B ArTF:RlAL RESPIRATION 



209 



medium containing eitlier kiftate and f umaratc or lactate 

 and nitrate, but not on one containing only one of these 

 substances (see Table 17). 



Table 17 



Proteus vulgaris can activate nitrate as hydrogen 

 acceptor, but not fumarate, and therefore it is capable of 

 anaerobic growth on a lact at e+ nitrate medium but not on 

 lactate + fumarate. Finally, Alcaligenes fcemlis, which 

 will activate neither fumarate nor nitrate, cannot be 

 induced to grow anaerobically on either of the media. 



Esch. coll contains enzymes which can activate 

 glucose, glyceraldehyde, glycerol, acetate, butyrate, 

 Z-glutamate, lactate, malate, pyruvate and even mole- 

 cular hydrogen as donators of hydrogen to fumarate 

 as acceptor under anaerobic conditions. 



The majority of bacteria can reduce nitrates to nitrites, 

 and many of these can further reduce nitrites to ammonia ; 

 one group, the denitrifying bacteria like Pseudomonas 

 fluorescens, reduces nitrites with production of gaseous 

 nitrogen. Some organisms while unable to reduce nitrates 

 are able to reduce nitrites. Among the organisms which 

 are capable of reducing nitrates to nitrites but not further 

 are the Vibrios ; some of these, such as V. comma, can 

 also produce indole from the tryptophane in peptone 

 and use is made of this property in their diagnosis. On 



