FlhD/FlhC is a regulator of anaerobic respiration and the Entner-Doudoroff pathway through induction of the methyl-accepting chemotaxis protein Aer - PubMed (original) (raw)

FlhD/FlhC is a regulator of anaerobic respiration and the Entner-Doudoroff pathway through induction of the methyl-accepting chemotaxis protein Aer

Birgit M Prüss et al. J Bacteriol. 2003 Jan.

Abstract

The regulation by two transcriptional activators of flagellar expression (FlhD and FlhC) and the chemotaxis methyl-accepting protein Aer was studied with glass slide DNA microarrays. An flhD::Kan insertion and an aer deletion were independently introduced into two Escherichia coli K-12 strains, and the effects upon gene regulation were investigated. Altogether, the flhD::Kan insertion altered the expression of 29 operons of known function. Among them was Aer, which in turn regulated a subset of these operons, namely, the ones involved in anaerobic respiration and the Entner-Doudoroff pathway. In addition, FlhD/FlhC repressed enzymes involved in aerobic respiration and regulated many other metabolic enzymes and transporters in an Aer-independent manner. Expression of 12 genes of uncharacterized function was also affected. FlhD increased gltBD, gcvTHP, and ompT expression. The regulation of half of these genes was subsequently confirmed with reporter gene fusions, enzyme assays, and real-time PCR. Growth phenotypes of flhD and flhC mutants were determined with Phenotype MicroArrays and correlated with gene expression.

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Figures

FIG. 1.

FIG. 1.

Pathways of FlhD regulation. The cartoon describes the operons that were regulated by FlhD, FlhD/FlhC, or Aer as determined by gene array. Operons that were confirmed by reporter gene fusion, enzyme assay, or real-time PCR are printed in boldface. Also included are targets that were previously identified (references and , indicated by superscript numerals 1 and 2, respectively).

FIG. 2.

FIG. 2.

Flow chart of respiration. The chart is drawn in a way that electrons flow from the left to the right. At the far left are electron donors, in the middle are quinones, and at the far right are electron acceptors. Genes encoding dehydrogenases are in the circles to the left, and genes encoding terminal reductases are in the circles to the right. Light gray circles above the dotted line indicate components of the aerobic respiratory chain, and dark gray circles below the dotted line indicate components of anaerobic respiration. All genes that are regulated by FlhD/FlhC, as determined by gene array, are printed in boldface. Genes that are repressed are underlined. All target operons except napF were confirmed with reporter gene fusions.

FIG. 3.

FIG. 3.

Phenotype MicroArrays. Cultures of MC1000, MC1000 flhD::Kan, YK410, YK4131, and YK4136 were inoculated onto PM1 (carbon sources) (A) and PM3 (nitrogen sources) (B) plates. Growth was determined as the OD630 after 24 h. The values for the wild-type (WT) cultures were divided by the values for the mutants. The figure shows the growth ratios for the strain couples MC1000-MC1000 flhD::Kan, YK410-YK4131, and YK410-YK4136. Error bars indicate the standard deviations derived from two to five independent experiments.

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