Genetics and Microbiology 29 



is relentless anyhow) at the expense of thoughtful search 

 for procedures to detect and electively enrich the variants 

 that serve some specific purpose, an approach we have in- 

 herited in large part from the Delft school of microbiology. 

 Some helpful methods have been developed (32) for the 

 isolation of the biochemical variants that Davis has so 

 skillfully exploited. 



Genefic RecombJnafion 



All this bears more heavily on the general utility of 

 microorganisms in genetic research than on the genetics 

 of particular microbes. Once given that microbes are dif- 

 ferentiated into more than the rhetorical "bag of enzymes," 

 as already proved by mutation research, we must look 

 more deeply into the organization of different microbes, 

 and for this, genetic recombination is the most versatile 

 tool now at hand. After all, most experimentation consists 

 of putting together two reactants and waiting to see what 

 happens. Synthetic chemical reagents are too crudely de- 

 signed for us to tell very much about their ultimate effect 

 on genetic configuration, and we therefore seek the means 

 of combining the biological units themselves. Later, if we 

 can keep busy, patient, careful, and lucky, we may hope 

 to build genetic theories on cytological facts, but the pres- 

 ent foundation of unarguable correlations is still unsteady, 

 perhaps owing to technical difficulties as much as to the 

 unavoidable subjectivity of cytological conviction. If they 

 are cells, bacteria do have organized nuclei and some 

 approximation to mitosis, but we lack the very criteria 

 of proof on which we can readily judge current contro- 

 versies on particular manifestations of these forms. 



Genetic recombination includes any process of the co- 

 alescence within one cell or organism of genetic factors 

 from two or more parents. Its best known manifestation 



