Survival stages of a psychrotrophic Cytophaga johnsonae strain

Abstract

Cells of a psychrotrophic strain of Cytophaga johnsonae, when exposed to starvation in a mineral salts medium, produced short viable rods, viable coccoids, and moribund elongated cells as a function of the incubation temperature. Starvation for 14 days or longer resulted in an increase of the cellular DNA to protein ratio. While rod-shaped cells possessed an intermediate layer identified as murein sacculus, coccoid cells displayed the common properties of spheroplasts, and their formation was frequently preceded by a pestlelike intermediate stage. During survival, substrate affinities (1/Km) for transport, respiration, and incorporation of glucose increased in both rod and coccoid cells. The rods appeared to possess dual, concentration-dependent metabolic pathways for glucose. Glucose incorporation by starved cells into macromolecular pools had lower Km values (10 to 203 times lower) than the values found for exponentially growing and nonviable rods. Coccoid cells demonstrated a slightly increased resistance to mild heat stress compared with log phase cells but were equally susceptible to ultrasonic vibration and ultraviolet irradiation. The data obtained indicated that unbalanced cellular divisions of multinucleate cells at low temperature and starvation result in coccoid cells. The coccoid cells are probably the survival forms in nature when low temperatures and nutrient deprivation exist.