Transposon-induced mutations in two loci of Listeria monocytogenes serotype 1/2a result in phage resistance and lack of N-acetylglucosamine in the teichoic acid of the cell wall

Teichoic acid-associated N-acetylglucosamine and rhamnose have been shown t o serve as phage receptors in Listeria monocytogenes serotype 1/2a, We gene rated and characterized two single-copy Tn916 Delta E mutants which were re sistant to phage A118 and several other serotype 1/2a-specific phages. In o ne mutant the insertion was immediately upstream of the recently identified ptsHI locus, which encodes two proteins of the phosphoenolpyruvate-depende nt carbohydrate uptake system, whereas in the other the insertion was immed iately upstream of an operon whose most distal gene was clpC, involved in s tress responses and virulence. Transduction experiments confirmed the assoc iation of the phage-resistant phenotype of these mutants with the transposo n insertion. Phage A118 resistance of the mutants could be attributed to in ability of the phage to adsorb onto the mutant cells, and biochemical analy sis of cell wall composition showed that the teichoic acids of both mutants were deficient in N-acectylglucosamine. Rhamnose and other teichoic acid a nd cell wall components were not affected.