Naphthalene-utilizing and mercury-resistant bacteria isolated from an acidic environment

Soil samples were taken from areas of low pH (2.5-3.5) surrounding an outdoor coal storage pile. These samples were added to medium with naphthalene as the sole carbon source to enrich for organisms capable of degrading polycyclic aromatic hydrocarbons (PAH) at low pH. Five such bacterial strains were isolated. Sequencing of the 16S rDNA showed them to be members of the genera Clavibacter, Arthrobacter and Acidocella. These organisms were all capable of growth with naphthalene as a sole carbon source at low pH. The genes nahAc, nahAd, phnAc, nahH, xylE or GST, which are known to be associated with PAH degradation were not detected. Isolate 10, the Acidocella strain, tolerated high levels of mercury. PCR amplification and sequencing of genes from the mer operon from isolate 10 DNA suggested that mercury is transported into the bacterial cell and subsequently detoxified since the enzymes encoded by genes in this operon are involved in these processes.