Glucose decoration on wall-teichoic acid is required for phage adsorption and InlB-mediated virulence inListeria ivanovii

Abstract

Listeria ivanovii (Liv) is an intracellular Gram-positive pathogen that primarily infects ruminants, but also occasionally causes enteric infections in humans. Albeit rare, this bacterium possesses the capacity to cross the intestinal epithelium of humans, similar to its more frequently pathogenic cousin, Listeria monocytogenes (Lmo). Recent studies in Lmo have shown that specific glycosyl modifications on the cell wall-associated glycopolymers (termed wall-teichoic acid, or WTA) of Lmo are responsible for bacteriophage adsorption and retention of the major virulence factor, Internalin B (InlB). However, the relationship between InlB and WTA in Liv remains unclear. Here, we report the identification of the unique gene, liv1070 that encodes a putative glucosyltransferase in the polycistronic WTA gene cluster of the Liv WSLC 3009 genome. We found that in-frame deletion of liv1070 led to loss of the glucose substitution on WTA, as revealed by UPLC-MS analysis. Interestingly, the glucose-deficient mutant became resistant to phage B025 infection due to an inability of the phage to adsorb to the bacterial surface, a binding process mediated by the receptor-binding protein B025_Gp17. As expected, deletion of liv1070 led to loss of InlB retention to the bacterial cell wall, which corresponded to a drastic decrease in cellular invasion. Genetic complementation of liv1070 restored the characteristic phenotypes, including glucose decoration, phage adsorption, and cellular invasion. Taken together, our data demonstrate that an interplay between phage, bacteria, and host cells also exists in Listeria ivanovii, suggesting the trade-off between phage resistance and virulence attenuation may be a general feature in the Listeria genus.