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Microorganisms are an important part of atmospheric particulate matter and are closely related to human health. In this paper, the variations in the characteristics of the chemical components and bacterial communities in PM10 and PM2.5 grouped according to season, pollution degree, particle size, and winter heating stage were studied. The influence of environmental factors on community structure was also analyzed. The results showed that seasonal variations were significant. NO3- contributed the most to the formation of particulate matter in spring and winter, while SO42- contributed the most in summer and autumn. The community structures in summer and autumn were similar, while the community structure in spring was significantly different. The dominant phyla were similar among seasons, but their proportions were different. The dominant genera were no-rank_c_Cyanobacteria, Acidovorax, Escherichia-Shigella and Sphingomonas in spring; Massilia, Bacillus, Acinetobacter, Rhodococcus, and Brevibacillus in summer and autumn; and Rhodococcus in winter. The atmospheric microorganisms in Beijing mainly came from soil, water, and plants. The few pathogens detected were mainly affected by the microbial source on the sampling day, regardless of pollution level. RDA (redundancy analysis) showed that the bacterial community was positively correlated with the concentration of particulate matter and that the wind speed in spring was positively correlated with NO3- levels, NH4+ levels, temperature, and relative humidity in summer and autumn, but there was no clear consistency among winter samples. This study comprehensively analyzed the variations in the characteristics of the airborne bacterial community in Beijing over one year and provided a reference for understanding the source, mechanism, and assessment of the health effects of different air qualities.

Using reclaimed water as a resource for landscape water replenishment may alleviate the major problems of water resource shortages and water environment pollution. However, the safety of the water and the risk of eutrophication remain doubted by the public. Our study aimed to reveal the difference between natural water and reclaimed water and to discuss the rationality of reclaimed water replenishment from the perspective of microorganisms. We analyzed the microbial community structures in natural water, reclaimed water and natural biofilms and the community succession was clarified along the ecological niches, water resources, liquidity and time using 16S rRNA gene amplicon sequencing. Primary biofilms without the original community were added to study the formation of microbial community structures under reclaimed water acclimation. The results showed that the difference caused by ecological niches was more than those caused by the liquidity of water and different water resources. No significant difference was found in the microbial diversity and community structure caused by the addition of reclaimed water. Based on the microbial analysis, reclaimed water replenishment is a feasible solution that can be used for supplying river water. Innovatively, we introduced the study of biofilms and determined that the monitoring of biofilms or sediments closely related to water was also important for the early warning of water bloom, providing a unique perspective for the management of eutrophication.

Using reclaimed water as a resource for landscape water replenishment may alleviate the major problems of water resource shortages and water environment pollution. However, the safety of the reclaimed water and the risk of eutrophication caused by the reclaimed water replenishment are unclear to the public and to the research community. This study aimed to reveal the differences between natural water and reclaimed water and to discuss the rationality of reclaimed water replenishment from the perspective of microorganisms. The microbial community structures in natural water, reclaimed water and natural biofilms were analyzed, and the community succession was clarified along the ecological niches, water resources, fluidity and time using 16S rRNA gene amplicon sequencing. Primary biofilms without the original community were added to study the formation of microbial community structures under reclaimed water acclimation. The results showed that the difference caused by ecological niches was more than those caused by the fluidity of water and different water resources. No significant difference caused by the addition of reclaimed water was found in the microbial diversity and community structure. Based on the results of microbial analysis, reclaimed water replenishment is a feasible solution that can be used for supplying river water.

Complete-nitrifying bacteria (comammox) play important roles in nitrogen-overloading aquatic systems. However, the understanding of the environmental relevance is still limited. Here, we studied the responses of comammox bacteria (Nitrospira inopinata) in a tributary of the Yellow River, with the water and sediment, microbial, seasonal, and chemical variations considered. Illumina sequencing indicated that the predominant phyla in the river sediment were Proterobacteria, Bacteroidetes, Actinobacteria, and Chloroflex. Quantitative PCR revealed that N. inopinata-like comammox were approximately twice as abundant in the water during the wet season and in the sediment during the dry season than that of other conditions. Significant correlations were found between the abundance of N. inopinata-like comammox and pH (r = 0.58), temperature (r = 0.63), and dissolved oxygen (r = - 0.77). The abundance of N. inopinata-like comammox was higher than that of ammonia oxidizing archaea (AOA), and lower than that of ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB). Furthermore, a significant correlation was discovered between N. inopinata-like comammox and NOB (r = 0.60), and so was anammox bacteria (r = 0.358). Interestingly, N. inopinata-like comammox also showed positive relationships with denitrifying microbes (r = 0.559).

