The ferredoxin-encoding fdxN gene of the filamentous cyanobacterium Anabaena variabilis ATCC 29413 is not essential for nitrogen fixation.

In contrast to that of Anabaena sp. PCC7120, the fdxN gene in Anabaena variabilis ATCC 29413 is not interrupted by a 55-kb DNA element, making this strain more suitable for genetic analysis of fdxN independent of the developmentally regulated excision during heterocyst formation. As a basis for mutational analysis, the fdxN gene of A.