COMMUNAL ACTIVITY OF BACTERIA 259 



flasks. If the purely quantitative relations stated above held here, 

 it would be necessary to transfer 6,000 cells into this volume of 

 gentian-violet broth in order to obtain growth. Here 30 organisms 

 perform not merely 30 times the work of one but at least 200 times 

 that amount. This discrepancy between the work actually accom- 

 plished by the 30 individuals and that which they might be expected 

 to accomplish on a quantitative basis is what is meant by the ex- 

 pression "the communal activity of bacteria." Such an expression 

 implies interreactions not yet proven for bacteria. Here, as in many 

 other places in the present summary, we come upon apparently 

 well-demonstrated facts for which the physiological explanation is 

 as yet lacking. 



On single bacteria, the amount of gentian violet does have some 

 effect. Thus B. coli isolated into more than 0.8 cc. of the broth used 

 in these experiments did not grow. If isolated into o.i cc, 60 per 

 cent of the isolations yielded growth. The corresponding ratio for 

 30 cells would be 3.0, yet the facts are that 60 per cent of successful 

 inoculations occurred when 30 individuals were introduced into a 

 liter of such broth, which is more than 333 times the expectation 

 based on the performance of a single cell. Volume alone was not 

 responsible for these results, as some of the early work of Drzewina 

 and Bohn might indicate, for when single-cell inoculations of B. 

 coli were made into a liter of plain broth, growth occurred in 75 

 per cent of the cases. 



It seems clear, as Churchman and Kahn conclude, that 30 cells 

 are able to accomplish much more than 30 times as much as a single 

 cell, and that this excess of ability of the 30 is an expression of 

 communal activity of bacteria, whatever that may be.^ 



' The results just recorded are mainly concerned with homotypic relations. Castel- 

 lani (1926) has described somewhat similar relationships as holding for heterotj^ic 

 colonies of yeasts and bacteria. Bakers' yeast, for example, is a mixture of one or more 

 yeasts and one or more bacteria and produces fermentation over a wider range of carbo- 

 hydrates than will the individual organisms used separately in pure cultures. The mix- 

 ture Bacillus typhosus plus B. morgan! produces gaseous fermentation in maltose, manni- 

 tol, and sorbite; B. typhosus alone produces acidity only, never gas; and B. morgan! 

 alone produces neither gas nor acidity from these substances. The opposite result may 

 also be found. For example, Manila tropicalis ferments saccharose, producing gas; but 

 when mixed with Bacillus typhosus, it loses this property. Buchanan and Fulmer 

 (1930a) summarize many similar relations between bacteria and other organisms. 



