LIFE-CYCLES IN BACTERIA Iig 



falls upon a suitable substrate, it releases the thousands of niicrocysts which 

 it contains, and each ot these germinates to form a vegetative bacterium, the 

 whole constituting the swarm. 



The swarm moves out over the substrate, feeding and multiplying as it 

 goes. From time to time fruiting bodies are produced, under the influence of 

 a specific factor elaborated by the vegetative cells. These are formed bv the 

 aggregation of vegetative bacteria, some of which arc transformed into 

 niicrocysts, and some of which are sacrificed to assist in the formation of the 

 stalk and wall of the fruiting body. The mature fruiting body, in some genera, 

 is of great complexity, and may be borne upon a long stalk, in others it is 

 sessile and simple in form. When ripe, the fruiting body is released from its 

 stem and blows away in the wind. If it alights upon a suitable substrate it 

 germinates and releases the swarm to repeat the cycle. 



This type of multicellularity is not pecuhar to myxobacteria. It occurs 

 also in an interesting group of organisms, the Acrasiecu. In this case the unit 

 of the swarm is an amoeboid cell instead of a bacterium, but the cycle is in 

 every other way similar. Myxobacteria and Acrasiea' arc probably not in 

 any way related, but have merely adopted a similar mode of life. They also 

 resemble one another in being predatory upon saprophytic bacteria, in the 

 soil, although pathogenic myxe^bacteria do exist. 



C: THE LIFE-CYCLE IN EUBACTERIA 



(1,^,5,7,28,37,38 ) 



The condition in eubacteria and myxobacteria is not dissimilar, although 

 superficially it may appear to be so. Bacteriologists working with pure 

 cultures upon otherwise sterile media mav derive a false impression of the 

 extent to which the distribution of bacteria is achieved by single cells, whether 

 spores or otherwise, inaugurating new growth. Such conditions do not 

 obtain in nature. The soil, which is the natural habitat of most bacteria, 

 'swarms with micro-organisms of every kind, and competition must often 



