92 Microbes and You 



ment of the spheres in pairs will eventually predominate in the 

 mature culture. 



RODS 

 In contrast to the cocci, rod-shaped bacteria can only divide one 

 way— at right angles to the long axis, and this limits the number of 

 possible arrangements such rods can have. 



Diplobacillus 



If the single rod divides and the two newly formed rods adhere 

 to one another, the result is a diplobacillus. 



Streptobacillus 



Should the diplobacillus in turn divide and the four rods form 

 a chain, we speak of this arrangement as a streptobacillus. 



SPIRALS 

 Spirals do not ordinarily remain in close proximity after the 

 signal for them to divide has been relayed to the proper trigger 

 mechanism. It is relatively uncommon, therefore, to see spirals in 

 any arrangement other than singles and occasionally pairs. The 

 looseness or the tightness of the twists in a spiral are also of some 

 diagnostic significance. The tight cork-screw appearance of a 

 living syphilis germ (Treponema pallidum) as it spins its way 

 through the fluid obtained from a suspected lesion being examined 

 under the darkfield microscope is so characteristic that a trained 

 observer can confirm a clinical diagnosis of this terrible disease. 

 In trench mouth the appearance of long, loose spirals found in 

 association with fusiform bacteria (rods pointed at each end) in 

 a stained smear made from material swabbed from the gum line 

 of the teeth is a laboratory confirmation of a clinical diagnosis of 

 this troublesome affliction. 



THE WEIGHT OF BACTERIA 



A curious individual might be tempted to speculate as to the 

 weight of a single bacterium. To dismiss the inquiry by stating 

 that they don't weigh very much is avoiding the issue. People 



