The effect of pH on the selection of carbaryl‐degrading bacteria from garden soil

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Abstract
At an alkaline pH and in an aqueous solution carbaryl hydrolyzes to form 1-naphthol, methylamine and CO2, but it is much more stable at an acid pH. Soil perfusion column experiments indicated that the rate of carbaryl degradation at pH 6.0-7.0 was limited by the rate of chemical hydrolysis. Bacterial communities of at least 12 and 14 members were selected in continuous cultures using carbaryl as the sole C and N source at pH 6.0. These communities were supported by the slow formation of hydrolysis products and a carbaryl-degrading bacterium was not selected after > 2000 h. A bacterial community of at least 8 members was selected using equimolar 1-naphthol and methylamine as its sole C and N source. In contrast, after a lag of between 10-50 days, soil perfusion column and continuous culture enrichments at pH 5.2 and 5.0, respectively, led to the selection of a Pseudomonas sp. which could utilize carbaryl as its sole C and N source.