90 Microbes and You 



Since multiplication of true bacteria occurs at right angles to the 

 long axis (although there is evidence that at least some spirilla 

 multiply by longitudinal division), it should become apparent that 

 if complete separation of cells does not materialize after fission, the 

 possible arrangement of the cells will depend upon the original 

 shape of the organism. Since cocci possess no long axis, division 

 can take place at any angle with the result that the following 

 arrangements can and do exist: 



SPHERES 

 Coccus — Individual spheres 



(Coccus comes from the Greek kokkos, meaning berry.) 



Diplococcus 



This is formed by simple division of a sphere into two cocci 

 which remain attached. Such an arrangement is relatively common 

 and includes such organisms as the pneumococcus (Diplococcus 

 pneumoniae), the gonococcus {Neisseria gonorrheae), and the 

 meningococcus (Neisseria intracellularis) . While all three of these 

 examples happen to be pathogens, it is not the intention to imply 

 that all diplococci are disease-producers. 



Streptococcus 



Continued division of a diplococcus in the same plane forms a 

 chain of spheres resembling a strand of beads. The organism 

 (Streptococcus lactis) which plays such an important role in the 

 souring of milk and dairy products is an example of this beaded 

 arrangement. Streptococcus pyogenes, which is the etiological 

 agent in a number of human and possibly animal infections, is 

 another example of chain formation. 



Tetrads 



When a diplococcus divides in such a manner as to form a group 

 of four spheres in the same plane, rather than in a straight line, we 



