Studies on the Stability of the Na'^ Requirement 



487 



in trypticase agar prepared witliout Na"^. Morphologically the 

 isolates were all found to be gram negative pleomorphic motile 

 rods indistinguishable from the parent culture. A summary of the 

 results of a few biochemical tests is presented in Table 5. All of 

 the cultures behaved in the same way except in the gelatin lique- 

 faction and niti'ate reduction tests. None of the derived cultines 

 was capable of liquefying gelatin either in the presence or ab- 

 sence of Na"^, though the original culture was an active gelatin 

 liquefier. Eight of the fourteen isolates behaved like the parent 

 culture in being unable to reduce nitrate, while three reduced it 

 slightly and three gave a strong positive test. Another difference 

 between the parent and the cultures derived by U. V. iiTadiation 

 lay in their capacity to autolyze. It is typical of organism B-16 and 

 other marine bacteria examined here that once growth has ceased 

 in a culture the cells autolyze rapidly on further incubation. The 

 mutant cultures, however, did not autolyze detectably under the 

 same conditions even when Na^ was added. The culture adapted 

 to grow in the trypticase medium without added NaCl was in- 

 distinguishable from the parent in its reactions in all of the tests. 

 Since ultraviolet-induced mutants of organism B-16 still 



TABLE 5 



Comparison of Results of Biochemical Tests on Marine Bacterium B-16, 

 Adapted B-16 and 14 Isolates Derived From B-16 by Ultra-Violet 



Irradiation 



^ Stratiform. 



- One of the eight isolates demonstrated slight stratiform liquefaction. The cells 



in all sixteen cultures were morphologically indistinguishable and were gram 



negative, motile rods. 

 3 Acid and gas formation negative from glucose, arabinose, maltose, sucrose, dul- 



citol, lactose. 



