Aromatic hydrocarbon degradation genes from chronically polluted Subantarctic marine sediments

Abstract

Aim: The goal of this study was to identify functional targets to detect polycyclic aromatic hydrocarbon (PAH)-degrading bacterial populations in cold marine ecosystems.

Methods and results: We designed a degenerate primer set targeting genes encoding the alpha subunit of PAH-dioxygenases from Gram-positive bacteria. This primer set was used to amplify gene fragments from metagenomic DNA isolated from Subantarctic marine sediments (Ushuaia Bay, Argentina). These gene fragments were cloned and sequenced. We identified 14 distinct groups of genes, most of them showing significant relatedness with dioxygenases from Gram-positive bacteria of the genera Rhodococcus, Mycobacterium, Nocardioides, Terrabacter and Bacillus. The level of identity with these genes, however, was low to moderate (33-62% at the amino acid level).

Conclusion: These results indicate the presence of a high diversity of hitherto unidentified dioxygenase genes in this cold polluted environment.

Significance and impact of the study: Subantarctic marine ecosystems are particularly vulnerable to hydrocarbon pollution, and the development of environmental restoration strategies for these environments is pressing. The information obtained in this work will be the starting point for the design of quantitative molecular tools to analyse the abundance and dynamics of these aromatic hydrocarbon-degrading bacterial populations in the marine environment.