The decomposition of formates by Bacillus coli communis

Abstract

Many observations have been made on the variability of gas production by intestinal bacteria under natural conditions (see Penfold (1911) and Arkwright (1913), where literature is quoted). Penfold has found that by artificial selection of Bacillus coli communis in the presence of sodium chloroacetate, strains may be isolated which produce no gas from glucose and gas in lessened amount from mannitol, although in both cases acid is produced as with the normal organism. The writer has also shown that by artificial selection of B. coli communis by the chloroacetate method of Penfold, various stages between the original gas-producing and the selected non-gas-producing strain may be obtained, and the changes have been found to be associated in part with the disappearance of the enzyme which decomposes formic acid (1914). It was found that two kinds of artificially selected strains could be produced from the original strain of B. coli communis ; one unable to decompose formic acid, and the other still able to bring about this decomposition provided glucose were present. The artificially selected organism, which could not decompose formates even in the presence of glucose, was likewise unable to produce gas from mannitol, whereas the organism which still retained the power of decomposing formates was also able to produce gas from mannitol, although it produced this gas in an amount approximately equal to one-half of that produced under the same conditions by the original B. coli communis from which it was derived. It seemed, therefore, likely that by a closer study of the manner in which formic acid is decomposed by the natural and artificially selected varieties of intestinal bacilli it might be possible to gain information concerning the mechanism of the change brought about in the organism by growth on chloroacetate agar which leads to the selection of strains in some cases unable to decompose formic acid and in other cases unable to produce it to the same extent as the normal strains from which they have been derived.