Abstract
Malaysia has a great number of hot springs, especially along the flank of the Banjaran Titiwangsa mountain range. Biological studies of the Malaysian hot springs are rare because of the lack of comprehensive information on their microbial communities. In this study, we report a cultivation-independent census to describe microbial communities in six hot springs. The Ulu Slim (US), Sungai Klah (SK), Dusun Tua (DT), Sungai Serai (SS), Semenyih (SE), and Ayer Hangat (AH) hot springs exhibit circumneutral pH with temperatures ranging from 43°C to 90°C. Genomic DNA was extracted from environmental samples and the V3–V4 hypervariable regions of 16S rRNA genes were amplified, sequenced, and analyzed. High-throughput sequencing analysis showed that microbial richness was high in all samples as indicated by the detection of 6,334–26,244 operational taxonomy units. In total, 59, 61, 72, 73, 65, and 52 bacterial phyla were identified in the US, SK, DT, SS, SE, and AH hot springs, respectively. Generally, Firmicutes and Proteobacteria dominated the bacterial communities in all hot springs. Archaeal communities mainly consisted of Crenarchaeota, Euryarchaeota, and Parvarchaeota. In beta diversity analysis, the hot spring microbial memberships were clustered primarily on the basis of temperature and salinity. Canonical correlation analysis to assess the relationship between the microbial communities and physicochemical variables revealed that diversity patterns were best explained by a combination of physicochemical variables, rather than by individual abiotic variables such as temperature and salinity.
Highlights
The study of extremophiles provides insights into the origin and evolution of life
Data on microbial diversity in Sungai Klahb (SK) were previously reported by our group (Chan et al, 2015) and were compared with data for the other five hot springs studied in the current work (Figure 1, Table 1)
Candidatus Rhabdochlamydia (Kostanjšek et al, 2004), an intracellular bacterium that was first found in the terrestrial isopod Porcellio scaber appeared to be one of the dominant genera in SE. This finding suggests that endosymbiosis of thermophilic microbiota can occur in the hot springs and is not restricted to SE, and possibly occurs in Dusun Tua (DT), where we discovered tiny reddish crustaceans
Summary
Biologists believe that extremophiles inhabiting extreme environments such as hot springs are the closest living descendents of the earliest life forms on earth (Woese et al, 1990; Olsen et al, 1994). These extreme environments comprise relatively simple microbial ecosystems as compared with more complex environments such as soils (Xu et al, 2014), wastewater (Shanks et al, 2013), marine sediments (Zheng et al, 2014), and the human gastrointestinal tract (Trosvik and de Muinck, 2015). As the maximum temperature for photosynthesis is 75◦C (Ferris and Ward, 1997), Cyanobacteria and Chloroflexi are not predominantly present in hot springs with temperatures higher that this threshold
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