512 PSEUDOMONAS 



Ps. cyanogena is a motile bacillus possessing polar flagella. It forms two pigments : 

 one fluorescent, the other varying in colour from blue to brown or black. In milk with 

 an acid reaction it gives rise to a bright blue colour. It is the cause of epidemics of 

 " blue milk." 



Pseudomonas denitrificans. — ^This organism was originally described by Chris- 

 tensen (1903-04) under the name of Bacillus denitrificans fluorescens. Two varieties 

 were recognized, A and B : variety A was isolated from garden earth, and was 

 able to reduce nitrates to gaseous nitrogen ; variety B was isolated from horse 

 dung, and was able to reduce nitrites, but not nitrates, to gaseous nitrogen. 



Variety ^ is a small bacillus, 0-5-1 -25 fi X 0-5-0-7 fx. It is surrounded by a large 

 capsule, measuring 2-5 /n in diameter. Appears to be slightly motile. Often shows 

 bipolar staining. Is Gram-negative. Grows freely at 25° C. Colonies on agar are 2-3 

 mm. in diameter after 3 days, and are circular, with an entire edge ; they have an opales- 

 cent sheen. In an agar stroke culture a whitish glistening growth is formed and the agar 

 is coloured bright green. In gelatin stab there is a filiform growth, and a whitish surface 

 growth with a lobate edge ; the gelatin is not liquefied. In a gelatin stroke culture there 

 is a dirty-white layer of growth, which fluoresces brilliantly in transmitted light ; the 

 gelatin is coloured bright-green. In broth there is a dense turbidity, and a very thick 

 wrinkled surface pelUcle, which climbs up the walls of the tabe. In 0-2 per cent, nitrate 

 broth a dense turbidity is produced, and a foam, due to the liberation of gaseous nitrogen, 

 is seen, reaching its maximum in 40 hours ; the nitrate is not completely destroyed, even 

 in 3 weeks. 



Variety 5 is a larger bacillus, 1-3 /i long by 0'5-l-25 /* broad, and is surrounded by 

 a capsule. Motility doubtful. Gram-negative. It is unable to reduce nitrates to nitrites, 

 but is able to reduce nitrites to gaseous nitrogen. Colonies on agar are 2-5-3-5 mm. in 

 diameter after 2 to 3 days, and are flat, whitish, and so fluid that they may flow over 

 the agar if the plate is stood on edge. In agar stroke culture there is a thinnish filiform 

 grey growth, having an effuse iridescent peripheral extension ; after 10 daj^s the agar 

 is slightly coffee-coloured. In gelatin stroke culture there is a greyish or slightly brownish 

 layer of growth, which fluoresces strongly in transmitted light ; the gelatin is coloured 

 brown. In broth there is a dense turbidity, and a thin, iridescent surface pellicle. 



Pseudomonas cavise. — ^This name was suggested by Scherago (1937) for a capsulated 

 organism that he isolated from the blood and viscera of young guinea-pigs dying from 

 a rapid bactersemic infection. Its general properties are as follows : Gram-negative rods, 

 1-5 yu long by 0-6-0-75 /x broad, occurring singly and in pairs end-to-end. Actively motile 

 by 1 to 3 polar flageUa. Encapsulated when isolated from the animal body. Surface 

 colonies on agar are 1-3 mm. in diameter, convex, smooth, iridescent and translucent, 

 with a finely granular structure. In agar slope cultvu-es the medium becomes greenish- 

 yellow in a week, and later turns brownish-yellow. Uniform turbidity in broth with a 

 surface ring and peUicle and a heavy granular deposit, light yellow in colour. Infundi- 

 buliform Uquefaction of gelatin, complete in 2 days. Scanty, gUstening, light yellowish - 

 orange growth on potato. Aerobic, facultatively anaerobic. Grows well at 22° C. and 

 37° C. Acid in dextrose, maltose, mannitol, lactose, sucrose and salicin. Litmus milk, 

 acidified, coagulated, and partly peptonized. Indole and ammonia formed, but not 

 HjS or catalase. Nitrates reduced to nitrites. M.R. +, V. P. —, M.B. reduced. Repro- 

 duces the natural disease when inoculated parenteraUy into young guinea-pigs. Produces 

 rapidly fatal septicaemia in mice inoculated intraperitoneally. Apparently non-pathogenic 

 to rabbits. 



