Network Analysis for Prioritizing Biodegradation Metabolites of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons
(PAHs) are a diverse group of
environmental contaminants released during the combustion of organic
materials and the production and utilization of fossil fuels. Once
released, PAHs deposit in soil and water bodies where they are subjected
to environmental transport and transformations. As they degrade, intermediate
transformation products may play an important role in their environmental
impact. However, studying the effects of these degradation products
has proven challenging because of the complexity, transience, and
low concentration of many intermediates. Herein, a novel integration
of a pathway prediction system and network theory was developed and
applied to a set of four PAHs to demonstrate a possible solution to
this challenge. Network analysis techniques were employed to refine
the thousands of potential outputs and elucidate compounds of interest.
Using these tools, we determined correlations between PAH degradation
network data and intermediate metabolite structures, gaining information
about the chemical characteristics of compounds based on their placement
within the degradation network. Upon applying our developed filtering
algorithm, we are able to predict up to 48% of the most common transformation
products identified in a comprehensive empirical literature review.
Additionally, our integrated approach uncovers potential metabolites
which connect those found by past empirical studies but are currently
undetected, thereby filling in the gaps of information in PAH degradation
pathways.