208 



ORDER I. PSEUDOMONADALES 



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 chromogenesi 



2. Pink to dark red chromogenesis. 



B. Nitrites produced from nitrates. 



II. Gas produced from nitrates. 



A. Produces acid from glucose. 



B. Does not produce acid from glucose. 



1. Halobacterium salinarium. 



2. Halobacterium cutirubrum. 



3. Halobacterium halobium. 



4. Halobacterium marismortui. 



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 



