Study On Diversity And Coexistence Of Candidatus Methylomirabilis Oxyfera-like And Anammox Bacteria In Sediments Of Lake Tangxun And Lake Liangzi

Nitrogen is an important nutrient element in lakes.Microorganisms of denitrifying anaerobic methane oxidation(n-damo)and anaerobic ammonia oxidation(anammox)play an important role in the biogeochemical cycle of nitrogen in lakes.The main microorganisms dominanting the n-damo reaction are the NC10 phylum bacteria Candidatus Methylomirabilis oxyfera(M.oxyfera),and the microorganisms dominanting the anammox reaction are anammox bacteria.In this study,Lake Tangxun,a typical eutrophic lake in the middle reaches of the Yangtze River,and Lake Liangzi,a medium eutrophic lake,were cloned,sequenced and quantified using the 16 S rRNA specific primers of M.oxyfera bacteria and anammox bacteria respectively.The spatial distribution of the community structure and abundance of M.oxyfera-like bacteria and anammox bacteria in the lakes was studied.The coexistence of these two bacteria in freshwater lakes was explored.Finally,the effects of environmental factors on the diversity and abundance distribution of the two species of bacteria were discussed in order to understand the nitrogen cycle in lakes and provide a theoretical basis for the restoration of eutrophication in the water.The main results are as follows:1.The co-occurrence of M.oxyfera-like bacteria and anammox bacteria in sediment at different depths of Lake Tangxun and Lake Liangzi was successfully detected by cloning sequencing and quantitative PCR.The result is confirmed that the widespread distribution of M.oxyfera-like bacteria in the sediments of freshwater lakes,which provides favorable evidence for the co-occurrence of these two kinds of bacteria in aquatic ecosystem.2.Phylogenetic analysis showed that M.oxyfera-like bacteria in Lake Tangxun and Lake Liangzi had complex community structure,and the gene sequences of M.oxyfera-like bacteria in the two lakes were similar to many others environments of published literature.In the sediments of the two lakes,the anammox bacteria affiliated to Candidatus Brocadia genus and some of the sequences of the sediments of Lake Liangzi had a high affinity with the Candidatus Anammoxoglobus genus.3.The analysis of biodiversity and community structure showed that the diversity of M.oxyfera-like bacteria and anammox bacteria in different sampling sites of Lake Tangxun had great differences,and the diversity of M.oxyfera-like bacteria and anammox bacteria in different sampling depths of Lake Liangzi showed the characteristics that the shallow layer was higher than the deep layer.The inorganic nitrogen indexes,such as ammonium nitrogen,nitrate nitrogen and nitrite nitrogen had a great influence on the formation of community structure of M.oxyfera-like and anammox bacteria in the two lakes.4.Quantitative analysis showed that the distribution of both M.oxyfera-like bacteria and anammox bacteria in the sediments of Lake Tangxun and Lake Liangzi had spatial heterogeneity.In the horizontal distribution,the two kinds of bacteria in Lake Tangxun have obvious heterogeneity,which is manifested in the higher abundance of bacteria in the sampling area with the stronger anthropogenic pollution interference.In the vertical distribution,the abundance of M.oxyfera-like and anammox bacteria decreased with depth in two lakes.The abundance ratios of anammox bacteria to M.oxyfera-like bacteria(a/M)decreased with depth in two lakes.5.RDA correlation analysis showed that the nitrate is the most important factor affecting the quantitative distribution of the two bacteria among all physical and chemical properties of Lake Tangxun and Lake Liangzi.In the sediments of the Lake Tangxun,the abundance of M.oxyfera-like and anammox bacteria is positively correlated with ammonium,nitrate,total nitrogen and organic matter.and was weakly positively correlated with nitrate and pH.Anammox bacteria and nitrate nitrogen are negative correlation.In Lake Liangzi,both M.oxyfera-like and anammox bacteria showed positive correlation with organic matter.And the anammox was positively correlated with total nitrogen,while other environmental factors were negatively correlated with the number of two bacteria.The Quantitative ratio of anammox bacteria to M.oxyfera-like bacteria was positively correlated with nitrate nitrogen in sediments of both Lake Tangxun and Lake Liangzi.