Escherichia coli L-19 isolated from a healthy individual did not agglutinate with any of 21 polyvalent antisera that cover 174 E. coli O-serogroups. The strain was studied in respect to the O-antigen (O-specific polysaccharide, OPS) structure and genetics. The LPS was isolated by phenol-water extraction of bacterial cells and cleaved by mild acid hydrolysis to yield the OPS. The OPS was studied by sugar and methylation analyses, along with 1D and 2D (1)H and (13)C NMR spectroscopy. The established structure of the linear tetrasaccharide repeating unit was found to be unique among known bacterial polysaccharide structures. A peculiar component of the L-19 OPS was an amide of glucuronic acid with 2-amino-1,3-propanediol (2-amino-2-deoxyglycerol) (GroN). The O-antigen gene cluster of L-19 between the conserved genes galF and gnd was sequenced, and gene functions were tentatively assigned by a comparison with sequences in the available databases and found to be in agreement with the OPS structure. Except for putative genes for synthesis and transfer of GroN, the sequences in the L-19 O-antigen gene cluster were little related to those of reference strains of the 174 known E. coli O-serogroups. The data obtained suggest that L-19 can be considered as a candidate for a new E. coli O-serogroup.

NMR, structure, Escherichia coli, O-specific polysaccharide, O-antigen gene clustere

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,4,4,6	x?GroN	61.9	54.2	61.9
3,4,4	bDGlcpA	102.6	71.7	80.2	73.1	76.2	172.0
3,4	bDGlcp	105.4	74.7	75.3	80.2	77.7	61.4
3	bDGalpA	102.8	76.3	71.5	81.4	77.7	175.8
2	Ac	176.2	23.8
	bDGlcpN	102.5	56.6	83.3	70.1	77.1	62.6


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,4,4,6	x?GroN	3.66-3.71	4.04	3.66-3.71
3,4,4	bDGlcpA	4.63	3.63	3.61	3.58	3.91	-
3,4	bDGlcp	4.70	3.39	3.65	3.64	3.59	3.91-4.02
3	bDGalpA	4.81	3.60	3.68	4.46	4.77	-
2	Ac	-	2.03
	bDGlcpN	4.94	3.88	3.83	3.50	3.47	3.75-3.93


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,4,4,6	x?GroN	61.9/3.66-3.71	54.2/4.04	61.9/3.66-3.71
3,4,4	bDGlcpA	102.6/4.63	71.7/3.63	80.2/3.61	73.1/3.58	76.2/3.91	
3,4	bDGlcp	105.4/4.70	74.7/3.39	75.3/3.65	80.2/3.64	77.7/3.59	61.4/3.91-4.02
3	bDGalpA	102.8/4.81	76.3/3.60	71.5/3.68	81.4/4.46	77.7/4.77	
2	Ac		23.8/2.03
	bDGlcpN	102.5/4.94	56.6/3.88	83.3/3.83	70.1/3.50	77.1/3.47	62.6/3.75-3.93

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

*O[C@H]1[C@H](O)[C@@H](C(=O)NC(CO)CO)O[C@@H](O[C@@H]2[C@@H](CO)O[C@@H](O[C@H]3[C@@H](C(=O)O)O[C@@H](O[C@@H]4[C@@H](NC(C)=O)[C@H](*)O[C@H](CO)[C@H]4O)[C@H](O)[C@H]3O)[C@H](O)[C@H]2O)[C@@H]1O

790.678 g/mol (C₂₉H₄₆R₂N₂O₂₃, R = next and previous repeats, not counted in mol weight)