CHAPTER VI 

 POOD REQUIREMENTS OF BACTERIA 



What do the tiny microbes feed upon? Is it possible that the 

 good Samaritan and outlaw in bacterial society feed upon the 

 same food? If so, one builds from it magnificent dynamos of 

 usefulness; the other, tiny yet powerful engines of destruction. 

 Man's food consists of proteins, carbohydrates, fats, vitamins, ash, 

 and water: that of wheat, water, carbon dioxid, and ash. Some 

 bacteria are like man, others are like the wheat in their food 

 requirements. Out of the eighty known elements only ten are 

 necessary for bacteria; three of these are gases — ^hydrogen, nitro- 

 gen, and oxygen; four are metals — ^potassium, calcium, magne- 

 sium, and iron. Three are non-metallic solids — carbon, sulfur, 

 and phosphorus. Three of these compose the bulk of the bacterial 

 body; some of the others are needed only in small quantities. 

 Nevertheless, each is essential, and the p-rowth of the cell is lim- 

 ited by the one present in least concentration as compared with 

 the organism's requirements. This is a universal law, holding for 

 all living cells. The great difference is in the form in which 

 the various elements are required by the different plants and ani- 

 mals. Man needs his carbon as fats, starches, or sugars. Higher 

 plants require it as carbon dioxid, whereas some bacteria will 

 utilize it as horn, wood, or even coal. 



How Bacteria Feed. — Man takes his food into the stomach 

 and pours out upon it the digestive juices. These render it soluble 

 and change it into substances which the body can use. It then 

 diffuses into the blood and is carried to all parts of the body. 

 Bacteria have no stomachs; hence, they pour their digestive juices 

 into the medium in which they are living. These digest the 

 food which diffuses into the body. Incidentally, the higher plants 

 seize upon the digested food and use it for the building of their 



