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Applied and Environmental Microbiology, July 2007, p. 4279-4285, Vol. 73, No. 13
0099-2240/07/$08.00+0     doi:10.1128/AEM.00020-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Multilocus Sequence Analysis Reveals that Vibrio harveyi and V. campbellii Are Distinct Species ^,

Department of Genetics, Institute of Biology, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil,¹ CIAD Mazatlan Unit for Aquaculture, AP 711 Mazatlan, Sinaloa 82000, Mexico,² Nacional Laboratory for Scientific Computing, Department of Applied and Computational Mathematics, Laboratory of Bioinformatics, Av. Getúlio Vargas 333, Quitandinha, 25651-070, Petropolis, RJ, Brazil,³ Laboratory of Microbiology, Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate 041-8611, Japan⁴

Received 4 January 2007/ Accepted 26 April 2007

Identification and classification of Vibrio species have relied upon band pattern methods (e.g., amplified fragment length polymorphism) and DNA-DNA hybridization. However, data generated by these methods cannot be used to build an online electronic taxonomy. In order to overcome these limitations, we developed the first standard multilocus sequence scheme focused on the ubiquitous and pathogenic Vibrio harveyi species group (i.e., V. harveyi, V. campbellii, V. rotiferianus, and a new as yet unnamed species). We examined a collection of 104 isolates from different geographical regions and hosts using segments of seven housekeeping genes. These two species formed separated clusters on the basis of topA, pyrH, ftsZ, and mreB gene sequences. The phylogenetic picture obtained by the other three loci, i.e., gyrB, recA, and gapA, was more complex though. V. campbellii appeared nested within V. harveyi in the recA trees, whereas V. harveyi formed a tight nested cluster within V. campbellii by gapA. The gyrB gene had no taxonomic resolution and grouped the two species together. The fuzziness observed in these three genes seems not be related to recombination but to low divergence due to the accumulation of only a few substitutions. In spite of this, the concatenated sequences provided evidence that the two species form two separated clusters. These clusters did not arise by recombination but by accumulation of point mutations. V. harveyi and V. campbellii isolates can be readily identified through the open database resource developed in this study (http://www.taxvibrio.lncc.br/). We argue that the species should be defined by evolutionary criteria. Strains of the same species will share at least 95% concatenated sequence similarity using the seven loci, and, most importantly, cospecific strains will form cohesive readily recognizable phylogenetic clades.

Published ahead of print on 4 May 2007.

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

This article has been cited by other articles:

• Thompson, C. C., Thompson, F. L., Vicente, A. C. P. (2008). Identification of Vibrio cholerae and Vibrio mimicus by multilocus sequence analysis (MLSA). Int. J. Syst. Evol. Microbiol. 58: 617-621 [Abstract] [Full Text]  
• Sawabe, T., Kita-Tsukamoto, K., Thompson, F. L. (2007). Inferring the Evolutionary History of Vibrios by Means of Multilocus Sequence Analysis. J. Bacteriol. 189: 7932-7936 [Abstract] [Full Text]