Degradation capacity of a 1,2,4-trichlorobenzene mineralizing microbial community for traces of organochlorine pesticides

A soil-borne microbial community isolated from a contaminated site was previously shown to mineralize 1,2,4-trichlorobenzene (1,2,4-TCB) under aerobic conditions. The key degrader in this community was identified as Bordetella sp. F2. The objective of the study was to test the capacity of the microbial community to degrade a complex mixture of 27 organochlorine compounds and pesticides (OCPs) commonly detected in the environment. The hypothesis was that the microbes would utilize the OCPs as carbon sources at the low concentrations of these compounds, found in natural waters and soil solution. The study was carried out in liquid culture and the changes in concentration of the OCPs were monitored using GC-MS. Data analysis was done using a multivariate analysis method similar to Principal Response Curve (PRC) analysis. Contrary to expectations, the data analysis showed a general trend where higher concentrations were observed in the microbially treated samples relative to the controls. The observed trend was attributed to decreased volatilization due to sorption of the chemicals by microbes since most of the compounds in the cocktail had high Kow values. Nevertheless, when using adequate statistical methods for analysing the very complex data set, correlation of Kow and KH values with the loadings of the PRCs showed that three chlorinated mono-aromatics — pentachlorobenzene, pentachloroanisole and octachloroanisole — were amenable to degradation. This provided indications that the community could hold promise for the degradation of higher-chlorinated mono-aromatic OCPs.