Two distinct gene clusters encode pyrene degradation in Mycobacterium sp. strain S65

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) like pyrene are persistent environmental pollutants from fuel combustion.
• Microbial degradation is a key process for remediating PAH-contaminated sites.
• Understanding the genetic basis of PAH degradation in bacteria is crucial for bioremediation strategies.

Purpose of the Study:

• To isolate and characterize a bacterium capable of degrading pyrene.
• To investigate the genetic organization and regulation of pyrene degradation genes in the isolated strain.
• To explore the potential for enhanced pyrene mineralization through co-substrates.

Main Methods:

• Isolation and identification of a pyrene-degrading bacterium (Mycobacterium sp. strain S65).
• Growth experiments using various PAHs as sole carbon sources and co-substrates.
• Southern hybridization to identify dioxygenase gene homologues.
• RT-PCR to analyze gene expression during growth on different carbon sources.

Main Results:

• Mycobacterium sp. strain S65 was isolated and shown to utilize pyrene, phenanthrene, and fluoranthene.
• Two distinct gene clusters, each containing dioxygenase and alcohol dehydrogenase genes, were identified in strain S65.
• Gene expression analysis confirmed induction of these clusters during growth on pyrene and phenanthrene.
• Pyrene degradation was enhanced by co-substrates like benz[a]anthracene and benzo[a]pyrene.

Conclusions:

• Mycobacterium sp. strain S65 is a promising agent for pyrene bioremediation.
• The presence of two separate pyrene degradation gene clusters suggests genome duplication events and provides a model for studying PAH degradation evolution.
• Further research into these gene clusters can advance our understanding of high-molecular-weight PAH metabolism in bacteria.