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Uptake of inorganic carbon in the cyanobacterium Synechocystis PCC6803: physiological and genetic evidence for a high‐affinity uptake system
Author(s) -
Bédu S.,
Pozuelos P.,
Cami B.,
Joset F.
Publication year - 1995
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1995.mmi_18030559.x
Subject(s) - biology , cyanobacteria , synechocystis , total inorganic carbon , carbon fibers , biochemistry , bacteria , genetics , ecology , carbon dioxide , materials science , composite number , composite material
Synechocystis PCC6803 displays two inorganic carbon‐uptake processes, a low‐affinity one (apparent K m : 300–400 µM) functional in cells grown under standard or limiting inorganic carbon concentrations, and one with a higher affinity (60±12 µM), detected only in cells adapted to limiting inorganic carbon conditions. A mutational and screening procedure allowed the isolation of a mutant deficient in the high‐affinity system, but only slightly impaired in its growth capacities. The mutated genomic region revealed two open reading frames (ORFs), possibly belonging to an operonic structure. A clone in which the downstream ORF, hatR ( h igh‐ a ffinity t ransport), had been inactivated showed a phenotype close to that of the original mutant. Inactivation of the other ORF, hatA , yielded a clone unable to grow in limiting inorganic carbon conditions. The deduced HatA protein showed no homology with any registered protein. It possessed three hydrophobic domains, including a putative signal peptide. Several hypotheses are considered as to its role. The deduced HatR protein, which possessed the features characteristic of the response regulators of the two‐component regulatory systems ubiquitous in bacteria, might be a regulator controlling the activity of the high‐affinity transport process. It would belong to the subclass of these molecules lacking the DNA‐binding domain.