Changes in growth parameters of Pseudomonas pseudoalcaligenes after ten months culturing at increasing temperature

Abstract In this paper, we report the thermal adaptation of Pseudomonas pseudoalcaligenes, characterized as changes in growth parameters. Six clones derived from a single colony of P. pseudoalcaligenes were cultured in two different temperature regimes for 10 months, with three clones forming the control group, cultured at a constant temperature, and another three clones forming the high-temperature (HT) group, cultured at increasing temperature (from 41 to 47 degrees C). Three growth parameters were measured: the lag time (lambda), which is the period between the time of transfer to a new medium and the time when the cell replication starts; the maximum growth rate (mu(m)); and the maximum yield (A). These three parameters are major components of bacterial fitness. The Gompertz and logistic models were used to estimate these three parameters. The two models gave almost identical estimates, but the Gompertz model had R(2) values consistently larger than the logistic model. The HT clones had significantly shorter lambda, but higher mu(m) and A than the control clones when both were grown at the originally stressful temperature of 45 degrees C, suggesting significant thermal adaptation. Interestingly, the HT clones grew equally well as the control clones at 35 degrees C, i.e. improved performance at 45 degrees C was not associated with a reduced performance at 35 degrees C.