CHAPTER VIII 



BACTERIA m THE INDUSTRIES. UTILITARIAN BACTERIOLOGY 



Because of the fact that pathogenic bacteria received the major atten- 

 tion at the beginning of modern bacteriological study, the general opinion 

 gained credence that all bacteria were harmful or objectionable in some 

 way. This is far from the actual fact. The useful bacteria by far exceed 

 the harmful kinds. Not only is this true, but many of the harmful forms 

 are converted into various beneficial uses. The useful bacteria are alto- 

 gether too much neglected by the student of bacteriology. In a book 

 of such limited scope it is not possible to mention all of the uses to which 

 bacteria are put in the industries,, or the ultilitarian part they play in hu- 

 man economy. The following discussion is intended to indicate the 

 importance of the various microorganisms in som.e of the human activities, 



I. Bacteria in Agriculture 



Introduction. — Without bacteria the higher plants and animals could 

 not exist. As is known the carnivorous animals (meat eating) seize 

 upon herbivorous animals (plant eating) as their food supply and the 

 herbivora feed upon the higher plants which in turn obtain their nourish- 

 ment from the soil. Now, soil is nothing more nor less than a mixture 

 of dead organic matter, bacteria, sand particles, certain chemical com- 

 pounds, with a variable amount of moisture. The dead organic matter, 

 commonly called humus, is derived from decomposed plants and animals 

 upon which the soil bacteria feed, in the presence of air (oxygen), warmth 

 and moisture. The sand particles are derived from disintegrating rock 

 (the result of bacterial activity, weathering, and water erosion effects), 

 and the chemical compounds, so essential to plant life, are derived from 

 water solutions and through bacterial activity. 



It is general knowledge that as soon as a plant or animal dies, it is 

 at once decomposed by the so-called rotting bacteria. This is the ultimate 

 end of all living things. These decomposed plants and animals become 

 mixed with the soil and add to its fertility or productiveness. It is also 

 general knowledge, based upon daily observation, that organic matter 

 which is freely exposed to air and warmth, and in the presence of moisture, 

 undergoes bacterial decomposition. There are indeed many conditions 

 which modify these bacterial activities, such as temperature, air supply, 



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