previously. using global transcription profile approach icmF gene or Vibrio cholerae was identified as an in vivo induced gene. In the present study. the icmF gene of V. cholerae 0395 was cloned. sequenced. and used to construct an icmF insertion mutant. This IcmF is homologous to Legionella pneumophila IcmF, belonging to the icm cassette responsible for macrophage killing and intracellular survival of the organism. The icmF insertion mutant exhibited reduced motility and increased adherence to human intestinal epithelial cells. The presence of ATP-GTP-binding site suggests further a possible role of IcmF as a signaling molecule. Triparental-mating assay. with the mutant as a recipient, showed higher conjugation frequency than wild type. We propose that the increased adherence to epithelial cell line and increased conjugation frequency of the mutant result from some sort of cell surface reorganization. (C) 2002 Elsevier Science (USA). All rights reserved.