MICROCOCCI 491 



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RHINE WATER MICROCOCCUS ' (Burri) 



LIQUEFIES GELATINE 



Authority. Burri, Ueber einige zum Zwecke der Artcharakterisirung an- 

 zuivendende bacterioloc/ische Untersiichungsmethodcn nebst Beschreibunq von 

 zivei neuen aus Rheinwasser isolirten Bacterien, Muenchen, 1893 (Olden- 

 bourg). 



Where Found. In the Eiver Rhine in the vicinity of Cologne. 



Microscopic Appearance. Cocci varying in diameter from ^ to 1^ /*, the 

 majority, however, measure | to 1 /*. Hardly ever quite round, but mostly flat- 

 tened. Occurs in tetrads occasionally ; no real chains are formed ; three 

 individuals, however, sometimes hang together. Not motile. Is readily 

 stained by the ordinary aqueous solutions of aniline colours. 



Cultures. 



GELATINE PLATES. The surface colonies are visible in from two to three 

 days as minute white dots, which under a low power are seen to be circular discs 

 with a slightly irregular edge, which is distinctly granular. After seven days the 

 colonies are still very small, and begin to sink in the softened gelatine. Some 

 weeks later each colony rests in a depression filled with stringy, liquid gelatine. 

 The depth colonies, under a low power, are mostly lenticular in shape, and 

 exhibit granular structure near the periphery. 



GELATINE TUBES. After two days a slight depression is visible at the point of 

 inoculation which later resembles an air-bubble. At the end of eight days a 

 long but very narrow funnel is formed containing quite clear liquid in the upper 

 part, whilst at the bottom a white granular deposit collects, and a pellicle 

 forms on the surface. The growth is very slow ; later numerous fine floc- 

 culent particles pervade the otherwise clear liquid. 



GLYCERINE-AGAR PLATES. At 30 C. after about two days pure white, soft, 

 very shining, slightly convex discs make their appearance. Under a low power 

 the rim is distinctly granular, but with a higher power the whole of the con- 

 tents are seen to be granular ; towards the periphery the granulation becomes 

 less and less compact, and gradually becomes disintegrated. The contents are 

 viscid. The depth colonies resemble those found on gelatine plates. 



GLYCERINE-AGAR TUBES. At 30 C or 37 C. after twenty-four hours a white, 

 shining, smeary, viscid, and irregular expansion appears all along the streak of 

 the needle. The growth does not later increase very materially in extent. 



POTATOES. On slightly acid potatoes it produces a flat, white, and restricted 

 expansion, which later becomes rather thicker, but remains flat. The growth 

 is viscid and stringy. On potatoes treated with O05 per cent, of carbonate of 

 soda it only grows very feebly. 



BROTH. At 30 C. in twenty-four hours the liquid is very turbid, and never 

 subsequently becomes clear. A finely granular white deposit collects at the 

 bottom. 



STERILISED MILK. No appreciable growth and no coagulation. After four- 

 teen days the milk has a slightly acid reaction. 



Remarks. Grows very slowly at from 20 to 22 C., but develops rapidly at from 

 30 to 37 C. Vigorous broth-cultures can resist half an hour's exposure to 60 C., but 

 they are destroyed at 80 C., also when boiled once and for a short time. Develops 

 best on neutral or slightly acid media. An addition of 0'3 per cent, of carbonate of 

 soda to the culture material entirely stops its growth. No gas is produced even in 

 media containing dextrin*. Not pathogenic to guinea-pigs. 



