110 CHEMISTRY OF BACTERIA ASD THEIR PRODUCTS 



Numerous invosti<2:ators have reported that the insoluble bacterial cell 

 wall consists chiefly- of chitin, which on being split with acids yields 

 80 to 90 per cent, of the nitrogenous carbohydrate, glucosamin.^^ The 

 distinction is a very important one, since cellulose is a typically vege- 

 table product, while chitin is eciually typically animal in origin, being 

 found chiefly in the shells of lobsters and crabs, the wings and cover- 

 ings of flies, beetles, etc. Chitin seems to be a polymeric form of 

 glucose-amine,^'"" an amino-carbohydrate, just as cellulose is a polymer 

 of a simpler carbohydrate. Other carbohydrates seem to be scanty in 

 the bacterial cell, but Tamura ^^''^ does not accept the chitinous nature 

 of bacterial carbohydrate, finding in tubercle and diphtheria bacilli a 

 hemicellulose, apparently a pentosan yielding 1-arabinose on hydro- 

 lysis. Wester ^^"^ found no chitin in several varieties of bacteria, and 

 cellulose only in 7>. .ri/liuuDi ; he therefore considers it probable that 

 bacterial cell walls do not always consist of the same substance. Cramer 

 could find no glucose in any variety, although there are some bacteria 

 that contain material reacting like starch with iodin. Levene,^*' how- 

 ever, found in B. tuhcixulosis a substance with the properties of 

 glyco<:'('ii. 



Bacterial Fats. — By staining methods, fats have been recognized in 

 many species, and by extraction with fat solvents lecithin, cholesterol, 

 simple fats, and specific bacterial fats have been isolated ; this is par- 

 ticularly true of B. tuberculosis, which owes its characteristic staining 

 ])roperties to the specific fat-like bodies which make up a large pro- 

 portion of its entire mass.^^ Numerous studies of these fats of 

 B. tuherculosis have been made ^^ and by using different extractives, 

 from 20 to 40 per cent, of the entire weight of the bacilli has been 

 found s()lul)le in fat solvents. Kresling found that the substance 

 soluble in chloroform had the following composition: 



Free fatty acid 14. ."^R per cent. 



Neutral fats and fatty acid osters 77.2.5 " " 



Alcohols obtained from fatty acid esters .... 30.10 " " 



Lecithin " O.lfi " 



Substances soluble in water 0.73 " " 



Bulloch and ^Maclcod found that ethereal extracts did not contain 

 the acid-fast substance which they consider to be a wax-like alcohol, 

 soluble in hot, but insoluble in cold absolute alcohol or in ether. 

 The simple fats seem to be formed by oleic, isocetinic, and myristinic 



wall of veasts contains a hemicellulose and a nianno-dextran. See also Kozniewski, 

 Zeit. phvsiol. Chem.. 1914 (00). 208. 



mSeoViehofer. Ber. Dent, riiem. fies.. 1012 (301. 443. 



i-'i Mor;rulis states that chitin consists of two j)arts. one containincr all the 

 glucose and amino <:roups. tlie other bcin? a stable nitrogenous compound yielding 

 no plucoHC. (Science. l!»lf. (44). SCO.) 



isbZeit. physiol. Cliem.. 1014 (.SO). 304. 



I'-cPharm. Wcekbhid.. lOlC. (.".3). 11S3. 



11 Jour. Med. Research. 1001 (0), 13r>. 



"Sec Tamils and Pai.miez. Compt. Rend. Soc. Riol.. lOO.") i,-)!)), 701. 



J 8 For literature see Bulloch iiiid MachMKl. .Tour, of lly-^i.-ne. 1004 (4). 1. 



