Humboldt-Stiftung, 1894, 19; not Halophilus Sturges and Heideman (nomen nudum), Abst. of Bact., 8, 1924, 14; not Halobacterium Schoop (nomen nudum), Zent. f. Bakt., I Abt., Orig., 134., 1935, 26; Halobacter Anderson, Applied Microbiol., 2, 1954, 66.)
Ha.lo.bac.te'ri.um. Gr. noun hals salt; Gr. dim. noun bacterium a small rod; M.L. neut.n. Halobacterium the salt bacterium.
Obligate halophilic, rod-shaped bacteria which are highly pleomorphic. Require at least 12 per cent salt for growth, and will live even in saturated brine solutions. Motile species are polar flagellate; some species are non-motile. Gram-negative. Usually chromogenic, producing non-water-soluble, carotenoid pigments which vary in shade from colorless to orange or even brilliant red. Carbohydrates may or may not be attacked without the production of visible gas. Nitrates are reduced, occasionally with the production of gas. Found in tidal pools, especially in the tropics, salt ponds, salt seas or other places where heavy brines occur naturally; also found on salted fish, salted hides and similar materials.
The type species is Halobacterium salinarium Elazari-Volcani.
Key to the species of genus Halobacterium.
I. Gas not produced from nitrates.
- A. Nitrites not produced from nitrates.
- 1. Pale pink to scarlet chromogenesis.
1. Halobacterium salinarium.
- 2. Pink to dark red chromogenesis.
2. Halobacterium cutirubrum.
- B. Nitrites produced from nitrates.
3. Halobacterium halobium.
II. Gas produced from nitrates.
- A. Produces acid from glucose.
4. Halobacterium marismortui.
- B. Does not produce acid from glucose.
5. Halobacterium trapanicum.
1. Halobacterium salinarium (Harrison and Kennedy, 1922) Elazari-Volcani, 1940. {Pseudomonas salinaria Harrison and Ken- nedy, Trans. Royal Soc. of Canada, 16, 1922, 121; Flavobacterium (Halobacterium) salinarium Elazari-Volcani, Studies on the Microflora of the Dead Sea. Thesis, Hebrew Univ., Jerusalem, 1940, 59.) sa.li.na'ri.um. L. adj. salinarius of salt works. Occurs as spheres and rods. The spheres are 0.8 to 1.4 microns in diameter. The rods, 0.6 to 1.5 by 1.0 to 6.0 microns, occur singly as ovoid, amoeboid, clavate, cuneate, trun- cate, spindle- and club-shaped, pyriform and other irregular forms. Age of culture and nature of medium influence the size and shape of cells. Reproduction is by means of fission but apparently also by budding. Motile by means of a polar flagellum at one or both poles. Gram-negative. Does not grow on ordinary culture media unless supplemented with 16 to 35 per cent sodium chloride and 2 per cent MgS04-7H20 (Katznelson and Lochhead, Jour. Bact., 64, 1952, 97) . Grows well on salted fish and hides. Gelatin (salt) : Slow liquefaction (Katz- nelson and Lochhead, loc. cit.). Codfish agar colonies (16 to 30 per cent salt) : In seven days punctiform, smooth, raised, entire, granular, pale pink to scarlet (Ridgway chart), 1.5 mm in diameter. Milk salt agar (24 to 35 per cent salt) : Pink colonies 4 to 5 mm in diameter, be- coming scarlet. Putrefactive odor. Definite proteolytic zones develop (Lochhead, Can. Jour. Res., 10, 1934, 275). Codfish agar slant (16 to 35 per cent salt) : In seven days moderate, filiform, slightly raised, glistening, smooth, translucent, bright red, viscid. Unpleasant odor. Milk salt agar slants (24 to 35 per cent
