Sex in Bacteria 



Evidence from Morphology * 



W. G. HUTCHINSON, Laboratory of Microbiology, 

 Department of Botan\', University of Pennsylvania, 

 Philadelphia, Pennsylvania 



HENRY STEMPEN, Department of Bacteriology and Immunology, 

 Jefferson Medical College, Philadelphia, Pennsylvania 



The assumption that bacteria, together with blue-green algae, repre- 

 sent unique types of organisms lacking any mode of sexual reproduc- 

 tion has for many years challenged investigators in their search for 

 such a phenomenon. Until recent years the methods of approach have 

 been largely cytological with little apparent effort to correlate cyto- 

 logical and genetic evidence in the same organism. Genetic evidence 

 for the existence of sexuality in bacteria is convincing (Lederberg, 

 1947; McElroy and Friedman, 1951), whereas the cytological evi- 

 dence thus far presented is at most only suggestive. 



By analogy with known sexual organisms, the demonstration of 

 sexual reproduction in bacteria would require the fusion of gametes 

 or of cells morphologically similar to vegetative cells. Such cell fusion 

 could either be complete to form a single cell or incomplete as in 

 conjugation. After fusion, nuclear material from the participants 

 would be expected to fuse and later to segregate in preparation for 

 the ultimate repetition of the process. 



Sexuality in bacteria has also been claimed to occur by the fusion 

 and segregation of nuclear material within single cells. Such a phe- 

 nomenon, as well as cell fusion, has been reported to precede spore 

 formation (as reviewed by Bisset, 1950, and Knaysi, 1951). On the 

 other hand, DeLamater and Hunter (1952) and Lamanna (1952) 

 discredit the occurrence of a sexual process in the formation of bac- 

 terial spores. Bisset (1950) has described "sexual vegetative reproduc- 

 tion" in which the nuclear material in vegetative cells fuses and is 

 later thought to segregate. Microcyst formation is likewise thought 



* This work has been supported in part by the Philadelphia Lager Beer 

 Brewers' Association. 



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