The ionic interaction of Klebsiella pneumoniae K2 capsule and core lipopolysaccharide

Abstract

The complete structures of LPS core types 1 and 2 fromKlebsiella pneumoniaehave been described by other authors. They are characterized by a lack of phosphoryl residues, but they contain galacturonic acid (GalA) residues, which contribute to the necessary negative charges. The presence of a capsule was determined in core-LPS non-polar mutants from strains 52145 (O1 : K2), DL1 (O1 : K1) and C3 (O8 : K66). O-antigen ligase (waaL) mutants produced a capsule. Core mutants containing the GalA residues were capsulated, while those lacking the residues were non capsulated. Since the proteins involved in the transfer of GalA (WabG) and glucosamine residues (WabH) are known, the chemical basis of the capsular-K2–cell-surface association was studied. Phenol/water extracts fromK. pneumoniae52145ΔwabH waaLand 52145ΔwaaLmutants, but not those from fromK. pneumoniae52145ΔwabG waaLmutant, contained both LPS and capsular polysaccharide, even after hydrophobic chromatography. The two polysaccharides were dissociated by gel-filtration chromatography, eluting with detergent and metal-ion chelators. From these results, it is concluded that the K2 capsular polysaccharide is associated by an ionic interaction to the LPS through the negative charge provided by the carboxyl groups of the GalA residues.