Introduction 



Bacteriology emerged as a definite branch of science as a result of the monu- 

 mental and immortal researches of Pasteur and Koch. When in 1876 Robert 

 Koch, for the first time in history, propagated a pathogenic bacterium in pure 

 culture outside the body, he not only established Bacillus anthracis as the cause 

 of a specific disease in cattle, but he inaugurated a method of investigation of 

 disease in general which is still pursued with unabated vigor. The decade immedi- 

 ately following Koch's epoch-making introduction of solid culture media for the 

 isolation and growth of bacteria ranks as one of the brightest in the history of 

 medicine because of the number, variety, and brilliance of the discoveries made 

 in that period. These discoveries, which, as Koch himself expressed it, came "as 

 easily as ripe apples fall from a tree," were all dependent upon and resulted from 

 the evolution of correct methods for the "in vitro" growth of bacteria. 



The fundamental principles elaborated at that time, of which the most im- 

 portant was the introduction of the "poured plate" method for isolation of pure 

 cultures, still constitute the foundation of bacteriological research. Nevertheless, 

 it has become more and more apparent that a successful attack upon the problems 

 still unsolved is closely related to, if not dependent upon, a thorough understand- 

 ing of the minutiae influencing bacterial nutrition. With a suitable culture 

 medium, properly used, advances in bacteriology are more readily made than 

 when either the medium or method of use is inadequate. The bacteriologist of 

 today is, therefore, largely concerned with the evolution of methods for the 

 development and maintenance of growth of bacteria, upon which an understand- 

 ing of the biological and biochemical phenomena resulting from bacterial activity 

 must largely be dependent. 



The chemical analyses of bacteria indicate that they are essentially water plants, 

 the protoplasm of which contains chemical elements found in other types of plant 

 protein (Ford). In order to build up the cells of bacteria in their anabolic phase, 

 the protoplasmic elements must be found in the immediate environment. So vast 

 is the problem of bacterial metabolism, and so numerous and diverse are the 

 minutiae it includes, that a comprehensive discussion of its ramifications is pre- 

 cluded here. It is the purpose of this discussion to present briefly only some of 

 the outstanding developments in this phase of bacteriology, especially as they con- 

 cern the evolution of new methods for the cultivation and study of bacteria. 



Almost without exception wherever bacteria occur in nature, and this is particu- 

 larly true of the pathogenic forms, nitrogenous materials and carbohydrates are 

 present. These are utilized in the maintenance of growth and for the furtherance 

 of bacterial activities. So complex is the structure of many of these substances, 

 however, that before they can be utilized by bacteria they must be broken down 

 into simpler compounds. Such alterations are effected by processes of hydrolysis, 

 oxidation, reduction, deamination, etc., and are the result of bacterial activities of 

 primary and essential importance. These changes are ascribed to the activities 

 of bacterial enzymes which, obviously, are both numerous and varied. The proc- 

 esses involved, as well as their end-products, are exceedingly complex; those of 

 fermentation, for example, result in the production of such end products as acids, 

 alcohols, ketones, and gases including hydrogen, carbon dioxide, methane, etc. 



Abstract as such studies of bacterial metabolism may seem, their practical 

 application is soon apparent. From these studies has come a better understanding 

 of the nutritional needs of bacteria, and from this in turn has come the develop- 

 ment of culture media productive of rapid and luxuriant growth — essential req- 

 uisites for the isolation and study of specific organisms. 



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