Oxidation and evolution of molecular hydrogen by microorganisms.

I. Autotrophic organism .................................................................... 44 1. Photosynthetic microorganisms .......................................................... 44 2. The hydrogen bacteria.................................................................. 45 3. Sulfate reducing bacteria................................................................ 46 II. Heterotrophic organism ................................................................... 46 1. The clostridia ... ..................................................................... 46 A. Carbohydrates and related compounds as precursors and acceptors of H. .............. 46 a. The importance of metals......................................................... 47 b. Clostridium kluyvers ............................................................... 47 c. Clostridium aceticum .............................................................. 48 B. Organic nitrogen compounds as precursors and acceptors of H ........................ 48 2. Veillonella gazogenes (Micrococcue lactilyticus); M. aerogenes.............................. 49 3. Diplococcus glycinophilus ................................................................ 50 4. The methane bacteria................................................................... 50 5. The colon-aerogenes bacteria............................................................ 52 A. Influence of nutritional factors on H, metabolism.................................... 53 a. Oxygen........................................................................... 53 b. Formate and fermentable carbohydrates ........................................... 53 c. Amino acids and ammonia......................................................... 54 d. Nitrate and fumarate.............................................................. 55 e. Metals............................................................................ 56 f. Other factors..................................................................... 57 B. Mechanism of the hydrogenylase reaction............................................ 57 C. The exchange reaction............................................................... 61 D. Oxidation of H2 with various acceptors.............................................. 62 a. Fumarate ......................................................................... 62 b. Nitrate........................................................................... 63 c. Methylene blue and other acceptors............................................... 64 6. Hydrogenase in organisms which do not oxidize nor produce H2 during "normal" metabolism.................................................................................... 65