Glucose metabolism in batch and continuous cultures of Gluconacetobacter diazotrophicus PAL 3.
Periplasmic glucose oxidation (by way of a pyrrolo-quinoline-quinone [PQQ]-linked glucose dehydrogenase [GDH]) was observed in continuous cultures of Gluconacetobacter diazotrophicus regardless of the carbon source (glucose or gluconate) and the nitrogen source (N(2) or NH(3)). Its synthesis was stimulated by conditions of high energetic demand (i.e., N(2)-fixation) and/or C-limitation. Under C-excess conditions, PQQ-GDH synthesis increased with the glucose concentration in the culture medium. In batch cultures, PQQ-GDH was actively expressed in very early stages with higher activities under conditions of N(2)-fixation. Hexokinase activity was almost absent under any culture condition. Cytoplasmic nicotinamide adenine dinucleotide (NAD)-linked glucose dehydrogenase (GDH) was expressed in continuous cultures under all tested conditions, and its synthesis increased with the glucose concentration. In contrast, low activities of this enzyme were detected in batch cultures. Periplasmic oxidation, by way of PQQ-GDH, seems to be the principal pathway for metabolism of glucose in G. Diazotrophicus, and NAD-GDH is an alternative route under certain environmental conditions.
Centro de Investigación y Desarrollo en Fermentaciones Industriales CINDEFI (CONICET-UNLP), Calles 47 y 115 (1900), La Plata, Argentina. boiardi@quimica.unlp.edu.ar
María F
MF
Luna
Cecilia E
CE
Bernardelli
María L
ML
Galar
José L
JL
Boiardi
D018929:Cell Culture Techniques; D003593:Cytoplasm / Q000201:enzymology; D041821:Gluconacetobacter / Q000201:enzymology* / Q000254:growth & development*; D005947:Glucose / Q000378:metabolism*; D042843:Glucose 1-Dehydrogenase / Q000032:analysis / Q000378:metabolism; D005948:Glucose Dehydrogenases / Q000032:analysis / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D010084:Oxidation-Reduction; D019897:Periplasm / Q000201:enzymology
D005948:Glucose Dehydrogenases; D042843:Glucose 1-Dehydrogenase; C033955:glucose dehydrogenase (pyrroloquinoline-quinone); D006593:Hexokinase; D005947:Glucose; D009584:Nitrogen