EFFECTS OF SUDDEN TEMPERATURE SHIFTS ON PURE CULTURES OF FOUR STRAINS OF FRESHWATER BACTERIA

Three psychrotrophic and one mesophilic strains were isolated from winter water samples of different freshwater biotopes and identified as Cytophaga johnsonae (C-21), Cytophaga sp. (M-17), Pseudomonas fluorescens (KD), and Enterobacter cloacae (BS-2). Temperature shift-up experiments with emphasis on low temperatures were carried out with aerated pure batch cultures in glucose mineral medium. The effects of sudden temperature increases on growth rates and substrate conversion were investigated. All three psychrotrophic strains in the temperature increase experiments at low temperatures showed differing reactions within the linear zone of the Arrhenius plot. The C. johnsonae (C-21) shift-up cultures adjusted the growth rate immediately to the rate of the temperature adapted cultures, whereas Cytophaga sp. (M-17) shift-up cultures showed a lower and P. fluorescens (KD) a higher growth rate. The mesophilic E. cloacae (BS-2), like C. johnsonae (C-21), adjusted immediately to the new growth rate. Substrate conversion increased in all experiments immediately after the shift-up. The extracellular substrate conversion by P. fluorescens (KD) of glucose to gluconate and 2-ketogluconate was particularly affected by the sudden temperature increase. © 1979 Springer-Verlag New York Inc.