Microbial degraders play crucial roles in wastewater treatment processes, but their use is limited as most microbes are yet unculturable. Stable isotope probing (SIP) is a cultivation-independent technique identifying functional-yet-uncultivable microbes in ambient environment, but is unsatisfactory for substrates with low assimilation rate owing to the low isotope incorporation into DNA. In this study, we used acetonitrile as the target low-assimilation chemical in many wastewater treatment plants and attempted to identify the active acetonitrile degraders in the activated sludge, via DNA-SIP and magnetic-nanoparticle mediated isolation (MMI) which is another cultivation-independent approach without the requirement of substrate labeling. The two approaches identified different active acetonitrile degraders in a 3-day short-term anaerobic ammonium oxidation (ANAMMOX). MMI enriched significantly more acetonitrile-degraders than SIP, showing the advantages in identifying the active degraders for low-assimilation substrates. Sequencing batch reactor (SBR, 30-day degradation) helped in more incorporation of 15N-labeled acetonitrile into the active degraders, thus the same acetonitrile-degraders and acetonitrile-degrading genes were identified by SIP and MMI. Different acetonitrile degraders between ANAMMOX and SBR were attributed to the distinct hydrological conditions. Our study for the first time explored the succession of acetonitrile-degraders in wastewater and identified the active acetonitrile-degraders which could be further enriched for enhancing acetonitrile degradation performance. These findings provide new insights into the acetonitrile metabolic process in wastewater treatment plants and offer suggestive conclusions for selecting appropriate treatment strategy in wastewater management.

In this study, particulate matter (PM) with aerodynamic diameters of ≤2.5 and ≤10 μm (PM2.5 and PM10, respectively), which was found at different concentrations in spring, was collected in Beijing. The chemical composition and bacterial community diversity of PM were determined, and the relationship between them was studied by 16S rRNA sequencing and mathematical statistics. Chemical composition analysis revealed greater relative percentages of total organic compounds (TOC) and secondary ions (NO3−, SO42−, and NH4+). The concentrations of Ca2+, Na+, Mg2+, K+ and SO42− increased in high-concentration PM, which was associated with the contribution of soil, dust and soot. Microbiological analysis revealed 1191 operational taxonomic units. Microbial community structure was stable at the phylum level. The most abundant phyla were Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. Community clustering analysis at the genus level showed that the difference in bacterial community structure between different PM concentrations (clean air vs. smog) was greater than that between different particle sizes. The dominant genera varied in different concentrations of PM. An unclassified genus of Cyanobacteria and Comamonadaceae were most abundant in low- and high-concentration PM, respectively. The microbial community structure was dynamic at the genus level due to different environmental factors. The dominant bacteria in high-concentration PM were widely distributed in soils, indicating that the soil contributed more to the increase in the PM. The individual microbes that were detected did not increase significantly as the PM concentration increased. The bacterial community structure was strongly correlated with K+, Ca2+, Na+, Mg2+, SO42− and TOC in high-concentration PM and had a good correlation with NO3−, Cl−, NH4+ and TIC in low-concentration PM. Soil and dust contributed to the increase in the concentration of the particles, and the relevant chemical components also produced differences in the bacterial community structure in different concentrations of PM.

In recent years, the effect of formaldehyde on microorganisms and body had become a global public health issue. The multistage combination of anaerobic and aerobic process was adopted to treat paraformaldehyde wastewater. Microbial community structure in different reaction stages was analyzed through high-throughput sequencing. Results showed that multistage A-O activated sludge process positively influenced polyformaldehyde wastewater. The removal rates of formaldehyde were basically stable at more than 99% and those of COD were about 89%. Analysis of the microbial diversity index indicated that the microbial diversity of the reactor was high, and the treatment effect was good. Moreover, microbial community had certain similarity in the same system. Microbial communities in different units also showed typical representative characteristics affected by working conditions and influent concentrations. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant fungal genera in the phylum level of community composition. As to family and genus levels, Peptostreptococcaceae was distributed at various stages and the dominant in this system. This bacterium also played an important role in organic matter removal, particularly decomposition of the acidified middle metabolites. In addition, Rhodobacteraceae and Rhodocyclaceae were the formaldehyde-degrading bacteria found in the reactor.