Open AccessHeterotrophic Metabolism of the Chemolithotroph Thiobacillus ferrooxidansOpen Access
D. G. Lundgren
journal of bacteriology
PublisherAmerican Society for Microbiology
Glucose-6-phosphate dehydrogenase and the enzymes of the Entner-Doudoroff pathway, 6-phosphogluconate dehydrase and 2-keto-3-deoxy-6-phosphogluconate aldolase (assayed together), are induced during heterotrophic growth ofThiobacillus ferrooxidans on an iron-glucose-supplemented medium or on glucose alone. By contrast, autotrophic cells (iron-grown) contain low levels of these enzymes. Fructose 1, 6-diphosphate aldolase, an enzyme of the Embden-Meyerhof pathway, is present at low levels irrespective of the growth medium, suggesting that this enzyme is not involved in energy-yielding reactions but merely provides intermediates for biosynthesis. The Entner-Doudoroff and pentose-phosphate pathways are the principle means through which glucose is dissimilated and is presumed to be concerned with energy production. Isotopic studies showed that a high rate of CO2 formation from specifically labeled glucose came from carbon atoms 1 and 4. An unexpectedly high rate of evolution of CO2 also came from carbon 6, suggesting that the triose phosphate formed during glucose breakdown and specifically as a result of 2-keto-3-deoxy-6-phosphogluconate aldolase activity, was metabolized via some unorthodox metabolic route. Cells grown in the iron-supplemented and glucose-salts media have a complete tricarboxylic acid cycle, whereas autotrophically grownT. ferrooxidans lacked both α-ketoglutarate dehydrogenase and reduced nicotinamide adenine dinucleotide oxidase. Two isocitrate dehydrogenases [nicotinamide adenine dinucleotide (NAD) and NAD phosphate (NADP) specific] were present. NAD-linked enzyme was constitutive, whereas the NADP-linked enzyme was induced upon adaptation of autotrophic cells to heterotrophic growth.
Subject(s)aldolase a , bacteria , biochemistry , biology , citric acid cycle , dehydrogenase , dihydroxyacetone phosphate , ecology , energy source , enzyme , fructose bisphosphate aldolase , genetics , glycolysis , heterotroph , isocitrate dehydrogenase , metabolism , nad+ kinase , nicotinamide adenine dinucleotide , nicotinamide adenine dinucleotide phosphate , oxidase test , pentose phosphate pathway , renewable energy , thiobacillus
SCImago Journal Rank1.652
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