Conversion of Vibrio eltor MAK757 to Classical Biotype: Role of Phage PS166

Abstract

Temperate phage PS166 infection of Vibrio eltor MAK757 resulted in complete changes in all biotype-specific determinants. About 10% of the PS166 lysogens of MAK757 lost their eltor-specific determinants, namely, the ability to produce soluble hemolysin, cell-associated hemagglutinin for chicken erythrocytes, and resistance to polymyxin B, as well as resistance to Mukherjee's group IV phage and sensitivity to eltor phage e4. These lysogens were found to have acquired the properties of classical strains, most significantly becoming sensitive to group IV phage but resistant to eltor-specific e4. The remainder of these lysogens, however, retained their parental biotype and serotype but acquired auxotrophy for glycine and histidine. The differential behavior of the two types of lysogen was due to the integration of the phage PS166 genome at different locations in the host chromosome. A 800-bp BglII fragment was found to contain the attP site. Phage PS166 has a polyhedral head (95 nm in diameter) and a contractile tail (98 nm in length). The phage chromosome is a linear double-stranded DNA of 110 kb and a G + C content of 58.7%.

New Variants of Vibrio cholerae O1 Biotype El Tor with Attributes of the Classical Biotype from Hospitalized Patients with Acute Diarrhea in Bangladesh

“…With a V. cholerae genomic microarray that displayed more than 93% of the predicted genes of the whole genome sequence of El Tor strain N16961, Dziejman et al (9) showed that only seven genes were absent solely in classical strains but present in other strains, leading them to speculate that classical biotype strains may be derived from a primordial environmental strain that was more El Tor like than previously thought. Mitra et al have previously reported the involvement of bacteriophage PS166 in the acquisition of some classical biotypespecific properties by El Tor strains (22,23). Insertion of lysogenic phage genomes in the bacterial chromosome leading to the activation or inactivation of certain genes or expression of new phage-encoded genes is a natural phenomenon in the origination of genetic diversity.…”

Genomic Relatedness of the New Matlab Variants of Vibrio cholerae O1 to the Classical and El Tor Biotypes as Determined by Pulsed-Field Gel Electrophoresis

“…Mitra et al (15,16) already described phage genome involvement in the acquisition of some classical biotype specific properties by El Tor strains. However, the exact mechanism of In 1961, with the beginning of the seventh pandemic the classical strains were gradually replaced by the El Tor biotype, and in Bangladesh the gradual replacement occurred from 1968.…”