiae (20.56%) were dominant at the phylum level, and Acinetobacter (35.01%) and Roseomonas (8.24%) were dominant at the genus level. Multivariate analysis showed that the potential pathogenic bacterial community was significantly different among the four sections in the Pearl River. Both physicochemical factors (e.g., NO₃–N, and suspended solids) and land use (e.g., urban land and forest) significantly shaped the pathogen community structure. However, spatial effects contributed more to the variation of pathogen community based on variation partitioning and path analysis. Null model based normalized stochasticity ratio analysis further indicated that the stochastic process rather than deterministic process dominated the assembly mechanisms by controlling the spatial patterns of potential pathogens. In conclusion, high-throughput sequencing shows great potential for monitoring the potential pathogens, and provided more comprehensive information on the potentially pathogenic community. Our study highlighted the importance of considering the influences of dispersal-related processes in future risk assessments for the prevention and control of pathogenic bacteria.

Heat stress (HS) during gestation has been associated with negative outcomes, such as preterm birth or postnatal metabolic syndromes. The intestinal microbiota is a unique ecosystem playing an essential role in mediating the metabolism and health of mammals. Here we hypothesize late gestational HS alters maternal microbial transmission and structures offspring’s intestinal microbiota and serum metabolic profiles. Our results show maternal HS alters bacterial β-diversity and composition in sows and their piglets. In the maternal intestine, genera Ruminococcaceae UCG-005, [Eubacterium] coprostanoligenes group and Halomonas are higher by HS (q < 0.05), whereas the populations of Streptococcus, Bacteroidales RF16 group_norank and Roseburia are decreased (q < 0.05). In the maternal vagina, HS mainly elevates the proportions of phylum Bacteroidetes and Fusobacteria (q < 0.05), whereas reduces the population of Clostridiales Family XI (q < 0.05). In the neonatal intestine, maternal HS promotes the population of Proteobacteria but reduces the relative abundance of Firmicutes (q < 0.05). Moreover, the core Operational taxonomic units (OTU) analysis indicates the proportions of Clostridium sensu stricto 1, Romboutsia and Turicibacter are decreased by maternal HS in the intestinal and vaginal co-transmission, whereas that of phylum Proteobacteria and Epsilonbacteraeota, such as Escherichia-Shigella, Klebsiella, Acinetobacter, and Comamonas are increased in both the intestinal and vaginal co-transmission and the vagina. Additionally, Aeromonas is the only genus that is transmitted from environmental sources. Lastly, we evaluate the importance of neonatal differential OTU for the differential serum metabolites. The results indicate Acinetobacter significantly contributes to the differences in the adrenocorticotropic hormone (ACTH) and glucose levels due to HS (P < 0.05). Further, Stenotrophomonas is the most important variable for Cholesterol, low-density lipoprotein (LDL), diamine oxidase (DAO), blood urea nitrogen (BUN) and 5-hydroxytryptamine (5-HT) (P < 0.10). Overall, our data provides evidence for the maternal HS in establishing the neonatal microbiota via affecting maternal transmission, which in turn affects the maintenance of metabolic health.

The bioremediation of historic industrial contaminated sites is a complex process. Co-contamination, often with lead which was commonly added to gasoline until 16 years ago is one of the biggest challenges affecting the clean-up of these sites. In this study, the effect of heavy metals, as co-contaminant, together with total petroleum hydrocarbons (TPH) is reported, in terms of remaining soil toxicity and the structure of the microbial communities. Contaminated soil samples from a relatively hot and dry climate in Western Australia were collected (n = 27). Analysis of soils showed the presence of both contaminants, TPHs and heavy metals. The Microtox test confirmed that their co-presence elevated the remaining ecotoxicity. Toxicity was correlated with the presence of lead, zinc and TPH (0.893, 0.599 and 0.488), respectively, assessed using Pearson Correlation coefficient factor. Next Generation Sequencing of soil bacterial 16S rRNA, revealed a lack of dominate genera; however, despite the variation in soil type, a few genera including Azospirillum spp. and Conexibacter were present in most soil samples (85% and 82% of all soils, respectively). Likewise, many genera of hydrocarbon-degrading bacteria were identified in all soil samples. Streptomyces spp. was presented in 93% of the samples with abundance between 7% and 40%. In contrast, Acinetobacter spp. was found in only one sample but was a dominant member of (45%) of the microbial community. In addition, some bacterial genera were correlated to the presence of the heavy metals, such as Geodermatophilus spp., Rhodovibrio spp. and Rubrobacter spp. which were correlated with copper, lead and zinc, respectively. This study concludes that TPH and heavy metal co-contamination significantly elevated the associated toxicity. This is an important consideration when carrying out risk assessment associated with natural attenuation. This study also improves knowledge about the dynamics of microbial communities in mixed contamination scenarios.

