Genetic evidence that hepA gene is involved in the normal deposition of the envelope of both heterocysts and akinetes in Anabaena variabilis ATCC 29413.

The hepA gene in Anabaena sp. strain PCC 7120 is required for normal formation of the polysaccharide layer of the heterocyst envelope. A plasmid bearing hepA, interrupted by a neomycin-resistance cassette, was transferred by conjugation to wild type Anabaena variabilis ATCC 29413, so that the interrupted hepA gene replaced a homologous sequence. In the recombinant exconjugants, the envelopes of akinetes as well as of heterocysts were altered.