MUTAGENESIS AND ISOLATION OF MORPHOLOGICAL MUTANTS IMPAIRED IN NITROGEN‐FIXING CAPACITY FROM A CYNAOBACTERIUM GLOEOTRICHIA GHOSEI

Abstract

Ultraviolet (u.v.) irradiation and treatment with nitrosoguanidine (NTG) were used to produce mutants of the cyanobacterium Gloeotrichia ghosei. Three non‐nitrogen fixing (nif−) mutants, which were also altered in their morphological characteristics, were isolated. They were designated as fil1 het+, fil1 het++ and pol− her−. The first two mutants formed heterocysts and exhibited polarity while the third (i.e. pol− het−) had neither heterocysts nor polarity. The fil1 het+strain had a developmental pattern similar to that of the parent alga, but with longer filaments, while the fil1 het++ strain formed chains of intercalary heterocysts and the long filaments showed evidence of intercalary polarity. The isolation of these mutants demonstrates the feasibility of using Gloeotrichia to relate developmental morphology to nitrogen fixation and heterocyst differentiation in a filamentous cyanobacterium. Copyright © 1986, Wiley Blackwell. All rights reserved