Transfer of the catabolic plasmid RP4::Tn4371 to indigenous soil bacteria and its effect on respiration and biphenyl breakdown

Abstract

The catabolic plasmid RP4::Tn4371, containing the genes for biphenyl and 4-chlorobiphenyl catabolism, was transferred from Enterobacter agglomerans DMK3 to indigenous bacteria in biphenyl amended sandy soil, although the donor survived for only 3 days. Proliferation of transconjugants above a detectable level required presence of the concomitant pollutant biphenyl. Different Gram-negative bacterial species, tentatively identified as Pseudomonas chlororaphis, Pseudomonas corrugata and Comamonas sp., had taken up the plasmid and were able to express the biphenyl degradation genes. These genera have, until now, not been reported to express the biphenyl degradative genes. The soil had a high natural catabolic capacity for biphenyl. Notwithstanding this, out of 8 trials in which DMK3 was inoculated, 2 were found not to respond but 6 had an increased biphenyl degradation and concomitant increased oxygen consumption. The results indicate that seeding of RP4::Tn4371 generates a variety of transconjugants and holds potential for increasing the soil biodegradation capacity towards chlorinated biphenyl analogues. © 1994.