CHAPTER IV.
CELL GROUPINGS.
It has been stated that bacteria reproduce by transverse division, that is, division across the long axis. Following repeated divisions the new cells may or may not remain attached. In the latter case the bacteria occur as separate isolated individuals. In the former, arrangements characteristic of the particular organism almost invariably result. These arrangements are best described as cell groupings or growth forms.
Fig. 41.—Streptospirillum grouping.
Fig. 42.—Diplobacillus grouping.
In the case of spiral forms it is obvious that there is only one possible grouping, that is, in chains of two or more individuals adherent end to end. A chain of two spirilla might be called a diplospirillum (διπλός = double); of three or more, a streptospirillum (στρεπτός = necklace, chain) ([Fig. 41]). These terms are rarely used, since spirilla do not ordinarily remain attached. Likewise the bacillus can grow only in chains of two or more, and the terms diplobacillus ([Fig. 42]), bacilli in groups of two, and streptobacillus ([Fig. 43]), bacilli in chains are frequently used. Still the terms thread, filament, or chain are more common for streptobacillus.
Fig. 43.—Streptobacillus
grouping.