TYPES OF COLON-AEROGENES GROUP IN WATER 325 



No. 6. Davis Brook. This is a very small stream in the Maine 

 woods. About 1 mile above the point where the sample was taken 

 it flows from a small but very deep pond fed l)y submerged springs. 

 On the upper end of this pond is a summer camp. Considering the 

 very small flow from the pond there is only a remote probability of 

 any contamination from this camp affecting the stream. 



One of the 4 cultures isolated was of the B. coli type. Two of the 

 B. aerogenes cultures did not ferment adonite or starch and one fer- 

 mented starch but the fermentation of adonite was not determined. 



Lactose broth tubes inoculated with 1 cc. of water gave small 

 amounts of gas in forty-eight hours. 



No. 5. Small Brook. This is a very small stream flowing through 

 dense woods except that at about a mile above where the sample was 

 taken it crosses a highway. 



Lactose broth inoculated with 10 cc. of water gave a small amount 

 of gas in forty-eight hours. Of the 4 gas forming cultures isolated 2 

 were of the B. coli type, one was a high ratio liquefier and one was a 

 B. aerogenes which failed to ferment adonite. 



CONCLUSIONS 



Through its^ greater resistance to the unfavorable conditions 

 found in w^ater the B. aerogenes type is able to survive longer 

 than B. coli. This was apparent in the water held in bottles, 

 in the sewage held in parchment sacs, in running water and in 

 polluted streams. From this we may draw the inference that 

 water near the source of pollution should contain a greater pro- 

 portion of B. coli to B. aerogenes than after the processes of self 

 purification have had an opportunity to act. This was found 

 to be the case in two sewage polluted streams. In each case 

 the gas forming bacteria isolated above the source of pollution 

 consisted largely of B. aerogenes cultures, while immediately 

 below the sewers a majority of the cultures isolated were of the 

 B. coli type. 



At lower points on the streams the proportion of B. aerogenes 

 increased again. In the only case in which suitable determi- 

 nations were made it was found that a similar relation existed 

 between the fecal and nonfecal types of B. aerogenes. 



THE JOURNAL OF BACTERIOLOGT, VOL. Ill, NO. 4 



