(164aq) Effect of Alternative Sigma Factors on Metabolic Activity in E. coli

Microbial bioproduction offers several advantages compared to conventional chemical synthesis including use of renewable substrates, catalysis by highly specific enzymes, and processing under labile conditions. To be efficient, bioproduction requires a balance of energy between production of the desired metabolite and general maintenance for cellular growth and function. We hypothesize that alternative sigma factors, which are naturally used by cells to shift metabolic state, can be used similarly to direct expression and resources towards heterologous pathways. Sigma factors control the start of transcription by binding to RNA polymerase (RNAP) and subsequent promoter interaction. Competition for RNAP is thought to occur when multiple sigma factors are present, permitting rerouting of transcriptional resources. We are investigating this competition through controlled and induced expression of non-native, alternative sigma factors B, F, and G from B. subtilis in E. coli. We have shown that these sigma factors are functional in E. coli, directing expression of a GFP reporter when paired with their cognate promoter. Upon sigma factor production, we observe a decrease in cellular growth rate which we believe is due to sigma factor competition for RNAP resources. We are currently confirming our hypothesis using qRT-PCR to show the downregulation of native transcription when non-native sigma factors are present as well as apply the sigma factors to direct expression of a heterologous pathway.