bi()C1ii:mi(\i. \c'n\ i'|-ii;s 



159 



t;iti\-(>ly ;md (iu:iiitit;ili\-cly, .-i .s|,il»l(> and 

 cliaractcristic properly of the cell under fixed 

 {'ou(iitions of j^rowlh. Addition of glucose 

 to the niediuin in wliieh N. griscufi wa.s {>;ro\\ n 

 reiluced the concent ration of some of the 

 amino acids (arfiinine, histi(hn(>, lysine), hut 

 not of otliei's (t ryptoplian). The iiitr()j;en 

 content of tlie cuHure was about 10. o per 

 cent, inde])endent of adiHtion of suji;ar. 



Witter {Wr.VA) was unable to find either 

 chitiu or a definite nucleus in the species of 

 actinomycetes examined, a characteristic 

 that (Ustinji;uishes them definitely from the 

 true funi2;i (See also Schmidt). Hagcdorn 

 established an isoelectric point for actino- 

 mycetes also similar to that of bacteria. 



Detailed cell wall studies support the bac- 

 terial natun^ of the actinomycetes. Xo evi- 

 dence was found of the presence of polymers, 

 such as chitin, mannan, glucan, or cellulose, 

 which are found in yeasts and true fungi. 

 The cell wall composition in all of the acti- 

 nomycetes studies resembled the cell wall 

 composition of gram-positive bacteria. The 

 majority of the streptomycetes are lysed by 

 lysozyme; this property is characteristic of 

 many gram-positive bacteria and has been 

 shown to be due to lysis of the cell wall. 



Avery and Blank (19.5()) could not find 

 any chitin or cellulose in representative cul- 

 tures belonging to the genera Actinomyces, 

 Xocardia, Strcptomyces, and Micromono- 

 spora. They concluded on the basis of these 

 and other data that these organisms belong 

 to the bacteria rather than the fungi. An 

 analysis of a polysaccharide isolated from 

 cultures of Nocardia astcroides contained 

 arabinose and galactose in a molar ratio of 

 1.7:1. By isolation in crystalline form, the 

 two monosaccharides wei-e identified as 

 D-arabino.se and D-galactose. Partial hy- 

 drolysis showed that some of the D-arabi- 

 nose units in the polysaccharide were in the 

 fiu'anoside ring whereas the D-galactose 

 units possessed the pyranoside structure. 

 Methylation studies showed that the poly- 



saccharide was a branched struct lU'e of J)- 

 aral)inose and l)-galactose units with soin(^ 

 of the arabinose forming nonredncing, ter- 

 minal residues. This e\idence points further 

 to the close taxonomic relationship between 

 .\ . (isfcroidrs and M ycohaclcriiim liihrrculosis 

 (Bishop and lilank). 



-Vccording to (iuinand d <il. {\\)')H), the 

 mycelium of X . aslcrnidcs yielded on extrac- 

 tion with 1:1 alcohol-ether and chloroform, 

 a mixture of lipoproteids, consisting partly 

 of peptides containing six amino acids and 

 partly of acid lipids. 



Romano and Nickerson made a study of 

 the cell wall of S. fradiae. The cells were first 

 broken in the Mickle disintegrator; the cell 

 walls were then readily lysed by lysozyme. 

 On hydrolysis with 2 A'' hydrochloric acid, 

 reducing substances, accounted for largely 

 by hexosamine, were liberated. The cell wall, 

 like that of gram-positive bacteria, appears 

 to contain a mucopolysaccharide in associa- 

 tion with protein. 



According to Sohler and Honiano, the cell 

 wall of Strcptomyces spcM'ies is mucoid in 

 nature, is lysed by lysozyme, and contains 

 considerable amounts of hexosamine (Table 

 35). On the other hand, the cell wall of 

 Nocardia is not susceptible to the action of 

 lysozyme, contains much smaller amounts of 

 hexosamine, but contains 10 per cent pen- 

 tose, tentatively identified as arabinose. 



Further results on the chemical composi- 

 tion of the cell walls of actinomycetes were 

 reported by Sohler et al. (1957). The action 

 of lysozyme upon the mycelium is limited 

 primarily to the cell wall, since isolated cell 

 walls were completely lysed. The cell wall of 

 »S'. fradiae was found to l)e composed of a 

 mucopolysaccharide of which the major 

 carbohydrate constituent is glucosamine. 

 This was demonstrated by chromatography 

 and paper electrophoresis. The absence of 

 X-acetylglucosamine, together with the fact 

 that the cell wall is completely soluble in hot 

 alkali, eliminates the possil)ility of beta- 



