118 



NOTES ON VIBRIO DENITRIFICANS, SEWERIN. 



By R. Greig Smith, M.Sc, Macleay Bacteriologist 

 TO THE Society. 



(Plate xi.) 



In examining the bacteria contained in a sample of disinte- 

 ii'ratino- cement which was obtained from one of the canals used 

 for conveying the Sydney Water Supply, an organism which had 

 some curious features was isolated. It is identical in form 

 with Rhizohium leguminosarum, the nodule organism of the 

 Leguminosa?, but differs from it in the power of growing on 

 ordinary media as well as in media containing . little nutriment. 

 Although so like the nodule organism which is supposed to 

 convert free nitrogen into combined forms or to assist the plant 

 to do so, this organism does almost exactly the opposite and 

 reduces nitrate to nitrogen gas. 



The investigation of the organism in subculture showed it to 

 be Vibrio denitrificans, Sewerin, but for some time it could not 

 be identified with this organism, because a true vibrion form 

 could not be observed. By using a low magnification and 

 observing overstained films, bent forms can be seen, but by 

 examining a properly stained film with the oil-immersion (No. 4 

 ocular and yV oil objective, Leitz) the bent forms are clearly seen 

 to be double organisms bent at the point of attachment. The 

 individual cells are straight. 



Like Rhizohium leguyninosarum, the organisms appear in a 

 variety of forms, as the coccus (0-8 /a), oval cells (0-6 : 1*0 /x), rods 

 with rounded ends (0-6 : 2/i), exclamation mark (!), conical cells, 

 y, Y and double cells bent at an angle. They stain readily with 



