34^ Journal of Agricultural Research voi. xvi, no. 12 



DiASTATic ACTION ON STARCH. — This test was made by the method of 

 Allen. ^ All the cultures of Ps. caudatus studied, except the nonchromo- 

 genic strain, gave a strong reaction, but the nonchromogenic strain showed 

 no digestion of the starch. These results were the same upon frequent 

 repetition of the test. 



Action on milk. — No change in appearance or reaction. 



Production of indol. — The results of this test have generally been 

 negative, although a few cultures have shown a weak reaction. It is not 

 impossible that they would all produce indol if tested under conditions 

 favorable to the growth of this organism; but the test has always been 

 made in liquid media (Dunham's solution), and as yet no effort has been 

 made to improve the technic. 



BRIEF SUMMARY OF CHARACTERISTICS OF TYPICAL PSEUDOMONAS CAUDATUS 



In the following summary the characteristics written within paren- 

 theses apply to typical cultures only (including the strain studied by 

 Bright); the other characteristics apply to all the stiains studied: 



Morphology: lyong, slender, granular, Gram-negative rods, about 0.2 m in diameter, 

 with a single polar flagellum. No spores. Old cultures often appear like cocci, 0.2 

 to 0.4 n in diameter. 



Growth on agar: Soft, smooth (cadmium orange). 



Gelatin colonies: Small (to medium sized) — i. e., up to i cm. in diameter (orange, 

 structure radiate), edge entire. 



Relation to oxygen: Strictly aerobic. 



Ammonia produced from organic nitrogenous matter. 



Acid production: (from dextrose, sucrose, and lactose) but not from glycerin. 



Nitrates reduced to nitrate and ammonia (with accumulation of nitrite) . 



DiASTlTiC ACTION ON STARCH: (strong). 



Milk unchanged. 



SUMMARY 



(i) The statement recently made by one of the authors that non-spore- 

 forming bacteria are most active in manured soil has been verified. This 

 is contrary to the generally accepted idea that spore-forming bacteria are 

 the important ammonifiers in soil. 



(2) Of these non-spore-forming organisms that are especially active in 

 manured soil, two of the most easily recognized are Psetidomonas fiuores- 

 cens (Fliigge) Migula and Ps. caudatus (Wright) Conn. They have 

 therefore been selected for special study. 



(3) Pure cultures of Ps. fluorescens and Ps. caudatus multiply much 

 more rapidly in sterilized manured soil than do pure cultures of Bacillus 

 cereus Frankland (selected as a typical spore former). 



(4) When sterilized manured soil is inoculated with a mixture of these 

 three organisms in pure culture, the two non-spore formers immediately 

 gain the ascendency, B. cereus occurring in too small numbers for detec- 

 tion by the ordinary methods of study. 



■ AtLEN, Paul W. Op. cit., 1918. 



