AEEOBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 295 



Thermal death point. Organisms survived heating in broth 

 in the Arnold steriHzer for one hour. Survived autoclaving 

 up to and including 19 pounds pressure, but were destroyed 

 by 20 pounds pressure. 



Bacillus mesentericus (Fliigge) Migula 1900 



This organism was first described by Fliigge in 1886 (Flugge, 

 1886) as a species distinct from Bacillus mesentericus-vulgatus 

 and named Bacillus mesentericus-fuscus. We have isolated a 

 number of organisms which correspond to the description given 

 by Flugge and also by Chester. It is one of the less common 

 of the aerobic spore-bearing bacteria but occurs in milk, soil, 

 dust and water. 



Morphology. Organisms about the same in morphology as 

 Bacillus mesentericus-vulgatus. On agar cultures in 24 hours 

 they are homogeneous rods measuring 0.5 by 1.5 to 3 microns. 

 Sometimes shorter forms predominate in the cultures, a little 

 over a micron in length. On glucose agar they are thicker 

 and longer measuring 0.75 by 2 to 5 microns, with many long 

 forms measuring 6 to 8 microns in length. (Figures 8 and 9.) 



Motility. Active motility, progressive and rotatory, in young 

 cultures. 



Staining properties. Gram-positive. 



Spore formation. Spores begin to form in 24 hours on plain 

 and on glucose agar. By the end of 48 hours they are very 

 abundant. They appear in the center or towards one end of 

 the rods and do not bulge the organism appreciably. The free 

 spores are cylindrical and may retain equal bits of protoplasm 

 at each end or this protoplasm may be unequal in amount 

 giving a characteristic appearance to the spore. They measure 

 about 0.5 by 1.125 microns. They rapidly lose their protoplasm 

 and become slightly more oval, measuring 0.5 by 0.75 microns. 



Agar slant. Soft white or cream-white growth somewhat 

 translucent when old, spreading but little from ohe line of inocula- 

 tion except in the presence of water of condensation. Easily 

 Ufted from the agar. Edges of growth irregular or serrate. 

 Growth does not become dry or wrinkled. 



