ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 233 



the ordinary media, and best at 10" C.-20° C. Its growth is stopped 

 at 87° C. 



Two new Fluorescent Denitrifying Bacteria.* — H. R. Christensen, 

 in the course of studies on earth bacteria, has come across two new 

 denitrifying bacteria which differ from Bac. pyocyaneus and Bac. 

 fliiorescens liquifaciens in not liquefying gelatin. As culture media he 

 used the following : — (1) Nitrate and nitrite bouillon : 5 gr. Liebig's 

 extract ; 5 gr. peptone (Merck, Darmstadt) ; 2 gr. KN0 3 or KN0 2 ; 

 1000 cc. tap water. (2) Meat peptone bouillon : 5 gr. Liebig's extract ; 

 5 gr. peptone ; 1000 cc. tap water. (3) Meat peptone-gelatin or agar : 

 5 gr. Liebig's extract ; 5 gr. peptone ; 120 gr. gelatin or 10 gr. agar ; 

 1000 cc. tap water. All the media were made slightly alkaline with 

 Iv 2 C0 3 . The first form, named by the author Bac. denitrificans 

 fliiorescens a, when grown on agar or gelatin, measures 0*5-1 "25/4 

 by • 5-0 * 75/*. It is larger, however, when grown in bouillon, and in 

 anaerobic cultures takes the form of a large ovoid with polar staining. 

 It is enveloped in a mucus capsule. There is very slight or doubtful 

 movement. The organism stains well with carbol-fuchsin, but not with 

 Gram. It does not liquefy gelatin, but imparts to it a bright green 

 tinge. Anaerobically the growth is very slow. 



The second form, Bac. denitrificans fliiorescens f3, measures 0" 5-1* 5ft 

 by • 5-1//. from agar, more from bouillon. Many are spherical. It has a 

 zig-zag or twisting movement. It stains readily with carbol-fuchsin, 

 but not with Gram. It does not liquefy gelatin, but imparts to it a 

 brown tint. It also grows anaerobically, but slowly. 



Both decompose the nitrate or nitrite with the evolution of free 

 nitrogen. 



Anaerobes and Symbiosis. f — Bienstock has carried out numerous 

 experiments on the question of a natural symbiosis of putrefactive 

 anaerobes with aerobic bacteria. Using as a representative of the former, 

 chiefly B. putrifict/s (Bienstock), he cultivated it with a large number of 

 different aerobes, in the following manner : Shreds of fibrin, well washed 

 and sterilised in Uschinsky's fluid, were inoculated with the aerobe, and 

 after some days B. pidrificus was added. It was observed that amongst 

 aerobes there were some which favoured the development of the anaerobe 

 and also the putrefaction of the fibrin ; on the other hand others, while 

 not preventing the development of the organism, retarded putrefaction. 

 Several other anaerobes were used with similar results. Search was also 

 made in cultures of many aerobes for the ferment suggested by 

 Kedrowsky as the essential for the aerobic growth of anaerobes. The 

 cultures were filtered, and killed in various ways ; but the results with 

 over thirty species were, except in the case of B. pyocyaneus, uniformly 

 negative. B. pidrificus neither grew nor caused putrefaction, as with 

 living aerobes. If, however, fibrin, in Uschinsky-Fraenkel fluid con- 

 taining 1*2 p.c. sugar, is inoculated with B. pyocyaneus, it shows after 

 some days change in texture, it loses its white colour, and from being 

 firm becomes flabby ; if now the culture be killed by heat to 100° C, 



* Centralbl. Bakt. 2" Abt.. si. (1903) pp. 190-4. 

 t Ann. Instit. Past., xvii. (1903) pp. 850-G. 



April 20th, 1004 R 



