Abs&aet-'I&e fatty acid composition of the blubgnen alga, A~JUC~&S ~~, was investigated by gasliquid chromatography at four W-t growth temperaturea with illumination, aeration, cell density, medium composition, and growth rate kept constant. At all temperaturea pahuitic acid and a Woic acid presumed to be pahnitoleic totaled approximately 90% of the fatty acids present but the ratio of the hexedecenoic to palmitic decreased as the tempemture was raised. An octadecenoic and tctnufecen oic (probably oleic and myristoleic, respe&+) were also present and traces of a heptadecenoic acid and of others were detected. At 26", 32", and 35", the ratio of total unsaturated to saturated acids rema&d approximately 1-O although the qualitative composition changed, but at 41' the saturated acids predominated, the ratio being@7. In cxmtrast to other algae and higher plants, polyunsaturated acids were absent in &ucy8& which in this way resembIes the photosynthetic bacteria

Analyses of the lipids in five species of blue-green algae show that the fatty acids are largely the C(16) and C(18) acids. The only alga that could be grown heterotrophically, Chlorogloea, formed the triply unsaturated C(18) acid in the light but only the doubly unsaturated C(18) acid in the dark. Examination of these results and the results of others suggest that, except for one species, the more highly unsaturated acids are found in the morphologically more complex algae. The fatty acid compositions of blue-green algae are different from the fatty acid composition of the other prokaryotic organisms, the bacteria. It is speculated that the diversity of the patterns of fatty acid composition among the blue-green algae could be of phylogenetic significance.

Aqueous extraction of lyophilized Anacystis nidulans cells followed by chromatography on diethylaminoethyl cellulose separates three different c-type cytochromes. Of the two present in highest concentration, cytochrome-554 has a + 0.35-volt redox potential and resembles the cytochrome f of other photosynthetic tissues, while cytochrome-549 has a -0.26-volt potential. The possible participatidn of cytochrome-549 in electron transport in photosynthesis in this alga at a more negative oxidation-reduction potential than previously postulated for any cytochrome is inferred from the similarities in its spectra to the light-induced spectral changes in vivo observed by others.

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