KINETICS OF ACID TOXICITY IN CULTURES OF XANTHOMONAS-CAMPESTRIS

By adding acetic, pentanoic and octanoic acids to batch cultures of Xa nthomonas campestris a close correlation between the acid concentratio n 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 a cid toxicity. As the amount of acetic acid was increased the specific growth rate dropped to 0.08 h(-1) at 5 mM and 0.07 h(-1) at 9.99 mM. P entanoic acid produced a decrease of the specific growth rate to 0.06 h(-1) at 3.92 mM. Octanoic acid produced a greater effect on the speci fic growth rate. At 0.69 mM the specific growth rate was reduced to 0. 09 h(-1) and then it dropped to 0.06 h(-1) at 1.39 mM. The lag phase l ength was increased as the result of the activation of the tolerance m echanism. The octanoic acid produced a 40 h lag in the culture contain ing 1.39 mM total acid concentration. The cells in contact with 0.69 m M octanoic acid had a lag phase of 5 h, twice that obtained in the aci d-free cultures. Acetic and pentanoic acids at 9.99 and 3.92 mM, incre ased the lag phases to 30 and 6 h, respectively. (C) 1996 Academic Pre ss Limited