BACTERIAL METABOLISM WITHIX THE BODY 665 



B. Bacterial Metabolism 



1. General Relations Between Surface and Volume 



of Bacteria and the General Energy 



Requirements of Bacteria 



Bacteria in common with all living things exhibit two distinct phases 

 in their life history the anabolic or structural phase, and the katabolic or 

 energy phase. Of these, while no absolutely sharp line of demarcation 

 can always be determined, the manifestations and significance of the latter 

 phase are by far the more conspicuous, inasmuch as the amount of material 

 transformed into energy and heat far exceeds that entering into the body 

 of the organism and the replacements of structural wear and tear, and 

 losses incidental to the formation of enzymes and other essential nitrogen- 

 ous secretions and excretions. 



The bacteria differ quantitatively from the great majority of plants 

 and animals in their disproportionately large ratio between surface and 

 volume. An ordinary typhoid bacillus, for example, has a volume of 

 approximately 0.000000002 cubic millimeter. The surface area of a 

 bacterium of this size is nearly 0.00001 square millimeter. Inasmuch 

 as the energy requirement of organisms in general varies with the surface 

 area rather than with the volume (Du Bois), it is not surprising to find 

 that bacteria bring about transformations of nutritive material for meta- 

 bolic requirements considerably greater than their minute size would 

 appear to permit of at first sight. 2 



Bacterial cells exhibit no morphologically definable nucleus, 3 and the 

 complex phenomena attending nuclear division, so characteristic of more 

 highly organized cellular structures, is not a feature of bacterial multi- 

 plication. Hence, reproduction among bacteria is mechanically an ap- 

 parently simple process. It takes place by direct transverse fission, the 

 resulting parent and daughter cells being of approximately equal size. 



The rate of increase among bacteria is a geometrical progression which 

 in favorable mediums is theoretically maintained until the accumulation 

 of waste products and other environmental factors imposes a restraint 

 upon the process. 



Among the more rapidly growing organisms, as for example the cholera 

 vibrio, successive generations may appear at intervals as frequent as 



*A man of average figure, 200 cm. long and weighing 100 kg., would have a surface 

 area of about 2.36 square meters. It will be seen that the ratio between weight [or 

 volume] and surface in this instance is much more nearly equal than that of the 

 bacteria. 



'Bacterial cells are, however, rich in nuclear material. The chemical basis for 

 nuclei probably is quite uniformly distributed throughout the entire cell. 



