The metabolism of acetate by the blue-green algae, Anabaena variabilis and Anacystis nidulans.

The utilization of acetate by blue-green algae was examined and the activities of enzymes involved in its metabolism measured. Although acetate did not stimulate the endogenous respiration of these organisms, the oxidation of acetate was followed by the rate of release of [14C] carbon dioxide from [I-~~CC] and [2-l4CC] sodium acetate. Similarly, sodium acetate did not alter the rate of growth of Anabaenu variahilis and Anacystis nidulans but in A. variabilis it was found to contribute 7-2 "/b of the dry weight when cultures were gassed with air+CO, (95+5, vlv), and 16.9% when gassed with air alone. The presence of acetate in the growth medium did not alter the activity of the acetate-activating enzymes, glyoxylate cycle enzymes or two tricarboxy-lic acid cycle enzymes. The failure to show enzyme adaption by these organisms when supplied with an exogeneous substrate is discussed in relation to their hitherto apparently autotrophic nature. The blue-green algae, in spite of diverse ecological distribution, have markedly uniform nutrition. Most of the species examined are considered to be strict photo-autotrophs (Allen, 1952) and their failure to respond to external carbon sources other than carbon dioxide has been noted by many workers. Exceptions to this statement include Tolypothrix tenius, the growth of which is stimulated by glucose (Kiyo-hara et al. 1960; 1962) and ChlorogZoc.n.fi.itscliii, which has been reported to grow in the dark on sLicrose albeit the growth rate was expressed in terms of months rather than days (Fay, 1965). The incorporatioil of ['TI acetate into Nostoc II~USCOI'UYM and transformation into lipids has been known for some years (Allison et al. 1953); Moare & Moore (1965) described the photoassimilation of acetate by three blue-green algae and also showed major incorporation to be into the lipid fraction. The fact that CliIor.ogIsea fritscliii forms poly-/3-hydroxy butyrate only when grown in the presence of acetate, also indicates the utilization of this substrate by a blue-green alga (Carr, 1966). We therefore decided to examine in the blue-green algae the metabolism of acetate at the whole organism and enzyniic levels. Some preliminary results of this investigation have already been reported MRTffODS Organisnzs. We are grateful to the following for gifts of the cultures of the blue-green algae used: Anabaena variabilis (Kutzing) from Professor