Abstract
90% of the total number of cells in the human body consist of the normal
bacterial flora. These bacteria are mostly not harmful and, indeed, even
beneficial as long as they remain physiologically outside the body, e.g.,
within the gastro-intestinal tract. Normally, these bacteria live in
symbiosis with the host, promoting our survival by protecting the body
against pathogenic bacteria and aiding in the digestion of food.
The present thesis describes the structures of the cell wall
polysaccharides of Streptococcus mitis strains SK137, SK140, and SK598,
which are all part of the normal bacterial flora in the oral cavity.
Structural similarities between these polysaccharides and the
corresponding polysaccharides of the pathogenic Streptococcus pneumoniae
have been discovered and are discussed. This thesis also describes the
structure of the O-antigen of the non-epidemic Vibrio cholerae serogroup
06. Epidemic cholera is caused by V. cholerae serogroups 01 and 0139 and
the structural relationship between the 0-antigens of these non-epidemic
and epidemic strains was investigated here.
The primary analytical techniques employed here are nuclear magnetic
resonance (NMR) and mass spectrometry (MS). The products of chemical
degradation of the polysaccharides with different procedures were
identified by gas-liquid chromatography combined with mass spectrometry
(GLC-MS) and electrospray ionisation mass spectrometry (ESI-MS).
