ABSTRACT
Shewanella violacea DSS12 is facultative piezophile isolated from the deep-sea. The expression of cydDC genes (required for d-type cytochrome maturation) of the organism is regulated by hydrostatic pressure. In this study, we analyzed the nucleotide sequence upstream of cydDC in detail and found that there are putative binding sites for the NarL protein which is part of a two-component regulatory system also containing the sensor protein NarX. Furthermore, we identified the narQP genes (homologues of narXL) from S. violacea DSS12 and demonstrated the heterologous expression of narP in Escherichia coli. These results will be helpful in examining pressure regulation of gene expression in S. violacea at the molecular level.
Subject(s)
Gene Expression Regulation, Bacterial , Genes, Bacterial/genetics , Seawater/microbiology , Shewanella/genetics , Shewanella/metabolism , Amino Acid Sequence , Bacterial Proteins/chemistry , Bacterial Proteins/genetics , Escherichia coli/genetics , Molecular Sequence Data , Pacific Ocean , Recombinant Proteins/genetics , Sequence AlignmentABSTRACT
Shewanella violacea DSS12 is a psychrophilic facultative piezophile isolated from the deep sea. In a previous study, we have shown that the bacterium adapted its respiratory components to alteration in growth pressure. This appears to be one of the bacterial adaptation mechanisms to high pressures. In this study, we measured the respiratory activities of S. violacea grown under various pressures. There was no significant difference between the cells grown under atmospheric pressure and a high pressure of 50 MPa relative to oxygen consumption of the cell-free extracts and inhibition patterns in the presence of KCN and antimycin A. Antimycin A did not inhibit the activity completely regardless of growth pressure, suggesting that there were complex III-containing and -eliminating pathways operating in parallel. On the other hand, there was a difference in the terminal oxidase activities. Our results showed that an inhibitor- and pressure-resistant terminal oxidase was expressed in the cells grown under high pressure. This property should contribute to the high-pressure adaptation mechanisms of S. violacea.
Subject(s)
Oxygen Consumption , Shewanella/metabolism , Shewanella/physiology , Adaptation, Physiological , Antimycin A/pharmacology , Electron Transport Complex III/physiology , Enzyme Inhibitors/pharmacology , Hydrostatic Pressure , Metabolic Networks and Pathways , Potassium Cyanide/pharmacologyABSTRACT
The genes of cytochrome bd-encoding cydAB were identified from a deep-sea bacterium Shewanella violacea DSS12. These showed significant homologies with known cydAB gene sequences from various organisms. Additionally, highly conserved regions that are important for the enzymatic function were also conserved in cydA of S. violacea. Based on the results, transcriptional analysis of cydAB operon and cydDC operon (required for assembly of cytochrome bd) of S. violacea in microaerobic condition was performed under the growth condition of various pressures. The gene of cydA was expressed even under the condition of atmospheric pressure and its expression was enhanced with pressurization. On the other hand, the expression of cydC was strongly depressed under the condition of atmospheric pressure compared with the case under high pressure. It appeared spectrophotometrically that loss of cytochrome bd in S. violacea under atmospheric pressure shown in previous study is caused mainly by the loss of cydDC. Further, under the growth condition of atmospheric pressure, either less amount or no d-type cytochrome was expressed compared with the case of high-pressure condition even if the organism was grown under alkaline condition or in the presence of uncoupler, which are the inducible condition of d-type cytochrome in Escherichia coli. These results suggested that the significant amount of d-type cytochrome expression is specific event under the growth condition of high pressure.
