ANNUAL REPORT, 1937 27 



tion of a privately owned rural water supply frequently involves a serious financial 

 problem to the owner, and it is for this reason that research in the physiology of 

 the Coli-Aerogenes group was undertaken in the hope that more information 

 could be obtained as to methods of differentiating members of the group, in order 

 that a better understanding of their relative sanitary significance might result. 



The Influence of Bile and Bile Salts on Aerobacter Aerogenes. (James E. 

 Fuller.) A preliminary report has been made on this study (Mass. Expt. Sta. 

 Bui. 339, 1937). The study was undertaken to investigate the premise of certain 

 investigators that Escherichia coli may become Aerobacter aerogenes, and vice 

 versa, as a result of environment. Since bile is an important constituent of the 

 fecal mass in the human colon, it could be an important environmental factor 

 in converting Aerobacter aerogenes to Escherichia coli, if the premise should be 

 true. Twenty-five strains of Aerobacter aerogenes, originally isolated from water, 

 were cultivated for five months in one percent, and in five percent, concentrations 

 of bile and of bile salts (sodium glycocholate and sodium taurocholate). At the 

 end of five months' incubation the reactions of the strains to the difTerential tests 

 (Voges-Proskauer, methyl-red, sodium citrate, uric acid, and indol production), 

 and their morphology and staining characteristics were unaltered. This research 

 does not lend any support to the premise mentioned above. 



The Effect of Bacteriophage on Escherichia coli. (Amedeo Bondi, Jr. and 

 James E. Fuller.) This study, like the one above, was undertaken to investigate 

 the stability of members of the Coli-Aerogenes group. Bacteriophage is an en- 

 vironmental factor which, when it acts on a susceptible bacterial strain, sometimes 

 produces cultures quite different from the parent strain in appearance and be- 

 haviour. Several strains of Escherichia coli were subjected to the influence of a 

 strain of bacteriophage which was specific for one of the strains, but not for the 

 others. The biochemical reactions (lactose fermentation, indol production, and 

 the methyl-red, sodium citrate, and sodium malonate reactions) were not changed. 

 The strain subjected to the action of its specific bacteriophage yielded atypical 

 colonies on nutrient agar and on Endo's medium. Subcultures from these atypical 

 colonies were resistant to the action of the bacteriophage which had produced 

 them, and were agglutinated by higher dilutions of a specific serum than were 

 cultures of the same bacterial strain before it had been subjected to the action 

 of the bacteriophage. 



The Action of the Coli-Aerogenes Group on Erythrosin. (Ralph L. France.) 

 The results of this study are published in Zentralblatt fur Bakteriologie II Abt., 

 Bd. 97, 1937. 



A Study of the Eijkman Test. (Ralph L. France.) A pure culture study of 

 strains of the Coli-Aerogenes group indicate that the Escherichia coli strains are 

 the only ones that produce acid and gas in the Eijkman broth at 46° C. How- 

 ever, certain strains of intermediates and Aerobacter aerogenes produce acid, but 

 no gas, at 46° C. Further studies are being conducted to determine the extent of 

 growth of strains of intermediates and Aerobacter aerogenes in the Eijkman broth, 

 at 46°, 45°, 44°, and 43° C. 



The Tolerance of the Coli-Aerogenes Group for Brilliant Green. (Ralph L. 

 France.) No work has been done on this project since the last report of progress 

 (Mass. Expt. Sta. Bui. 339, 1937). The project will be completed this year. 



A Comparative Study of Proposed New Methods and the Standard Methods 

 for Obtaining Bacteria Counts of Milk Samples. (Ralph L. France.) The results 



