Glucose and glucose 6-phosphate as carbon sources in extra- and intracellular growth of enteroinvasive Escherichia coli and Salmonella enterica

Abstract

To study the role of carbohydrates, in particular glucose, glucose 6-phosphate and mannose, as carbon substrates for extra- and intracellular replication of facultative intracellular enteric bacteria, mutants of two enteroinvasiveEscherichia coli(EIEC) strains and aSalmonella entericaserovar Typhimurium isolate were constructed that were defective in the uptake of glucose and mannose (ΔptsG,manXYZ), glucose 6-phosphate (ΔuhpT) or all three carbohydrates (ΔptsG,manXYZ,uhpT). The ability of these mutants to grow in RPMI medium containing the respective carbohydrates and in Caco-2 cells was compared with that of the corresponding wild-type strains. In the three strains, deletions ofptsG,manXYZoruhpTresulted in considerably different levels of inhibition of growthin vitroin the presence of glucose, mannose and glucose 6-phosphate, respectively, but hardly reduced their capability for intracellular replication in Caco-2 cells. Even the triple mutants ΔptsG,manXYZ,uhpTof the three enterobacterial strains were still able to replicate in Caco-2 cells, albeit at strain-specific lower rates than the corresponding wild-type strains.