Abstract
Microbial mats are occasionally reported in thermal springs and information on such mats is very scarce. In this study, microbial mats were collected from two hot springs (Brandvlei (BV) and Calitzdorp (CA)), South Africa and subjected to scanning electron microscopy (SEM) and targeted 16S rRNA gene amplicon analysis using Next Generation Sequencing (NGS). Spring water temperature was 55°C for Brandvlei and 58°C for Calitzdorp while the pH of both springs was slightly acidic, with an almost identical pH range (6.2–6.3). NGS analysis resulted in a total of 4943 reads, 517 and 736 OTUs for BV and CA at, respectively, a combined total of 14 different phyla in both samples, 88 genera in CA compared to 45 in BV and 37.64% unclassified sequences in CA compared to 27.32% recorded in BV. Dominant bacterial genera in CA microbial mat were Proteobacteria (29.19%), Bacteroidetes (9.41%), Firmicutes (9.01%), Cyanobacteria (6.89%), Actinobacteria (2.65%), Deinococcus‐Thermus (2.57%), and Planctomycetes (1.94%) while the BV microbial mat was dominated by Bacteroidetes (47.3%), Deinococcus‐Thermus (12.35%), Proteobacteria (7.98%), and Planctomycetes (2.97%). Scanning electron microscopy results showed the presence of microbial filaments possibly resembling cyanobacteria, coccids, rod‐shaped bacteria and diatoms in both microbial mats. Dominant genera that were detected in this study have been linked to different biotechnological applications including hydrocarbon degradation, glycerol fermentation, anoxic‐fermentation, dehalogenation, and biomining processes. Overall, the results of this study exhibited thermophilic bacterial community structures with high diversity in microbial mats, which have a potential for biotechnological exploitation.
Highlights
Terrestrial hot springs support diverse groups of thermophilic prokaryotes whose presence and survival is largely determined by temperature and other abiotic factors including pH, redox potential, and hydrogen sulfide concentrations (Lau, Aitchison, & Pointing, 2009)
Anda et al (2015) investigated the population characteristics of thermophilic prokaryotic communities inhabiting the biofilms of a thermal karst system containing relatively high amounts of sulfide (215.3 mg/L), a temperature of 74°C and a slightly acidic pH and found it to be dominated only by sulfur oxidizing bacteria belonging to the genus Sulfurihydrogenibium
These thermal conditions could be favoring the proliferation of thermophilic microbial communities as suggested by Anda et al (2015) who indicated that microbial community composition is highly correlated with physicochemical parameters, including temperature
Summary
Terrestrial hot springs support diverse groups of thermophilic prokaryotes whose presence and survival is largely determined by temperature and other abiotic factors including pH, redox potential, and hydrogen sulfide concentrations (Lau, Aitchison, & Pointing, 2009). Microbial mats have been found to develop in a wide range of thermal habitats including hot springs, fumaroles, eruption vents, and on steaming. While microbial mats support a diverse range of microbial communities (Lau et al, 2009), temperature is a major factor in determining the dominating microbial mat members, especially the presence or absence of oxygenic and anoxygenic phototrophs (Coman, Drugǎ, Hegedus, Sicora, & Dragoş, 2013). Research focusing on microbial diversity of mats has been on the increase in different parts of the world (Anda et al, 2015; Coman et al, 2013; Lau et al, 2009) because the key findings show that these microbial mats have a wide range of microbial communities with potential for ecological importance and biotechnological applications in aquaculture, bioremediation, agriculture, and energy production (Mostafa & El-Gendy, 2013)
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