title: Ultrastructure of coccoid viable but non-culturable Vibrio cholerae.
abstract: Morphology of viable but non-culturable Vibrio cholerae was monitored for 2 years by scanning and transmission electron microscopy. Morphological changes included very small coccoid forms, after extended incubation at 4 degrees C and room temperature, and sequential transformation from curved rods to irregular (approximately 1 microm) rods to approximately 0.8 microm coccoid cells and, ultimately, to tiny coccoid forms (0.07-0.4 microm). Irregular rod-shaped and coccoid cells were equally distributed in microcosms during the first 30-60 days of incubation at both temperatures, but only coccoid cells were observed after incubation for 60 days at 4 degrees C. When V. cholerae O1 and O139, maintained for 30-60 days at both temperatures, were heated to 45 degrees C for 60 s, after serial passage through 0.45 microm and 0.1 microm filters, and plating on Luria-Bertania (LB) agar, only cells larger than 1 microm yielded colonies on LB agar. Approximately 0.1% of heat-treated cultures were culturable. Cell division in the smallest coccoid cells was observed, yielding daughter cells of equal size, whereas other coccoid cells revealed bleb-like, cell wall evagination, followed by transfer of nuclear material. Coccoid cells of V. cholerae O1 and O139 incubated at 4 degrees C for more than 1 year remained substrate responsive and antigenic.
authors.affiliation: Center of Marine Biotechnology, Columbus Center, University of Maryland Biotechnology Institute, 701 E. Pratt St., Suite 236, Baltimore, MD 21202, USA.
authors.forename: Saipin
authors.initials: S
authors.lastname: Chaiyanan
authors.forename: Sitthipan
authors.initials: S
authors.lastname: Chaiyanan
authors.forename: Christopher
authors.initials: C
authors.lastname: Grim
authors.forename: Timothy
authors.initials: T
authors.lastname: Maugel
authors.forename: Anwar
authors.initials: A
authors.lastname: Huq
authors.forename: Rita R
authors.initials: RR
authors.lastname: Colwell
mesh_terms: D000222:Adaptation, Physiological; D001422:Bacterial Adhesion; D001431:Bacteriological Techniques; D050296:Microbial Viability; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D012621:Seasons; D013696:Temperature; D041241:Vibrio cholerae O1 / Q000254:growth & development / Q000648:ultrastructure*; D041242:Vibrio cholerae O139 / Q000254:growth & development / Q000648:ultrastructure*