Structural Investigations on Cell Walls of Nocardia sp.

The walls of Nocardia kirovani are composed of three main constituents: the peptidoglycan matrix, a polysaccharide polymer and a variety of free and bound lipids. The free lipids represent 17.5% (dry weight) of the walls and consist for the major part of C16-18 fatty acids and nocardic acids, and for the minor part, of nocardones, triglycerides and carotenoid pigments. The nocardic acids were identified as tri- and tetra-unsaturated, α-branched, β-hydroxylated compounds C58H110O3--C66H124O3, the nocardones as tri- and tetra-unsaturated ketones C57H106O--C63H118O, and the main carotenoid pigment as phlei-xantophylle palmitate. Esters of glycerol with C14C16C18 fatty acids and, for some of them, with odd numbered poly-unsaturated acids containing 35 to 45 carbon atoms, were also identified, Bound lipids represent about 20% (dry weight) of the walls and consist mainly of nocardic acids probably ester-linked to an arabinogalactan polymer. The peptidoglycan (about 40% dry weight) is composed of β-1,4-N-acetylglucosaminyl-N-glycolylmuramic acid disaccharide units that are substituted by diamidated L-Ala-D-αGln-(L)- A2pm-(D)-NH2 tripeptides and diamidated L-Ala-D-αGln-(L)-A2pm-(D)-NH2(L)-D_Ala tetrapeptides, where A2pm is meso-diaminopimelic acid.Crosslinking between some of the peptide units is mediated through D-Ala-(D)-A2pm linkages (peptidoglycan of ehemotype I). [ABSTRACT FROM AUTHOR]