Oxidation-Reduction Potentials of Some Non-Sporulating Obligate Anaerobes

Abstract

Oxidation-reduction potential studies have been made on cultures of many aerobic and some sporulating anaerobic bacteria, but to our knowledge none has been made on the non-sporulating obligate anaerobes. The potentials produced by the latter group of organisms are of particular interest in connection with current theories as to the relation of such potentials to the growth of obligate anaerobes. A certain degree of negativity was thought to be necessary before the obligate anaerobes are able to initiate their growth processes. Experimental evidence of a positive limit of oxidation-reduction potential required for the germination of spores of Cl. tetani has been presented by Fildes 1 and by Knight and Fildes. 2 This positive limit was found to lie in the vicinity of E_h O at pH's close to neutrality. The potentials produced in cultures of the sporulating anaerobes are considerably more negative than this positive limit, usually being about 350 millivolts negative at reactions at or near neutrality. 3 In unpublished experiments one of us (W.B.) has found that several strains of Cl. botulinum produce potentials around 400 millivolts negative. That anaerobiosis is a matter of oxidation-reduction potential rather than simple absence of oxygen is a theory that has been generally accepted, 4 although there has been some dissent. 5

The technique used in the present experiment has been previously described. 6 The organisms were grown in a cystine glucose beef infusion broth, the pH varying between 6.4 and 6.9. Anaerobic conditions were produced and maintained by constant bubbling of oxygen-free nitrogen through the medium. Very heavy inoculums were used, usually 1 to 2 cc. of young cultures. Under these conditions we had no difficulty in growing the organisms.

With 2 exceptions, the strains used were isolated from the colons of patients suffering with ulcerative colitis. Strain 39 was isolated from the ulcerated colon of a monkey dying from bacillary dysentery (Flexner) and strain M1 was isolated from the colon of a healthy monkey.