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Identification of an extracytoplasmic function sigma factor that facilitates c ‐type cytochrome maturation and current generation under electrolyte‐flow conditions in Shewanella oneidensis MR ‐1
Author(s) -
Koga Ryota,
Matsumoto Akiho,
Kouzuma Atsushi,
Watanabe Kazuya
Publication year - 2020
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.15131
Subject(s) - shewanella oneidensis , biology , mutant , sigma factor , wild type , cytochrome , biofilm , gene , microbiology and biotechnology , gene expression , biochemistry , genetics , bacteria , promoter , enzyme
Summary Shewanella oneidensis MR‐1 was cultured on electrodes in electrochemical flow cells (EFCs), and transcriptome profiles of electrode‐attached cells grown under electrolyte‐flow conditions were compared with those under static (nonflow) conditions. Results revealed that, along with genes related to c ‐type cytochrome maturation (e.g., dsbD ), the SO_3096 gene encoding a putative extracytoplasmic function (ECF) sigma factor was significantly upregulated under electrolyte‐flow conditions. Compared to wild‐type MR‐1 (WT), an SO_3096‐deletion mutant (∆SO_3096) showed impaired biofilm formation and decreased current generation in EFCs, suggesting that SO_3096 plays critical roles in the interaction of MR‐1 cells with electrodes under electrolyte‐flow conditions. We also compared transcriptome profiles of WT and ∆SO_3096 grown in EFCs, confirming that many genes upregulated under the electrolyte‐flow conditions, including dsbD , are regulated by SO_3096. LacZ reporter assays showed that transcription from a promoter upstream of dsbD is activated by SO_3096. Measurement of current generated by a dsbD ‐deletion mutant revealed that this gene is essential for the transfer of electrons to electrodes. These results indicate that the SO_3096 gene product facilitates c ‐type cytochrome maturation and current generation under electrolyte‐flow conditions. The results also offer ecophysiological insights into how Shewanella regulates extracellular electron transfer to solid surfaces in the natural environment.