Dataset Information

The regulatory function of LexA is temperature-dependent in the deep-sea bacterium Shewanella piezotolerans WP3.

ABSTRACT: The SOS response addresses DNA lesions and is conserved in the bacterial domain. The response is governed by the DNA binding protein LexA, which has been characterized in model microorganisms such as Escherichia coli. However, our understanding of its roles in deep-sea bacteria is limited. Here, the influence of LexA on the phenotype and gene transcription of Shewanella piezotolerans WP3 (WP3) was investigated by constructing a lexA deletion strain (WP3?lexA), which was compared with the wild-type strain. No growth defect was observed for WP3?lexA. A total of 481 and 108 genes were differentially expressed at 20 and 4°C, respectively, as demonstrated by comparative whole genome microarray analysis. Furthermore, the swarming motility and dimethylsulfoxide reduction assay demonstrated that the function of LexA was related to temperature. The transcription of the lexA gene was up-regulated during cold acclimatization and after cold shock, indicating that the higher expression level of LexA at low temperatures may be responsible for its temperature-dependent functions. The deep-sea microorganism S. piezotolerans WP3 is the only bacterial species whose SOS regulator has been demonstrated to be significantly influenced by environmental temperatures to date. Our data support the hypothesis that SOS is a formidable strategy used by bacteria against various environmental stresses.

SUBMITTER: Jian H

PROVIDER: S-EPMC4471891 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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The regulatory function of LexA is temperature-dependent in the deep-sea bacterium Shewanella piezotolerans WP3.

Jian Huahua H Xiong Lei L He Ying Y Xiao Xiang X

Frontiers in microbiology 20150618

The SOS response addresses DNA lesions and is conserved in the bacterial domain. The response is governed by the DNA binding protein LexA, which has been characterized in model microorganisms such as Escherichia coli. However, our understanding of its roles in deep-sea bacteria is limited. Here, the influence of LexA on the phenotype and gene transcription of Shewanella piezotolerans WP3 (WP3) was investigated by constructing a lexA deletion strain (WP3ΔlexA), which was compared with the wild-ty ...[more]

PMID: 26150814

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Project description:Dimethyl sulfoxide (DMSO) acts as a substantial sink for dimethyl sulfide (DMS) in deep waters and is therefore considered a potential electron acceptor supporting abyssal ecosystems. Shewanella piezotolerans WP3 was isolated from west Pacific deep-sea sediments, and two functional DMSO respiratory subsystems are essential for maximum growth of WP3 under in situ conditions (4°C/20 MPa). However, the relationship between these two subsystems and the electron transport pathway underlying DMSO reduction by WP3 remain unknown. In this study, both DMSO reductases (type I and type VI) in WP3 were found to be functionally independent despite their close evolutionary relationship. Moreover, immunogold labeling of DMSO reductase subunits revealed that the type I DMSO reductase was localized on the outer leaflet of the outer membrane, whereas the type VI DMSO reductase was located within the periplasmic space. CymA, a cytoplasmic membrane-bound tetraheme c-type cytochrome, served as a preferential electron transport protein for the type I and type VI DMSO reductases, in which type VI accepted electrons from CymA in a DmsE- and DmsF-independent manner. Based on these results, we proposed a core electron transport model of DMSO reduction in the deep-sea bacterium S. piezotolerans WP3. These results collectively suggest that the possession of two sets of DMSO reductases with distinct subcellular localizations may be an adaptive strategy for WP3 to achieve maximum DMSO utilization in deep-sea environments.IMPORTANCE As the dominant methylated sulfur compound in deep oceanic water, dimethyl sulfoxide (DMSO) has been suggested to play an important role in the marine biogeochemical cycle of the volatile anti-greenhouse gas dimethyl sulfide (DMS). Two sets of DMSO respiratory systems in the deep-sea bacterium Shewanella piezotolerans WP3 have previously been identified to mediate DMSO reduction under in situ conditions (4°C/20 MPa). Here, we report that the two DMSO reductases (type I and type VI) in WP3 have distinct subcellular localizations, in which type I DMSO reductase is localized to the exterior surface of the outer membrane and type VI DMSO reductase resides in the periplasmic space. A core electron transport model of DMSO reduction in WP3 was constructed based on genetic and physiological data. These results will contribute to a comprehensive understanding of the adaptation mechanisms of anaerobic respiratory systems in benthic microorganisms.

Project description:Oxidative stresses commonly exist in natural environments, and microbes have developed a variety of defensive systems to counteract such events. Although increasing evidence has shown that high hydrostatic pressure (HHP) and low temperature (LT) induce antioxidant defense responses in cells, there is no direct evidence to prove the connection between antioxidant defense mechanisms and the adaptation of bacteria to HHP and LT. In this study, using the wild-type (WT) strain of a deep-sea bacterium, Shewanella piezotolerans WP3, as an ancestor, we obtained a mutant, OE100, with an enhanced antioxidant defense capacity by experimental evolution under H2O2 stress. Notably, OE100 exhibited better tolerance not only to H2O2 stress but also to HHP and LT (20 MPa and 4°C, respectively). Whole-genome sequencing identified a deletion mutation in the oxyR gene, which encodes the transcription factor that controls the oxidative stress response. Comparative transcriptome analysis showed that the genes associated with oxidative stress defense, anaerobic respiration, DNA repair, and the synthesis of flagella and bacteriophage were differentially expressed in OE100 compared with the WT at 20 MPa and 4°C. Genetic analysis of oxyR and ccpA2 indicated that the OxyR-regulated cytochrome c peroxidase CcpA2 significantly contributed to the adaptation of WP3 to HHP and LT. Taken together, these results confirmed the inherent relationship between antioxidant defense mechanisms and the adaptation of a benthic microorganism to HHP and LT.IMPORTANCE Oxidative stress exists in various niches, including the deep-sea ecosystem, which is an extreme environment with conditions of HHP and predominantly LT. Although previous studies have shown that HHP and LT induce antioxidant defense responses in cells, direct evidence to prove the connection between antioxidant defense mechanisms and the adaptation of bacteria to HHP and LT is lacking. In this work, using the deep-sea bacterium Shewanella piezotolerans WP3 as a model, we proved that enhancement of the adaptability of WP3 to HHP and LT can benefit from its antioxidant defense mechanism, which provided useful insight into the ecological roles of antioxidant genes in a benthic microorganism and contributed to an improved understanding of microbial adaptation strategies in deep-sea environments.

Dataset Information

The regulatory function of LexA is temperature-dependent in the deep-sea bacterium Shewanella piezotolerans WP3.

Publications

The regulatory function of LexA is temperature-dependent in the deep-sea bacterium Shewanella piezotolerans WP3.

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