The Gram-negative bovine pathogen Moraxella bovis is a causative agent of Infectious bovine keratoconjunctivitis, 'pink-eye' that affects cattle. Here we report that strain L183/2 has the same capsular polysaccharide (CPS) of unsulfated chondroitin, as does strain Mb25, whereas strain Epp63 does not express CPS. NMR analysis of the oligosaccharides (OS) derived from the lipooligosaccharides (LOS) in these three strains by NMR has shown that strain Mb25 and Epp63 have the same OS structure with a terminal N-acetylgalactosamine ((1S)-GalaNAc) residue →4,6-linked. Strain L183/2 lacks the (1 S)-GalaNAc residue. The biological role of M. bovis LOS was assessed by comparing the LOS from strains Epp63, Mb25 and L183/2 and truncated Epp63 LOS variants. LOS truncation affected M. bovis growth rate, susceptibility to antibiotics, detergents, bovine serum bactericidal activity, endotoxicity and adherence to HeLa cells.

capsular polysaccharide, NMR spectroscopy, endotoxin, lipooligosaccharide (LOS), Moraxella bovis, Structural characterisation, Bovine keratoconjunctivitis

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3	bDGlcpA	107.05	75.12	76.38	82.80	77.96	?
2	Ac	?	25.09
	bDGalpN	103.79	53.78	82.80	70.56	77.70	63.76


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3	bDGlcpA	4.56	3.40	3.65	3.84	3.83	-
2	Ac	-	2.05
	bDGalpN	4.54	4.04	3.84	4.15	3.73	3.82


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3	bDGlcpA	107.05/4.56	75.12/3.40	76.38/3.65	82.80/3.84	77.96/3.83	
2	Ac		25.09/2.05
	bDGalpN	103.79/4.54	53.78/4.04	82.80/3.84	70.56/4.15	77.70/3.73	63.76/3.82

The spectrum also has 2 signals at unknown positions (not plotted).

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@@H]1[C@@H](C(=O)O)O[C@@H](O[C@@H]2[C@@H](NC(C)=O)[C@H]([*])O[C@H](CO)[C@@H]2O)[C@H](O)[C@H]1O

379.318 g/mol (C₁₄H₂₁R₂NO₁₁, R = next and previous repeats, not counted in mol weight)