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J. Bacteriol., 06 1995, 3150-3157, Vol 177, No. 11
ML Montesinos, A Herrero and E Flores
Uptake of 16 amino acids by the filamentous, heterocyst-forming
cyanobacterium Anabaena sp. strain PCC 7120 was characterized with regard
to kinetic parameters of transport, intracellular accumulation of the
transported amino acids, and sensitivity of the transport process to energy
metabolism inhibitors. Mutants resistant to certain toxic analogs of some
amino acids were isolated that were impaired in amino acid transport.
Results obtained in this study, together with those reported previously (A.
Herrero and E. Flores, J. Biol. Chem. 265:3931-3935, 1990), suggest that
there are at least five amino acid transport systems in strain PCC 7120:
one high-affinity, active system for basic amino acids; one low-affinity,
passive system for basic amino acids; two high-affinity, active systems
with overlapping, but not identical, specificities for neutral amino acids;
and one putative system for acidic amino acids. Some of the amino acid
transport mutants were impaired in diazotrophic growth. These mutants were
unable to develop a normal percentage of heterocysts and normal nitrogenase
activity in response to nitrogen stepdown. Putative roles for the amino
acid transport systems in uptake of extracellular amino acids, recapture of
amino acids that have leaked from the cells, and intercellular transfer of
amino acids in the filaments of Anabaena sp. strain PCC 7120 are discussed.
Copyright © 1995, American Society for Microbiology
Amino acid transport systems required for diazotrophic growth in the cyanobacterium Anabaena sp. strain PCC 7120
Instituto de Bioquimica Vegetal y Fotosintesis, Universidad de Sevilla- Consejo Superior de Investigaciones Cientificas, Spain.
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