MICROBES-MAN'S MIGHTY MIDGETS 



Kenneth B. Raper 



In no other area of botanical science have greater advances been made dur- 

 ing the past half century than in applied microbiology, advances that have 

 come about largely through man's ability to isolate microscopic organisms in 

 pure culture and to grow these under defined conditions of nutrition and en- 

 vironment. Whereas thousands of new species and hundreds of new genera 

 have been described within this 50-year period, few additional major groups 

 of microorganisms have been revealed. It has been rather a period marked 

 by penetrating study and, not infrequently, re-evaluation. Much has been re- 

 vealed concerning their morphology, life cycles, genetical behavior, and me- 

 tabolism — and it is this newer knowledge of their vital processes that has 

 enabled man to enlist their aid so successfully in many and diverse ways. 

 In the early 1900's and for many years thereafter, attention was directed 

 largely along three often interrelated paths, namely (1) the collection, de- 

 scription, and categorization of the myriad types of microscopic life encoun- 

 tered on every hand; (2) the demonstration that certain of these microorgan- 

 isms were the diminutive antagonists in many types of disease; and (3) the 

 recognition that the ever-present microbes were the miscreants responsible for 

 the spoilage of foods and feed supplies. There was of course some compre- 

 hension of the beneficent activities of some of them, and there was the 

 beginning of a general belief that many microbes were man's true and helpful 

 friends. It was of course known that yeasts played an all-important role in 

 the leavening of bread, and their definitive role in the alcoholic fermentation 

 had been known since the pioneering work of Pasteur. The conversion of 

 ethyl alcohol to acetic acid by bacteria was well established for the vinegar 

 fermentation, as was the role of other bacteria in the manufacture of hard 

 cheeses. The fixation of atmospheric nitrogen by bacteria growing symbiotically 

 in the roots of leguminous plants had been demonstrated, and the responsible 

 role played by microorganisms in the decomposition of most types of organic 

 materials was widely if incompletely recognized. The capacity of anaerobic 



33 



