Effect of changes in the osmolarity of the growth medium on Vibrio cholerae cells

Abstract

The rate and extent of lysis of Vibrio cholerae cells under nongrowing conditions were dependent on the osmolarity of the growth medium. Gross alterations in cellular morphology were observed when V. chokrae cells were grown in media of high and low osmolarity. The rate of lysis of V. cholerae cells under nongrowing conditions increased after treatment with chloramphenicol. Chloramphenicol-treated V. cholerae 569B cells showed formation of sphaeroplast-like bodies in medium of high osmolarity, but not in low osmolarity. Changes in the osmolarity of the growth medium also regulated the expression of the outer membrane proteins. This regulation was abolished if V. cholerae cells were grown in Pi-depleted medium. Analysis of the lytic behavior and composition of outer membrane proteins of an osmotically fragile mutant strain revealed a similar dependence on the osmolarity of the growth medium. * Corresponding author. OmpC proteins (13, 36). The synthesis of the PhoE protein is derepressed upon phosphate starvation (25). It has also been suggested that the rigidity of the outer membranepeptidoglycan layer might also depend upon the specific major outer membrane protein present (13). It is in this context that the present report describes the changes in the lytic phenotype, cellular morphology, and composition of the outer membrane of a hypertoxinogenic strain (569B) of V. cholerae grown under various osmolarities and in phosphate-depleted (LP) growth medium. The lytic phenotype and cellular morphology were also affected drastically after treatment with chloramphenicol (CAM).

Cell surface characteristics of environmental and clinical isolates of Vibrio cholerae non-O1

“…In E. coli, the peptidoglycan network is thin but "more than a monolayer" (15). The peptidoglycan content of V. cholerae 569B is about 0.5% of the cellular dry weight, a percentage much lower than that in other gram-negative bacteria (17). The environmental non-Ol strains have about fivefold more peptidoglycan, and hence in these cells, the peptidoglycan network is probably more than a monolayer.…”

“…The crude-cell envelope was isolated as described previously (11,17). Fractionation into outer and inner membranes was carried out by treatment of the crude-cell envelope with 4 M urea for the analysis of LPS and phospholipids (16) and with 1% (wt/vol) Sarkosyl (CIBA-Geigy) as described previously (17). Contamination in the outer membrane preparation due to inner membrane was always less than 8% as determined by cytochrome assay (25).…”

“…The chromatogram was observed during a brief exposure to iodine vapor and developed in ninhydrin spray reagent (0.2% ninhydrin in acetone). For quantitative analysis, the spots containing the phospholipids were scraped into a tube and eluted by chloroform-methanol, and their phosphate contents were determined (17).…”

“…It thus appears that cells belonging to serovars 01 and non-O1 adapt themselves differently to tolerate environmental fluctuations. In view of the fact that the cell surfaces of 01 vibrios are fragile (16,17,26,27,30,31) and that the cell surface is the primary potential barrier between the cell and the environment, we wanted to examine whether the cell surfaces of non-O1 vibrios are relatively rigid and thus help these cells survive better in the environment. V.…”

Porins of Vibrio cholerae: purification and characterization of OmpU

“…The outer membrane of enteric pathogens is one of several factors that are involved in the interaction between the bacterium and the epithelial cell surface and confers resistance to the bacterium to bile salts and to host defense factors such as lysozyme and leukocyte proteins (20). To understand the regulatory network involved in the host-parasite interaction and its possible role in virulence, the outer membrane of Vibrio cholerae, a noninvasive gram-negative bacterium and the etiological agent of cholera, has been examined by several investigators (9,10,13,14). Some atypical features of the cell surface of V. cholerae have emerged from these studies.…”