Kinetics of acid toxicity in cultures of Xanthomonas campestris

By adding acetic, pentanoic and octanoic acids to batch cultures of Xanthomonas campestrisa close correlation between the acid concentration and the length of the lag phase and the value of the specific growth rate was obtained. The specific growth rate was largely affected by acid toxicity. As the amount of acetic acid was increased the specific growth rate dropped to 0.08 h −1at 5 m Mand 0.07 h −1at 9.99 m M. Pentanoic acid produced a decrease of the specific growth rate to 0.06 h −1at 3.92 m M. Octanoic acid produced a greater effect on the specific growth rate. At 0.69 m Mthe specific growth rate was reduced to 0.09 h −1and then it dropped to 0.06 h −1at 1.39 m M. The lag phase length was increased as the result of the activation of the tolerance mechanism. The octanoic acid produced a 40 h lag in the culture containing 1.39 m Mtotal acid concentration. The cells in contact with 0.69 m Moctanoic acid had a lag phase of 5 h, twice that obtained in the acid-free cultures. Acetic and pentanoic acids at 9.99 and 3.92 m M, increased the lag phases to 30 and 6 h, respectively.