Cell Walls of Nocardiae and Related Actinomycetes: Identification of the Genus Nocardia by Cell Wall Analysis

Abstract

The cell wall compositions of two strains of "true" nocardiae, Nocardia asteroides R 399 and N. caviae IM 1381, and two strains of "so-called nocardiae," N . piracicabensis and N. mediterranei, were determined. Two different methods were used for preparing the cell walls. In the one, the bacteria were sonically treated, and the cell walls were obtained by differential centrifugation; in the other, the bacteria were delipidated before sonic treatment. The cell walls of true nocardiae contain nocardic acids, identified by comparison with nocardic acids isolated from the whole cell. The peptidoglycan structures of the "true" and "so-called" nocardiae studied showed some important differences. I n the true nocardiae, the glycan strand is constituted of P-N-acetylglucosaminyl ( 1 -+ 4) N-glycolylmuramic acid, and muramic acid is N-acetylated in the strains of "so-called nocardiae," as it is in the majority of bacteria. In addition, the peptide monomers of true nocardiae are diamidated on both the a-carboxyl group of wglutamic acid and the (L) carboxyl group of meso-diaminopimelic acid, whereas the peptide monomers of the "socalled nocardiae" have only one amide substituent on the carboxyl group of mesodiaminopimelic acid. I t is difficult to differentiate without ambiguity members of the genus Nocardia from the mass of the other actinomycetes which contain major amounts of meso-diaminopimelic acid. Our results suggest that true nocardiae may be those actinomycetes whose cell walls contain, in addition to arabinose and galactose, N-glycolylmuramic acid in the glycan part of the peptidoglycan and diamidated peptides in the peptide part of the peptidoglycan. In addition, true nocardiae contain nocardic acids.The differentiation between nocardiae and related organisms is often quite difficult. Morphologically the genus Nocardia contains filamentous, branching bacteria (19). The validity of this characteristic as a differential criterion has been criticized in past years, and biochemical or chemical tests have been proposed to establish a more precise classification (20). Since the initial work of Cummins (7, 8), cell wall composition has proven to be most useful in classifying organisms belonging to the order Actinomycetales. For example, LL-diaminopimelic acid (Dpm) is found in the cell walls of streptomycetes and rneso-Dpm in the cell walls of nocardiae (2).Moreover, some sugars, such as arabinose and galactose, are found in the celi walls of nocardiae but not in those of streptomycetes. Recently it has been proposed that the specific lipids present in whole cells of nocardiae be used to differentiate nocardiae from streptomycetes (27) and from mycobacteria (17,21). Since the first isolation of nocardic acids from Nocardia asteroides (25) and the determination of their structure (3, 4), nocardic acids with related structures have been found in all the species of Nocardia so far examined. Nocardic acids are a-branched, P-hydroxylated acids of the mycolic type; they have recently been found in the cell walls of Nocardia ...

Taxonomic Significance of Cell-Wall Acyl Type in Corynebacterium-Mycobacterium-Nocardia Group by a Glycolate Test

“…In 1969, PETIT et al (11,12) and ADAM et al (13) found the occurrence of N-acetylglucosaminyl-j3-1,4 N-glycolylmuramic acid as the disaccharide unit in the cell wall of Mycobacterium smegmatis. The same structure has been found in other three Mycobacterium strains by AzUMA et al (14), and also in some Nocardia strains by MICHEL et al (15,16). These findings suggest that the structure of glycan moiety in cell-wall peptidoglycan may be useful as a new criterion of taxonomic importance (14,16).…”

“…The same structure has been found in other three Mycobacterium strains by AzUMA et al (14), and also in some Nocardia strains by MICHEL et al (15,16). These findings suggest that the structure of glycan moiety in cell-wall peptidoglycan may be useful as a new criterion of taxonomic importance (14,16). The analytical method of the glycan structure was, however, laborious and required purified cell-wall preparations, specific lytic enzymes, and some particular biochemical or analytical equipments.…”

Acyl Type of Bacterial Cell Wall: Its Simple Identification by Colorimetric Method

“…PETIT, ADAM, and others (7,8) reported that Mycobacterium smegmatis had an atypical glycan strand in its cell wall which was identified to be a repeated unit of disaccharide, N-acetylglucosaminyl-~3-1,4-N-glycolylmuramic acid, which was soon demonstrated by AzUMA et al (9) to be also present in three other mycobacteria but not in Corynebacterium fermentans or Streptomyces albus. The same glycan structure was also found in three strains of Nocardia (10,11).…”

“…For the sake of convenience, "glycolyl type" cell wall will be proposed for the name of this kind of bacterial cell wall, if ordinary cell wall could be called "acetyl type," concerning the acyl type of the glycan part of the peptidoglycan. Although it was not decided in this work which amino sugar is acylated with the glycolyl group, the occurrence of N-glycolylmuramic acid has been shown by Azuma et al in the strains of M. phlei ATCC 356, M. tuberculosis BCG, and M. kansasii P21 (9), and by Michel and the co-worker in N. kirovani (10), N. asteroides R399, and N. caviae IM 1381 (11).…”

“…However, the method for determination of glycan structure so far reported is considerably time-consuming and laborious. The procedure involves preparation of a purified cell wall, enzymic fragmentation, gel filtration, and chromatographic or mass spectrometric identification (7)(8)(9)(10)(11).…”