Unique aspects of the cell surface polysaccharide of Pseudomonas phaseolicola as demonstrated by bacteriophage specificity.

Bacteriophage 12P caused lysis of Pseudomonas phaseolicola but not other pathogenic or saprophytic pseudomonads. Specificity of the bacteriophage may depend on recognition of some unique feature of the P. phaseolicola cell surface polysaccharides. Exopolysaccharide (EPS) and lipopolysaccharide (LPS) from P. phaseolicola were more efficient at inhibiting bacteriophage attachment than were identically prepared extracts from five other pseudomonad species. Mutants of P. phaseolicola with bacteriophage resistance produced EPS and LPS different in amount and composition from those of the parental strain. Thus, in some manner the EPS and LPS structures of P. phaseolicola are distinct from those of other plant pathogenic and saprophytic species. The difference may prevent recognition and initiation of resistance events when P. phaseolicola challenges its susceptible host plant, bean.