Molecular analysis of the rstR and orfU genes of the CTX prophages integrated in the small chromosomes of environmental Vibrio cholerae non-O1, non-O139 strains.
The ctxAB genes encoding cholera toxin, reside in the genome of a filamentous bacteriophage CTXphi. The presence of CTX prophage in non-epidemic environmental Vibrio cholerae strains is rare. The CTX prophage, the lysogenic form of CTXphi in V. cholerae, is comprised of the 'RS2' and the 'Core'. Analysis of the rstR gene present in the RS2 region of the CTX prophage revealed the presence of new alleles of the prophages in four environmental non-O1, non-O139 strains VCE22 (O36), VCE228 (O27), VCE232 (O4) and VCE233 (O27), and the CTX prophages are located in the small chromosomes. Phylogenetic analysis based on the nucleotide sequences of the rstR and orfU (present in the core) genes of these prophages placed them in a single unique cluster, which is distally located compared with that of epidemic V. cholerae O1 strains. Further analysis indicated that the genome of the prophage present in the strain VCE22 is devoid of the ctxAB genes, called pre-CTX prophage and the strain also possess the toxin-coregulated pilus protein coding gene tcpA of classical type, another important pathogenicity determining locus of the epidemic V. cholerae strains. Comparative analysis of the nucleotide sequences of the rstR and orfU genes indicated that the pre-CTX prophage of VCE22 might be the progenitor of new alleles of the CTX prophages present in these environmental strains.
National Institute of Cholera and Enteric Diseases, P-33, CIT Road Scheme XM, Beliaghata, Kolkata 700010, India.
Tanuja
T
Bhattacharya
Souvik
S
Chatterjee
Diganta
D
Maiti
Rupak K
RK
Bhadra
Yoshifumi
Y
Takeda
G Balakrish
GB
Nair
Ranjan K
RK
Nandy
D001426:Bacterial Proteins / Q000235:genetics*; D002772:Cholera Toxin / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics / Q000821:virology; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D036781:Fimbriae Proteins / Q000235:genetics; D005814:Genes, Viral; D017912:Inovirus / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D039002:Prophages / Q000235:genetics*; D012097:Repressor Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014734:Vibrio cholerae / Q000145:classification / Q000302:isolation & purification / Q000821:virology*; D044163:Vibrio cholerae non-O1 / Q000821:virology*
D001426:Bacterial Proteins; D004279:DNA, Viral; D012097:Repressor Proteins; C107871:RstR protein, Vibrio cholerae; C085807:TcpA protein, Vibrio cholerae; D036781:Fimbriae Proteins; D002772:Cholera Toxin