168 BACTERIOLOGICAL CHEMISTRY 



O 



^\/^\/i% 1 



lU 3 



■^ . The position of the two hydi'oxyl 

 OH 



groups is unknown, but they are probably not in the 

 2:3 or 2:5 positions. The growth of streptococci is 

 partially inhibited by 3 X 10"' molar concentrations and 

 completely inhibited by 1 to 2 X 10~^ molar iodinin. 

 Phenazine di-N-oxide has a similar but weaker effect. 

 When groAvn in the presence of sub -inhibitory quantities of 

 iodinin or phenazine di-N-oxide, organisms multiply and 

 destroy the compounds, probably by reduction. Extracts 

 of a wide variety of yeasts, bacteria and plant and 

 animal tissues have no effect on the inhibition, but those 

 which are active contain anthraquinones or naphtho- 

 quinones. Pure hydroxyanthraquinones and 2-methyl- 

 1 : 4 -naphthoquinone (vitamin K) antagonise 2 x 10~^ 

 molar iodinin at concentrations between 5 X 10~' and 

 5 X 10~® molar, the iodinin being destroyed. The 

 destruction does not take place in the absence of the 

 organisms. It is suggested that the quinones are probably 

 concerned in hydrogen transportase systems which can 

 be interfered with by iodinin or phenazine di-N -oxide. 



Notatin. — Penicillium notatum, during growth on a 

 modified Czapek-Dox medium, produces an antibiotic 

 which is different from penicillin (see p. 171). It has been 

 called notatin, penicillin-A, penicillin-B, or penatin. 

 The formation of notatin is repressed by the addition of 

 corn-steep liquor, yeast extract, brown sugar or malt 

 extract to the Czapek-Dox medium. It can be separated 

 by concentration of the culture filtrate and precipitation 

 with acetone, or by tannic acid. It is a buff coloured 



