Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Recent fluctuations in oil prices and 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. In this study, we performed a proteome analysis to identify differentially expressed proteins in the presence of octanoic acid, expecting to elucidate its toxicity mechanism, which could, in turn, be used to describe toxicity mechanisms of other polyketide-based molecules. Differential two-dimensional gel electrophoresis and MS analysis enabled the identification of the differentially expressed proteins that exhibited the largest change in expression. 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. Proteins PoxB (down-regulated) and TrxA (up-regulated) were identified by gel-matching methods using online databases. Subsequent metabolic and biochemical analyses have been focused on OmpF, due to its importance in transport of fatty acids and key nutrients across the membrane, as well as most likely affecting membrane fluidity. The remaining proteins, which can be mainly divided into structural, transport, and oxidative stress functions, have also sparked new hypotheses about fatty acid toxicity mechanisms and will be studied to develop design strategies for a strain that is highly-tolerant to short-chain fatty acids.