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Applied and Environmental Microbiology, May 2009, p. 2802-2810, Vol. 75, No. 9
0099-2240/09/$08.00+0     doi:10.1128/AEM.01698-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Osmoadaptation among Vibrio Species and Unique Genomic Features and Physiological Responses of Vibrio parahaemolyticus ^,

Lynn M. Naughton,^1,2 Seth L. Blumerman,¹ Megan Carlberg,¹ and E. Fidelma Boyd^1*

Department of Biological Sciences, University of Delaware, Newark, Delaware 19716,¹ Department of Microbiology, National University of Ireland, University College Cork, Cork, Ireland²

Received 23 July 2008/ Accepted 26 February 2009

Vibrio parahaemolyticus is a moderately halophilic bacterium found in estuarine and marine coastal ecosystems worldwide. Although the ability of V. parahaemolyticus to grow and proliferate in fluctuating saline environments is well known, the underlying molecular mechanisms of osmoadaptation are unknown. We performed an in silico analysis of V. parahaemolyticus strain RIMD2210633 for genes homologous to osmotic stress response genes in other bacteria. We uncovered two putative compatible solute synthesis systems (encoded by ectABC and betABI) and six putative compatible solute transporters (encoded by four bcct loci and two proVWX loci). An ectoine synthesis system clustered with a betaine/carnitine/choline transporter and a ProU transporter (encoded by homologues of proVWX from Escherichia coli), and a betaine synthesis system clustered with a ProU transporter (encoded by homologues of proVXW from Pseudomonas syringae). This is at least double the number present in V. cholerae, V. fischeri, or V. vulnificus. Six additional Vibrio species contain both ectABC and betABI, i.e., V. alginolyticus 12G01, V. angustum, V. harveyi BAA-1116, V. splendidus LGP32, Vibrio sp. strain MED222, and Vibrio sp. strain Ex25. V. harveyi HY01 and V. splendidus 12B01 only encoded the betaine system. In addition, V. alginolyticus had a compendium of systems identical to that found in V. parahaemolyticus. Comparative physiological analysis of RIMD2210633 with V. vulnificus YJ016, V. cholerae N16961, and V. fischeri ES114 grown at different salinities and temperatures demonstrated that V. parahaemolyticus had a growth advantage under all of the conditions examined. We demonstrate, by one-dimensional nuclear magnetic resonance analysis, that V. parahaemolyticus is capable of de novo synthesis of ectoine at high salinity whereas a ectB knockout strain is not. We constructed a single-knockout mutation in proU1, but no growth defect was noted, indicating transporter system redundancy. We complemented E. coli MKH13, a compatible solute transporter-negative strain, with bcct2 and demonstrated uptake of betaine at high salt concentrations.

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* Corresponding author. Mailing address: Department of Biological Sciences, University of Delaware, Newark, DE 19716. Phone: (302) 831-1088. Fax: (302) 831-2281. E-mail: fboyd{at}udel.edu

Published ahead of print on 13 March 2009.

Supplemental material for this article may be found at http://aem.asm.org/.

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Applied and Environmental Microbiology, May 2009, p. 2802-2810, Vol. 75, No. 9
0099-2240/09/$08.00+0     doi:10.1128/AEM.01698-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.