Isolation and characterisation of the biological repeating unit of cepacian, the exopolysaccharide produced by Burkholderia cepacia complex bacteria

The repeating unit of cepacian, the exopolysaccharide produced by the majority of the Burkholderia cepacia complex microorganisms, was isolated from inner bacterial membranes and investigated by mass spectrometry. The data obtained led to the determination of its structure, thus disclosing the oligosaccharidic sequence synthesised by bacteria, and gave also information on the biosynthetic pathway of cepacian repeating unit, thanks to the presence of saccharidic intermediates shorter than the repeating unit. In addition, from zero to four acetyl substituents were detected on the repeating unit before the polymerisation process which takes place in the periplasmic space. The procedure used can be conveniently exploited as an alternative route to the structural determination of bacteria exopolysaccharides, particularly useful for complex repeating units.