Comparative studies on bacterial cytochromes. 1955.

Abstract

Abstract 1. 1. All photosynthetic bacteria appear to contain cytochromes of the “c” type together with associated enzymic activities, such as DPNH-linked reductase, oxidase and photo-oxidase. This is true of strict anaerobes as well as facultative bacteria. There also appears to be a general distribution of other hematin compounds, such as cytochromes of the “b” type, as well as of the new hematin compounds tentatively referred to as “pseudohemoglobins”. 2. 2. Two species of denitrifiers (facultative anaerobes) have also been examined and found to contain cytochromes of the “c” type. One of these species yields a cytochrome c which spectroscopically and enzymically resembles mammalian cytochrome c, whereas the other contains a cytochrome very similar in spectroscopic properties, oxidation potential and enzymic behavior to the cytochromes of “c” type found in photosynthetic bacteria. 3. 3. The oxidation potentials of the various cytochromes of “c” type have been measured over a wide range of pH values. These results indicate that each microorganism examined has a cytochrome c unique to itself, but that all the “c” cytochromes isolated from the facultative photohetertrophs have potentials much more oxidizing than those of cytochrome c as prepared from yeast or mammalian tissue. 4. 4. These results are discussed and correlated with the overall physiology of the bacteria. Their significance for the general problem of transfer and storage of light energy in photosynthesis is indicated.