Colonial Opacity Variations among the Choleragenic Vibrios

Abstract

Cultures of Vibrio cholerae 01, biotype El Tor, from the current epidemic of cholera in the Western Hemisphere, and of the new V. cholerae serogroup 0139, from the current outbreak in India and Bangladesh, revealed marked colonial heterogeneity when received by the authors. By comparison with reference colony types, using a stereoscope and transmitted oblique illumination, colonies of approximately 10 different degrees of opacity could be distinguished. In contrast, strains freshly isolated from patients and rapidly and carefully preserved were more homogeneous although still differentiable by this technique. These (and older) observations prompted the questions: (1) why is a V. cholerae colony opaque or translucent? and (2) what benefit is it to the vibrios to vary their colonial appearance? The observed changes in colonial opacity, which are reversible, are sometimes (rarely) accompanied by changes in virulence for infant rabbits and, more frequently, by other phenotypic variations including the ability to produce poly-p-hydroxybutyrate inclusion bodies on glycerol-containing medium, the degree of encapsulation in 0139, changes in outer-membrane proteins, alteration in lipopolysaccharide structure, changes in expression of glycolytic pathways, and differences in ability to survive under adverse conditions. Colonial variations in choleragenic vibrios are phenotypically multifactorial. The genetic mechanisms(s) underlying the observed phenotypic changes remain to be defined.Keywords : Vibrio cholerae, colonial variation, opacity, poly-P-hydroxybutyrate (PHB), capsules INTRODUCTIONCholera vibrios have long been known to be mercurial in their ability to exhibit variations in colonial morphology. Robert Koch was the first to observe that the colonial appearance of cholera vibrios was distinct from that of other bacterial species (Pollitzer, 1959, p. 125). Soon thereafter, Kolle and Gotschlich (Pollitzer, 1959, pp. 452-456), and subsequently others, noted that vibrio subcultures contained opaque (0) and translucent (T) colonial variants. Lankford (1960) observed that nearly all colonies of classical biotype Vibrio cholerae on primary culture from patients in Calcutta, India, in 1953, and in Bangkok, Thailand, in 1958, were of a single characteristic ' typically opaque and striated ' colony type, whereas most stock cultures of V. cholerae Abbreviations: LOS, lipooligosaccharide; MR, methyl red; OU, opacity unit; PHB, poly-P-hydroxybutyrate; VP, Voges-Proskauer.were mixtures of colony types or pure types differing from each other. Colonies which deviated from the ' typical ' colony type usually had reduced virulence for 13-d-old chicken embryos (Lankford, 1960 ;Gardner et al., 1964). The apparent homogeneity of fresh isolates has also been the author's (R. A. F.'s) experience during cholera epidemics of El Tor and classical biotypes in the Philippines, India, Vietnam and Thailand during the period from 1961to 1967. In 1966, it was noted (Finkelstein, 1966 that stock cultures of El Tor biotype V. cholerae sent f...

Role for the major outer-membrane protein from Vibrio anguillarum in bile resistance and biofilm formation

“…Interestingly, the translucent ompU mutant (lane 7) contains predominately the medium molecular mass O-antigen and very little of the lipid A core. This LPS profile is similar to a translucent variant of a wild-type V. cholerae strain (Finkelstein et al, 1997). These data suggest that changes in the OMP content can alter the amount and length of the smooth LPS in the outer leaflet of the cell.…”

Characterization and possible functions of a new filamentous bacteriophage from Vibrio cholerae 0139

“…Other cultures were from ATCC, J. Johnson (VA Medical Center, Baltimore, MD, USA), J. Mekalanos (Harvard Medical School, Boston, MA, USA), G. B. Nair (National Institute of Cholera and Enteric Diseases, Calcutta, India), Y. Takeda (International Medical Center of Japan, Tokyo, Japan), R. Taylor (Dartmouth Medical School, Hanover, NH, USA), K. Wachsmuth (Centers for Disease Control and Prevention, Atlanta, GA, USA) and our laboratory collection ( University of Missouri, MO, USA). Colony morphology and opacity were evaluated as previously described (Finkelstein et al, 1997). T o evaluate the potential role of TcpA as a receptor (Waldor & Mekalanos, 1996) for phage 493, ToxR-mutants of A 527-493 were made according to a modification of a previously described technique (Waldor & Mekalanos, 1994).…”

“…Growing cells were picked from the centre of plaques and streaked for single colonies. Stereoscopic examination of these colonies using transmitted oblique illumination (Finkelstein et al, 1997) revealed that marked alteration in colonial morphology occurred as a result of infection with phage 493 (Fig. La, b).…”

Identification and Characterization of a Phase-Variable NonfimbrialSalmonella typhimuriumGene That Alters O-Antigen Production

“…To our knowledge, this is the first report of phase-variable expression of O antigen in S. typhimurium. There is precedence for phase-variable expression of LPS in other bacterial genera, including Vibrio (14), Neisseria (2,43,48), Haemophilus (42,53,54), and Chlamydia (30).…”