THE CULTURE OF THE SULPHUR BACTERLi 51 



3 flasks containing live autotrophic bacillus + CO^ from atmosphere 



+ sulphur bacteria. 

 3 flasks containing dead autotrophic bacillus + CO, from atmosphere 



+ sulphur bacteria. 

 3 flasks containing autotrophic bacillus — CO, from atmosphere 



+ sulphur bacteria. 

 I flask containing live autotrophic bacillus + CO, from atmosphere 



— sulphur bacteria. 



I flask containing dead autotrophic bacillus -)- CO, from atmosphere 



— sulphur bacteria. 



1 flask containing autotrophic bacillus — COj from atmosphere 



— sulphur bacteria. 



The results were inconclusive, the first nine flasks showing 

 equal growth, and the last three, of course, none. 



I'ests to ascertain if H.jS is necessary to purple sulphur 

 bacteria. — Flasks infected with sulphur bacteria were treated 

 as follows : — 



Results. 



1. Placed in air ........ 



2. Placed in HjS gas ....... Strong growth 



3. Usual salts added, 0-5 per cent, sodium thiosulphate + air 



+ light 



4. Usual salts added, 0-5 per cent, sodium thiosulphate + air 



-light .0 



5. Usual salts added, 0-5 per cent, sodium thiosulphate — air 



+ hght 



6. Usual salts added, 0-5 per cent, sodium thiosulphate — air 



- light 



7 . Sodium bisulphate, sodium sulphide, sodium thiosulphate, 



potassium sulphide, calcium sulphide, iron sulphide, 



each used in turn in place of HgS gas . . . all 



Hence he concluded that HgS gas is a necessary addition. 

 Tests to ascertain the necessity of light to the purple sulphur 

 bacteria : — 



1. Lieske's solution (see p. 44) .... 



2. ,, ,, + dextrose, 0-15 per cent. . 



3. ,, ,, + calcium lactate, 0-15 per cent. . 



4. ,, ,, + pot. formate, o' 1 5 per cent. 



5. Ammonium sulphate, 0'075 per cent. ; 



+ dextrose, o'lj percent. . 



6. ,, ,, 00-75 per cent. ; 



+ calc. lactate, o"i5 per cent. 



7. ,, ,, 0-075 per cent. ; 



+ pot. formate, o"i5 per cent. 



From which he concludes that hght is necessary 



