CHAPTER II 

 THE CHEMICAL STRUCTURE OF BACTERIA^ 



TRAUGOTT BAUMGARTEL 

 Technischen Hochschule, Munich, Germany- 

 Like all plant and animal organisms, bacteria require ten elements — carbon, hy- 

 drogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium, magnesium, and 

 iron — as indispensable building stones for their body substance. 



While bacteria take the metals (potassium, calcium, magnesium, and iron) as well 

 as the metalloids (phosphorus and sulphur) mostly in the form of simple mineral salts 

 and satisfy their need for hydrogen and oxygen chiefly from water, they are able, in 

 the assimilation of carbon and nitrogen, to utilize numerous and widely diverse sources 

 of nutrition. All substances — from complex natural compounds like proteins and poly- 

 saccharides down to their simple cleavage and decomposition products and the very 

 elements like nitrogen and hydrogen — can be utilized by the bacteria in their metab- 

 olism and modified in many ways. For example, in their carbon nutrition they util- 

 ize in this way complex plant as well as animal substances, proteins and their cleavage 

 and decomposition products, carbohydrates, fats, alcohols, acids, carbohydrates, car- 

 bon dioxide, carbon monoxide, and methane. Thus, the bacteria, in spite of all ad- 

 vantages and choice of many food substances, show an unparalleled ability for ad- 

 justment to the sources of food offered them. Furthermore, the entire process of nu- 

 trition in the bacteria is in large part dependent on the hydrogen and oxygen content 

 of the culture medium as well as on the reaction and temperature. 



For these reasons, the chemical composition of different kinds of bacteria varies 

 markedly; even in one and the same kind of bacteria there are considerable variations, 

 so that generally valid statements about the chemical composition of the body sub- 

 stance of bacteria can be made only with due consideration of the breadth of their bi- 

 ological variations. 



THE WATER CONTENT OF BACTERIA 



In order to determine the water content of bacteria by chemical analysis, the usual 

 procedure is carefully to scrape off the colonies grown on solid medium, centrifugate 

 the liquid growth promptly, and weigh the material thus obtained in its moist, living 

 condition ("fresh weight") ; afterward, dry it at ioo°-iio° C. and weigh it again ("dry 

 weight"). The difference between the fresh weight and the dry weight — expressed per 

 loo gm. of fresh mass of culture — is of course the water content. In this way it has 

 been determined that the water content of most kinds of bacteria is rather high. On 

 the average it amounts to between 75 and 85 per cent of the fresh weight. There are 

 rather wide fluctuations according to the kind of bacteria and the growth of the organ- 

 ism chosen (whether on solid or liquid medium), and also according to the age of the 



' For a more extensive summary, cf . Baumgartel, T. : Grundriss der theoretischen Bakteriologie. 

 Berlin, 1924. 



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