CHAPTER X 



The Genetics of Bacteria 



A: GENETICAL CONI- 1 R M A TION OF CYTOLOGY 



(6. S. II, 12, 13, 14) 



m NY organism which Hvcs and rcprcHluccs its kind must possess a 

 L\ mcclianism of inheritance, and there is no reason to heheve that 

 -^ -^ this mechanism in bacteria is different from that which is found in 

 other Hving cells. The necessity for a linear arrangement of genes was 

 emphasised by Lmdegren in 1935, and shortly afterwards the short, 

 chromosome-like body, whose existence he postulated, was described, or 

 redescribed with great clarity by Stille (1937), Piekarski (1937), and Robinow 

 (1942), so that its existence and nature have become generally recognised. 

 After a period in which multiple or even branched chromosomes were 

 postulated, for which there is no acceptable cytological evidence, the single 

 chromost^me has been genetically vindicated (Jinks, 1954). 



Granted the existence ot a chromosome-like body, it must be presumed 

 that the genes which it carries are susceptible to the same hazards and chances 

 of alteration or injury as the genes of other cells. Thus true, genetic mutation 

 must be responsible, in bacteria as in other living organisms, for the appearance 

 ot permanent, heritable variation. 



Such genetic evidence as is available supports the picture of the nuclear 

 structure and sexual behaviour o( bacteria which has been drawn in the 

 previous pages of this book. In a review, Lederberg (1948) has stated : 

 " The evidence suggests that this bacterium [Bact. coli) has a life-cycle com- 

 parable to Zy^^osacclumnnyces : the vegetative cells are haploid (but not 

 necessarily uninucleate) ; fertihsation is homothallic or unrestricted genetically ; 

 the putative zygote undergoes immediate reduction without any intervening 

 mitosis." To which it need only be added that this state ot affairs is not 

 pecuHar to Bact. coli, but is common to most other bacteria for which evidence 

 is available. 



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