Pivotal role of O-antigenic polysaccharide display in the sensitivity against phage tail-like particles in environmental Pseudomonas kin competition

Environmental pseudomonads colonize various niches including
insect and plant environments. When invading these environments, bacteria
are confronted with the resident microbiota. To cope with closely related
strains they deploy narrow-spectrum weaponry such as tailocins, i.e phage
tail-like particles. Little is known about the receptors for these
tailocins especially among phylogenetically closely related species. Here,
we studied the interaction between an R-tailocin from Pseudomonas
protegens CHA0 and a targeted kin, Pseudomonas protegens Pf-5. Using
genome-wide transposon insertion sequencing, we identified that
lipopolysaccharides are involved in the sensitivity of Pf-5 towards the
tailocin of CHA0. By generating Pf-5 lipopolysaccharide mutants and
exposing them to extracted tailocin, we specified the two O-antigenic
polysaccharides (O-PS) targeted by the tailocin. We affirmed the role of
these O-PS through competition assays in vitro as well as in insects.
Further, we demonstrate that O-PS are double-edge swords that are
responsible for the sensitivity of P. protegens towards phage tail-like
particles produced by their kin, but shield bacteria from the immune
system of the insect. Our results shed light on the trade-off that
bacteria are confronted with, where specific O-PS decorations can both be
of benefit or disadvantage depending on the host environment and its
bacterial inhabitants.