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Appl. Environ. Microbiol., Jan 1996, 26-32, Vol 62, No. 1
V Warikoo, MJ McInerney, JA Robinson and JM Suflita
Benzoate degradation by an anaerobic, syntrophic bacterium, strain SB, in
coculture with Desulfovibrio sp. strain G-11 reached a threshold value
which depended on the amount of acetate added and ranged from about 2.5 to
29.9 (mu)M. Increasing acetate concentrations also uncompetitively
inhibited benzoate degradation. The apparent V(infmax) and apparent K(infm)
for benzoate degradation decreased with increasing acetate concentration,
but the benzoate degradation capacities (V(infmax)/K(infm)) of cell
suspensions remained comparable. The addition of an acetate-using bacterium
to cocultures after the threshold was reached resulted in the degradation
of benzoate to below the detection limit. Mathematical simulations showed
that the benzoate threshold was not predicted by the inhibitory effect of
acetate on benzoate degradation kinetics. With nitrate instead of sulfate
as the terminal electron acceptor, no benzoate threshold was observed in
the presence of 20 mM acetate even though the kinetics of benzoate
degradation were slower with nitrate rather than sulfate as the electron
acceptor. When strain SB was grown with Desulfovibrio sp. strain DG2 that
had a fourfold-lower V(infmax) for hydrogen use than strain G-11, the
V(infmax) for benzoate degradation was 37-fold lower than that of strain
SB-G-11 cocultures. The Gibb's free energy for benzoate degradation was
less negative in cell suspensions with a threshold than in suspensions
without a threshold. These studies showed that the threshold was not a
function of the inhibition of benzoate degradation by acetate or the
toxicity of the undissociated form of acetate. Rather, a critical or
minimal Gibb's free energy may exist where thermodynamic constraints
preclude further benzoate degradation.
Copyright © 1996, American Society for Microbiology
Interspecies Acetate Transfer Influences the Extent of Anaerobic Benzoate Degradation by Syntrophic Consortia
Department of Botany and Microbiology, University of Oklahoma, Norman, Oklahoma 73019-0245, and Worldwide Animal Health Product Development, The UpJohn Company, Kalamazoo, Michigan 49001
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