The stable stabilization of uranium (U) in iron (Fe) containing environments is restricted by the reoxidation of UO₂. In the current study, based on air reoxidation tests, we propose a novel two steps accumulation method to enrich microbial consortia from paddy soil. The constructed microbial consortia, denoted as the Fe–U bacteria, can co-precipitate U and Fe to form stable Fe–U solids. Column experiments running for 4 months demonstrated the production of U(IV)–O–Fe(II) precipitates containing maximum of 39.51% uranium in the presence of Fe–U bacteria. The reoxidation experiments revealed the U(IV)–O–Fe(II) precipitates were more stable than UO₂. 16S rDNA high throughput sequencing analysis demonstrated that Acinetobacter and Stenotrophomonas were responsible for Fe and U precipitation, while, Caulobacteraceae and Aminobacter were crucial for the formation of U(VI)-PO₄ chemicals. The proposed two steps accumulation method has an extraordinary application potential in stable immobilization of uranium in iron containing environments.

Chlordane is an organochlorine pesticide that is applied extensively. Residual concentrations that remain in soils after application are highly toxic to soil organisms, particularly affecting the earthworm gut and indigenous soil microorganisms. However, response mechanisms of the earthworm gut and indigenous soil microorganism communities to chlordane exposure are not well known. In this study, earthworms (Metaphire guillelmi) were exposed to chlordane-contaminated soils to investigate their response mechanisms over a gradient of chlordane toxicity. Results from high-throughput sequencing and network analysis showed that the bacterial composition in the earthworm gut varied more significantly than that in indigenous soil microbial communities under different concentrations of chlordane stress (2.3–60.8 mg kg⁻¹; p < 0.05). However, keystone species of Flavobacterium, Candidatus Nitrososphaera, and Acinetobacter remained stable in both the earthworm gut and bacterial communities despite varying degrees of chlordane exposure, and their relative abundance was slightly higher in the low-concentration treatment group (T1, T2) than in the high-concentration treatment group (T3, T4). Additionally, network analysis demonstrated that the average value of the mean degree of centrality, closeness centrality, and eigenvector centrality of all keystone species screened by four methods (MetagenomeSeq, LEfSe, OPLS-DA, Random Forest) were 161.3, 0.5, and 0.63, respectively, and that these were significantly higher (p < 0.05) than values for non-keystone species (84.9, 0.4, and 0.2, respectively). Keystone species had greater network connectivity and a stronger capacity to degrade pesticides and transform carbon and nitrogen than non-keystone species. The keystone species, which were closely related to the microbial community in soil indigenous flora and earthworm intestinal flora, could resist chlordane stress and undertake pesticide degradation. These results have increased understanding of the role of the earthworm gut and indigenous soil bacteria in resisting chlordane stress and sustaining microbial equilibrium in soil.

