fluorescent, diffusible pigments of a greenish, bluish, violet, lilac, rose, yellow or other color. Sometimes the pigments are bright red or yellow and non-diffusible; there are many species that fail to develop any pigmentation. The majority of species oxidize glucose to gluconic acid, 2-ketogluconic acid or other intermediates. Usually inactive in the oxidation of lactose. Nitrates are frequently reduced either to nitrites, ammonia or to free nitrogen. Some species split fat and/or attack hydrocarbons. Many species are found in soil and water, including sea water or even heavy brines. Many are plant pathogens; very few are animal pathogens.
The borderline between the straight rods found in Pseudomonas and the curved rods found in Vibrio is not sharp: occasionally curved rods may occur in species that normally are composed of straight rods, this variation sometimes being dependent upon the medium used. Recently, however, Shewan, Hodgkiss and Liston (Nature, 173, 1954, 208) have described a method employing antibiotics and a vibriostatic agent whereby a sharper differentiation between pseudomonads and vibrios may possibly be effected. Future studies of this nature may show that some of the species in the genus Pseudomonas should be transferred to the genus Vibrio, and vice versa.
The type species is Pseudomonas aeruginosa (Schroeter) Migula.
Key to the species of genus Pseudomonas.
I. Soil and water forms. A few species are pathogenic to warm- and cold-blooded vertebrates.
- A. Soil and fresh-water forms (a few are pathogenic).
- 1. Produce diffusible pigments, usually of a yellow, green or blue color; may be fluorescent. (Soluble pigments are not formed in all media. Furthermore, the ability to produce such pigments may be lost. Therefore, failure to observe soluble-pigment formation does not preclude identity with species listed in this category.)
- a. Grow in gelatin.
- b. Gelatin liquefied.
- c. Polar flagellate.
- d. Grows readily at 42°C. on ordinary media,
- e. Milk becomes alkaline.
- d. Grows readily at 42°C. on ordinary media,
- c. Polar flagellate.
- b. Gelatin liquefied.
- a. Grow in gelatin.
- 1. Produce diffusible pigments, usually of a yellow, green or blue color; may be fluorescent. (Soluble pigments are not formed in all media. Furthermore, the ability to produce such pigments may be lost. Therefore, failure to observe soluble-pigment formation does not preclude identity with species listed in this category.)
1. Pseudomonas aeruginosa.
- ee. Milk acidified.
2. Pseudomonas pseudomallei.
- dd. Grow poorly or not at all at 42° C.
- e. Grow readily at 37° C.
- f. Not known to attack cellulose.
- g. Milk becomes alkaline, indole not produced.
- f. Not known to attack cellulose.
- e. Grow readily at 37° C.
- dd. Grow poorly or not at all at 42° C.
3. Pseudomonas reptilivora.
- gg. Milk acidified, indole produced.
4. Pseudomonas caviae.
- ggg. Action on milk and indole production unrecorded.
5. Pseudomonas boreopolis.
- ff. Attack cellulose.
- g. Milk becomes alkaline, coagulated and peptonized, and litmus is reduced.
- ff. Attack cellulose.
6. Pseudomonas effusa.
- gg. No growth in milk.
7. Pseudomonas ephemerocyanea.
