3 6 THE BACTERIAL CELL 



37. Quantitative and Qualitative Selective Power. 



The proportions of the constituents present in the available nutriment 

 or nutrient medium supplied seldom correspond to [the requirements of the 

 organism which has to make good therefrom losses of'substance or energy. It 

 will then take from the supply the substances of which it has need, and leave the 

 residuum entirely untouched, only when the former are present in abundance. 

 This faculty, entitled quantitative selective capacity, is possessed by all living 

 organisms, and among them bacteria. Kappes, in his treatise already referred 

 to, gives very instructive examples of this as well. He compared the composition 

 of the bacterial crop with that of the soil (nutrient medium) in which it was 

 grown ; in this case peptonised meat extract, agar-agar. This contained, apart 

 from the 1.5 per cent, of agar-agar, which does not come under further con- 

 sideration here, altogether 2.5 per cent, of actual nutrient materials, and yielded 

 0.3 per cent, of dry bacterial substance; that is to say, only 12 per cent, of the 

 total nutriment was extracted. The relative proportions of the individual 

 constituents in the medium on the one hand and in the crop on the other proved 

 very different. Thus, for instance, the ratio of CaO : MgO was in the medium 

 0.70 : 0.44; in the crop, 0.56 : 1.05. Of nitrogenous substances (N x 6.25) the 

 former contained 42.5 per cent., calculated on the dry substance, and the latter 

 71.2 per cent., and so on. 



The requirements of bacteria in respect of ash constituents were first 

 investigated by NAGELI (IV.), in 1879. SPRENGEL (I.) was admittedly the first 

 to demonstrate that higher plants (Phanerogamia) absolutely require for the 

 construction of their cells a number of mineral substances, viz., K,0, CaO, MgO, 

 Fe s O 3 , P Z O 5 , SO 3 , all of which must be present, and in sufficient quantity, before 

 the phanerogamic plant can thrive. With the Cryptogamia the case is, however, 

 different. According to N'ageli, the fission fungi (tested by him in this connection) 

 are less exacting, since potassium can be replaced by rubidium or caesium without 

 detriment, so far as the fungi are concerned, though not by the alkaline earths. 



Of the latter it is sufficient when one of the following, CaO. BaO, SrO, MgO, 

 is present ; iron can be dispensed with. It follows therefrom that not only 

 quantitative but also qualitative powers of selection are possessed by bacteria. 

 An authoritative confirmation of N'ageli's discovery is highly desirable, and 

 would prove a very thankworthy task if conjoined with observations on the 

 formative influence of the individual ash constituents. A typical example of 

 this kind of study, alike instructive, stimulating, and worthy of imitation, has 

 been made by Winogradsky on a film yeast, and will be referred to in the second 

 volume. A preliminary step in this direction was taken by A. K. FEDOROLF (I.) 

 in 1895, who, in continuing an investigation commenced by Gamaleja, found that 

 while lithium chloride caused abnormal cell forms in Bacillus megatherium, B. 

 typhi abdominalis, Vibrio cholerce asiaticce, and Bacterium coli commune, it had no 

 apparent influence on the cells of Bacillus subtilis, B. anthracis, and other microbes. 



The quantitative selective power referred to above must not be understood 

 in the sense that the organisms inhabiting the nutrient medium always have 

 the same composition, irrespective of the relative proportions of its nutrient 

 constituents. E. CRAMER (1.) studied this matter exhaustively in relation to 

 several pathogenic bacteria and Micrococcus prodigiosus, and arrived at the con- 

 clusion that a typical composition of any species is out of the question. Accord- 

 ing to the kind of medium, the temperature and age of the cultui-e, and other 

 conditions, it may happen that one crop will contain twice as much of a particular 

 constituent as another crop. Thus, for example, the amount of dry matter varied 

 from 15.9 to 26.0 per cent., and of ash from 1.60 to 3.21 per cent. 



