Glucose Decoration on Wall Teichoic Acid Is Required for Phage Adsorption and InIB-Mediated Virulence in Listeria ivanovii

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 [WTA]) of Lmo are responsible for bacteriophage adsorption and retention of the major virulence factor internalin B (InIB). However, the relationship between InIB and WTA in Liv remains unclear. Here, we report the identification of the unique gene liv1070, which 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 ultraperformance liquid chromatography-mass spectrometry (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 InIB retention on 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 that the trade-off between phage resistance and virulence attenuation may be a general feature in the genus Listeria. IMPORTANCE Listeria ivanovii is a Gram-positive bacterial pathogen known to cause enteric infection in rodents and ruminants and occasionally in immunocompromised humans. Recent investigations revealed that in its better-known cousin Listeria monocytogenes, strains develop resistance to bacteriophage attack due to loss of glycosylated surface receptors, which subsequently results in disconnection of one of the bacterium's major virulence factors, InIB. However, the situation in L ivanovii remains unclear. Here, we show that L ivanovii acquires phage resistance following deletion of a unique glycosyltransferase. This deletion also leads to dysfunction of InIB, making the resulting strain unable to invade host cells. Overall, this study suggests that the interplay between phage, bacteria, and the host may be a feature common to the genus Listeria.

Automated summary

This study reveals that Listeria ivanovii interacts with phages, bacteria, and host cells, suggesting a common feature in the genus Listeria. Deletion of a unique glycosyltransferase in L ivanovii led to phage resistance and dysfunction of a major virulence factor, resulting in the strain's inability to invade host cells.