ISSN:
1432-072X
Keywords:
Anabaena
;
Heterocysts
;
Nitrogenase
;
Oxygen-protection
;
Mutants
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Mutants of Anabaena sp. PCC 7120 with O2-sensitive acetylene-reducing activity were studied to identify envelope components that contribute to the barrier limiting diffusion of oxygen into the heterocyst. Mutant strain EF114, deficient in a heterocyst-specific glycolipid, reduced acetylene only under strictly anaerobic conditions. Analysis of in vivo O2 uptake as a function of dissolved pO2 showed that EF114 has lost the low affinity, diffusion-limited respiratory component associated with heterocysts in wild-type filaments. The low affinity respiratory activity was also lost in EF116, a mutant in which the cohesiveness of the outer polysaccharide layer was reduced. Restoration of aerobic nitrogen fixation in a spontaneous revertant of EF116 and in a strain complemented with cosmid 41E11 was associated with restoration of the low affinity component of respiratory activity. The results provide evidence that the barrier to diffusion of gas into heterocysts depends upon both the glycolipid layer and the polysaccharide layer of the heterocyst envelope.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00454860
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