Chlorobenzoate catabolism and interactions between Alcaligenes and Pseudomonas species from Bloody Run Creek

Abstract

A mixed community of bacteria from surface runoff waters of the Hyde Park industrial landfill was enriched on 3-chlorobenzoate. Alcaligenes and Pseudomonas species were dominant in the community. Alcaligenes sp. BR60 carried an unstable plasmid specifying 3-chlorobenzoate catabolism. Metabolites detected in culture supernatants included chlorocatechol and chloro-cis, cismuconic acid. Oxygen uptake in the presence of 3- and 4-substituted methyl-catechols revealed a catechol-1,2-oxygenase activity specific for substituted catechols with very limited activity for catechol. The isolate grew very slowly on benzoate. Alcaligenes sp. BR60 was isolated in co-culture with Pseudomonas fluorescens NR52. The latter contained no detectable plasmids and did not grow on benzoate or any of the chlorobenzoates in pure culture. Growth of the co-culture in Bloody Run Creek water supplemented with 3-chlorobenzoate indicated that phosphate concentrations in the water severely limited biodegradation. Under phosphate limited conditions in continuous culture, Pseudomonas fluorescens NR52 effectively scavenged available phosphate when it was present at a ratio of 1 cell to 20 of Alcaligenes sp. BR60. Under these conditions the growth of Alcaligenes sp. BR60 on 3-chlorobenzoate was reduced 5 fold, the frequency of plasmid deletion mutants increased, and 96% of the contaminant remained in the outflow in the form of the starting material or metabolites. No evidence was found for conjugation of the plasmid determining chlorobenzoate catabolism in Alcaligenes sp. BR60 to P. fluorescens NR52.