On the nature of the cytochrome oxidase reactions in cyanobacteria

Phototrophically and heterotrophically grown intact resting cell suspensions of the freshwater cyanobacteria, Nostoc sp. strain MAC and Aphanocapsa sp. strain 6714, were examined for cytochrome oxidase activity using the quantitative microbiological oxidase test. The oxidase assay colorimetrically measures the oxidation of the reduced electron donor, N,N,N',N'-tetramethyl-p-pheny1enediamine (or TMPD). Anacystis nidulans strain TX20, which can only be grown phototrophica11y, was also analyzed in a similar manner for comparative purposes. The TMPD oxidase assay as employed originally was developed for surveying the cytochrome oxidase activities of bacteria and represents a modification of the qualitative Kovacs oxidase test. This test is used routinely today in diagnostic microbiology and measures the rate of oxidation of colorless reduced TMPD to the oxidized product Wurster's blue. A meaningful oxidase reaction occurs only in the presence of both molecular 02 as well as an active cytochrome oxidase. [...]