Some Biochemical Differences 



433 



>-IOOr 



0.2 0.3 0.34 



NnCI MOLARITY 



Fig. 3. Osmotic fragility of O.F.V.s from Desulfovihrio desxilfuricans. Os- 

 motically fragile vibrios were prepared (see text) in environments of diverse 

 salinities. They were made from Q ^^^ salt-water strain El Agheila Z, ^ the 

 fresh water Hildenborough strain and ^ the Hildenborough strain adapted 

 to a saline environment and the extents of lysis measured after 60 minutes 



at 37 C. 



significantly to alter the optical density by dilution, and the tubes 

 were incubated at 40 C for one hour. The optical densities of the 

 suspension after incul:)ation were used to obtain Figure 3. In spite 

 of the cultural habit of the salt-water strain, its O.F.V.s were 

 less fragile than those from the fresh water strain; training the 

 fresh water strain to a salt water habit had caused its O.F.V.s to 

 take on the characters of the natinal salt water type. 



( II ) Secretion of Mucin 



Slime fomiation by D. clesulfuricans in various conditions has 

 been mentioned by several workers (8, 20, 23). Casual obser- 

 vation at the National Chemical Laboratory had suggested that 

 slime was to be found most often in old cultures of salt water 

 varieties and a systematic experiment was designed to test this 

 belief, making use of an increase in the \ iscosity of the culture 

 that characterized the appearance of slime. Figure 4 shows the 

 results of the experiment, in which the Hildenbrough strain, 

 its salt-adapted variant and strain El Agheila Z were grown at 



