38 DAIRY BACTERIOLOGY 



stab cultures in saccharose gelatine. Some species liquefy this 

 medium after some time, though they do not decompose casein. 

 The Leuconostocs (Fig. 12, p. 7), which may give a deal of 

 trouble in beet sugar manufacture, are Betacocci. They grow 

 at temperatures as low as 5 C., and some species thrive better 

 at room temperature than at 30 C. The sour cabbage bac- 

 terium, Sc. brassicce, also belongs to this group. 



FIG. 44. Various Betacocci in Stab Cultures in Cane-sugar Gelatine. 



Group B. The bacteria belonging to this group are not true 

 lactic acid bacteria, differing from the forms hitherto described 

 in forming catalase, reducing nitrates and generally growing well 

 on the surface of solid media. 



The microbacteria are very small rods, usually only 0-3 to 0-4 /z 

 thick, which stand fairly high temperatures, and are therefore to 

 be found in pasteurised milk. They form lactic acid, and some of 

 them (Bacillus acidophilus) are common intestinal organisms. To 

 these bacteria are related a group of small rod bacteria which 

 liquefy gelatine, but only produce traces of acid. 



The tetracocci include the acid-producing forms of the Micro- 

 cocci and Sarcince. Division into these two groups is not feasible, 

 and confusion may even occur with the Streptococcus group, as 

 many of the Tetracocci appear as diplococci ; they may, however, 

 readily be distinguished by their power to decompose hydrogen 

 peroxide, for, as mentioned above, they differ from the true lactic 

 acid bacteria in producing catalase. They produce less lactic acid 



