322 



SCIENCE 



[N. S. Vol. XL VII. No. 1213 



those which oxidize C, N, S and Fe, then fol- 

 lows the statement : 



It seems fairly certain from the important part 

 played by carbon compounds in the vital activities 

 of our common bacteria, especially as a source of 

 energy, that the carbon oxidizers are the forerun- 

 ners of the bacteria of to-day. 



The author then concludes that the most 

 primitive types must he those capahle of oxi- 

 dizing methane, followed by those which oxi- 

 dize carbon monoxid, and, most astounding, 

 those capable "of utilizing CO^." A careful 

 scrutiny of the text will lead to no conclusion 

 but that "utilizing" is here used to indicate 

 " oxidizing." This inference is strengthened 

 by a second statement even more surprising. 



Since the ammonia and nitrate oxidizers (or 

 nitrifiers) also assimilate large amounts of car- 

 bon-dioxide (Jensen) they would seem to fall in 

 line along with the organisms capable of oitain- 

 ing their energy from carbon dioxide.2 



By what mystic process an organism may 

 secure energy from 00. is not explained. The 

 assumption that carbon-oxidizing forms are 

 most primitive is scarcely proved. In fact, 

 study of the oligocarbophiloua organisms, that 

 is, forms which can utilize 00^ in the build- 

 ing up of food or protoplasm indicates that 

 the more primitive of the modern types may 

 be among the nitrifying and the sulphur bac- 

 teria. An analysis of the conditions upon the 

 earth in early times as jwstulated by the au- 

 thor and elaborated by Osborn would seem to 

 indicate that they would be even more favor- 

 able to the development of ammonia or sulphur 

 oxidizers than for methane oxidizers. It 

 should be emphasized that all organisms of 

 types not using organic carbon must have 

 some source of energy which will enable the 

 protoplasm to take up 00,, replace the oxygen 

 in part with hydrogen and build up complex 

 organic compounds. The energy for this 

 transformation might have come from the oxi- 

 dation of ammonia or sulphur. Oertainly 

 ground waters laden with hydrogen sulphide 

 must have reached the surface of the primi- 

 tive earth much as they do to-day. Further- 

 more, the consistent development of the pig- 



2 Italics not in or 



ment bacteriopurpurin by most members of the 

 modern large group of sulphur bacteria, to- 

 gether with the marked phototaxis of this 

 group, might be interpreted as evidence that 

 the sun's rays had some influence almost from 

 the beginning in the explanation of energy 

 source in 00, assimilation. In other words, 

 early coordination of photosynthesis with 

 ehemosynthesis can not be ignored as a possi- 

 bility. 



It may be noted further that to discuss 

 primitive bacteria as capable of utilizing 

 formic acid, acetic acid and alcohol is some- 

 what anachronistic. These substances are the 

 results of the growth or fermentative power of 

 organisms which stand higher in the scale of 

 evolution. Where could the primitive organ- 

 isms find these complex compounds to work on? 



The author next calls attention to the fact 

 that certain organisms changed their habit of 

 life from that of obligate aerobes, using at- 

 mospheric oxygen, to that of facultative an- 

 aerobes, "utilizing combined oxygen for 

 intracellular combustion." The statement is 

 made that the " prototrophic denitrifying bac- 

 teria are most probably the progenitors of this 

 group." The statement requires some analy- 

 sis. One would infer that prototrophic denitri- 

 fiers are common and well known. As a matter 

 of fact, the denitrifying organisms are almost 

 without exception anything but prototrophic. 

 When one wdshes to demonstrate denitrification 

 in the laboratory it is customary to add a 

 suitable organism to an aqueous solution of 

 nitrate and organic carbon compounds. 

 Under anaerobic conditions the oxygen is re- 

 moved in whole or in part from the nitrogen, 

 and used for oxidizing the carbon compounds 

 present. The only exception to this rule 

 known to the writer is the peculiar organism 

 described by Beijerinck which will grow in 

 the presence of free sulphur, nitrate and car- 

 bon dioxide in the absence of atmospheric oxy- 

 gen, oxidizing the sulphur and using the 

 energy thus gained apparently in the assimi- 

 lation of 00„. It would seem that such a 

 form would be much more closely related to 

 the TMohacteria than to the other denitrifiers. 

 To make his point. Dr. Kligler should cite 

 some examples of " prototrophic denitrifiers." 



