title: Analysis of hydrogenase 1 levels reveals an intimate link between carbon and hydrogen metabolism in Escherichia coli K-12.
abstract: Two of the three [NiFe]-hydrogenases (Hyd) of Escherichia coli have a hydrogen-uptake function in anaerobic metabolism. While Hyd-2 is maximally synthesized when the bacterium grows by fumarate respiration, Hyd-1 synthesis shows a correlation with fermentation of sugar substrates. In an attempt to advance our knowledge on the physiological function of Hyd-1 during fermentative growth, we examined Hyd-1 activity and levels in various derivatives of E. coli K-12 MC4100 with specific defects in sugar utilization. MC4100 lacks a functional fructose phosphotransferase system (PTS) and therefore grows more slowly under anaerobic conditions in rich medium in the presence of d-fructose compared with d-glucose. Growth in the presence of fructose resulted in an approximately 10-fold increase in Hyd-1 levels in comparison with growth under the same conditions with glucose. This increase in the amount of Hyd-1 was not due to regulation at the transcriptional level. Reintroduction of a functional fruBKA-encoded fructose PTS into MC4100 restored growth on d-fructose and reduced Hyd-1 levels to those observed after growth on d-glucose. Reducing the rate of glucose uptake by introducing a mutation in the gene encoding the cAMP receptor protein, or consumption through glycolysis, by introducing a mutation in phosphoglucose isomerase, increased Hyd-1 levels during growth on glucose. These results suggest that the ability to oxidize hydrogen by Hyd-1 shows a strong correlation with the rate of carbon flow through glycolysis and provides a direct link between hydrogen, carbon and energy metabolism.
authors.affiliation: Institute for Biology/Microbiology, Martin-Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale), Germany.
authors.forename: Constanze
authors.initials: C
authors.lastname: Pinske
authors.affiliation: Division of Molecular Microbiology, University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: McDowall
authors.affiliation: Division of Molecular Microbiology, University of Dundee, Dundee DD1 5EH, UK.
authors.forename: Frank
authors.initials: F
authors.lastname: Sargent
authors.affiliation: Institute for Biology/Microbiology, Martin-Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale), Germany.
authors.forename: R Gary
authors.initials: RG
authors.lastname: Sawers
mesh_terms: D000693:Anaerobiosis; D002244:Carbon / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D004734:Energy Metabolism; D048168:Escherichia coli K12 / Q000201:enzymology* / Q000378:metabolism*; D005285:Fermentation; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D053858:Metabolic Networks and Pathways; D010088:Oxidoreductases / Q000378:metabolism*
chemical_list: D003470:Culture Media; D005632:Fructose; D002244:Carbon; D006859:Hydrogen; D010088:Oxidoreductases; C029746:uptake hydrogenase; D005947:Glucose