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Physiological and evolutionary studies of NAP systems in Shewanella piezotolerans WP3.

ABSTRACT: Most of the Shewanella species contain two periplasmic nitrate reductases (NAP-? and NAP-?), which is a unique feature of this genus. In the present study, the physiological function and evolutionary relationship of the two NAP systems were studied in the deep-sea bacterium Shewanella piezotolerans WP3. Both of the WP3 nap gene clusters: nap-? (napD1A1B1C) and nap-? (napD2A2B2) were shown to be involved in nitrate respiration. Phylogenetic analyses suggest that NAP-? originated earlier than NAP-?. Tetraheme cytochromes NapC and CymA were found to be the major electron deliver proteins, and CymA also served as a sole electron transporter towards nitrite reductase. Interestingly, a ?napA2 mutant with the single functional NAP-? system showed better growth than the wild-type strain, when grown in nitrate medium, and it had a selective advantage to the wild-type strain. On the basis of these results, we proposed the evolution direction of nitrate respiration system in Shewanella: from a single NAP-? to NAP-? and NAP-? both, followed by the evolution to a single NAP-?. Moreover, the data presented here will be very useful for the designed engineering of Shewanella for more efficient respiring capabilities for environmental bioremediation.

SUBMITTER: Chen Y

PROVIDER: S-EPMC3105760 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Physiological and evolutionary studies of NAP systems in Shewanella piezotolerans WP3.

Chen Ying Y Wang Fengping F Xu Jun J Mehmood Muhammad Aamer MA Xiao Xiang X

The ISME journal 20101202 5

Most of the Shewanella species contain two periplasmic nitrate reductases (NAP-α and NAP-β), which is a unique feature of this genus. In the present study, the physiological function and evolutionary relationship of the two NAP systems were studied in the deep-sea bacterium Shewanella piezotolerans WP3. Both of the WP3 nap gene clusters: nap-α (napD1A1B1C) and nap-β (napD2A2B2) were shown to be involved in nitrate respiration. Phylogenetic analyses suggest that NAP-β originated earlier than NAP- ...[more]

PMID: 21124486

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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.

Dataset Information

Physiological and evolutionary studies of NAP systems in Shewanella piezotolerans WP3.

Publications

Physiological and evolutionary studies of NAP systems in Shewanella piezotolerans WP3.

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