Diversity and Activity of Sulfate-Reducing Prokaryotes in Kamchatka Hot Springs.

Evgenii N Frolov,Elizaveta A Bonch-Osmolovskaya,Alexander Y Merkel,Nikolay V Pimenov,Nikolay A Chernyh,Alexandra V Gololobova,Alexandra A Klyukina

doi:10.3390/microorganisms9102072

Evgenii N Frolov, Elizaveta A Bonch-Osmolovskaya + Show 5 more

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https://doi.org/10.3390/microorganisms9102072

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Abstract

Microbial communities of the Kamchatka Peninsula terrestrial hot springs were studied using radioisotopic and cultural approaches, as well as by the amplification and sequencing of dsrB and 16S rRNA genes fragments. Radioisotopic experiments with 35S-labeled sulfate showed that microbial communities of the Kamchatka hot springs are actively reducing sulfate. Both the cultivation experiments and the results of dsrB and 16S rRNA genes fragments analyses indicated the presence of microorganisms participating in the reductive part of the sulfur cycle. It was found that sulfate-reducing prokaryotes (SRP) belonging to Desulfobacterota, Nitrospirota and Firmicutes phyla inhabited neutral and slightly acidic hot springs, while bacteria of phylum Thermodesulofobiota preferred moderately acidic hot springs. In high-temperature acidic springs sulfate reduction was mediated by archaea of the phylum Crenarchaeota, chemoorganoheterotrophic representatives of genus Vulcanisaeta being the most probable candidates. The 16S rRNA taxonomic profiling showed that in most of the studied communities SRP was present only as a minor component. Only in one microbial community, the representatives of genus Vulcanisaeta comprised a significant group. Thus, in spite of comparatively low sulfate concentrations in terrestrial hot springs of the Kamchatka, phylogenetically and metabolically diverse groups of sulfate-reducing prokaryotes are operating there coupling carbon and sulfur cycles in these habitats.

Highlights

Dissimilatory sulfate reduction is a process of enormous environmental and biogeochemical relevance, which is carried out by numerous sulfate-reducing prokaryotes (SRP)
Desulfobacterota includes the taxa previously classified in the phylum Thermodesulfobacteria, and these reclassifications imply that the ability of sulfate reduction was vertically inherited in the Thermodesulfobacteria rather than laterally acquired as previously inferred [3]
Using 16S rRNA high-throughput sequencing, we showed that this association consisted of bacterial genera Thermodesulforhabdus (74% of all sequences of 16S rRNA gene fragments) and Thermoanaerobacter (23% of all sequences)

Summary

Introduction

Dissimilatory sulfate reduction is a process of enormous environmental and biogeochemical relevance, which is carried out by numerous SRP. The vast variety of currently known SRP includes species belonging to four phylogenetic lineages of bacteria (Desulfobacterota, Nitrospirota, Thermodesulfobiota and Firmicutes), and two phyla of archaea (Euryarchaeota and Crenarchaeota) [1,2,3]. Desulfobacterota includes the taxa previously classified in the phylum Thermodesulfobacteria, and these reclassifications imply that the ability of sulfate reduction was vertically inherited in the Thermodesulfobacteria rather than laterally acquired as previously inferred [3]. The ability to perform sulfate reduction was predicted for “Candidatus Thermonerobacter thiotrophicus”, which is affiliated with the Bacteroides/Ignavibacteria/Chlorobi group [4]. Most SRP are mesophiles, but there are several thermophilic species. Thermophilic SRP includes representatives of bacterial genera Thermodesulfovibrio, Microorganisms 2021, 9, 2072.

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