In this study, the seasonal characteristics of microbial community compositions at different sites in a river under anthropogenic disturbances (Maozhou River) were analyzed using Illumina HiSeq sequencing. Taxonomic analysis revealed that Proteobacteria was the most abundant phylum in all sites, followed by Actinobacteria, Bacteroidetes, Chloroflexi, Acidobacteria and Firmicutes. The variations of the community diversities and compositions between the seasons were not significant. However, significant differences between sites as well as water and sediment samples were observed. These results indicated that sites under different levels of anthropogenic disturbances have selected distinct bacterial communities. pH, dissolved oxygen (DO), concentrations of total nitrogen (TN) and heavy metals were the main factors that influence the diversity and the composition of bacterial community. Specifically, the relative abundance of Proteobacteria was negatively correlated with pH and DO and positively correlated with TN, while Actinobacteria and Verrucomicrobia showed the opposite pattern. Moreover, positive correlations between the relative abundances of Firmicutes and Bacteroidetes and the concentration of heavy metals were also found. Results of functional prediction analysis showed no significant differences of the carbon, nitrogen and phosphorus metabolism across the sites and seasons. Potential pathogens such as Vibrio, Arcobacter, Acinetobacter and Pseudomonas were found in these samples, which may pose potential risks for environment and human health. This study reveals the effect of anthropogenic activities on the riverine bacterial community compositions and provides new insights into the relationships between the environmental factors and the bacterial community distributions in a freshwater ecosystem under anthropogenic disturbances.

Variations in methane (CH₄) and carbon dioxide (CO₂) emissions in municipal sewer driven by pollution sources are complex and multifaceted. It is important to investigate the role of dissolved organic matter (DOM) components and microbiota to better understand what and how those variations occurred. For this purpose, this study provides a systematic assessment based on short-term in-sewer conditioned cultivations, in conjunction with a field survey in four typical sewers in Shanghai Megacity. The results are as follows: (1) Sediment plays a main role in driving the sewer carbon emission behavior owing to its strong associations with the utilized substrates and predominant microbes that significantly promoted the gas fluxes (genera Bacteroidete_vadinHA17, Candidatus_competibacter, and Methanospirillum). (2) Aquatic DOM in overlying water is an indispensable factor in promoting total carbon emissions, yet the dominant microbes present there inversely correlated with gas fluxes (genera Methanothermobacter and Bacteroides). (3) The total fluxes of both CH₄ and CO₂ enhanced by pavement runoff were limited. Its high COD-CH₄/CO₂ conversion efficiencies can be ascribed to its dominant anthropogenic humic-like components and the emerged aquatic tyrosine-like components. (4) Domestic sewage can significantly enhance the total fluxes because of its high concentration of bioavailable DOM. However, these substrates, which were more suitable for supporting microbial growth, as well as the substrate competition caused by sulfate reduction and the nitrogen cycle (revealed by the dominant functional microbes genera Acinetobacter, Pseudomonas, Dechloromona, and Candidatus_competibacter and their correlations with indicators), seemed to be responsible for the low COD-CH₄/CO₂ conversion efficiencies of domestic sewage. (5) A field survey indicated the distinct features of carbon emissions of sewer sewage discharged from different catchments. An extreme hydraulic condition in a sewer in the absence of influent showed unexpectedly high levels of CO₂, while a small amount of CH₄ emissions.

Cadmium (II) can potentially alter the microbial community structure and molecular ecological network in activated sludge systems. In this study, we used Illumina sequencing combined with an RMT-based network approach to show the response of the microbial community and its network structure to Cd (II) in activated sludge systems. The results demonstrated that 1 mg/L Cd (II) did not have chronic negative effects on chemical oxygen demand (COD) reduction and denitrification processes, but negatively affected the nitrification process and phosphorus removal. In contrast, 10 mg/L Cd (II) adversely affected both COD and nutrient removal, and reduced the microbial diversity and changed the overall microbial community structure. The relative abundances of Nitrosomonadaceae, Nitrospira, Accumulibacter and Acinetobacter, which are involved in nitrogen removal, significantly decreased with increases in the Cd (II) concentration. In addition, molecular ecological network analysis showed that the networks sizes in the presence of higher levels of Cd (II) were smaller than in the control, but the nodes were more closely connected with neighbors. These shifts in bacterial abundance and the bacterial network structure may be responsible for the deterioration of COD and nutrient removal. Overall, this study provides new insights into the effects of Cd (II) on the bacterial community and its interactions in activated sludge systems.