Controlling the Growth Rate of Escherichia coli by Limiting the Supply of Carbon in an Amylose-Amylase Nutrient System.

Abstract

Bacteria in their natural habitat are often faced with adequate yet poor environmental conditions that limit their growth. Under such conditions, Escherichia coli ( E. coli ) cells have been shown to adapt and respond to their environment by altering the transcription of many genes involved in carbon and energy metabolism as well as the uptake of available carbon sources. Furthermore, previous studies have demonstrated that in environments with limiting nutrient, the rate of growth becomes proportional to the extracellular concentration of the limiting nutrient. In this study, such principles were exploited to devise a method by which the growth rate of E. coli could be specifically controlled through a controlled maltose-liberating amylose-amylase system. The effect of different amylase concentrations on the growth rate of E. coli in minimal media containing amylose were evaluated by turbidity-based growth curves. Our study suggested that there were no significant differences between the growth rates of the cells grown in the presence of different amylase concentrations. However, the cell production levels appeared to increase with increasing concentrations of the amylase. The similar growth rates could arise if the levels of maltose produced by the amylase are sufficient to saturate transport. The different production levels corresponded with different lag phases, and might indicate that the cells are sufficiently damaged or stressed at levels of maltose that are insufficient to sustain growth increases.