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Adaptation in bacterial flagellar and motility systems: from regulon members to 'foraging'-like behavior in E. coli.

Zhao K, Liu M, Burgess RR - Nucleic Acids Res. (2007)

Bottom Line: Bacterial flagellar motility and chemotaxis help cells to reach the most favorable environments and to successfully compete with other micro-organisms in response to external stimuli.To define the physiological role of these two regulators, we carried out transcription profiling experiments to identify, on a genome-wide basis, genes under the control of these two regulators.In addition, the synchronized pattern of increasing CRP activity causing increasing FlhDC expression with decreasing carbon source quality, together with the apparent coupling of motility activity with the activation of motility and chemotaxis genes in poor quality carbon sources, highlights the importance of CRP activation in allowing E. coli to devote progressively more of its limited reserves to search out better conditions.

View Article: PubMed Central - PubMed

Affiliation: McArdle Laboratory for Cancer Research, Department of Genetics, University of Wisconsin, Madison, WI 53706, USA.

ABSTRACT
Bacterial flagellar motility and chemotaxis help cells to reach the most favorable environments and to successfully compete with other micro-organisms in response to external stimuli. Escherichia coli is a motile gram-negative bacterium, and the flagellar regulon in E. coli is controlled by a master regulator FlhDC as well as a second regulator, flagellum-specific sigma factor, sigma(F). To define the physiological role of these two regulators, we carried out transcription profiling experiments to identify, on a genome-wide basis, genes under the control of these two regulators. In addition, the synchronized pattern of increasing CRP activity causing increasing FlhDC expression with decreasing carbon source quality, together with the apparent coupling of motility activity with the activation of motility and chemotaxis genes in poor quality carbon sources, highlights the importance of CRP activation in allowing E. coli to devote progressively more of its limited reserves to search out better conditions. In adaptation to a variety of carbon sources, the motile bacteria carry out tactical responses by increasing flagellar operation but restricting costly flagellar synthesis, indicating its capability of strategically using the precious energy in nutrient-poor environments for maximizing survival.

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Confirmation of FlhDC and σF deletion and overexpression in respective strains. (A) RT-PCR analysis of flhD, flhC and fliA expression in deletion strains. RNA isolated from each strain was converted to cDNA and PCR-amplified with primers specific for flhD, flhC and fliA. DnaK served as positive control. Expression of DnaK can be detected by RT-PCR in the wild-type strain as well as in flhDC and fliA mutant strains. Expression of flhD, flhC or fliA can only be detected in wild-type strain, but the expression of these genes is absent in the respective mutants. (B) Motility in E. coli wild-type strain and flhDC and fliA mutant strains. The flhDC and fliA deletion strains lose their motility on soft tryptone swarm agar. The motility can be recovered from these mutant strains by in vivo expression of FlhDC or σF from a plasmid-borne flhDC or fliA gene, respectively. (C) RT-PCR analysis of flhD, flhC and fliA expression in overexpression strains. Compared with the transcript level of control (dnaK), a significant increase of transcripts of flhD, flhC and fliA expression can be seen after a 5-min induction.
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Figure 1: Confirmation of FlhDC and σF deletion and overexpression in respective strains. (A) RT-PCR analysis of flhD, flhC and fliA expression in deletion strains. RNA isolated from each strain was converted to cDNA and PCR-amplified with primers specific for flhD, flhC and fliA. DnaK served as positive control. Expression of DnaK can be detected by RT-PCR in the wild-type strain as well as in flhDC and fliA mutant strains. Expression of flhD, flhC or fliA can only be detected in wild-type strain, but the expression of these genes is absent in the respective mutants. (B) Motility in E. coli wild-type strain and flhDC and fliA mutant strains. The flhDC and fliA deletion strains lose their motility on soft tryptone swarm agar. The motility can be recovered from these mutant strains by in vivo expression of FlhDC or σF from a plasmid-borne flhDC or fliA gene, respectively. (C) RT-PCR analysis of flhD, flhC and fliA expression in overexpression strains. Compared with the transcript level of control (dnaK), a significant increase of transcripts of flhD, flhC and fliA expression can be seen after a 5-min induction.

