Abstract
Identifying nitrogen-transforming genes and the microbial community in the lacustrine sedimentary environment is critical for revealing nitrogen cycle processes in eutrophic lakes. In this study, we examined the diversity and abundance of ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), denitrifying bacteria (DNB), and anammox bacteria (AAOB) in different trophic status regions of Lake Taihu using the amoA, Arch-amoA, nirS, and hzo genes as functional markers. Quantitative Polymerase Chain Reaction (qPCR) results indicated that the abundance of the nirS gene was the highest, while the amoA gene had the lowest abundance in all regions. Except for the primary inflow area of Lake Taihu, Arch-amoA gene abundance was higher than the hzo gene in three lake bays, and the abundance of the nirS gene increased with decreasing trophic status. The opposite pattern was observed for the amoA, Arch-amoA, and hzo genes. Phylogenetic analyses showed that the predominant AOB and AOA were Nitrosomonas and Nitrosopumilus maritimus, respectively, and the proportion of Nitrosomonas in the eutrophic region (87.9%) was higher than that in the mesotrophic region (71.1%). Brocadia and Anammoxoglobus were the two predominant AAOB in Lake Taihu. Five novel unknown phylotypes of AAOB were observed, and Cluster AAOB-B was only observed in the inflow area with a proportion of 32%. In the DNB community, Flavobacterium occurred at a higher proportion (22.6–38.2%) in all regions, the proportion of Arthrobacter in the mesotrophic region (3.6%) was significantly lower than that in the eutrophic region (15.6%), and the proportions of Cluster DNB-E in the inflow area (24.5%) was significantly higher than that in the lake bay (7.3%). The canonical correspondence analysis demonstrated that the substrate concentration in sedimentary environments, such as NOx--N in the sediment, NH4+-N in the pore water, and the total organic matter, were the key factors that determined the nitrogen-transforming microbial community. However, the temperature was also a predominant factor affecting the AOA and AAOB communities.
Highlights
Nitrogen is a limiting nutritional factor in the primary productivity of lakes and is one of the primary factors contributing to the eutrophication of lakes [1]
While the average value of NH4 + -N decreased in the same direction as Trophic Status Indices (TSIs) (Figure S1-a), the concentration of NO3 − -N in the research area did not show significant variation (Figure S1-b)
(Figure S1-c) and NOx − -N (Figure S1-d) in the sediments decreased with decreasing trophic status
Summary
Nitrogen is a limiting nutritional factor in the primary productivity of lakes and is one of the primary factors contributing to the eutrophication of lakes [1]. As the primary driving force of the nitrogen cycle, nitrogen-transforming bacteria affect the occurrence of various forms of nitrogen and their characteristics [2]. Research on the nitrogen-transforming bacterial community and. Res. Public Health 2019, 16, 2298; doi:10.3390/ijerph16132298 www.mdpi.com/journal/ijerph
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