396 PHYSIOLOGY OF BACTERIA 



The surface of the cells is important because all metabolism takes 

 place through this surface only. It is 



aS = 2 X 0.4 X TT X 1.5 + 2 X 0.4 X 0.4 X TT = 4.77^^ 



These figures mean little, unless we compare them with things we 

 can really conceive. We cannot imagine the size of ju^ or yu^. One 

 c.c. of a full grown culture of Bad. coli contains about one billion 

 cells. The space occupied by these is 



0.75 X 10-9 X 10« mm.3 = 0.75 mm.^ 



One billion bacteria occupy a space smaller than 1 mm.^, or less than 

 0.1 % of the volume of the liquid in which they grew. The weight of 

 these is 0.8 mg. or, in other words, 1 mg. of moist bacteria contains 

 about 1,250,000,000 cells. 



The solids of Bad. coli have been determined to 26.65%, of which 

 17.2% is protein. The weight of one dry cell would then be 2.2 X 

 10-1° jjig^ aji(j I jng^ of (jry cells would contain about 4,500,000,000 

 cells. MacNeal found 5,500,000,000 dry cells of Bad. coli to weigh 

 1 mg. 



The bacteria solids of 1 liter of a full grown broth culture amount 

 to 220 mg. Moyer (1929) found for Bad. aerogenes in the average 

 of 8 experiments, 308 mg. of dry bacteria per liter if fed with glycerol, 

 and 562 mg. if fed with glucose. It is easy to see how near this comes 

 to a catalyst, considering the rapid rate of decomposition brought 

 about by only 0.3 gm. of substance per liter. 



This rate of decomposition is explainable only by the enormous 

 surface. The surface of the bacteria in this one liter of broth culture 

 amounts to 4.77 X lO*^^^ = 4.7m2 = about fifty square feet, which 

 is enormous considering the 800 mgs. of bacteria bodies. The same 

 ratio of surface to weight with man would amount to 0.47 square 

 kilometers or 130 acres. 



There is one group of organisms still smaller than bacteria, i.e. the 

 bacteriophage. Their size has been estimated to only 20m/x, or 

 0.02/i. Assuming them to be spheres, their volume would be 0.01 X 

 0.01 X 0.01 X TT X Vs^JL^ = 4.2 X lO-^M^ = 4.2 X lO-^^ ^m.^. Since 

 one cell of Bad. coli had the volume of 0.75^^ it is 180,000 times as 

 large as a bacteriophage. The surface of a bacteriophage is 4 X tt X 

 0.01 X 0.01 = 12.5 X 10-V'. 



One mg. of bacteriophage contains 225,000,000,000,000 cells, and 

 their surface is 0.28 m.^. 



