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Abstract

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.