A 14-kilodalton inner membrane protein of Vibrio cholerae biotype e1 tor confers resistance to group IV choleraphage infection to classical vibrios

Abstract

Choleraphage +149 differentiates the two biotypes, classical and el tor, of Vibrio cholerae. This phage cannot replicate in V. cholerae biotype el tor cells because the concatemeric DNA intermediates produced are unstable and cannot be chased to mature phage DNA. A V. cholerae biotype el tor gene coding for a 14,000-Da inner membrane protein which destabilizes the concatemeric DNA intermediates by hindering their binding to the cell membrane has been identified. Presumably, a 22,000-Da V. cholerae biotype el tor protein might also have a role in conferring phage +149 resistance to cells belonging to the biotype el tor. A nucleotide sequence homologous to the 1.2-kb V. cholerae biotype el tor DNA coding for both the 14,000-and 22,000-Da proteins is present in all strains of classical vibrios but is not transcribed. The nucleotide sequence of the gene coding for the 14,000-Da protein has been determined.Vibrio cholerae strains of serotype 01 comprise two different biotypes, classical and el tor. Of the seven pandemics of cholera recorded in recent times, V. cholerae biotype el tor has been identified as the causative agent of the seventh pandemic, while the previous ones were due to the classical strains. Recently, there has been a resurgence of classical vibrios in certain areas of endemicity (33). In spite of broad similarities in the nature of infection by the classical and el tor vibrios, important differences exist in the epidemiology of el tor compared with that of classical vibrios. The ratio of asymptomatic infection to clinical illness is greater with the el tor biotype than with the classical vibrios (2), and the el tor vibrios survive longer under unfavorable conditions. Both the classical and the el tor strains of V. cholerae react with V. cholerae antisera, and taxonomic studies have shown that these two biotypes are the same species (12). They are isogenic, and tests to distinguish them often give ambiguous results (16). One of the most reliable criteria differentiating between these two biotypes is their susceptibility to group IV choleraphages. This group of choleraphages can infect and lyse all strains of classical vibrios but none of the el tor biotype (24). Phage 4149 adsorbs irreversibly to the biotype el tor cells, and 50% of the injected phage DNA binds to the cell membrane. Synthesis of monomeric phage DNA continued, similar to that observed for the permissive host. However, the concatemeric DNA intermediates produced were unstable and could not be chased to mature phage DNA (9). Although most of the early proteins are made, only some of the late proteins were transiently synthesized for infection in el tor cells. Formation and stabilization of concatemeric DNA structures essential for the synthesis of mature phage DNA and their packaging into phage heads are not hindered in V. cholerae biotype el tor cells for the replication of choleraphage 4138 belonging to serological group II. This phage also contains a linear double-stranded circularly permuted DNA molecule and can replicate in both V....

The El Tor Biotype of Vibrio cholerae Exhibits a Growth Advantage in the Stationary Phase in Mixed Cultures with the Classical Biotype

“…When required, the LB medium was buffered to pH 7.2 with 100 mM HEPES buffer. A synthetic salt solution containing 30 mM KH 2 PO 4 , 2 mM NH 4 Cl, 85 mM NaCl, 1 mM MgSO 4 , and trace amounts of FeCl 3 in 50 mM Tris-HCl (pH 7.2 or 8.5) supplemented with 0.2% Casamino Acids or individual amino acids (0.5%) was used in some experiments.…”

“…Several biochemical tests, including hemolysis (2,23), hemagglutination of chicken erythrocytes (14), resistance to polymyxin B (13), bacteriophage-mediated lysis (4,6,27), and acetoin synthesis (15), are used to distinguish strains of the El Tor from the classical biotype. Many studies have revealed dramatic differences in regulation of virulence gene expression between the El Tor and classical biotypes (1,8,16,19).…”

Suppressed Induction of Proinflammatory Cytokines by a Unique Metabolite Produced by Vibrio cholerae O1 El Tor Biotype in Cultured Host Cells

“…Furthermore, transcriptional profiling experiments found that 524 genes are differentially expressed between the two biotypes under conditions that induce virulence expression in the Classical biotype. Biochemical behaviors such as hemolysis, hemagglutination of chicken erythrocytes (23), resistance to polymyxin B (18), bacteriophage-mediated lysis (4), and acetoin synthesis (28) are used to distinguish El Tor from Classical biotype strains. Acetoin biosynthesis in the presence of exogenous sugar such as glucose is crucial for biotyping the seventh pandemic El Tor strains and O139 strains (24).…”

Intracellular Replication of Choleraphage φ92

“…Most of the choleraphages examined so far contain linear double-stranded DNA that is circularly permuted [3][4][5][6][7]. Among the choleraphages, phage Ê149, belonging to the serological group IV, has been examined in detail because of its immense taxonomic importance.…”