Glucose can be transported and utilized in Escherichia coli by an altered or overproduced N-acetylglucosamine phosphotransferase system (PTS).

Abstract

Escherichia coli Δglk ΔmanZ ΔptsG glucose- strains that lack the glucose phosphotransferase system (PTS) and the mannose PTS as well as glucokinase have been widely used by researchers studying the PTS. In this study we show that both fast- and slow-growing spontaneous glucose+ revertants can be readily obtained from Δglk ΔmanZ ΔptsG glucose- strains. All of the fast-growing revertants either altered the N-acetylglucosamine PTS or caused its overproduction by inactivating the NagC repressor protein, which regulates the N-acetylglucosamine PTS, and these revertants could utilize either glucose or N-acetylglucosamine as a sole carbon source. When a ΔnagE deletion, which abolishes the N-acetylglucosamine PTS, was introduced into the Δglk ΔmanZ ΔptsG glucose- strains, fast-growing revertants could no longer be isolated. Based on our results and other studies, it is clear that the N-acetylglucosamine PTS is the most easily adaptable PTS for transporting and phosphorylating glucose, other than the glucose PTS and mannose PTS, which are the primary glucose transport systems. While the slow-growing glucose+revertants were not characterized, they were likely mutations that other researchers have observed before and affect other PTSs or sugar kinases.