STUDIES ON THERMOPHILIC BACTERIA. I 357 



believed that the temperature relations of the thermophilic group 

 of microorganisms is a subject worthy of intensive study, a sepa- 

 rate investigation on this subject was initiated which is now near- 

 ing completion in this laboratory. 



V. DISCUSSION 



A comparative study of 52 strains of thermophilic bacteria 

 from water indicates a group in which the characteristics are not 

 widel}^ divergent. All of the strains were spore formers and all 

 Uquefied gelatin. When separated into groups according to the 

 "group number" they fell into nine groups. JNIost of these groups 

 were defined by differences in the terminal reaction in glycerol 

 and carbohydrate media. If these determinations are neglected 

 all of the strains would have fallen into one group. 



A survey of the literature on thermophilic bacteria indicates 

 that many of the strains there described have been superficially 

 studied and that new strains have been named without sufficient 

 data. Consequently many of the names which are used for 

 thermophilic bacteria are being appUed to the same organism. 



Without exception the 52 cultures which were used in this 

 study formed spores and in this characteristic seem to agree with 

 most of thermophilic bacteria which have been described in the 

 literature. This then seems to be the most common characteris- 

 tic of members of this group. It has also been the basis for in- 

 cluding among the thermophilic bacteria, bacteria which do not 

 belong there. Spore formation when taken into consideration 

 along with the pecufiar reaction to temperature makes the ther- 

 mophilic bacteria a difficult group for canners of foods, for in- 

 stance, to cope with. The abiUty to form spores allows the 

 thermophilic bacteria to survive the process and perhaps to de- 

 velop when the cans are stacked in the warehouse. The recent 

 publications of Weinzirl, Cheney, Bigelow and Esty, and others 

 have indicated the significance of these bacteria. They are also 

 related to certain phases of the dairy industry. Fliigge, Leich- 

 mann, Russell and Hastings have found that they are able to 

 survive pasteurization temperatures. 



