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Appl. Environ. Microbiol., Dec 1995, 4152-4159, Vol 61, No. 12
CB Miguez, CW Greer, JM Ingram and RA MacLeod
The mechanism of uptake of benzoic and 2,4-dichlorobenzoic acid (2,4-DCBA)
by Alcaligenes denitrificans BRI 3010 and BRI 6011 and Pseudomonas sp.
strain B13, three organisms capable of degrading various isomers of
chlorinated benzoic acids, was investigated. In all three organisms, uptake
of benzoic acid was inducible. For benzoic acid uptake into BRI 3010,
monophasic saturation kinetics with apparent K(infm) and V(infmax) values
of 1.4 (mu)M and 3.2 nmol/min/mg of cell dry weight, respectively, were
obtained. For BRI 6011, biphasic saturation kinetics were observed,
suggesting the presence of two uptake systems for benzoic acid with
distinct K(infm) (0.72 and 5.3 (mu)M) and V(infmax) (3.3 and 4.6
nmol/min/mg of cell dry weight) values. BRI 3010 and BRI 6011 accumulated
benzoic acid against a concentration gradient by a factor of 8 and 10,
respectively. A wide range of structural analogs, at 50-fold excess
concentrations, inhibited benzoic acid uptake by BRI 3010 and BRI 6011,
whereas with B13, only 3-chlorobenzoic acid was an effective inhibitor. For
BRI 3010 and BRI 6011, the inhibition by the structural analogs was not of
a competitive nature. Uptake of benzoic acid by BRI 3010 and BRI 6011 was
inhibited by KCN, by the protonophore 3,5,3(prm1),
4(prm1)-tetrachlorosalicylanilide (TCS), and, for BRI 6011, by anaerobiosis
unless nitrate was present, thus indicating that energy was required for
the uptake process. Uptake of 2,4-DCBA by BRI 6011 was constitutive and
saturation uptake kinetics were not observed. Uptake of 2,4-DCBA by BRI
6011 was inhibited by KCN, TCS, and anaerobiosis even if nitrate was
present, but the compound was not accumulated intracellularly against a
concentration gradient. Uptake of 2,4-DCBA by BRI 6011 appears to occur by
passive diffusion into the cell down its concentration gradient, which is
maintained by the intracellular metabolism of the compound. This process
could play an important role in the degradation of xenobiotic compounds by
microorganisms.
Copyright © 1995, American Society for Microbiology
Uptake of Benzoic Acid and Chloro-Substituted Benzoic Acids by Alcaligenes denitrificans BRI 3010 and BRI 6011
Department of Natural Resource Sciences, McGill University, Ste. Anne de Bellevue, Quebec, Canada H9X 1C0, and Environmental Engineering, Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec, Canada H4P 2R2
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