Genetic Basis of Naphthalene and Phenanthrene Degradation by Phyllosphere Bacterial Strains Alcaligenes faecalis and Alcaligenes sp. 11SO

Abstract

Two bacterial strains, Alcaligenes feacalis and Alcaligenes sp. 11SO isolated from the phyllosphere of four ornamental plant species, Ixora chinensis, Ervatamia divaricata, Hibiscus rosa-sinensis and Amaranthus cruentus found in five highly polluted sites in Sri Lanka, showed a higher level of phenanthrene and naphthalene degradation ability. Both these strains harbor plasmids conferring them resistance to ampicillin. Curing of these strains of their plasmid drastically reduced the ability to degrade the hydrocarbons. Upon transformation of these plasmids into E.coli JM109 enable it to degrade the two hydrocarbons efficiently. Plasmid encoded phenanthrene and naphthalene degradation suggested the presence of required catabolic genes in these plasmids. PCR amplification with degenerate primers and comparison of their nucleotide sequences with Genbank sequences indicated that plasmids of those bacterial strains harbor the genes nahR, nahU involved in naphthalene degradation and phnG for phenanthrene degradation. RFLP and nucleotide sequence comparison of nahU and nahR amplicons revealed that both of these genes in two bacterial strains are homologous. But, phnG gene copies of two bacterial strains exist as two distinct alleles.