222 CONTROL OF ROPE IN BREAD 



no general agreement as to the kind or quantity of acid that should 

 be employed, or the scientific explanation of its action. 



The present investigation has been upon a strain of Bacillus mesen- 

 tericus isolated from a ropy loaf and characterized by one of us. In 

 addition three other cultures, from two other sources, have been 

 examined and appear to be identical. 



The bacteriological study of the bacillus, which belongs to the Bacillus 

 mesentericus group, is not completed and there has been no opportunity 

 for comparison with cultures from other sources. Since a number of 

 bacteria, all probably closely related, have been described as causes 

 of ropy bread and since the bacteriological data are meager and not 

 recent, it seems best, for the present, not to name the organism iso- 

 lated in this vicinity. Its relationship to the production of character- 

 istic rope has been proved beyond question, and the four cultures 

 from three different local sources are identical. 



The bacillus is a motile. Gram-positive, spore-bearing bacillus. In 

 24 hour cultures on plain agar its dimensions average 2.5 microns by 

 0.5 to 0.75 microns. The ends of the rods are rounded. The spores 

 are ovoid in shape and are situated approximately in the middle of 

 the bacilli. The width of the spores slightly exceeds that of the rods 

 and they measure 0.5 to 1.75 microns by 0.75 to 0.85 microns. The 

 spores are produced in great abundance in cultures less than 24 hours 

 old and are extremely resistartt to boiling. 



The bacillus is a strict aerobe. It grows readily on all ordinary 

 media, resulting in a decrease of acidity. Coagulated blood serum is 

 completely liquefied. Litmus milk is rapidly curdled and liquefied. 

 The litmus is reduced in the depths of the medium but at the sur- 

 face the color becomes deeper blue. Cultures in agar are odorless, 

 but in wheat flour media the characteristic odor of ropy bread is 

 produced. 



The colonies on agar media are flat, finely granular, dull white or 

 grayish, with irregular margins. In 24 hours the colonies become 

 wrinkled or thrown into coarsely irregular elevations, and the mar- 

 gins become convoluted or arborescent. Colonies several days old 

 develop a brownish tint which is more marked upon media contain- 

 ing carbohydrates. On liquid media a wrinkled and convoluted 

 pelHcle is formed; turbidity develops slowly, and begins beneath the 

 surface pellicle. 



