CHAPTER 3 



THE BIOLOGICAL CHARACTERISTICS OF BACTERIA 

 METABOLISM 



The Chemical Constitution of Bacterial Cells. 



It would seem that bacterial cells are formed on tlie same general chemical 

 pattern as the cells of other living organisms, with certain characteristics that 

 ally them closely to the fungi. The determination of the exact chemical compo- 

 sition of any given bacterial species or strain is rendered peculiarly difl&cult by 

 variations induced by differences in the nutrient media in which they are grown. 

 (See Cramer 1891-97, NicoUe and Alilaire 1909, Dawson 1919, Fulmer et al. 1921, 

 Hunter 1923, Buchanan and Fulmer 1928-30, Eckstein and Soule 1931.) Apart 

 from the variability induced by environmental factors, any bacterial species or 

 strain may give rise to variants that differ sharply from the parental type in certain 

 of their metabolic activities. When due allowance is made for these disturbing 

 factors, the technical problem remains a difficult one. The collection of an adequate 

 mass of bacterial cells for detailed chemical analysis makes large demands op time 

 and apparatus ; and the use of the chemically complex media that are necessary 

 to secure abundant growth of certain bacterial species greatly increases the difficulty 

 of interpreting the analytical results, particularly in regard to any constituents 

 that are present in small amount. It is not therefore surprising that our knowledge 

 is as yet fragmentary. 



The difference in chemical constitution between different bacterial genera or 

 species are, as would be expected, wider than between different strains or variants 

 belonging to a single species. In this section we may confine our attention in the 

 main to those chemical constituents that are shared by bacterial cells in general, 

 noting in passing certain divergencies that serve to illustrate the kind of differences 

 in chemical structure that have been observed. 



The Water Content of the Bacterial Cell. — In common with all living cells bacteria 

 contain a high proportion of water. Estimations of the water content of different 

 bacteria carried out by different observers have varied widely and figures as 

 high as 90 per cent, have sometimes been recorded ; but those given by Nicolle 

 and Alilaire (1909) range, with few exceptions, from 73 per cent. {Bad. coli) to 

 80 per cent. {Proteiis vulgaris). 



The Ash Content of Bacteria. — The figures recorded for the ash content of 

 bacteria vary very widely. Buchanan and Fulmer (1928-30) quote figures ranging 

 from 2-0 to 13-94 per cent, of dry weight, omitting one widely discrepant figure. 

 It seems probable that the ash content is particularly liable to be affected by the 

 medium on which the bacterium is grown. Thus Fulmer and his colleagues (1921) 

 record a reduction in the ash content of a yeast from 6-3 per cent, to 3-0 per cent, 

 as the result of growing it in a medium free from magnesium and calcium salts. 



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