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

The cgtA gene product is a member of the subfamily of small GTP-binding pro teins that have been identified in diverse organisms ranging from bacteria to humans. In bacteria that sporulate or display another special developmen tal programme, this gene (referred to as cgtA, obg or yhbZ) appears to be i nvolved in the regulation of these processes. However, this gene has also b een found to be essential in all bacterial species investigated to date, al though its role in bacteria that do not sporulate and do not undergo a spec ific development remains unknown. Here the authors characterize a Vibrio ha rveyi mutant bearing a transposon insertion into the cgtA gene. This mutant reveals a multiple phenotype: it grows more slowly than the wild-type stra in in a rich medium; its growth is completely inhibited in minimal media; i fs survival in 3% NaCl is dramatically reduced; it is very sensitive to UV irradiation; it is more susceptible to mutation upon treatment with differe nt mutagens; its luminescence is decreased; its quorum-sensing regulation i s less effective than in the wild-type strain; and the elongated shape of t he mutant cells may suggest problems with the regulation of cell division a nd/or DNA replication. These defects in diverse cellular processes found in the insertional cgtA mutant of V. harveyi indicate that in a bacterium tha t does not sporulate and does not display other special development program mes, the CgtA protein is involved in the regulation of many crucial biochem ical reactions, possibly at the stage of signal transduction.