Comparison of global transcription responses allows identification of Vibrio cholerae genes differentially expressed following infection

Abstract

Comparison of global transcription profiles of Vibrio cholerae grown in vitro and in vivo revealed that 20% of the genome was repressed and about 5% was induced under in vivo conditions. Hybridization with the cloned genes revealed that the virulence genes ctx, toxR, toxT and tcpA were induced under in vivo conditions. Dissection of two in vivo induced cosmids identified another set of three genes homologous to cheY1 involved in motility and chemotaxis, pnuC encoding the major component of the nicotinamide mononucleotide transport system and icmF belonging to a cassette involved in multiplication inside host cells. These results demonstrate that the global transcription profile approach might be a powerful method for identification of differentially expressed transcripts under in vivo conditions. ß

Characterization of theicmHandicmFGenes Required forLegionella pneumophilaIntracellular Growth, Genes That Are Present in Many Bacteria Associated with Eukaryotic Cells

“…1) were found to affect the ability of the bacteria to enter eukaryotic cells (21). Moreover, the expression of an icmF-homologous gene in V. cholerae was found to be induced during infection (15,16). It is important to mention that in several cases a gene region containing homologues to the L. pneumophila icmF and icmH genes was found in one or two species that belong to the same genus, and the genes were always found in the more pathogenic species.…”

“…In the other bacteria in which proteins homologous to IcmF and IcmH were found, these proteins were encoded by genes in a large region that contained between 10 and 15 genes; however, L. pneumophila does not contain homologues to the proteins other than IcmH and IcmF. In three cases, this large gene region was shown to participate in the interaction of the bacteria with eukaryotic cells (4,15,16,21,47). This information might indicate that the Icm/Dot proteins probably originated from at least three different evolutionary sources: (i) 18 Icm/Dot proteins probably originated from an IncI conjugative plasmid; (ii) IcmH and IcmF probably originated from a common ancestral system, from which L. pneumophila and the other bacteria obtained their icmH and icmF homologues; (iii) IcmWS and IcmRQ have unknown evolutionary origins, but since there are no homologues of these proteins in the other two systems described, it is most likely that these proteins have a third (or third and fourth) evolutionary origin.…”

Type VI secretion: a beginner's guide

“…In the same year, the gene cluster icmGCDJBF on the chromosome of Legionella pneumophila was shown to be required for the killing of human macrophages [5]. In 2000, Das and co-workers from Calcutta, India, discovered a homologue of icmF in Vibrio cholerae that was induced in a rabbit ileal loop model of infection [6].…”

Nooks and Crannies in Type VI Secretion Regulation

“…The Burkholderia pseudomallei Tss5 and S. enterica Sci T6SS and the Francisella pathogenicity island (FPI) T6SS of F. tularensis are upregulated inside macrophages (30,34,62,82,97); indeed, the sci cluster is necessary for delaying phagocytosis, whereas the FPI cluster is necessary for intracellular survival. Similarly, the V. cholerae T6SS vas genes are expressed in a rabbit ileal loop model of infection (33). Upon phagocytosis, production of the Vas T6SS induces cytoskeleton rearrangements through the secretion of the actin cross-linking domain of VgrG (68).…”

“…Based on these homologies, it has been proposed that the assembled secretion system may resemble an upside-down bacteriophage (56,63) in which the additional bacteriophage-unrelated genes may participate in the assembly of the structure or its stabilization. Indeed, two subunits resemble the IcmF and IcmH proteins that stabilize the type IV secretion systems in Legionella pneumophila (22,33), whereas other T6SS-associated genes encode putative cytoplasmic proteins, an outer membrane lipoprotein (3), or inner membrane proteins, including a cell wall binding protein that anchors the secretion system to the peptidoglycan layer (4). The virulence factors secreted through these apparatuses are not identified yet, but in several cases, the VgrG proteins carry a supplementary C-terminal effector module (86,88).…”