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Presence of the cell wall glycopolymer rhamnan was established for members of the genus Curtobacterium (family Microbacteriaceae) by using chemical and NMR spectroscopic methods. The rhamnan with the repeating unit, →2)-α-L-Rhap-(1→3)-α-L-Rhap-(1→, was found in C. flaccumfaciens pv. flaccumfaciens VKM Ас-1923T, C. flaccumfaciens pv. poinsettiae VKM Ас-1924T, C. pusillum VKM Ac-2099T, C. herbarum VKM Ac-2512T, and Curtobacterium sp. VKM Ac-1811. Each of the studied strains also contained a second, acidic phosphate-free polysaccharide. NMR spectra of these polysaccharides differed, indicating the structural differences. Cell wall hydrolysates of all studied strains were found to contain rhamnose, mannose, glucose, galactose, and glucosamine. Further research will facilitate more detailed characterization of the composition of cell wall glycopolymers in Curtobacterium species, as well as evaluation of their taxonomic significance. The data on the polymer structure will contribute to understanding of the mechanisms of colonization and infection of higher organisms by Curtobacterium species and bacterial interaction in microbial communities and with abiotic environmental objects.

The structures of three cell wall glycopolymers of the phytopathogen Rathayibacter tritici VKM Ac-1603T (family Microbacteriaceae, order Micrococcales, class Actinobacteria) were established by chemical methods and NMR spectroscopy. Polymer 1 is a branched rhamnomannan with the repeating unit →3)-α-[β-D-Xylp-(1→2)]-D-Manp-(1→2)-α-D-Rhap-(1→3)-α-D-Manp-(1→2)-α-D-Rhap-(1→; polymer 2 is a linear rhamnomannan with the repeating unit →2)-α-D-Manp-(1→2)-α-D-Rhap-(1→3)-α-D-Manp-(1→2)-α-D-Rhap-(1→; polymer 3 is a branched teichuronic acid containing monosaccharide residues GlcA, Gal, Man, and Glc at a 1:1:1:5 ratio (see the text for the structures). It has been demonstrated that representatives of four Rathayibacter species studied to date (R. tritici VKM Ac-1603T, R. iranicus VKM Ac-1602T, R. toxicus VKM Ac-1600 and “Rathayibacter tanaceti” VKM Ac-2596) contain differing patterns of phosphate-free glycopolymers. At the same time, the above Rathayibacter strains have a common property — the presence of rhamnomannans with D-rhamnose. These rhamnomannans may be linear or branched and differing in the positions of glycosidic bonds and side substituents. The presence in the cell wall of rhamnomannans with D-rhamnose may serve as useful chemotaxonomic marker of the genus Rathayibacter.

Some peculiarities of the lipid composition of the outer membrane of the marine Gram-negative bacterium Chryseobacterium indoltheticum CIP 103168T have been studied. It is found that C. indoltheticum cells do not contain phosphatidylglycerol. Lipopolysaccharide could not be extracted by conventional methods; therefore, lipid A was isolated by hydrolysis of whole bacterial cells with 10% acetic acid with subsequent treatment with a chloroform: methanol mixture. The isolated lipid A has an unusual monosaccharide structure and constitutes 1-phosphate-D-glucosamine acylated with (R)-3-hydroxy-15-methylhexadecanoic and (R)-3-hydroxy-13-methyltetradecanoic acids at C2 and C3 atoms, respectively. The C. indoltheticum cells are shown to have a capsule; its polysaccharide apparently fulfils the LPS function.

The hydrolysis of defatted cells of the marine bacterium Chryseobacterium scophtalmum CIP 104199T with 10% acetic acid (3 h, 100°C) led to an unusual lipid A (LA) (yield 0.6%), obtained for the first time. Using chemical analysis, FAB MS, and NMR spectroscopy, it was shown to be D-glucosamine 1-phosphate acylated with (R)-3-hydroxy-15-methylhexadecanoic and (R)-3-hydroxy-13-methyltetroadecanoic acids at the C2 and C3 atoms, respectively. It is similar to the monosaccharide biosynthetic precursor of lipopolysaccharide (LPS), so-called lipid X (LX). Unlike LX, LA can be isolated by the treatment of bacteria with organic solvents only after the preliminary acidic hydrolysis of the cells, which suggests that LA might be strongly, probably chemically, linked to other components of the outer membrane. However, LPS cannot be such a component, because extraction with phenol-water or phenol-chloroform-petroleum ether mixtures in high yields (5.34% and 0.5%, respectively) leads to preparations that do not contain 3-deoxy-D-manno-oct-2-ulopyranosonic acid, 3-hydroxyalkanoic acids, or LA.