Sweet and sour: how cell surface glycosylation affects phage sensitivity and virulence
Martin J. Loessner
Bacteriophages frequently use cell-wall carbohydrates as specific ligands for recognition and binding, important for both entry and exit from a bacterial host cell. While phage challenge may result in altered surface glycosylation of resistant bacteria, these mutants often suffer from significant trade-offs between gain of phage insensitivity and attenuation of virulence, environmental fitness, or other properties. I will present the case of the Gram-positive pathogen Listeria monocytogenes, where phage-induced loss of specific sugars from cell wall teichoic acids results in serovar conversion and lack of cell wall-associated virulence factors.
License to lyse: factors impacting endolysin lytic action on Gram-positive bacteria
Recombinant phage endolysins can in general access the cell wall of Gram-positive bacteria because these lack an outer membrane. Under favourable conditions, the enzymes can cut the cell wall and cause cell lysis, setting the basis for their exploration as enzybiotics. However, in conditions promoting bacterial growth, cells can be much less susceptible to endolysin attack. In this talk I will present factors involved in this endolysin tolerance and how to subvert it to improve lysis. I will also briefly mention other endolysin features that have been, so far, mostly disregarded.
Plaque development reveals a mode of bacterial tolerance to phage
We investigated plaque development by lytic phages infecting their Bacillus subtilis host. We revealed that plaque spread is limited by activation of a transient phage tolerance response in non-infected bacteria in response to lysis of their neighbors.
This temporary tolerance is achieved by remodeling of bacterial surface components to restrict phage attachment.