20 MASS. EXPERIMENT STATION BULLETIN 327 



The Study of Media Employed in, or Suggested for, the Bacterio- 

 logical Analysis of Water. (James E. Fuller and Evelyn D. Kimball.) This 

 study was undertaken for the purpose of determining the suitability of the 

 media in question for eliminating false presumptive tests caused by lactose- 

 fermenting bacteria or combinations of bacteria not of the Coli-Aerogenes 

 group, and for distinguishing the more significant from the less significant 

 members of the Coli-Aerogenes group of bacteria. Media studied were lactose 

 broth, brilliant green lactose peptone bile, the Dominick and Lauter medium, 

 Endo's agar, eosin methylene blue agar, the Tonney and Noble ferrocyanide 

 citrate agar, and MacConkey's bile salt agar. All media were prepared ac- 

 cording to directions in the seventh edition of the Standard Methods of Water 

 Analysis. Of the fluid media the brilliant green lactose peptone bile was most 

 effective in eliminating organisms which have been shown to interfere with 

 true presumptive tests, and those which may produce false presumptive tests. 

 Of the solid media the Tonney and Noble agar seems to offer much promise 

 for the elimination of Gram-positive organisms which in symbiosis give false 

 presumptive tests. This medium verified the claims made for it by its origi- 

 nators in differentiating pure cultures of Escherichia coli and Aerobacter aerog- 

 enes. It was not so effective with intermediate members of the group. 



Detection and Significance of Escherichia Coli in Commercial Fish 

 and Fillets. (Francis P. Griffiths of the U. S. Bureau of Fisheries, James E. 

 Fuller, and Ralph L. France. ) This was a joint study of the U. S. Bureau of 

 Fisheries and the Massachusetts Experiment Station. Twenty commercial 

 haddock fillets and five eviscerated whole haddock purchased at local retail 

 markets were examined for the presence of bacteria of the Coli-Aerogenes 

 group. Weighed portions of ground fish flesh were inoculated into brilliant 

 green lactose peptone bile broth. All organisms producing gas in this medium 

 were isolated and their reactions determined by means of Endo's agar, Koser's 

 sodium citrate medium, indol production, and the Voges-Proskauer and methyl 

 red tests. Typical Escherichia coli was found on sixteen of the fillets and two 

 of the eviscerated fish. Intermediate members of the Coli-Aerogenes group 

 were frequently encountered on both fish and fillets. It seems probable that 

 contamination of these fisheries products with bacteria of the Coli-Aerogenes 

 group occurs after the fish are caught, and results from more or less careless 

 methods of storage and marketing. It is suggested that the determination of 

 bacteria of the Coli-Aerogenes group may be employed as a means of deter- 

 mining the cleanliness of methods by which fisheries products are handled. 



Studies in Acid Production by Escherichia Coli and Aerobacter Aero- 

 genes. (A. V. Syrocki, James E. Fuller, and Ralph L. France. ) A report of 

 preliminary work on this study has been published (Jour. Bad. 30: 211, 1935.) 

 Briefly, the study showed that when pure cultures of Escherichia coli and Aero- 

 bacter aerogenes were grown in the Clark and Lubs medium containing 0.3 per- 

 cent buffer (K 2 HP0 4 ) and a small amount of finely ground iron metal, the 

 iron dissolved in the acid produced by Escherichia coli, while the buffer pre- 

 vented the production of sufficient acid by Aerobacter aerogenes to dissolve the 

 iron. Dissolved iron was indicated by the addition of potassium ferricyanide 

 solution to the cultures after incubation. Additional work is being done with 

 intermediate members of the Coli-Aerogenes group of bacteria. In general 

 the test for dissolved iron agreed with the methyl red test. Disagreement is 

 noticed especially with organisms giving a weak methyl red positive test. 

 These organisms frequently gave a negative test for dissolved iron. 



