Abstract
Lonar Lake is a hypersaline and hyperalkaline soda lake and the only meteorite impact crater in the world situated in basalt rocks. Although culture-dependent studies have been reported, a comprehensive understanding of microbial community composition and structure in Lonar Lake remains elusive. In the present study, microbial community structure associated with Lonar Lake sediment and water samples was investigated using high-throughput sequencing. Microbial diversity analysis revealed the existence of diverse, yet largely consistent communities. Proteobacteria (30%), Actinobacteria (24%), Firmicutes (11%), and Cyanobacteria (5%) predominated in the sequencing survey, whereas Bacteroidetes (1.12%), BD1-5 (0.5%), Nitrospirae (0.41%), and Verrucomicrobia (0.28%) were detected in relatively minor abundances in the Lonar Lake ecosystem. Within the Proteobacteria phylum, the Gammaproteobacteria represented the most abundantly detected class (21–47%) within sediment samples, but only a minor population in the water samples. Proteobacteria and Firmicutes were found at significantly higher abundance (p ≥ 0.05) in sediment samples, whereas members of Actinobacteria, Candidate division TM7 and Cyanobacteria (p ≥ 0.05) were significantly abundant in water samples. Compared to the microbial communities of other hypersaline soda lakes, those of Lonar Lake formed a distinct cluster, suggesting a different microbial community composition and structure. Here we report for the first time, the difference in composition of indigenous microbial communities between the sediment and water samples of Lonar Lake. An improved census of microbial community structure in this Lake ecosystem provides a foundation for exploring microbial biogeochemical cycling and microbial function in hypersaline lake environments.
Highlights
Occurring alkaline water bodies are unique and important ecosystems that offer valuable insights into how microbial communities cope with extreme growth conditions
Three sediment samples (S1, S2, and S3) from 40 to 50 cm depth and three corresponding water samples (W1, W2, and W3) from 10 to 20 cm depth used in this study were collected from three different locations (19◦98.222′N, 76◦50.698′E; 19◦97.435′N, 76◦50.342′E; 19◦97.532′N, 76◦51.337′E; respectively) of the Lonar Lake located in Buldhana district, Maharashtra, India during October 2013
All samples exhibited characteristic geochemical properties associated with a hypersaline soda lake, with respect to pH, salinity, Total organic carbon (TOC), total N, total P, CO23−, and Cl− content (Table 1)
Summary
Occurring alkaline water bodies are unique and important ecosystems that offer valuable insights into how microbial communities cope with extreme growth conditions. Microbial life in sediments of this lake was previously examined using clone libraries and Denaturant Gradient Gel Electrophoresis, revealing the presence of the bacterial phyla Firmicutes, Proteobacteria, and Actinobacteria (Wani et al, 2006; Surakasi et al, 2010). Since these technologies offer only limited resolution, the phylogenetic profile of this lake’s microbial communities in water column and sediment remains rudimentary and only offers limited insights into associated microbial processes. The aim of this study is to obtain a detailed view of the bacterial diversity and community structure in Lonar Lake water and sediment using a high-throughput 16S rRNA gene sequencing approach, to improve our understanding of autochthonous community composition within this complex and extreme lake ecosystem
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