A Vibrio harveyi insertional mutant in the cgtA (obg, yhbZ) gene, whose homologues are present in diverse organisms ranging from bacteria to humans and are essential genes in many bacterial species

Laboratory of Molecular Biology (affiliated with the University of Gda sk), Institute of Biochemistry and Biophysics, Polish Academy of Sciences, K adki 24, 80-822 Gda sk, Poland 1 Department of Molecular Biology, University of Gda sk, Kladki 24, 80-822 Gda sk, Poland 2 Marine Biology Center, Polish Academy of Sciences, w. Wojciecha 5, 81-347 Gdynia, Poland 3 Author for correspondence: Grzegorz W grzyn. Tel: +48 58 346 3014. Fax: +48 58 301 0072. e-mail: wegrzyn{at}biotech.univ.gda.pl The cgtA gene product is a member of the subfamily of small GTP-binding proteins that have been identified in diverse organisms ranging from bacteria to humans. In bacteria that sporulate or display another special developmental programme, this gene (referred to as cgtA , obg or yhbZ ) appears to be involved in the regulation of these processes. However, this gene has also been found to be essential in all bacterial species investigated to date, although its role in bacteria that do not sporulate and do not undergo a specific development remains unknown. Here the authors characterize a Vibrio harveyi mutant bearing a transposon insertion into the cgtA gene. This mutant reveals a multiple phenotype: it grows more slowly than the wild-type strain in a rich medium; its growth is completely inhibited in minimal media; its survival in 3% NaCl is dramatically reduced; it is very sensitive to UV irradiation; it is more susceptible to mutation upon treatment with different mutagens; its luminescence is decreased; its quorum-sensing regulation is less effective than in the wild-type strain; and the elongated shape of the mutant cells may suggest problems with the regulation of cell division and/or DNA replication. These defects in diverse cellular processes found in the insertional cgtA mutant of V. harveyi indicate that in a bacterium that does not sporulate and does not display other special development programmes, the CgtA protein is involved in the regulation of many crucial biochemical reactions, possibly at the stage of signal transduction. Keywords: cgtA gene, GTP-binding protein, bioluminescence, signal transduction Abbreviations: DAPI, 4',6-diamidino-2-phenylindole The GenBank accession number for the sequence reported in this paper is AF247677 .