Effect of temperature, growth rate, and nutrient limitation on the yield and composition of three bacterial isolates from an arctic soil grown in continuous culture

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Abstract
Three bacterial isolates from an arctic meadow soil, Pseudomonas M216, Bacillus M153, and Arthrobacter M51, were grown continuously in carbon-and nitrogen-limiting media at 15 and 5 °C at three dilution rates from 0.04 to 0.01 h−1. Measurements of yield, viability, endogenous oxygen-uptake rate, and cell composition indicated that in general, these isolates were well adapted for growth at low rates and low temperature under nutrient limitation. Changes in cell composition with temperature, growth rate, and nutrient limitation followed patterns similar to those observed in organisms studied in other laboratories. Yields were higher at 15 than at 5 °C in Pseudomonas M216 and Arthrobacter M51 and the endogenous respiration rate tended to decrease with decreasing dilution rate. Substrate affinity (Ks) and μmax varied with temperature, and Pseudomonas M216 exhibited the lowest Ks for carbon and nitrogen and highest μmax under the growth conditions studied, except at 15 °C under carbon limitation where Arthrobacter M51 exhibited the lowest Ks. Only Bacillus M153 exhibited a significant loss in viability at low dilution rates and a detectable specific maintenance rate (0.0077 h−1), factors which may contribute to the low isolation frequency of the genus at the meadow site.