Phylogenetic and phenotypic diversity of 4-chlorobenzoate-degrading bacteria isolated from soils

Twenty numerically dominant 4-chlorobenzoate (4-CBA)-degrading bacteria were isolated from agricultural soils. The isolates were able to utilize 4-CBA as a sole source of carbon and energy. A total of 65% of the isolates was identified to the species level by fatty acid methyl ester (FAME) analysis, and the isolates were strains of Micrococcus, Pseudomonas, Oerskovia, Cellulomonas, and Arthrobacter species. The chromosomal DNA patterns of the isolates obtained by polymerase chain reaction (PCR) amplification of repetitive extragenic palindromic (REP) sequences were distinct from each other. Most of the isolates grew rapidly in 4-CBA medium, but their substrate utilization capabilities were generally restricted. Plasmid DNAs were detected from 55% of the isolates, and one strain, HR7, was shown to have self-transmissible, 4-CBA degradative plasmids. 4-CBA degradative enzymes were inducible by the presence of 4-CBA and most of the isolates appeared to mineralize it through 4-hydroxybenzoate rather than 4-chlorocatechol.