DIVERSITY AMONG AROMATIC HYDROCARBON-DEGRADING BACTERIA AND THEIR META-CLEAVAGE GENES

Sixty-one strains of bacteria capable of growth on 4-methyl benzoic ac id (29 isolates) or naphthalene (32 isolates) as the sole source of ca rbon and energy were isolated from sediments and water samples from th e River Tyne, UK. Random amplification of polymorphic DNA from genomic DNA extracted from the different strains demonstrated that 14 of the 4-methyl benzoate-degrading isolates were unique and the remainder fel l into seven groups containing two or three isolates that produced ide ntical banding patterns. Thirteen of the naphthalene-degrading isolate s were unique and nine groups with two or three identical representati ves encompassed all other isolates. Screening of the bacterial strains for the presence of genes homologous to xylE, nahC and bphC by polyme rase chain reaction and dot blot hybridization demonstrated that most strains harboured xylE- and/or nahC-like genes and only a single isola te was found that did not harbour any of these genes. None of the isol ates harboured bphC-like genes. It was concluded that, while considera ble diversity existed in host strains isolated using a single simple e nrichment procedure, the extradiol dioxygenase genes involved in aroma tic ring cleavage, present in these strains, were conserved to a consi derable degree.