Genetic Potential of Dissulfurimicrobium hydrothermale, an Obligate Sulfur-Disproportionating Thermophilic Microorganism

Stéven Yvenou,Maxime Allioux,Galina Slobodkina,Karine Alain,Alexander Slobodkin,Mohamed Jebbar

doi:10.3390/microorganisms10010060

Abstract

The biochemical pathways of anaerobic sulfur disproportionation are only partially deciphered, and the mechanisms involved in the first step of S0-disproportionation remain unknown. Here, we present the results of sequencing and analysis of the complete genome of Dissulfurimicrobium hydrothermale strain Sh68T, one of two strains isolated to date known to grow exclusively by anaerobic disproportionation of inorganic sulfur compounds. Dissulfurimicrobium hydrothermale Sh68T is a motile, thermophilic, anaerobic, chemolithoautotrophic microorganism isolated from a hydrothermal pond at Uzon caldera, Kamchatka, Russia. It is able to produce energy and grow by disproportionation of elemental sulfur, sulfite and thiosulfate. Its genome consists of a circular chromosome of 2,025,450 base pairs, has a G + C content of 49.66% and a completion of 97.6%. Genomic data suggest that CO2 assimilation is carried out by the Wood–Ljungdhal pathway and that central anabolism involves the gluconeogenesis pathway. The genome of strain Sh68T encodes the complete gene set of the dissimilatory sulfate reduction pathway, some of which are likely to be involved in sulfur disproportionation. A short sequence protein of unknown function present in the genome of strain Sh68T is conserved in the genomes of a large panel of other S0-disproportionating bacteria and was absent from the genomes of microorganisms incapable of elemental sulfur disproportionation. We propose that this protein may be involved in the first step of elemental sulfur disproportionation, as S0 is poorly soluble and unable to cross the cytoplasmic membrane in this form.

Highlights

Chemolithotrophic microorganisms derive the energy necessary for their growth by transforming mineral species by oxidation–reduction reactions
The disproportionation (=dismutation) of inorganic sulfur compounds (ISC) is to some extent outside this general framework. It is a scarcely studied metabolism, found in three bacterial phyla (Firmicutes, Nitrospirota and Desulfobacterota), which is distinguished by the ability to use only a single mineral species (S0, S2 O3 2−, SO3 2− ) as creativecommons.org/licenses/by/
Dissulfurimicrobium hydrothermale, which belongs to the phylum Desulfobacterota, is one of the two strains identified to date that derives its energy and growth solely from the disproportionation of inorganic sulfur compounds

Summary

Introduction

Chemolithotrophic microorganisms derive the energy necessary for their growth by transforming mineral species by oxidation–reduction reactions They transform a wide variety of mineral species in both oxidized and reduced states, which can be used as electron donors or as terminal electron acceptors, respectively. With the exception of fermentation, all these metabolisms are based on the use of a reduced compound (organic or inorganic) as an electron donor and a more oxidized one as a terminal electron acceptor. The disproportionation (=dismutation) of inorganic sulfur compounds (ISC) is to some extent outside this general framework It is a scarcely studied metabolism, found in three bacterial phyla (Firmicutes, Nitrospirota and Desulfobacterota (including Thermodesulfobacteriales and various orders previously classified in the Deltaproteobacteria)), which is distinguished by the ability to use only a single mineral species (S0 , S2 O3 2− , SO3 2− ) as creativecommons.org/licenses/by/

Objectives

Methods

Results

Conclusion