NUTRITION OF MICRO-ORGANISMS 



Pantoyltaurine Resistance 



Sulphonamide-resistant streptococci are sensitive to pantoyl- 

 taurine,^^ whilst pantoyltaurine-resistant strains, produced by repeated 

 subculturing of the organisms in presence of the inhibitor, were as 

 susceptible to sulphanilamide as were normal strains, ^^ showing that 

 cross-resistance does not necessarily develop to different chemothera- 

 peutic agents. The variable resistance to pantoyltaurine of different 

 natural and experimentally produced strains of C. diphtheriae was 

 correlated with their ability to grow with /3-alanine in place of panto- 

 thenic acid. Resistant strains synthesised pantothenic acid during 

 growth, and the ability to perform this synthesis is believed to explain 

 their resistance. 



The resistance developed by Str. haemolyticus , however, appeared 

 to be due to a different mechanism, as many of the naturally resistant 

 and all the experimentally produced resistant strains, needed panto- 

 thenic acid during growth. The pantoyltaurine-fast streptococci and 

 some pantoyltaurine-insensitive strains were made susceptible to 

 pantoyltaurine by the addition of salicylic acid, suggesting that pantoyl- 

 taurine-resistant streptococci possessed metabolic processes alternative 

 to those affected by pantoyltaurine and inhibited by salicylic acid. 



A connection between the specific antibacterial action of salicylic 

 acid on Staphylococcus aureus and pantothenic acid had been estab- 

 lished earlier by G. Ivanovics,^^ who showed that this antibacterial 

 action could be neutralised by small amounts of pantothenic acid or 

 pantolactone, but not by j3-alanine ; the degree of inhibition was pro- 

 portional to the pantothenic acid concentration. With Proteus 

 morganii, inhibition of growth by salicylic acid was similarly neutral- 

 ised by pantothenic acid, but in this instance the degree of inhibition 

 was independent of the amount of pantothenic acid. Pr. morganii, 

 unlike Staph, aureus, cannot synthesise pantothenic acid or pantoic 

 acid. Several amino acids were able to antagonise the effect of 

 salicylic acid, the most effective being methionine. Thus, the specific 

 antibacterial effect of salicylic acid appears to be associated with 

 the inhibition of an enzymic process for synthesising pantoic acid. 

 This is supported by the observation ^^ that pantoic acid was nine 

 times as effective as pantolactone in antagonising the inhibitory 

 action of salicylic acid on E. coli, which suggests moreover, that 

 pantoic acid, rather than pantolactone, is the precursor of pantothenic 

 acid. 



It seems evident, therefore, that pantoyltaurine and salicylic acid 

 each block a different route to pantothenic acid synthesis or utilisation. 



There also appears to be a connection between the antibacterial 

 action of sulphapyridine and pantothenic acid, for it has been observed 



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