Replication of Vibrio cholerae classical CTX phage

Abstract

The toxigenic classical and El Tor biotype Vibrio cholerae serogroup O1 strains are generated by lysogenization of host-type-specific cholera toxin phages (CTX phages). Experimental evidence of the replication and transmission of an El Tor biotype-specific CTX phage, CTX-1, has explained the evolution of V. cholerae El Tor biotype strains. The generation of classical biotype strains has not been demonstrated in the laboratory, and the classical biotypespecific CTX phage, CTX-cla, is considered to be defective with regard to replication. However, the identification of atypical El Tor strains that contain CTX-cla-like phage, CTX-2, indicates that CTX-cla and CTX-2 replicate and can be transmitted to V. cholerae strains. The replication of CTX-cla and CTX-2 phages and the transduction of El Tor biotype strains by various CTX phages under laboratory conditions are demonstrated in this report. We have established a plasmid-based CTX phage replication system that supports the replication of CTX-1, CTX-cla, CTX-2, and CTX-O139. The replication of CTX-2 from the tandem repeat of lysogenic CTX-2 in Wave 2 El Tor strains is also presented. El Tor biotype strains can be transduced by CTX phages in vitro by introducing a point mutation in toxT, the transcriptional activator of the tcp (toxin coregulated pilus) gene cluster and the cholera toxin gene. This mutation also increases the expression of cholera toxin in El Tor strains in a sample single-phase culture. Our results thus constitute experimental evidence of the genetic mechanism of the evolution of V. cholerae.Vibrio cholerae | cholera toxin | CTX phage | biotype

Design and Construction of Vibrio cholerae Strains That Harbor Various CTX Prophage Arrays

“…CTX phages are generally transmitted by transduction of V. cholerae strains, but chitin-mediated uptake of CTX phage by non-toxigenic V. cholerae strains was also reported (Waldor and Mekalanos, 1996 ; Udden et al, 2008 ). The replication and transduction of CTX phages have been verified both in vivo and under laboratory conditions (Waldor and Mekalanos, 1996 ; Kim et al, 2017 ). The transmission of the CTX-1 phage to the classical biotype strains, and more recently, the transmission of CTX-2/CTX-cla phages to the El Tor biotype strains, indicates that the replication and maintenance of a CTX phage is not host biotype-specific (Waldor and Mekalanos, 1996 ; Kim et al, 2017 ).…”

“…The replication and transduction of CTX phages have been verified both in vivo and under laboratory conditions (Waldor and Mekalanos, 1996 ; Kim et al, 2017 ). The transmission of the CTX-1 phage to the classical biotype strains, and more recently, the transmission of CTX-2/CTX-cla phages to the El Tor biotype strains, indicates that the replication and maintenance of a CTX phage is not host biotype-specific (Waldor and Mekalanos, 1996 ; Kim et al, 2017 ). The replication of CTX-cla and CTX-2 is as efficient as that of CTX-1 under laboratory conditions, suggesting that it is highly likely that the CTX-2 or CTX-cla phages are widespread in nature.…”

“…The mosaic CTX phages in atypical El Tor strains are generated by recombination between two different types of CTX prophages in the host V. cholerae cell (Kim et al, 2014 , 2017 ). Such inter-phage recombination is possible because V. cholerae strains contain two chromosomes and the CTX phages can be integrated into either one (Das et al, 2013 ).…”

Alterations in glucose metabolism in Vibrio cholerae serogroup O1 El Tor biotype strains

“…El Tor strains-B33, MJ1236, and MG116025[12][13][14] , and two Wave 3 El Tor strains-IB4122 and IB5230-were acquired to monitor their viability in the presence of glucose in media15,16 . IB5230 is the 2010 Haitian cholera outbreak strain17 .…”

The role of bacteriophages in mixed microbial communities and populations of Pseudomonas aeruginosa

“…and Pf6 that can affect the host, is unclear. The presence of two filamentous phage in a bacterial host is not unprecedented as Vibrio cholerae also has two copies of the CTX filamentous phage (Davis et al, 2000;Kim et al, 2017). The CTX phage is present either separately on the two chromosomes (as in the classical strains), or as tandem repeats in the El Tor or O139 biotypes (Davis et al, 2000).…”