446 Physiology 



out added thiamine, acetate has supported growth in all-glass culture 

 vessels (73, 390) — about one per cent of the growth obtained with thia- 

 mine. In thiamine-supplemented acetate medium, growth of C. para- 

 rnecimn has been tripled by raising the carbon dioxide concentration 

 from that of the atmosphere to 100 mm Hg at atmospheric pressure (428). 

 Similar stimulation by carbon dioxide had previously been detected in 

 peptone media (245). Certain alcohols (467), fatty acids (299, 467), and 

 carbohydrates (321, 327) also accelerate growth in peptone media, al- 

 though a number of these supplements have not yet been tested as carbon 

 sources in heteroaiuotrophic nutrition. 



Phytomonadida. As inorganic nitrogen somxes in "photoautotorphic" 

 nutrition, ammonium salts have been more satisfactory than nitrates for 

 Haematococcus pluvialis (340) and Lobomonas piriformis (422). No 

 appreciable differences have been reported for Chlamydomonas agloe- 

 formis (340), Chlorogonium elongatum, and C. euchlorum (321). How- 

 ever, comparative tests of nitrates and ammonium salts over an adequate 

 range of salt and hydrogen-ion concentrations have not been reported. 



In heteroautotrophic nutrition Polytoma ocellatum has been grown in 

 a nitrate medium (353), but species of PolytomeUa and other species of 

 Polytoma apparently are limited to an ammonium-N source. This situa- 

 tion deserves further investigation in view of Lwoff's (347) characteriza- 

 tion of an autotroph as an organism which can reduce nitrate in an 

 inorganic medium. 



Organic nitrogen sources have not been investigated extensively but 

 growth on asparagine or a single amino acid has been reported for species 

 of Chlamydomonas and Haematococcus (340, 367), Chlorogonium (350, 

 457), Lobomonas in darkness (422), Polytoma (340, 360, 452, 458), and 

 PolytomeUa (342, 455, 458). 



Acetate, butyrate, and lactate are good carbon sources in heteroauto- 

 trophic nutrition. A number of other substrates probably would be satis- 

 factory since salts of additional acids, including propionic, valerianic, and 

 caproic (323, 456, 463, 464, 465, 466), and also certain alcohols (467) 

 accelerate growth of various colorless species in peptone media. Certain 

 carbohydrates also have stimulated growth of Polytoma (360, 361) and 

 PolytomeUa (342) but may or may not be adequate substrates in hetero- 

 autotrophic nutrition. The ability to use an amino acid, as the sole source 

 of nitrogen, carbon, and energy, has not yet been demonstrated. 



Several green species — Chlorogonium elongatum (321), C. euchlorum 

 (321, 350), Lobomonas piriformis (422), Chlamydomonas agloeformis, 

 and Haematococciis pluvialis (367) — have been grown in darkness, par- 

 ticularly in peptone media supplemented with acetate, and are obviously 

 facultative heterotrophs. Under such conditions, acetate is a rather satis- 

 factory substitute for photosynthesis. On the other hand, Chlamydomonas 

 moewusii is an obligate phototroph in a wide variety of media (315). 



