418 STATE BOARD OF AGRICULTURE. 



THE DEVELOPMENT OF SOME BUTTER BACTERIA AT A LOW 



TEMPERATURE. 



In the presence of mixed cultures, temperature is such an important 

 factor that special attention has been given to it in some work which has been 

 carried on at this station during the past j^ear. In attempting to discover 

 the nature of the changes which take place in butter stored at a Ioav tem- 

 perature for a considerable period of time, the initial content of micro- 

 organisms in the butter — bacteria, j^easts and molds — capab'e of developing 

 under standard laboratory conditions was at first determined. At the same 

 time and from the same dilutions other plates were made, using whey gela- 

 tin prepared according to the method of Conn, (Bacteria in Milk and its 

 Products, 1903, p. 270) and incubating in one of the cold storage rooms 

 where a temperature of 4°-5° C. was maintained. Whey gelatin was used 

 as it was thought 'at that time that this medium was one which would allow 

 the development of the maximum number of organisms. Subsequent work 

 has not entirely substantiated this view. 



It was at fu'st intended to watch the plates carefully and to count and 

 isolate all micro-organisms which might develop, at a time sufficiently early 

 to prevent disastrous liquefaction of the gelatin. It was found, on obser- 

 vation, that no serious liquefaction took place in 30 days, and all plates were, 

 therefore, held and counted at the end of this rather long period. 



The isolated micro-organisms were allowed to develop in broth for about 

 two days, plated out on gelatin and isolated from these plates to slant agar 

 tubes; these cultures being compared with the descriptions of the original 

 colonies from which they were first isolated. Sub-cultures vrere then run 

 in broth, gelatin, miik, potato, 1% dextrose, lactose and saccharose 

 broth in fermentation tubes, and in Dunham's solution for indol. Full de- 

 scriptions of all cultural characteristics w^ere preserved. 



As shown by the tables, the counts of the plates held at the low tem- 

 perature are very much low^er than the standard counts, but, on the other 

 hand, they are much higher than had been anticipated. Typical lactic 

 organisms {Bad lactis acidi) developed in numbers equal to about one- 

 third of the number developing normally. Other microbes did not, as a 

 rule, fare so well but were observed in considerable numbers, the acid pro- 

 ducers — both liquefiere and non-liquefiers — appearing in rather larger 

 numbers, relatively, than those not splitting the sugars. This may be due 

 to their greater resistance to cold or to their greater inhibition in the stand- 

 ard plates. 



Most of the yeasts, both non-liquefying and liquefying, found in the stand- 

 ard plates, were also met with in the low temperature plates, though some- 

 what less numerous. One variety often gave rise to a form 

 of colony not often found in this work. The colony 

 became first umbonate^ later this projection extended 

 vertically to some distance forming what might almost be called a stem, 

 which sometimes bent over and touched the surface of the gelatin outside the 

 base of the colony. 



Aside from the cultural characteristics mentioned, the work sho^^-^ that 



