title: A cyanobacterial recombination study, involving an efficient N2-fixing non-heterocystous partner.
abstract: Many filamentous cyanobacteria fix atmospheric nitrogen under natural conditions in specialized anaerobic compartments, heterocysts, interspersed between vegetative cells, which provide protection to the O2-sensitive nitrogenase. A few unicellular cyanobacterial strains are also known to fix nitrogen aerobically at a slower rate. Filamentous cyanobacteria lacking heterocysts are not known so far to fix nitrogen. We describe the isolation and purification of a non-heterocystous filamentous cyanobacterium from the fronds of the water-fern Azolla, fixing nitrogen at 18.7+/-0.2 n moles ethylene microg Chl. a(-1) h(-1) when grown in nitrogen-free medium at a low level of oxygen between two layers of agar. This strain of Anabaena azollae has been designated as het- nif+ (non-heterocystous and nitrogen-fixing), and is found to be easily and effectively preserved in nitrogen-free medium in standard synthetic cyanobacterial nutrient medium (pH 8.5) at a continuous light intensity of 2800 lx at 25+/-1 degrees C. This het- nif+ strain is an effective donor of the nif+ marker to a het+ nif- strain of another cyanobacterium, Nostoc muscorum, when both are grown together in a recombination study.
authors.affiliation: Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India.
authors.forename: A
authors.initials: A
authors.lastname: Vaishampayan
authors.forename: R P
authors.initials: RP
authors.lastname: Sinha
authors.forename: A K
authors.initials: AK
authors.lastname: Gupta
authors.forename: D P
authors.initials: DP
authors.lastname: Häder
mesh_terms: D017033:Anabaena / Q000235:genetics*; D000458:Cyanobacteria / Q000235:genetics*; D009586:Nitrogen Fixation / Q000235:genetics*; D010944:Plants / Q000382:microbiology; D011995:Recombination, Genetic