44 CONDITIONS OF BACTERIAL LIFE. 



apparent injurious influence upon fungi, which remain absolutely 

 undeveloped in an atmosphere of pure CO2 (C. Frankel, Z. H. V, 

 332). 



Sulphuretted hydrogen appears to be well borne by 



anaerobes (see above); other varieties are very susceptible 

 to large quantities, as, for example, Bact. Pfliigeri (photo- 

 genic bacillus) (Lehmann and Tollhausen, C. B. v, 785). 



6. INFLUENCE OF TEMPERATURE ON THE 

 LIFE OF BACTERIA. 



Every variety of bacterium demands a certain tempera- 

 ture of the nutrient substratum. Vegetative bacterial 

 life is possible from 0° to 70°, some varieties thriving at 

 the upper and some at the lower extreme. For each va- 

 riety the minimum and maximum temperatures lie about 

 30° apart, ^ and we may form a comprehensive classifica- 

 tion dependent upon the temperature required somewhat 

 as follows: 



Psychrophilic bacteria : minimum at 0°, optimum at 

 15° to 20°, maximum at about 30°. Most water bacteria 

 belong here; for example, many phosphorescent bacteria 

 of the sea. (Compare Forster, C. B. xii, 431.) 



Mesophilic bacteria : minimum at 10° to 15°, optimum 

 at 37°, maximum at about 45°. Here belong all varieties 

 pathogenic for man, since one condition for a pathogenic 

 action is an acclimatization to the body temperature. 



The B. Tulgatus connects this and the following group, as it still 

 grows well at 50°. 



Thermophilic bacteria: minimum, 40° to 49°; opti- 

 mum, 50° to 55°; maximum, 60° to 70° Here belong 

 many bacteria of the soil, and almost all spore-producing 

 bacilli of the family of B. mesentericus (Globie, Z H iii 

 294). s, . . , 



More lately Lydia Eabinowitsch has somewhat more closely described 

 eight thermophilic facultative anaerobes, all of which are spore-produc- 



'Bao. vulgatns thrives, to be sure, from 15° to 50°, a variety of 

 Globig also from 15° to 68°, but such wide intervals of favorable tem- 

 perature are very rare. Globig found the range of temperature at 

 which thermophilic varieties will develop to be very narrow • for ex- 

 ample, he could grow one variety only from 54° to 65°. 



