ISSN:
1432-072X
Keywords:
Azospirillum brasilense
;
Biphasic nitrogenase activity
;
Biphasic growth
;
Glutamine synthetase
;
Glutamate dehydrogenase
;
Alanine aminotransferase
;
Poly-3-hydroxybutanoic acid accumulation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Long lasting batch cultures of Azospirillum brasilense SP 7 ATCC 29145 grown in liquid malate medium for 8–14 days without any fixed nitrogen source exhibited a biphasic nitrogenase activity, when incubated under gas atmospheres of 99.0% N2 and 1.0% O2 or 99.5% N2 and 0.5% O2 respectively. Maximum specific nitrogenase activity was 1100 nmol C2H4·mg protein-1·h-1. Poly-3-hydroxybutanoic acid (PHBA) synthesis and growth of the cells also showed two phases. Maxima and minima of glutamine synthetase activity developed synchronously with nitrogenase activity, whereas those of glutamate dehydrogenase and alanine aminotransferase were reverse. During a 192 h period of growth protein increased 3–4-fold and PHBA 25 fold. At maximum accumulation of the polymer the PHBA-nitrogen ratio was 6:1 or 8:1. Azospirillum brasilense was also able to fix nitrogen on agar surfaces exposed to air, but nitrogen fixation was monophasic under these conditions during a 14 d period. Specific nitrogenase activity was dependent on the type and concentration of the source of fixed nitrogen (leucine, ammonia) in solidified media. With 1 mM leucine maximum specific nitrogenase activity was 110 nmol C2H4·mg protein-1·h-1.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00406160
