title: Growth rates of a pseudomonad on 2,4-dichlorophenoxyacetic acid and 2,4-dichlorophenol.
abstract: The growth of a pseudomonad on 2,4-D (2,4-dichlorophenoxyacetic acid) and 2,4-DCP (2,4-dichlorophenol) was studied in batch and continuous culture. The optimum growth rate using 2,4-D was 0.14/h at 25 C in a pH range from 6.2 to 6.9. Highest specific growth rate using 2,4-DCP was 0.12/h at 25 C in a pH range from 7.1 to 7.8. Growth was strongly inhibited by 2,4-DCP above a concentration of 25 mg/liter whereas no appreciable inhibition was observed with 2,4-D at concentrations up to 2,000 mg per liter. Growth on 2,4-DCP was described by Monod kinetics at subinhibitory concentrations but the inhibition by 2,4-DCP exhibited an unusual linear response to substrate concentration, and did not fit a model based on noncompetitive inhibition. The lag phase of batch cultures was found to depend on both 2,4-DCP concentration and prior adaptation of the inoculum. A study such as this on the kinetics of growth on related substrates may be useful as a method of finding the rate-limiting step in a metabolic sequence.
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology*; D005470:Fluorometry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D010636:Phenols / Q000494:pharmacology*; D011549:Pseudomonas / Q000187:drug effects / Q000254:growth & development*; D013696:Temperature; D014871:Water Microbiology
chemical_list: D007220:Industrial Waste; D010636:Phenols; D015084:2,4-Dichlorophenoxyacetic Acid