Exploration of Microbial Diversity and Community Structure of Lonar Lake: The Only Hypersaline Meteorite Crater Lake within Basalt Rock

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.

Keywords: 16S rRNA gene; India; Lonar Lake; basalt rock; microbial diversity; soda lake.

Figure 1

Distribution of major phylogenetic groups of bacteria in (A) across the sediment and water samples, and (B) overall distribution between sediment and water samples of the Lonar Lake. Bacterial abundance in the sediment sample has a positive difference between proportions (blue circles), whereas bacterial abundance in the water sample has a negative difference between proportions (red circles). Bars on the left represent the proportion of each bacterial phyla abundance in the samples. Bacterial abundance difference with a p-value of >0.05 were considered to be significant.

Figure 2

Venn diagram demonstrating unique and shared OTUs at family level (A) among the sediment samples and (B) among the water samples of the Lonar Lake.

Figure 3

Heat map shows distribution of major bacterial group (detected five or more than five samples) at family level.

Figure 4

Co-occurrence analysis of the bacteria members (A) sediment samples and (B) water samples of Lonar Lake at family level. Diagram shows the interactions among different bacteria. Red line indicates negative association and green line indicates positive association. The thickness of the line indicates strength of interaction and the size of the bubble indicates the relative abundance of bacterial members.

Figure 5

Comparative analysis of bacterial community composition (A) among the present samples as well as those reported earlier from diverse hypersaline lake ecosystem, (B) UPGMA cluster analysis among the samples based on abundance of different bacterial groups as detected in different lake system, (C) UPGMA cluster analysis among the bacterial groups detected in diverse lake system and (D) relative abundance of the bacterial phylum. The samples are denoted as follows: DL, Deep Lake (Colorado); LCKS30, Lake Chaka (China); LL, Lonar Lake (India); LCKS10, Lake Chaka (China); LCKS20, Lake Chaka (China); LCKS0, Lake Chaka (China); LCKS40, Lake Chaka (China); W3, Lonar Lake water (present study); W2, Lonar Lake water (present study); S3, Lonar Lake sediment (present study); S1, Lonar Lake sediment (present study); S2, Lonar Lake sediment (present study); SLC, Soap Lake Chemocline (Washington); W1, Lonar Lake water (present study); OL, Organic Lake (Eastern Antarctica); LCKW, Lake Chaka (China); LCKS20, Lake Chaka (China); SLMiS, Soap Lake Mixolimnion sediment (Washington); MLM, Mono Lake Monimolimnion (California); SLM, Soap Lake Monimolimnion (Washington); SLMi, Soap Lake Mixolimnion (Washington); EL, Echo Lake (Colorado); MLC, Mono Lake Chemocline (California); MLO, Mono Lake Oxycline (California); MLMi, Mono Lake Mixolimnion (California). The details of these samples are provided as Supplementary Information (Table S2).