[BERKELEY] MARLVE BACTERIA 29 



tion nor denitrification takes place, as in that of the culture in Medium 

 B inoculated with the 100 fathom sample, another explanation is 

 called for. In such cases the production of calcium carbonate un- 

 doubtedly results from the direct oxidation of the calcium acetate.^ 

 Since there is no other source of carbon for the utilization of the 

 bacteria than that of the calcium acetate it is clear that a proportion 

 of this carbon must be eliminated by their growth. This elimination 

 may perhaps be represented by some such equation as the following : — 

 Ca (COOCH3) 2 + O2 = Ca CO3 + 3 H2O + "3C" 



The presence of ammonia or other base is clearly unnecessary in 

 order that such a reaction may result in the formation of the normal 

 carbonate and a reaction of a similar kind must occur in any case where 

 no source of carbon other than that of an organic calcium salt is 

 present in a medium in which bacterial growth takes place. 



It seems questionable whether precipitation of calcium carbonate 

 in the manner in which it occurred in the cultures can be a factor 

 under the conditions which obtain in the open sea. Its occurrence 

 depends on the relative concentration of the calcium salts and the 

 carbonic acid present and under normal conditions in the sea this 

 relation is the reverse of that holding in the culture solutions. In 

 the latter case the concentration of calcium salts is high and that of 

 the carbonic acid nil ; in normal sea- water the concentration of calcium 

 salts is relatively low and that of carbonic acid high. In these cir- 

 cumstances bacterial production of CO2 would not lead to the precipi- 

 tation of calcium carbonate. If the equilibrium is upset by the pro- 

 duction of ammonia or by denitrification the case is altered and the 



1 The writer has been working on the fermentation of the Giant Kelp (macrocystis 

 pyrifera) since this paper was written. This fermentation has recently formed the 

 basis of a process for the production of Acetone conducted by the Hercules Powder 

 Company at San Diego, California. It is of interest in connection with the observa- 

 tion that bacteria capable of oxidizing organic salts to carbonates exist in the sea, 

 because the essential products of the fermentation are acetic acid and other members 

 of the fatty acid series. The fermentation process is a purely spontaneous one and 

 there is every reason to suppose that the kelp undergoes the same changes after death 

 in its natural habitat as it does in the factory. If this is the case, it follows that the 

 carbohydrate substances, of which the organic portion of kelp is almost entirely 

 composed, are constantly being returned to the sea in the form of fatty acids. These 

 would be neutralized by calcium carbonate, or similar basic substances, and the salts 

 formed would in due course be converted into carbonates by bacterial action. It 

 seems not unlikely that such a cycle of reactions between vegetable and mineral 

 material is common in the sea and accounts in great measure for the maintenance of 

 the balance between acids and bases. Similar reactions have been shown to occur in 

 soil under the influence of bacteria by Hall and Miller. (Proc. Roy. Soc. B., Vol. 

 77, 1905). 



