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U.S. BUREAU OF FISHERIES 



some slimy material but no particular indication of capsules. As 

 long as the purity of the cultures is in doubt, it is impossible to deter- 

 mine definitel}' the morphology of the organisms. (Several reisola- 

 tions of these cultures are being studied at present.) 



The best stains are carbol-erythrosin (Conn) and carbol-fuchsin. 

 The former requires about 10 minutes to stain and the latter 30 

 seconds to 1 minute. Carbol-erythrosin is supposed not to stain 



foreign matter to any great extent 

 but to be specific for bacterial 

 protoplasm. 



Colony formation and growth 

 characteristics. — On cellulose agar 

 plate cultures there are a number 

 of characteristic colonies that 

 regularly appear. A white colony 

 with a rhizoid appearance under 

 the microscope, a finely granular 

 internal structure, generally less 

 than 0.5 millimeter in diameter, 

 and surrounded by a halo of clear 

 agar where the cellulose has been 

 dissolved; a white punctiform col- 

 ony also about 0.5 millimeter 

 in diameter, undulate edge, and 

 finely granular internal structure 

 which also causes cellulose to be 

 dissolved; a yellow chromogenic 

 colony generally appearing as a 

 football-shaped deep colony that 

 sometimes breaks through the sur- 

 face and grows sparsely in a round 

 colony — the deep colony has a 

 finely granular structure, and the 

 surface colony looks rolled up like 

 globules of yellow fat on a wet 

 surface. In plate cultures of the 

 more active impure liquid cultures 

 one may find many other forms 

 which need not be described. 

 When slants are inoculated from 

 plates, in general, the growth is so 

 light, if there is any at all, that it 

 is hardly characteristic. 

 None of the ordinary methods for obtaining pure cultures of these 

 bacteria was successful. They do not grow well on solid media and 

 seem to lose their power to ferment cellulose ; accordingly the method 

 of picking colonies off plates has not yet worked successfully. How- 

 ever, there is no basis for the belief that these bacteria can not grow on 

 cellulose agar. The only limitation seems to be that the active 

 culture media should be streaked across the surface rather than broken 

 up into separate colonies. If the first procedure is adopted an inocu- 

 lation from the growth on agar into fresh media will cause fermentation, 

 whereas if the separate colonies are picked off and inoculated into 

 fresh media growth occurs but no cellulose fermentation. As has 



Figure :i— Cellulose-agiir plates with clear 

 zones showing the presence of colonies of cellu- 

 lose-digesting bacteria 



