A novel glutamate-dependent acid resistance among strains belonging to the Proteeae tribe of Enterobacteriaceae

Abstract

Morganella, Providencia and Proteus strains were capable of surviving pH 2.0 for 1 h if glutamate was present. These strains did not have glutamic acid decarboxylase activity and the gadAB genes were not detected in any of these bacteria. When exposed to pH 2.0 acid shocks, the survival rate of these bacteria was significantly increased with glutamate concentrations as low as 0.3 mM in the acid media. Escherichia coli cells incubated at pH 3.4 consumed four times more glutamate and produced at least 7-fold more γ-amino butyric acid than Morganella, Providencia and Proteus strains. These results indicate that strains belonging to the Proteeae tribe might have novel glutamate dependent acid-resistance mechanisms.