Acetylene reduction by nitrogen-fixing blue-green algae

Summary Known nitrogen-fixing species of blue-green algae are capable of reducing acetylene to ethylene, but acetylene is not reduced by Anacystis nidulans, which does not fix nitrogen. Cycad root nodules which contain blue-green algae as endophytes reduce acetylene. Acetylene reduction is inhibited by carbon monoxide. Nitrate or ammonium-nitrogen has no immediate effect on algae reducing acetylene, but algae grown on nitrate-nitrogen gradually lose their capacity to reduce acetylene. Nitrate-nitrogen also inhibits heterocyst formation in these algae and there is a fairly direct correlation between the abundance of heterocysts in a particular sample and its capacity to reduce acetylene. Aphanizomenon flosaquae reduces acetylene and fixes nitrogen in unialgal culture and there is strong presumptive evidence that these reductions are carried out by the alga rather than by associated bacteria. The molar ratios of ethylene: ammonia produced vary within the range 1.4–1.8.     

Lateral phase separations and perpendicular transport in membranes

A valinomycin-mediated potassium conductivity has been studied using a glass U-tube in which two aqueous compartments are separated by a fritted glass filter impregnated with valinomycin and one or more pure phospholipids. This system can be used to detect the beginning and end of lateral phase separations in binary lipid mixtures, and also demonstrates a pronounced maximum in electrical conductivity of dipalmitoyl phosphatidylcholine at the transition temperature, 41°C.