MICROBIAL CELL WALLS 



deal has been learned about the structure, functions, and 

 chemistry of the principal morphological entities (flagella, 

 capsules, walls, membranes, and nuclei) and various sub- 

 cellular particles and organelles of microorganisms.^- ^ 



That most bacteria, yeasts, fungi, and algae are sur- 

 rounded by a rigid wall was apparent to the early cytologists. 

 Indeed, it would seem that Leeuwenhoek was sufficiently 

 perspicacious to realize that his "animalcules" were bounded 

 by some sort of structure. From his letter to the Royal 

 Society (Dobell ^) it is evident that he looked and expected 

 to resolve what it was that "held them together." Little 

 time was lost between the introduction of methods for grow- 

 ing microorganisms in pure culture and the first attempt 

 to discover the chemical composition of a microbial cell 

 wall. Vincenzi,* as long ago as 1887, was the first to in- 

 vestigate what he believed to be the wall of Bacillus sub- 

 tilis. 



Most of the early studies of cell-wall composition were 

 based on analysis of material that resisted various solvents 

 and extraction procedures designed to remove cellular com- 

 ponents. We now know, of course, that the carbohydrate 

 chemist's addiction to extracting tissues with alkali to ob- 

 tain wall polysaccharides removed other constituents and 

 really left only part of the "native" cell wall. Methods 

 used for the isolation of chitin from higher organisms have 

 been applied to microorganisms, and X-ray data, together 

 with chemical analysis, have substantiated the presence of 

 a chitin-like polymer in the walls of some fungi.^-^ Thus 

 Blank ^ found that the "chitin" fraction of a number of 

 dermatophytes gave X-ray results and nitrogen values simi- 

 lar, if not identical, to those expected for pure chitin. 



It is now generally conceded that the polymers isolated 

 as "wall" or mycelial residues by extraction procedures 

 used in the earlier studies do not represent the entire chemi- 



