The O-polysaccharide (OPS) was isolated by mild acid degradation of the lipopolysaccharide of Enterobacter cloacae G3422 and studied by chemical methods, including sugar analyses, Smith degradation, and solvolysis with anhydrous trifluoroacetic acid, along with 1H and 13C NMR spectroscopy. The following structure of the branched tetrasaccharide repeating unit was established: The O-antigen gene cluster of Enterobacter cloacae G3422 was sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in a good agreement with the O-antigen structure.

Lipopolysaccharide, O-antigen, bacterial polysaccharide structure, O-antigen gene cluster, Enterobacter cloacae

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3	aDManp	103.5	71.2	71.5	68.0	74.4	61.7
3	aDManp	102.3	71.0	79.3	66.7	74.4	61.5
2	Ac	175.3	23.4
	aDGlcpN	92.3	53.7	78.4	72.0	72.8	62.3


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3	aDManp	5.11	4.08	3.89	3.65	3.78	3.85-3.90
3	aDManp	5.26	4.19	3.87	3.83	3.61	3.79-3.83
2	Ac	-	2.05-2.06
	aDGlcpN	5.16	4.00	3.91	3.62	3.89	3.77-3.91


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3	aDManp	103.5/5.11	71.2/4.08	71.5/3.89	68.0/3.65	74.4/3.78	61.7/3.85-3.90
3	aDManp	102.3/5.26	71.0/4.19	79.3/3.87	66.7/3.83	74.4/3.61	61.5/3.79-3.83
2	Ac		23.4/2.05-2.06
	aDGlcpN	92.3/5.16	53.7/4.00	78.4/3.91	72.0/3.62	72.8/3.89	62.3/3.77-3.91

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)N[C@H]1[C@@H](O)O[C@H](CO)[C@@H](O)[C@@H]1O[C@H]1O[C@H](CO)[C@@H](O)[C@H](O[C@H]2O[C@H](CO)[C@@H](O)[C@H](O)[C@@H]2O)[C@@H]1O

545.491 g/mol (C₂₀H₃₅NO₁₆)