Characterisation of a Listeria monocytogenes mutant deficient in D-arabitol fermentation.

We selected and analysed a Tn917-lac Listeria monocytogenes mutant deficient in D-arabitol fermentation. Comparison of the 310-aa-long translated partial sequence of the disrupted gene with known proteins showed similarity with the phosphotransferase system galactitol-specific enzyme IIC component of the alkaliphilic Bacillus halodurans (50% identity) and of Escherichia coli (36% identity). Fermentation of 18 other carbohydrates was unimpaired, suggesting the specificity of this transmembrane permease IIC for the pentitol D-arabitol. The deficiency in D-arabitol fermentation did not alter L. monocytogenes virulence in the BALB/c mouse model after intravenous and intragastric inoculations. This fully virulent mutant is a valuable tool to study L. monocytogenes oral infection, since the antibiotic resistance marker present on the Tn917-lac transposon will efficiently select L. monocytogenes against the intestinal microflora.