Differentiation of Certain Genera of Gram Negative Baeteria 509 



rod, which is fermentative in Hugh and Leifson's medium, forms 

 no gas from glucose and yet is insensitive to tiie pteridine com- 

 pound (0/129), Pseudomonas formicans appear to lack the 

 enzyme hychogenlyase, otherwise morphologically and biochemi- 

 cally it is more closely related to the Aeromonas group than to 

 the Vibrios and recent work by Liu (41), using the extracellular 

 antigens as a means of classification, suggests that in fact the 

 species Aeromonas liquefaciens and Pseudomonas formicans are 

 closely related. 



Bacterium, salmonicida is also a Gram negative rod, oxidase 

 positive, forming acid and gas from glucose, is fermentative in 

 Hugh and Leifson's medium but is non-motile. Liu believed B. 

 salmonicida to be a different organism from the Aeromonas 

 strains, with its lower optimum temperature, pigment formation 

 and lack of motility, yet he found some cross reactions with the 

 Aeromonas sp. and B. salmonicida and concluded that the latter 

 in fact belonged to this group. 



Recently we have been examining a large number of named 

 sti'ains of Vibrios, particularly in relation to the definition of 

 Vibrio given in our determinative scheme. The results are given in 

 Table 4. It will be noted that Vibrio comma, fresh water vibrios 

 of the Parachlora group. Vibrio foetus and Vibrio anguillarium 

 all fit in well to this definition. In agreement with Hugh and 

 Leifson (30), we consider that V. percolans and V. cuneatus are 

 not related eitlier morphologically or biochemically to Vibrio 

 ccnnma (39), and we would also exclude V. cyclosites, V. neo- 

 cistes (31), Vibrio jamaicaensis (11) and a few others. In our 

 hands, V. cuneatus appears to be a green fluorescent Pseu- 

 domonad (Group I), and V. percolans, V. cycloistes and V. 

 neocistes. Group III Pseudomonas spp. and V. famaicaenis, as 

 Caselitz later pointed out (12) is an Aeromonas sp. Vibrio al- 

 caligenes, it was proposed by Galarneavelt and Leifson (19), 

 should be given the new generic name of Lophomonas, but from 

 data axailable it fits well into our Group IV Pseudomonas sp. 



It will also be noted from Table 4 that some organisms for- 

 merly described as Pseudomonas sp. should, on physiological 

 and morphological grounds, now be placed in the Vibrio genus. 



