Em. Lyons et T. Thiel, CHARACTERIZATION OF NIFB, NIFS, AND NIFU GENES IN THE CYANOBACTERIUM ANABAENA-VARIABILIS - NIFB IS REQUIRED FOR THE VANADIUM-DEPENDENT NITROGENASE, Journal of bacteriology, 177(6), 1995, pp. 1570-1575
Anabaena variabilis ATCC 29413 is a heterotrophic, nitrogen-fixing cya
nobacterium containing both a Mo-dependent nitrogenase encoded by the
nif genes and V-dependent nitrogenase encoded by the vnf genes. The ni
fB, nifS, and nifU genes of A. variabilis were cloned, mapped, and par
tially sequenced. The fdxN gene was between nifB and nifS. Growth and
acetylene reduction assays using mild-type and mutant strains indicate
d that the nifB product (NifB) was required for nitrogen fixation not
only-by the enzyme encoded by the nif genes but also by the enzyme enc
oded by the vnf genes. Neither NifS nor NifU was essential for nitroge
n fixation in A. variabilis.