Structural diversity of O-polysaccharides and serological classification of Pseudomonas syringae pv. garcae and other strains of genomospecies 4

Novel O-serotypes were revealed among Pseudomonas syringae pv. garcae strains by using a set of mouse monoclonal antibodies specific to the lipopolysaccharide O-polysaccharide. Structural studies showed that the O-polysaccharide of P. syringae pv. garcae NCPPB 2708 is a hitherto unknown linear L-rhamnan lacking strict regularity and having two oligosaccharide repeating units I and II, which differ in the position of substitution in one of the rhamnose residues and have the following structures: (I: arrow right 3)- alpha -L-Rha (1 arrow right 2)- alpha -L-Rha (1 arrow right 2)- alpha -L-Rha-(1 arrow right 3)- alpha -L-Rha (1 arrow right ; II: arrow right 2)- alpha -L-Rha-(1 arrow right 3) alpha -L-Rha-(1 arrow right 2)- alpha -L-Rha-(1 arrow right 3)- alpha -L Rha (1 arrow right ). The branched O-polysaccharides of P. syringae pv. garcae ICMP 8047 and NCPPB 588 super(T) have the same L-rhamnan backbone with repeating units I and II and a lateral chain of alpha (1 arrow right 4)- or alpha (1 arrow right 3)-linked residues of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc). Several monoclonal antibody epitopes associated with the L-rhamnan backbone or the lateral alpha -D-Fuc3NAc residues were characterized.