Abstract
BackgroundShewanella oneidensis MR-1 is capable of reducing extracellular electron acceptors, such as metals and electrodes, through the Mtr respiratory pathway, which consists of the outer membrane cytochromes OmcA and MtrC and associated proteins MtrA and MtrB. These proteins are encoded in the mtr gene cluster (omcA-mtrCAB) in the MR-1 chromosome.ResultsHere, we investigated the transcriptional mechanisms for the mtr genes and demonstrated that omcA and mtrC are transcribed from two upstream promoters, PomcA and PmtrC, respectively. In vivo transcription and in vitro electrophoretic mobility shift assays revealed that a cAMP receptor protein (CRP) positively regulates the expression of the mtr genes by binding to the upstream regions of PomcA and PmtrC. However, the expression of omcA and mtrC was differentially regulated in response to culture conditions; specifically, the expression from PmtrC was higher under aerobic conditions than that under anaerobic conditions with fumarate as an electron acceptor, whereas expression from PomcA exhibited the opposite trend. Deletion of the region upstream of the CRP-binding site of PomcA resulted in a significant increase in promoter activity under aerobic conditions, demonstrating that the deleted region is involved in the negative regulation of PomcA.ConclusionsTaken together, the present results indicate that transcription of the mtr genes is regulated by multiple promoters and regulatory systems, including the CRP/cAMP-dependent regulatory system and yet-unidentified negative regulators.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0406-8) contains supplementary material, which is available to authorized users.
Highlights
Shewanella oneidensis MR-1 is capable of reducing extracellular electron acceptors, such as metals and electrodes, through the Mtr respiratory pathway, which consists of the outer membrane cytochromes OmcA and MtrC and associated proteins MtrA and MtrB
Beliaev et al [31] detected a transcription start point (TSP) located 119 bp upstream of the ATG start codon of mtrC (TSPmtrC; Figure 2B) using 5′ Rapid amplification of cDNA ends (RACE) PCR, and more recently, Shao et al [32] identified a TSP located 93 bp upstream of omcA (TSPomcA; Figure 2A) among the total of 2,531 TSPs detected in S. oneidensis MR-1 using 5′-end RNA sequencing
[35,36,37], suggesting that cyclic AMP (cAMP) receptor protein (CRP) directly binds to the DNA region upstream of TSP located bp upstream of omcA (TSPomcA)
Summary
Shewanella oneidensis MR-1 is capable of reducing extracellular electron acceptors, such as metals and electrodes, through the Mtr respiratory pathway, which consists of the outer membrane cytochromes OmcA and MtrC and associated proteins MtrA and MtrB. These proteins are encoded in the mtr gene cluster (omcA-mtrCAB) in the MR-1 chromosome. S. oneidensis MR-1 is the most extensively studied strain of Shewanella because of its annotated genome sequence [14], ease of genetic manipulation [5], and capability to directly transfer electrons to extracellular substances, such as metal oxides and electrodes, without exogenously added mediator [15]. Biochemical studies indicate that both MtrC and OmcA are able to transfer electrons to solid Fe(III) oxides [18,19], MtrC appears to play a dominant role in electron transfer to electrodes, whereas OmcA plays an greater role in attachment of cells to solid surfaces [22,23], indicating that functional differences exist between these two OM-cyts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
