Bacterial bioconcentration of chlorinated hydrocarbon insecticides from aqueous systems

The prevalence of chlorinated hydrocarbon insecticide uptake by chemoorganotrophic bacteria has been investigated. Thirteen bacterial species were observed to sorb and concentrate (bioconcentratc)α-chlordane,β-chlordane, dieldrin, heptachlor epoxide, and lindane from aqueous systems. Bioconcentration, as expressed by the ratio of cellular insecticide in ng/mg (dry wt) to supernatant insecticide in ng/μl, ranged from 10 for lindane byEnterobacter aerogenes to a high of 55,900 forβ-chlordane byCaulobacter vibrioides var.limonus. Amounts of cellular chlorinated hydrocarbon insecticides (CHI) detected and the bioconcentration ratios were observed to have the following order in magnitude:α- orβ-chlordane > dieldrin > heptachlor epoxide > lindane. This decreasing order was the inverse of reported water solubilities for the CHI and the inverse relationship was mathematically defined. The CHI were not easily removed from cells by washing (desorbing) and desorption was directly proportional to insecticide water solubility. Uptake of the CHI was rapid, near-maximum amounts being sorbed within 15 min, and pH 7 appeared optimal for bioconcentration as examined over the range pH 6 to 8. Implications of this investigation are that bioconcentration of CHI by bacteria might serve as a means of introducing these toxic compounds into aquatic food chains and that the bioconcentration phenomenon might lend itself as a treatment procedure for the intentional removal of residual CHI from water supplies and wastewater.