Speaker: Stefanie Barbirz, Medical School Berlin, Germany
Host: Marta Bally, Department of Clinical Microbiology
About the lecture:
The encounter with a cellular boundary is a central step in a viral life cycle to start transfer of genet-ic material into a host cell. Bacteriophages meet a plethora of bacterial surface structures, most of them highly diverse envelope glycans, but also glycan-based biofilms. Phage-host co-existence in these glycan matrices is tightly balanced, as they play dual roles both as protective shields and as phage receptors.
This talk will give an overview on how bacteriophages interact with polysaccha-rides as part of the bacterial envelope or of biofilms. We have analyzed bacteriophage mobility in polysaccharide-based biofilms by defining microviscosity parameters of the glycan matrix. We show which strategies phages have developed to remain mobile in highly viscous biofilms. Tailed bacteri-ophages infecting Gram-negative bacteria can use the outer O-antigen polysaccharide layer for infection. The interaction with this major outer membrane component has high regulatory impact on bacteriophages. In intact cells, the O-antigen serves as infection control point, whereas in outer membrane vesicles, the O-antigen mediates extracellular phage concentrations. In addition, isolat-ed lipopolysaccharide (LPS) fragments form membrane-like assemblies exposing O-antigen to inac-tivate phages. Using a set of Salmonella model phages of different tail architectures we show that phage particles work as molecular machines that can be triggered to release their DNA by O-antigen containing membranes. We show how the interplay of bacteriophage enzymatic activity, OM prop-erties and phage tail architecture leads to opening of the phage particle, illustrating the high regula-tory power of bacterial envelope glycans on bacteriophage infection
Integrated Biomedical Science Seminars: is a broad, open seminar series within life science.