Characterization of 3-chlorobenzoate degrading aerobic bacteria isolated under various environmental conditions

The rates of bacterial growth in nature are often restricted by low concent rations of oxygen or carbon substrates. In the present study the metabolic properties of 24 isolates that had been isolated using various concentratio ns of 3-chlorobenzoate, benzoate and oxygen as well as using continuous cul ture at high and low growth rates were determined to investigate the effect s of these parameters on the metabolism of monoaromatic compounds. Bacteria were enriched from different sampling sites and subsequently isolated. In batch culture this was done both under low oxygen (2% O-2) and air-saturate d concentrations. Chemostat enrichments were performed under either oxygen or 3-chlorobenzoate limiting conditions. Bacteria metabolizing aromatics wi th gentisate or protocatechuate as intermediates (gp bacteria) as well as b acteria metabolizing aromatic compounds via catechols (cat bacteria) were i solated from batch cultures when either benzoate or 3CBA were used as C sou rces, regardless of the enrichment conditions applied. In contrast, enrichm ents performed in chemostats at low dilution rates resulted in gp-type orga nisms only, whereas at high dilution rates cat-type organisms were enriched , irrespective of the oxygen and 3-chlorobenzoate concentration used during enrichment. It is noteworthy that the gp-type of bacteria possessed relati vely low Irm, values on 3CBA and benzoate along with relatively high substr ate and oxygen affinities for these compounds. This is in contrast with cat -type of bacteria, which seemed to be characterized by high maximum specifi c growth rates on the aromatic substrates and relatively high apparent half saturation constants. In contrast, bacteria degrading chlorobenzoate via g entisate or protocatechuate may possibly be better adapted to conditions le ading to growth at reduced rates such as low oxygen and low substrate conce ntrations. (C) 2000 Federation of European Microbiological Societies. Publi shed by Elsevier Science B.V. All rights reserved.