Apr. 22, i9i8 Bacterial Flora of Roquefort Cheese 231 



and coccus forms. The organisms that made up the shme were isolated 

 by plating on various kinds of agar, plain agar, Czapek's agar, cheese- 

 infusion agar, and plain agar to which lactic acid was added to eliminate 

 the growth of bacteria and to favor the growth of yeasts and molds. 

 The isolated bacteria were submitted to various tests commonly used for 

 the difiFerentiation of bacteria. The most frequently isolated organisms 

 found in the slime from the imported and the experimental cheeses was a 

 micrococcus which gave an abundant yellowish growth on agar slope, 

 liquefied gelatin very slightly, decomposed urea, and stopped the fer- 

 mentation of carbohydrates at a hydrogen-ion concentration of about 

 Ph = 5-6. Many other cocci differing only slightly from the description 

 above were isolated from the slime. Micrococci identical with these cocci 

 have been isolated commonly from aseptically drawn milk (2). It 

 appears, then, that the udder is the source of the predominating flora of 

 the cheese slime. There is apparently a selection of certain strains of 

 udder cocci. The majority of them curdle milk, but no micrococcus 

 isolated from cheese slime produced more than a slight acidity. 



Another coccus fairly common in the slime from both imported and 

 experimental cheese was exceedingly difficult to maintain on agar slopes. 

 It formed a faint growth on agar and failed to attack the nitrogenous 

 and carbohydrate test substances in broth cultures. It was surprising 

 to find an organism that was capable of withstanding the rigorous con- 

 ditions in the cheese slime and yet so delicate that it could scarcely be 

 maintained under artificial cultivation. 



The most frequently isolated rod form liquefied gelatin, decomposed 

 asparagin, and gave an alkaline reaction in broths containing various 

 carbohydrate test substances. Other rod forms differed slightly from 

 this one. 



Besides the types which have been briefly described as typical slime 

 organisms, various kinds of cocci and rods were isolated only once or 

 twice, which do not seem to be characteristic of the slime. For exam- 

 ple, Bacterium bulgaricum was isolated from the slime once. Occasional 

 colonies of mold, most frequently Penicillium roqueforti, appeared in the 

 cultures. 



None of the cheese-slime organisms were able to bring about any 

 pronounced changes in milk in pure culture, but when pure culture of 

 several types were inoculated together into milk their associative action 

 digested the casein very slowly. 



It would be a difficult matter to prove that these sluggish proteolytic 

 enzyms either do or do not influence the ripening of the cheese. Gratz 

 and Szanyi (5) made a careful chemical investigation of the action of 

 the enzyms of the slime upon the ripening of the interior of hard cheeses 

 of the Ovar and Trappist varieties on which the slime often becomes 

 heavy. The authors concluded that in hard cheese of the type studied 

 no ripening proceeds from the outside. The relative inactivity of the 



