Abstract
The study of microbial communities from extreme environments is a fascinating topic. With every study, biologists and ecologists reveal interesting facts and questions that dispel the old belief that these are inhospitable environments. In this work, we assess the microbial diversity of three hot springs from Neuquén, Argentina, using high-throughput amplicon sequencing. We predicted a distinct metabolic profile in the acidic and the circumneutral samples, with the first ones being dominated by chemolithotrophs and the second ones by chemoheterotrophs. Then, we collected data of the microbial communities of hot springs around the world in an effort to comprehend the roles of pH and temperature as shaping factors. Interestingly, there was a covariation between both parameters and the phylogenetic distance between communities; however, neither of them could explain much of the microbial profile in an ordination model. Moreover, there was no correlation between alpha diversity and these parameters. Therefore, the microbial communities’ profile seemed to have complex shaping factors beyond pH and temperature. Lastly, we looked for taxa associated with different environmental conditions. Several such taxa were found. For example, Hydrogenobaculum was frequently present in acidic springs, as was the Sulfolobaceae family; on the other hand, Candidatus Hydrothermae phylum was strongly associated with circumneutral conditions. Interestingly, some singularities related to sites featuring certain taxa were also observed.
Highlights
Geothermal areas have proven to be interesting environments for diverse scientific disciplines [1,2,3]
Many researchers have focused on the relation between microbial communities and environmental factors while taking different approaches, yet the general belief is that temperature is the main factor that drives the community structure [4,5,6]
Chemolithotrophic microorganisms prevailed, such as Acidithiobacillus spp., Leptospirillum spp. and Sulfobacillus spp.; in the circumneutral sample, there was a diversity of metabolisms, aerobic and anaerobic, but with chemoheterotrophic bacteria being dominant
Summary
Geothermal areas have proven to be interesting environments for diverse scientific disciplines [1,2,3]. Many researchers have focused on the relation between microbial communities and environmental factors while taking different approaches, yet the general belief is that temperature is the main factor that drives the community structure [4,5,6]. It may not be that simple, as Power et al [9] and Uribe-Lorio et al [10] have shown that pH has a strong influence in the communities’ structure, since the samples in both studies could be split in two clusters: one with acidic pH and the other one with circumneutral conditions. Purcell et al [12] studied hyperthermophilic and alkaline (pH 7.5–9 and 75–90 ◦C) hot springs of Thailand and concluded that the combined conditions of temperature and sulfide concentration were the most important factors that drove the diversity of bacteria and archaea. The relation between microbial communities and environmental factors is undoubtedly complex and yet to be dilucidated
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