Regulation of the FecI-type ECF sigma factor by transmembrane signalling.

Induction of the ferric citrate transport genes of Escherichia coli K-12 involves a signalling cascade that starts at the cell surface and proceeds to the cytoplasm. Three specific proteins are involved: FecA in the outer membrane, FecR in the cytoplasmic membrane, and FecI in the cytoplasm. The binding of dinuclear ferric citrate to FecA causes substantial structural changes in FecA, triggering the signal cascade.

Interactions between the outer membrane ferric citrate transporter FecA and TonB: studies of the FecA TonB box.

Both induction of transcription of the ferric citrate transport genes and transport of ferric citrate by the Escherichia coli outer membrane receptor FecA require energy derived from the proton motive force (PMF) of the inner membrane. The energy is transduced to FecA by the inner membrane complex, TonB, ExbB, and ExbD. Region 160 of TonB and the conserved TonB box of other TonB-dependent receptors are implicated as sites of interaction.

Up-regulation of both intimin and eae-independent adherence of shiga toxigenic Escherichia coli O157 by ler and phenotypic impact of a naturally occurring ler mutation.

Shiga toxigenic Escherichia coli (STEC) strains are important human pathogens which are capable of causing diarrhea, hemorrhagic colitis, and the potentially fatal hemolytic-uremic syndrome (HUS). An important virulence trait of certain STEC strains, such as those belonging to serogroup O157, is the capacity to produce attaching and effacing (A/E) lesions on enterocytes, a property encoded by the locus for enterocyte effacement (LEE). LEE contains the eae gene, which encodes intimin, an outer membrane protein which mediates the intimate attachment of bacteria to the host epithelial cell surface, and eae is routinely used as a marker for LEE-positive STEC strains.

Characterization of the Vibrio cholerae El Tor lipase operon lipAB and a protease gene downstream of the hly region.

We have cloned and sequenced a region encoding a lipase operon and a putative, previously uncharacterized metalloprotease of Vibrio cholerae O1. These lie downstream of hlyA and hlyB, which encode the El Tor hemolysin and methyl-accepting chemotactic factor, respectively. Previous reports identified the hlyC gene downstream of hlyAB, encoding an 18.

Comparison of the promoter proximal regions of the toxin-co-regulated tcp gene cluster in classical and El Tor strains of Vibrio cholerae O1.

A physical map has been constructed of the 5-kb XbaI fragment encoding the promoter proximal of region the tcp gene cluster encoding the toxin-coregulated pilus (TCP) of Vibrio cholerae. This fragment contains the major regulatory regions for TCP. Comparison of the nucleotide (nt) sequences from strains of the classical and El Tor biotypes demonstrates that the regions are essentially identical, with several notable exceptions.

Genetic organization and sequence of the promoter-distal region of the tcp gene cluster of Vibrio cholerae.

The nucleotide sequence of the promoter distal region of the major operon associated with biosynthesis of TCP, the toxin coregulated pilus of Vibrio cholerae has been determined. The genes tcpR, tcpD, tcpS, tcpT, tcpE and tcpF are organized to permit translational coupling and are followed by an inverted repeat structure which is likely to act as a strong Rho-independent terminator. TcpS and TcpF possess N-terminal signal sequences and would be expected to be periplasm and outer membrane located, respectively.

TCP pilus biosynthesis in Vibrio cholerae O1: gene sequence of tcpC encoding an outer membrane lipoprotein.

The nucleotide sequence of the tcpC gene has been determined. It encodes a 53995-Da protein precursor with a signal sequence and cleavage site typical of a number of outer membrane lipoproteins, which are cleaved by the equivalent of signal peptidase II (Lsp) of Escherichia coli. The location of the tcpC gene is such that it is predicted to be translationally coupled to the 5' and 3' flanking genes, tcpY and tcpD, respectively, indicating that it forms part of an operon.

Homology of TcpN, a putative regulatory protein of Vibrio cholerae, to the AraC family of transcriptional activators.

The nucleotide sequence has been determined for the gene designated tcpN, encoding a putative regulatory protein within the tcp gene cluster associated with the biosynthesis and assembly of the toxin-coregulated pilus of Vibrio cholerae. It is preceded by a powerful transcriptional terminator which presumably delimits the major tcp operon, but at its 3' end is translationally coupled to the gene, tcpJ, encoding the TCP pilin signal peptidase. The tcpN gene encodes a putative 276-residue protein of 31,890 Da.

Nucleotide sequence of the structural gene, tcpA, for a major pilin subunit of Vibrio cholerae.

The toxin co-regulated pilus (Tcp) of Vibrio cholerae appears to be a major protective antigen. By cosmid cloning we have isolated a number of clones capable of converting Tcp- El Tor strains of V. cholerae to Tcp+.