Chemical composition of cell-wall polysaccharides from leprosy-derived corynebacteria

Abstract

The importance of cell-wall components for bacterial taxonomy has been repeatedly stressed [1,2]. Microorganisms of genera Corynebacterium, Mycobacterium and Nocardia (CMN group) have envelopes of similar structure and contain 3 kinds of polymers: peptidoglycan, arabinogalactan and mycolates [3,4]. Lechevalier and Lechevalier [5] have classified different genera of Actinomyces into 9 cell-wall types (I-IX) differing in the major amino acid constituents of their cell walls and 4 whole-cell sugar patterns (A-D) by analysis of cell hydrolysates. Cell-wall type IV and whole-cell sugar pattern type A, which are characteristic of the CMN group of microorganisms, are known to contain arabinose and galactose in the approximate ratio of 5 : 2. Two kinds of microorganisms have been recognized in human leprosy lesions: (a) Mycobacterium leprae, acid-fast Gram-positive, which does not replicate in vitro; and (b) some non-acid-fast Gram-positive bacteria which multiply in axenic culture and were previously indicated as 'diphtheroids' because of their resemblance to Corynebacterium diphtheriae (cf. refs. 6 and 7 for review). These microorganisms were recently characterized as true corynebacteria according to their DNA base composition (56 to 58% GC) [8] and mycolic acid structure (polyunsaturated corynomycolic acids) [10,13]. Consequently, 'diphtheroids' were renamed as 'leprosy derived corynebacteria' (LDC) according to Barksdale [11]. The aim of the present study was the purification and analysis of cell-wall polysaccharides of 3 LDC and 2 reference microorganisms, Corynebacterium hoffmannii and Mycobacterium smegmatis.