Transcriptomic and proteomic insight into the mechanism of cyclooctasulfur‐ versus thiosulfate‐oxidation by the chemolithoautotroph Sulfurimonas denitrificans

Abstract

Summary Chemoautotrophic bacteria belonging to the genus Sulfurimonas (class Campylobacteria ) were previously identified as key players in the turnover of zero‐valence sulfur, a central intermediate in the marine sulfur cycle. S. denitrificans was further shown to be able to oxidize cyclooctasulfur (S 8 ). However, at present the mechanism of activation and metabolism of cyclooctasulfur is not known. Here, we assessed the transcriptome and proteome of S. denitrificans grown with either thiosulfate or S 8 as the electron donor. While the overall expression profiles under the two growth conditions were rather similar, distinct differences were observed that could be attributed to the utilization of S 8 . This included a higher abundance of expressed genes related to surface attachment in the presence of S 8 , and the differential regulation of the sulfur‐oxidation multienzyme complex (SOX), which in S. denitrificans is encoded in two gene clusters: soxABXY 1 Z 1 and soxCDY 2 Z 2 . While the proteins of both clusters were present with thiosulfate, only proteins of the soxCDY 2 Z 2 were detected at significant levels with S 8 . Based on these findings a model for the oxidation of S 8 is proposed. Our results have implications for interpreting metatranscriptomic and ‐proteomic data and for the observed high level of diversification of soxY 2 Z 2 among sulfur‐oxidizing Campylobacteria .

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