Influence of Temperature Adaptation on Glucose Metabolism in a Psychrotrophic Strain of Cytophaga johnsonae†

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Selective enrichment of yellow-orange-pigmented, gram-negative bacteria related to Cytophaga johnsonae from lake sediment was dependent on low temperatures (ca. 5°C). However, this temperature effect was abolished when excessive amounts of dissolved organic carbon (10 mM N-acetylglucosamine) were added. A psychrotrophic freshwater isolate of C. johnsonae was used to study the physiological versatility of this group. Exponential growth rates were found to be dependent on the temperature to which the cells used as the inocula were acclimated. Glucose incorporation and respiration were also dependent upon the acclimation temperature of the inocula. Patterns of 14CO2 evolution obtained from position-labeled [14C]glucose indicated that glucose was predominantly metabolized via the Embden-Meyerhof-Parnas pathway, which, however, was greatly reduced at 25°C when the concentration of glucose was as low as 5 μM/liter. Transport, respiration, and incorporation of glucose (0.2- to 20,000-μM/liter concentrations) into macromolecular cellular compounds were characterized by multiple Km values which were a function of substrate concentration and temperature. It appeared possible that these multiple Km values reflected the changing participation of the Embden-Meyerhof-Parnas pathway in glucose metabolism. These results may provide a physiological explanation for the selective enrichment of psychrotrophic freshwater cytophagas. Moreover, they exhibit the limits of interpreting kinetic data based on conventional heterotrophic potential measurements, especially when some complications may arise from temperature and substrate adaptations of the more versatile members of the chemoorganotrophic microflora such as C. johnsonae.

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