CHAPTER VII 



Life-Cycles in Bacteria 



A. GENERAL 



THE lifc-cyclcs of many bacteria arc simple and direct. A cell in the 

 resting stage is transplanted upon a new source of food. It germinates 

 into the vegetative form and multiplies by simple, asexual fission, as 

 well as by more complex methods (Chapter V). The nucleus of the vegetative 

 cell may adopt a variety of appearances. Often it is semi-permanently in the 

 active condition, without a nuclear membrane, and with the chromatinic 

 material in the form of chromosomes or chromosome complexes (Chapter IV). 

 When the food supply begins to be exhausted, and when the waste-products 

 of the culture have accumulated to such an extent as to interfere with metabolic 

 activity, a new generation of resting forms is produced, by a sexual process 

 (Chapter VI). The resting cells may be contained in elaborate fruiting bodies, 

 or may be free. They may or may not be especially resistant. The nucleus 

 is central and vesicular, often staining with an eccentric, chromatinic granule 

 (Chapter IV). 



In almost every case the diploid phase is short, fusion being almost 

 immediately followed by a reduction division (Chapters VI and X). 



B: THE LIFE-CYCLE IN MYXOBACTERIA 



(2, 3, 16, 29, 34, 35) 



The type of life-cycle described in the previous section is found in its 

 most advanced form in myxobacteria. 



The unit is the swarm. When a ripe fruiting body, usually whidborne, 



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