KINETIC COMPARISON OF 7 STRAINS OF 2,4-DICHLOROPHENOXYACETIC ACID-DEGRADING BACTERIA

Seven strains of 2,4-dichlorophenoxyacetic acid-degrading bacteria, including Pseudomonas, Alcaligenes, and Bordetella spp., were compared on the basis of growth kinetics. Estimates of maximum growth rate (mu(max), k1) and half-saturation growth constant (K(s), k3) were obtained by fitting substrate depletion curves to a four-parameter version of the integrated Monod equation. Estimates of K(s) ranged from 2.2-mu-g/ml (10-mu-M) to 33.8-mu-g/ml (154-mu-M), and estimates of mu(max) ranged from 0.20 h-1 (T(d) = 3.5 h) to 0.32 h-1 (T(d) = 2.2 h). Estimates of mu(max), but not K(s), were affected by changes in initial inoculum density. Maximum growth rates mu(max) were also estimated from turbidity measurements. They ranged from 0.10 h-1 (T(d) = 6.9 h) to 1.0 h-1 (T(d) = 0.7 h). There was no correlation between estimates of mu(max) derived from substrate depletion curves and those derived from turbidity measurements (P = 0.20).