Effects of interfacially-driven flow on the protein expression of Escherichia coli at physiological temperature

Abstract

This investigation assessed the effects of interfacially-driven shear flow on the ability of the bacterium Escherichia coli (E. coli) to produce green fluorescent protein (GFP). Shear forces at interfaces have been shown to effect the behavior of organisms,[2] however the characteristics of these effects are relatively unstudied. Furthermore, mixing and shearing of liquid medium is important for the growth of certain bacterial species,[24] is present in many physiological systems,[1] [2] and is necessary for fluidic bioreactors.[2] In this investigation, liquid bacterial cultures were grown for 2 hours under three different shear rates, with samples collected every 30 minutes. The optical density at 600 nm of these samples was measured to gauge growth rate, and numerical analysis of SDS-PAGE gels was conducted to produce an estimate of protein productivity for a given sample. In the allotted 2 hour time frame, different shear rates we found to be of too small magnitude to significantly affect growth rate when compared to quiescent controls. Cellular protein production was shown to be independent of growth rate, with samples which achieved overall lower growth rates, expressing similar levels of cellular GFP productivity. Therefore, E. coli may be grown at altered shear rates in order to achieve desired growing, mixing, or experimental conditions, without negatively impacting the protein productivity of the bacterium.