P162: Proteome analysis to study the response of Escherichia coli to toxic concentrations of fatty acids

Recent fluctuations in oil prices and the undesired gas emissions from operation of petrochemical industries have sparked widespread interest in the microbial production of carbon-based chemicals from biorenewable sources. Small polyketide-based molecules, such as short-chain fatty acids, are of special value for the chemical industry due to the wide range of products that can be derived from them.  However, a limiting factor for the microbial production of these molecules is their high toxicity.

By studying the response of E. coli to the presence of octanoic acid (C_8:0) in the medium, we expect to elucidate its toxicity mechanism, which could, in turn, be used to describe toxicity mechanisms of other polyketide-based molecules.  In this study, we performed a proteome analysis to identify differentially expressed proteins in the presence of octanoic acid.  Differential two-dimensional gel electrophoresis allowed the detection of more than 60 proteins that exhibited a greater than 5-fold differential expression in cultures exposed to octanoic acid.  Ten of these proteins, which exhibited the largest change in expression level, were identified via MS analysis: SodA, SodB, OmpF, PtsH, and PpiB were down-regulated in the presence of octanoic acid, while FliC, PflB, Lpd, RpsA, and Eno were up-regulated under the same conditions. These proteins, which can be mainly divided into structural, transport, and oxidative stress functions, have sparked new hypothesis about fatty acid toxicity mechanisms and are currently under study to develop design strategies for a strain that is highly-tolerant to short-chain fatty acids.