Substrate Specificity and Molecular Characterization of PAH-Degrading Anaerobic Enrichment Cultures Under Methanogenic Conditions

Abstract

Over the past several years, this lab has cultivated enriched anaerobic mixed cultures capable of degrading the low-molecular-weight polycyclic aromatic hydrocarbons (PAHs), naphthalene or phenanthrene, as a sole carbon source. Characterization of the enrichment cultures by 16S rDNA analysis revealed two unique populations, though they were initiated from the same sediment source. This study set out to determine the ability of these highly enriched communities to utilize a new carbon source, and to identify the effect of this shift on the population profile. The phenanthrene-degrading culture demonstrated significant naphthalene-degrading activity; however, the naphthalene-degrading culture was unable to degrade phenanthrene. Molecular characterization of these cultures showed a single species common to both original enrichment cultures and dominating in the population able to degrade both substrates. These results suggest that very few members of the mixed cultures participate in the degradation of PAHs, whereas the remaining members live off the metabolic byproducts.