Conjugal transfer of plasmid pNB2 to activated sludge bacteria leads to 3-chloroaniline degradation in enrichment cultures.

The involvement of the aniline-degradative plasmid pNB2 in degradation of 3-chloroaniline (3-CA) was investigated. Plate matings of a Pseudomonas putida strain containing pNB2 with a mixed bacterial culture derived from activated sludge was carried out. After inoculation of the mating mixtures into batch cultures containing 3-CA, degradation of the compound was observed. A total of five different transconjugant strains could be isolated from one of the batch cultures and two of them were able to degrade 3-CA. These two isolates were identified as Comamonas testosteroni by partial 16S rDNA sequencing. It can be assumed that pNB2 carries a part of the genes involved in the catabolism of 3-CA, but that completion of the pathway must be provided by chromosomal genes in the host strain. pNB2 is a candidate plasmid which can be used in plasmid-mediated bioaugmentation of wastewater bacteria involved in degradation of chlorinated anilines.