Comparison of enrichment methods for the isolation of pyrene-degrading bacteria

Pyrene is a relatively persistent 4-ring polyaromatic hydrocarbon (PAH) pollutant, and is often used as a model substrate in studies pertaining to high molecular weight PAH degradation. In this study, four previously reported enrichment methods were compared for the isolation of pyrene-degrading bacteria from an industrially contaminated soil. Each method was assessed for the ability to select for diversity and abundance of bacterial populations in liquid culture. Enrichment with pyrene and the co-substrate diesel was the most successful method in terms of diversity and abundance of culturable pyrene-degrading bacteria obtained. This was the only method that returned significantly increased numbers of isolates over those recovered from the original soil sample (p=0.029). Enrichment with pyrene and the co-substrate salicylate was the next most successful for these parameters. Pyrene and the co-substrate phenanthrene showed similar results to enrichment with pyrene alone for the selection of pyrene-degrading bacteria. The study identified an optimum enrichment technique for the isolation of PAH-degrading organisms. Six organisms were identified which may have potential application as inoculants for the bioremediation of contaminated soil.