Molecular Detection of Novel Anammox Bacterial Clusters in the Sediments of the Shallow Freshwater Lake Taihu

Abstract

Previous studies have demonstrated the wide occurrence of anaerobic ammonium oxidizing (anammox) bacteria; however, there is very limited information on the distribution of these bacteria in freshwater habitats. In this study, the anammox bacterial communities were detected by molecular analysis targeting the 16S rRNA genes in the sediments of Lake Taihu, a large and shallow eutrophic freshwater lake in China. The recovery of specific 16S rRNA sequences with two stable monophyletic clusters indicated that anammox bacteria were present in Lake Taihu. A phylogenetic analysis indicated that these two groups represent two novel lineages within the first subgroup of anammox bacteria, independent of the treeing methods. High intra-lake variability in anammox bacterial diversity and community composition was observed, in particular, based on a 1% cut-off of 16S rRNA sequence variation. The spatial variability was largely related to the substrate availability, which was denoted by the correlations between the relative abundance of the two Taihu anammox bacterial groups and the concentrations of ammonium and nitrite. This indicates that the niche differentiation of anammox bacteria is linked to the environmental heterogeneity. These findings suggest that the freshwater lakes may accommodate different anammox bacterial communities and, thus, expand our knowledge on the diversity and distribution of anammox bacteria. Supplemental materials are available for this article. Go to the publisher's online edition of Geomicrobiology Journal to view the free supplemental files.

Keywords:

• 16S ribosomal RNA
• anaerobic ammonium oxidation
• in situ detection
• lake sediment
• niche separation

Acknowledgments

The authors are grateful to Guang Gao and Jiang Ji for their kind assistance in sampling and laboratory work. We very much thank the two anonymous reviewers for constructive suggestions and insightful comments. This study was financially supported by NSFC (40730528) and the National Basic Research Program of China (2008CB418104). Y. Wu was supported by the China Postdoctoral Science Foundation (200801382 and 20080431127), by the Jiangsu Postdoctoral Research Funds (0702057C), and by a postdoctoral fellowship from K. C. Wong Education Foundation, Hong Kong.