A theory relating the action of salts on bacterial respiration to their influence on the solubility of proteins

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Abstract
The Ingram equation for the respiration of bacteria in strong salt solns., log R = A[long dash]Bc, where R is rate of respiration, c is molar conc. of salt, and A and B are constants, is analogous to the equation of Cohn for the salting out of proteins and other substances, log S = [beta][long dash]KI, where S is the solubility of the substance, / is the ionic strength (molar), and [beta] and K are constants. Assuming that R is proportional to the conc. of some substance S (a respiratory enzyme) in the cell which follows the salting out law, R = aS, the constants in the Ingram equation become A = log a + [beta] and [BETA][long dash]KI/c. The Ingram equation fits the influence of: KC1, NaCl, LiCl, MgCl2 and CaCl2 on the respiration of Bacillus cereus; NaCl, CaCl2 and MgCl2 on B. subtilis; NaCl on Sarcina lutea, Micrococcus subflavescens, Pseudomonas fluorescens and Escherichia coli. Bc/I for bacterial respiration has the range of magnitude of K for protein salting out. B is independent of temp. and pH. Hofmeister effects influence B and K to approx. the same degree. The threshold of ionic strength for salting out is about 6X as large as that for inhibition of bacterial respiration or for inhibition of partly purified lactic dehydrogenase of E. coli. On admitted scanty evidence, it is suggested that the depression of respiration by salts is explainable as salting out of respiratory enzymes, which are present in salt-sensitive form in most bacteria, but approach the stability of the common proteins in the case of halophilic bacteria.

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