Intra- and Intergeneric Relationships of Various Actinomycete Strains Based on the Acyl Types of the Muramyl Residue in Cell Wall Peptidoglycans Examined in a Glycolate Test

Abstract

A total of 106 actinomycete strains representing 40 genera were studied to gain a better understanding of their intra- and intergeneric relationships by examining the types of acyl groups on the muramyl residues of the peptidoglycans in a glycolate test. The glycolyl type was found in about 43% of the actinomycete strains examined. These strains were distributed in the following two characteristic taxa: the actinoplanetes and their relatives, including species of the genera Actinoplanes, Catellatospora, Couchioplanes, Dactylosporangium, Glycomyces, Micromonospora, and Pilimelia; and the nocardioforms and species of the related genera Gordona, Nocardia, Rhodococcus, Tsukamurella, and Mycobacterium. Only glycolyl type bacteria were found to be present among the strains of these genera tested, except for a few doubtful strains. In contrast, the acetyl type was found extensively in bacteria belonging to the families Pseudonocardiaceae, Streptomycetaceae, Streptosporangiaceae, and Thermomonosporaceae and other taxa. The pattern of acyl type distribution among the actinomycetes correlates very well with the cell wall chemotype sensu Lechevalier and Lechevalier; that is, the chemotype I and III genera were all acetyl type taxa, the chemotype II genera were glycolyl type taxa, and the chemotype IV genera were split into a glycolyl, mycolate-containing group and an acetyl, non-mycolate group. We discuss the idea that combination of both the acyl type system and the cell wall chemotype system should provide a more useful tool for taxonomy of members of the order Actinomycetales.