Anaerobic degradation of PAHs by TRIP

The anaerobic enrichment culture TRIP from Pitch Lake in Trinidad has been shown to degrade phenanthrene with sulfate as electron acceptor. Recent proteogenomic studies indicate that the main organism, cand. Desulfatiglans TRIP_1, which is thought to degrade phenanthrene, might also be able to degrade methylated aromatic compounds. The aim of the study presented here is to identify whether and how 2- and 3-methylphenanthrene are degraded by the TRIP culture. In accordance with previous studies, growth curves based on cell count reveal steady growth behavior with phenanthrene as substrate, as well as sulfate depletion and corresponding CO2 production. Experiments with the two isomers of methylphenanthrene indicate that TRIP is unable to degrade the methylated compounds, as neither consistent cell growth nor sulfate depletion and CO2 production could be seen. Putative metabolites from the hypothetical degradation pathway of methylphenanthrene and previously detected metabolites from phenanthrene degradation were searched. For this, cell free extracts of culture samples taken after 6 and 12 weeks of growth were subjected GC-MS. However, no metabolites of any of the three substrates could be detected, which is primarily attributed to too little cell numbers in all cultures and hence oo low concentrations of eventually produced metabolites. Furthermore, the crude oil degradation potential of the TRIP culture was investigated. Crude oil samples that had been incubated with TRIP and a second anaerobic enrichment culture from Pitch Lake for 16 months were analyzed regarding the molecular composition of the oil using FT-ICR-MS. The observation that the oil seemed to be left unaltered after 16 months indicates that none of the cultures is able to use it as carbon source in the given timeframe