Pseudodesulfovibrio cashew sp. Nov., a Novel Deep-Sea Sulfate-Reducing Bacterium, Linking Heavy Metal Resistance and Sulfur Cycle.

Rikuan Zheng,Shimei Wu,Chaomin Sun

doi:10.3390/microorganisms9020429

Abstract

Sulfur cycling is primarily driven by sulfate reduction mediated by sulfate-reducing bacteria (SRB) in marine sediments. The dissimilatory sulfate reduction drives the production of enormous quantities of reduced sulfide and thereby the formation of highly insoluble metal sulfides in marine sediments. Here, a novel sulfate-reducing bacterium designated Pseudodesulfovibrio cashew SRB007 was isolated and purified from the deep-sea cold seep and proposed to represent a novel species in the genus of Pseudodesulfovibrio. A detailed description of the phenotypic traits, phylogenetic status and central metabolisms of strain SRB007 allowed the reconstruction of the metabolic potential and lifestyle of a novel member of deep-sea SRB. Notably, P. cashew SRB007 showed a strong ability to resist and remove different heavy metal ions including Co2+, Ni2+, Cd2+ and Hg2+. The dissimilatory sulfate reduction was demonstrated to contribute to the prominent removal capability of P. cashew SRB007 against different heavy metals via the formation of insoluble metal sulfides.

Highlights

Sulfur is an essential element for life, which is widely found in the natural environment.The ocean represents a major reservoir of sulfur on Earth, with large quantities in the form of dissolved sulfate ion (SO4 2− ), which is the second most abundant anion next to chloride [1].Marine sediments are the main sink for sea-water sulfate and the sedimentary sulfur cycle is a major component of the global sulfur cycle [2,3]
The sulfur cycle of marine sediments is primarily driven by dissimilatory sulfate reduction (DSR), which is mediated by sulfate-reducing bacterium (SRB) in many anaerobic environments [2]
During isolation of uncultured microorganisms from the deep-sea cold seep, a potential novel species of SRB was obtained after several rounds of purification, which showed 97.34% similarity of 16S rRNA sequence to that of Pseudodesulfovibrio profundus DSM 11384T, the type strain of the genus Pseudodesulfovibrio, isolated from a deep sediment layer in the Japan Sea [16]

Summary

Introduction

Marine sediments are the main sink for sea-water sulfate and the sedimentary sulfur cycle is a major component of the global sulfur cycle [2,3]. The sulfur cycle of marine sediments is primarily driven by dissimilatory sulfate reduction (DSR), which is mediated by sulfate-reducing bacterium (SRB) in many anaerobic environments [2]. SRB mediate two sulfate-reduction pathways: assimilatory sulfate reduction (ASR) and dissimilatory sulfate reduction (DSR). The canonical microbial pathway for dissimilatory sulfate reduction involves the initial reduction of sulfate (SO4 2− ) to sulfite (SO3 2− ) by a combination of sulfate adenylyltransferase (Sat) and adenylyl-sulfate reductase (AprAB), followed by reduction of SO3 2− to H2 S (S2− ) by a single enzyme (bisulfite reductase) [5]. The other pathway involves several enzymes (such as sulfite reductase, trithionate reductase and thiosulfate reductase) and intermediates (such as trithionates and thiosulfates) [6]

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Discussion

Conclusion