The Cytochrome of Diphtheria Bacilli and its Relation to Diphtheria Toxin

Abstract

In the study of substances that may be involved in the oxidation-reduction processes of the living cell attention is drawn to the intracellular pigment cytochrome which was originally observed by McMunn 1 and has recently been rediscovered and renamed by Keilin. 2 This pigment is known only by the characteristic absorption spectrum which is given by the substance in the reduced state; the oxidized form shows no selective absorption or at most a faint shading. Among bacteria this pigment is found in all aerobic forms, and is most distinct in the macroaerophiles. It is absent from the obligate anaerobes. Its occurrence in B. diphtheriae has been observed by Yaoi 3 and Tamiya.

We have studied the occurrence of cytochrome in cultures and filtrates of different members of the diphtheria bacillus group. In masses of bacteria sedimented from cultures in broth the characteristic absorption spectrum may readily be seen with the spectroscope if a sufficiently intense beam of light is employed. The absorption bands occupy the wave lengths 613-595, 568-5615, 560-551, and 535-512. If the degree of absorption is great, a single broad band may be seen in place of two in the green, from 568 to 555. The number and position of the bands appear to be the same in the various members of the corynebacterium group. No differences have been seen between toxin-producing and non-toxin-producing strains of the species B. diphtheriae.

As with the cytochrome observed by Keilin in various materials, the absorption bands of these bacteria fade out when atmospheric oxygen is admitted to the suspension, and reappear when air is excluded or a strong reducing agent (hydrosulphite) is added.

In the examination of filtrates of the corynebacteria the cultures have been grown in the medium, and according to the procedure, employed for the production of diphtheria toxin, after adaptation of the individual strains to growth in a pellicle, After 9 or 10 days of growth the metabolized bouillon was passed through a Berkefeld candle under anaerobic conditions and examined spectroscopically in tubes 200 mm. in length.