PROFILING A MASS MURDERER. STRUCTURAL BIOLOGY OF LYTIC BACTERIOPHAGES.

Bacteriophages (phages) are viruses that infect bacteria, and are the smallest and
most abundant biological entities on Earth. To replicate, they use the bacterial host
machinery to either i) immediately produce new progeny after infection which leads
to the death of the infected cell (lytic pathway), or ii) integrate into the bacterial
chromosome as a prophage which allows establish a symbiotic relationship between
the parties (lysogenic pathway). The interaction begins with the recognition and
adsorption of the phage on the surface of the bacterium, which determines the
specificity and host range. Most known phages have a narrow host range, usually
infecting specific strains or isolates of a particular bacterial species. For such
recognition, virions have specific proteins that bind to receptors located on the
bacterial surface, such as LPS, EPS, outer membrane proteins, fimbriae, pili and
flagella. In recent decades, the interest in the use of phages as therapeutic agents
(phage therapy) in the biological control of infections by multidrug-resistant bacteria
has increased, as well as in the development of strategies for the biocontrol of
pathogenic species in agricultural crops. In this context, understanding the molecular
mechanisms underlying phage-bacteria interactions is crucial to obtain information
on how phages affect microbial populations and how they can be used in clinical and
biotechnological applications. Here, we present our results about the high-resolution
molecular structures involved in the infectious process of lytic bacteriophages that
interact and infect bacterial strains of relevance in medicine and agriculture.