SURFACE STRUCTURES 29 



Until recently, very little was known of the composition of bacterial 

 cell walls, although the evidence suggested that they resembled the cell walls 

 of plants in containing a large polysaccharide fraction, together with lipid 

 and nitrogenous components. Some parts of the lipid component probably 

 belongs to the cell membrane. Holdsworth (1952(7, 1952/)) isolated a protein- 

 carbohydrate complex from the cell wall of Corytiehacteriiiin diphthcriac, in 



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(Reproduced from the Journal of Genera! Microbiology.) 



CELL DIVISION IN COCCI 



A. Long-chained streptococcus, corresponding approximately to a rough 

 bacillus. Division is by the production of transverse septa. 



B. Short-chained streptococcus, corresponding to a smooth bacillus. 

 Division is by constriction of the cell wall, and each nuclear unit represents a 

 chromosome pair (Chapter IX). 



C. Septate staphylococcus. Resembles A, except that each septum is 

 produced at right-angles to the preceding one. This morphology is also typical 

 of the Gram-negative " diplococci." 



D. Unicellular coccus. Division is by constriction, but the organism 

 possesses a central, spherical nucleus (Chapter I\'). 



which the protein component differed in constitution from the intracellular 

 proteins. Holdsworth claims that the carbohydrate fraction is an oligo- 

 saccharide and polysaccharides have also been described from the same source. 

 Histochemically the cell walls and cross-walls of C. diplitlieriac and many 

 other species of bacteria can be demonstrated to contain polysaccharides, by 

 the use of periodic acid. 



