8 Perspectives in Microbiology 



manifestations themselves could not be inferred from stud- 

 ies on isolated fragments of the organism. The mere fact 

 that several examples have recently accumulated to show 

 that an organism cannot use a particular substrate, al- 

 though its enzymatic composition is such as to justify the 

 conclusion that it should, is a simple case in point. At 

 present this anomaly is attributed to permeability barriers 

 or to enzymatic organization; it must, however, be realized 

 that this explanation does not constitute a satisfactory one 

 in terms of better comprehended mechanisms, but actually 

 is hardly more than a paraphrase of the underlying observa- 

 tions. Let me emphasize that the point at issue is not that 

 our current knowledge of permeability problems is still 

 woefully incomplete, but that the mere detection of the 

 irregularities was the result of studies with living organ- 

 isms as well as with isolated enzyme extracts. Similarly, 

 the occurrence of adaptations and mutations could not, 

 I believe, have been surmised from experiments with crude 

 or crystalline enzyme preparations, but had to be estab- 

 lished by investigations with cell populations. 



So far as we can perceive at present, the basis of life is 

 matter, and the scientist must aim at an ultimate inter- 

 pretation of the manifestations of life in terms of mech- 

 anisms that govern the behavior of the elementary par- 

 ticles of matter. To achieve this, we must know the mani- 

 festations, however, and it is my contention that we can 

 discover them only by studies on living organisms. The 

 greater the complexity of the latter, the more difficult will 

 be the analysis of particular vital functions. Hence the 

 microorganisms, in view of their relative simplicity, appear 

 to provide promising material for further studies on the 

 fundamental aspects of life. 



Much has already been accomplished here, and there are 

 signs of increased activity along several lines. The rela- 

 tively recent developments demonstrating, for example, 

 that bacteria in general represent organized units com- 



