NET DETERIORATION IN LAKE ERIE 



155 



been mentioned, however, in the paragraph on colony morphology 

 there are halos around single colonies which indicate that cellulose 

 is being fermented. Except for the last fact one would be inclined 

 to believe the action an associative one. The inconsistency might 

 be explained by assuming that the colonies with halos around them 

 are impure or that other colonies near them were secreting an enzyme 

 which aided them to ferment cellulose. The frequency of the occur- 

 rence of yellow colonies when active cultures are plated out and the 

 presence of a yellow precipitate at the bottom of active liquid cultures 

 would lead one to suspect that this chromogenic organism had some- 

 thing to do with the cellulose fermentation. 



The yellow colonies, which all seem to have the same colony 

 morphology, grow but sparsely on cellulose agar. In shaken cultures 

 it is apparent that their oxygen requirements are very definite- — 



.^-— ^- 



GRAPHICAL PRESENTATION 



OF RESULTS or EXPERIMENT 4 

 Brsakina SiretTgfh of Tiwne 



-o — — o- A- Sterile CbnTrvl 



B-Disfilkrd rvarsr 



C-Tap Water 



O-Lake Water 



-£-Lake loafer r S//mr 

 - F' Oubos fl^eci/a t- ^fima 



A-^ 



^ 



^me in V^eeks 

 Figure 4. — Breaking strength of twine in experiment 4 



slightly below the concentration of the atmosphere. If they were 

 associated in the fermentation, its nearly anaerobic character would be 

 explained. 



The cultures seem to lose gradually their power to destroy paper 

 at the surface of Dubos media. This could be explained in one of 

 several ways: (1) That the cellulose of paper is different from that 

 of twine and more difficult to attack, and the power to attack it is 

 lost more quickly than the power to attack cotton fibers ; (2) that the 

 nitrogen found in the lumen of the cotton fiber is helpful for bacterial 

 growth and hence causes the cotton to be fermented more readily; 

 (3) that there are two distinct kinds of organisms acting in our 

 cultures — one aerobic which quickly loses its power to ferment cellulose 

 in culture media and one facultative or slightly anaerobic form which 

 can be cultured more easily. The results of the experiment with 



112709—30 2 



