Different functions assigned to NAD(H) and NADP(H) in light-dependent nitrogen fixation by heterocysts of Anabaena variabilis

Abstract We have directly selected thermosensitive alleles of cya and crp genes from the wild-type, and present preliminary characterization of these mutants. The selection procedure is based on prior growth of a mutagenized wild-type culture in a medium that counterselects, at low temperature, non-conditional relative to thermosensitive mutants, followed by routine selection of mutants at high temperature. This method should be applicable to various genetic systems.