96 THE CYTOLOGY AND LIFE-HISTORY OF BACTERIA 



In these organisms the branch appears first as a small, lateral bud in the 

 cell wall. It elongates, but before it attains to any great size, a septum is 

 formed, dividing it from the parent cell. The branch eventually breaks off 

 at this point and continues to grow as a separate fdament. This method of 

 branching is quite unlike that of streptomyces or fungi, in which the mature 

 branch remains attached to the main stem, and in which the cell itself is 

 branched. It more closely resembles the budding of yeasts, and results in 

 the production, not of a stable mycelium, but of an increased number of 

 individual fdaments. It may be considered to be a device designed to permit 

 simple, vegetative fission in a filamentous type of bacterium. 



This type of brandling is also found in " soil diphtheroids." These 

 bacteria have little resemblance to C. diphtheric^ but have this, and other 

 characters in common with actinomyces. 



Branching in streptomyces is a permanent and integral part of their 

 structure, and it results in the formation of a fungus-like mycelium, which 

 may be regarded as a single organism. Cell division takes place by the pro- 

 duction of transverse septa, often at considerable intervals, occasionally close 

 together. True myceha are not formed by other bacteria. Even in the case 

 of actinomyces and filamentous soil bacteria the mycelium-like tangle of 

 filaments, which may be produced, is in fact a mass of separate, filamentous 

 bacteria. These false mycelia and the true mycelium of streptomyces arc 

 both hablc to disintegrate into bacillary fragments, and reproduction, in tl 

 sense of distribution o£ the species, may occur from the dissemination of the 

 fragments, as well, in the case of streptomyces, as by the production of sp 



Branching in mycobacteria and coryncbactcria is even more transient 

 than in the case of actinomyces, and is confined to a number of specialised 

 strains. It is obvious that microscopic appearances suggestive of branching 

 must be regarded with caution when they occur in bacterial genera which 

 possess so complex a structure, and especially when this structure is not made 

 apparent by standard techniques. Many of the reports of branching in these 

 genera are thus of doubtful value. One of the main exceptions is the avian 

 strain of M. tuberculosis described by Brieger and Fell (1945), which branches 

 freely. In this case the appearance suggests that the branch is usually divided 

 from the main stem by a cell wall. Branching is unusual, although not 



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