Respiratory Studies of the Micrococci

Abstract

The respiratory activities of Micrococcus luteus, M. fiavus, M. aurantiacus, M. cinnebareus and M. freundenreichii were studied. Under the conditions of these expts., it was found that when methylene blue was used as the H acceptor, the substrates found to be most readily activated were raffinose, maltose, sucrose, glucose, ethyl alcohol, succinate, maleate, and glutamate. When O2 was used as the H acceptor the compounds most readily activated were sucrose, maltose, glucose, ethyl alcohol, succinate, lactate, glutamate, and asparagine. The oxygen uptake of most of the substrates was constant or decreased slightly with time, while some few of the substrates, mainly glutamate and dl-[beta]-phenylalanine, showed an increasing oxidation rate. The influence on the cells of several respiratory inhibitors showed that the dehydro-genases of M. luteus and M. flavus were stimulated by a cyanide conc. of 1.4 X 10-2 M, while the other organisms were inhibited by this conc. The specific dehydrogenases varied in their sensitivity toward inhibitors. Those which were active against the amino acids were most susceptible in that they were strongly inhibited by Na azide, Na monochloracetate and Na cyanide in a conc. of 1.4 X 10-5 M. Cyanide inhibition was generally decreased by methylene blue but was completely removed only in the case of M. flavus with sucrose as the substrate and M. aurantiacus with glucose as the substrate. Methylene blue when used alone exerted an influence on the cells. M. luteus and M. flavus were stimulated by the presence of 1 mg. of methylene blue in the presence of all substrates except succinate, while the other organisms were inhibited by this amount of methylene blue. M. freundenreichii was stimulated by 0.5 mg. in the presence of all the substrates except succinate, while M. aurantiacus and M. cinnebareus were inhibited by a conc. as low as 0.1 mg. Na monochloracetate in a conc. of 1.4 X 10-2 M inhibited the oxidation of all substrates with the exception of glucose, with which there was stimulation. With the exception of M. freundenreichii all the organisms possessed moderate polyphenol oxidase and catalase activity. Hydroquinone was not oxidized by any of the micrococci, while p-phenylenediamine was oxidized by all the organisms. This might indicate that cyto-chrome-b is abundant in the organisms and that cyto-chrome-c has a protein bearer which causes its potential to be negative with respect to hydroquinone and hence inactive.