CHAPTER VIII 



Macro for Illations 



A: THE MYXOBACTERIAL FRUITING BODY 



(ll, 12, 14) 



THE most perfect and elaborate multicellular structures formed by 

 bacteria are the fruiting bodies of myxobacteria. Other macroscopic 

 formations, however elaborate, are little but the result ot the reaction 

 between the growth potential of the organism and the physical restraint ot 

 the environment, and slight variations in the latter may aftect the result to an 

 apparently disproportionate extent. The fruiting body, however, although 

 it may be prevented, by unsuitable conditions, from forming at all, is otherwise 

 independent, in its form, of small environmental changes, and is characteristic 

 of the species. The co-ordination ot cellular activity which initiates the 

 formation of the fruiting body is stimulated by a specific substance, analogous 

 to a hormone which diffuses from the vegetative cells. 



The great majority of these cells are transtormcd into typical microcysts 

 and thus survive. Some are embodied in the stalk and envelope, and are 

 sacrificed. Little is known of the mode ot formation oi these structures. 

 It has been stated that the cells which take part in their formation are cemented 

 together by dried mucus, but this appears to be mere supposition. It is known 

 that the physical properties of the envelope vary considerably in dirterent 

 species, and it may even be entirely absent. The envelope varies especially 

 in its physical strength and in its resistance to water. The fruiting bodies 

 of some species of myxobacteria burst open as soon as they are wetted. Others 

 remain intact. This characteristic has been considered to be of taxonomic 

 value by some botanists, but there is no reason to believe that it indicates 

 biological relationship. Whether the variation is due to differences in structure 

 and composition of the envelope is not known. 



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