SEXUALITY IN BACTERIA lOp 



the nucleus may or may not be accompanied by complete division of the 

 cell. If the gametic nuclei fuse within the original cell, then the process is 

 autogamous, if the two gametes separate entirely and conjugate with other 

 partners, the process is sexual. Cytological and genetical evidence agree 

 that the former is most common but that the latter may occur upon 

 occasion. 



\n eubacteria and cytophagas the division and refusion of the nucleus 

 occurs in an elongated cell, often with a marked, central constriction, but in 

 most myxobactcria the cell is already spherical. 



A reduction process almost identical with that found in sporing genera 

 occurs in myxobactcria, cytophagas, non-sporing eubacteria and Nocardia, 

 as well as in Actinomyces (Section G below). The nucleus divides into two 

 unequal parts and the smaller of these is ehminated. As in the case of sporers, 

 sometimes more than one " polar body " is ehminated. 



E: SEXUAL FUSION IN THE SECONDARY 

 NUCLEAR PHASE 



(8, II, 23, 26, 27, 28) 



One of the first records of sexual fusion in a non-sporing bacterium was 

 made upon an organism in the secondary nuclear phase by Stoughton (1929, 

 1932). The condition is quite frequently adopted, in the latter stages of 

 vegetative growth, especially by bacteria of rough morphology (Chapter IV). 

 The bacterium contains a single, central, nuclear unit, probably a pair of 

 chromosome complexes, and may often produce the appearance of end-to-end 



Figs. 46 and 47 {See pp. 107 and 108) 

 THE CYTOLOGY OF MYXOBACTERIA 



(1), (3), (4) Myxococcus fulvus, germinating microcysts, Giemsax3000. 

 (2) Chondrococcus exiguus (as above). 



(5), (6) (8). M. fulvus, young vegetative cells, showing chromosomes, GiemsaxSOOO. 

 (7) Ch. exiguus (as 5). 



|9), (10) M. fulvus, burst microcysts, Giemsa x 3000. 



11) M. virescens, maturing culture, bacilli gathering to form microcysts, Giemsa x 3000. 

 ;i2) M. fulvus, maturing culture, Giemsa x 3000. 

 ;i3), (14), (15) M. fulvus, nuclear fusion, Giemsa X 3000. 

 ' ;i6), (17), (18), (19) M. fulvus, microcyst formation, Giemsa X 3000. 



