R. J. DUBOS 



metabolic channels and products, and the same biocatalysts which 

 constitute the mechanism of life in the highest and most evolved 

 organisms. For example, the oxidation of sulfur by the autoti'ophic 

 bacterium Thiobacillus thiooxidans depends upon an intimate linking 

 between oxidation and phosphate turnover; the oxidative phase is 

 accompanied by phosphate fixation and the reductive phase of carbon 

 dioxide fixation is accompanied by a release of phosphate (22). More- 

 over, Thiobacillus thiooxidans is fully equipped with the regular comple- 

 ment of water-soluble vitamins found in other living organisms: thia- 

 min, riboflavin, nicotinic acid, pantothenic acid, pyridoxine, biotin, 

 etc. (17). In other words, the mechanisms of energy transfer and of 

 intermediary metabolism are essentially as complex in the least exact- 

 ing bacteria as they are in the most fastidious organism. 



The chemistry of Thiobacillus thiooxidans is not unique among 

 bacteria; most of the known water-soluble vitamins — with the possible 

 exception of ascorbic acid — have now been found to be either produced 

 by, or required for the growth of, all the microbial species so far studied. 

 Fat-soluble vitamins also probably play a part in microbial metabolism 

 since at least one of them, vitamin K, is an essential growth factor for 

 Johne's bacillus {Mycobacterium paratuberculosis) and the other myco- 

 bacteria produce biologically active naphthoquinones during growth 

 (24). 



Thus, bacteria utilize the multiple and complex biocatalysts 

 which govern and integrate the metabolism of all living cells. More- 

 over, many bacteria, the autotrophic species for example, possess in 

 addition the ability to synthesize these same biocatalysts from inorganic 

 elements in the course of their growth in synthetic media, a property 

 which most plant and animal cells never possessed or have lost entirely. 

 The high degree of cellular organization required for the performance 

 and for the integration of these complex syntheses need not be em- 

 phasized; at the biochemical level, at least, there is no ground to 

 consider that bacteria represent primitive forms of life. The growth 

 requirements of autotrophic bacteria are extremely simple indeed, 

 but how complex their vital machinery, their performance, and their 

 products ! If they are truly the first representatives of life on earth, 

 they sprang, like Minerva, fully armed from the forehead of Jove. 



Simultaneously with the realization that the biochemical 

 processes of bacteria are no simpler than those of other organisms cane 



50 