Mentions: The sequenced E. coli K-12 strain MG1655 (λ− F−ilvG−rfb−50 rph-1, prototroph) (24), on which E. coli Affymetrix Genechip probe design is based, was chosen for our studies. E. coli FlhDC or σF in-frame deletion strains as well as FlhDC or σF overexpression strains were constructed as described in Zhao et al. (27) and in Experimental Procedures. RT-PCR was used to examine the expression of flhD, flhC and fliA in the respective deletion mutants before microarray analysis. As expected, the FlhDC mutant did not express flhD and flhC, and the σF mutant failed to express fliA (Figure 1A), confirming inactivation of these genes.Figure 1.


Adaptation in bacterial flagellar and motility systems: from regulon members to 'foraging'-like behavior in E. coli.

Zhao K, Liu M, Burgess RR - Nucleic Acids Res. (2007)

Confirmation of FlhDC and σF deletion and overexpression in respective strains. (A) RT-PCR analysis of flhD, flhC and fliA expression in deletion strains. RNA isolated from each strain was converted to cDNA and PCR-amplified with primers specific for flhD, flhC and fliA. DnaK served as positive control. Expression of DnaK can be detected by RT-PCR in the wild-type strain as well as in flhDC and fliA mutant strains. Expression of flhD, flhC or fliA can only be detected in wild-type strain, but the expression of these genes is absent in the respective mutants. (B) Motility in E. coli wild-type strain and flhDC and fliA mutant strains. The flhDC and fliA deletion strains lose their motility on soft tryptone swarm agar. The motility can be recovered from these mutant strains by in vivo expression of FlhDC or σF from a plasmid-borne flhDC or fliA gene, respectively. (C) RT-PCR analysis of flhD, flhC and fliA expression in overexpression strains. Compared with the transcript level of control (dnaK), a significant increase of transcripts of flhD, flhC and fliA expression can be seen after a 5-min induction.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1935009&req=5

Figure 1: Confirmation of FlhDC and σF deletion and overexpression in respective strains. (A) RT-PCR analysis of flhD, flhC and fliA expression in deletion strains. RNA isolated from each strain was converted to cDNA and PCR-amplified with primers specific for flhD, flhC and fliA. DnaK served as positive control. Expression of DnaK can be detected by RT-PCR in the wild-type strain as well as in flhDC and fliA mutant strains. Expression of flhD, flhC or fliA can only be detected in wild-type strain, but the expression of these genes is absent in the respective mutants. (B) Motility in E. coli wild-type strain and flhDC and fliA mutant strains. The flhDC and fliA deletion strains lose their motility on soft tryptone swarm agar. The motility can be recovered from these mutant strains by in vivo expression of FlhDC or σF from a plasmid-borne flhDC or fliA gene, respectively. (C) RT-PCR analysis of flhD, flhC and fliA expression in overexpression strains. Compared with the transcript level of control (dnaK), a significant increase of transcripts of flhD, flhC and fliA expression can be seen after a 5-min induction.
Mentions: The sequenced E. coli K-12 strain MG1655 (λ− F−ilvG−rfb−50 rph-1, prototroph) (24), on which E. coli Affymetrix Genechip probe design is based, was chosen for our studies. E. coli FlhDC or σF in-frame deletion strains as well as FlhDC or σF overexpression strains were constructed as described in Zhao et al. (27) and in Experimental Procedures. RT-PCR was used to examine the expression of flhD, flhC and fliA in the respective deletion mutants before microarray analysis. As expected, the FlhDC mutant did not express flhD and flhC, and the σF mutant failed to express fliA (Figure 1A), confirming inactivation of these genes.Figure 1.

Bottom Line: Bacterial flagellar motility and chemotaxis help cells to reach the most favorable environments and to successfully compete with other micro-organisms in response to external stimuli.To define the physiological role of these two regulators, we carried out transcription profiling experiments to identify, on a genome-wide basis, genes under the control of these two regulators.In addition, the synchronized pattern of increasing CRP activity causing increasing FlhDC expression with decreasing carbon source quality, together with the apparent coupling of motility activity with the activation of motility and chemotaxis genes in poor quality carbon sources, highlights the importance of CRP activation in allowing E. coli to devote progressively more of its limited reserves to search out better conditions.

View Article: PubMed Central - PubMed

Affiliation: McArdle Laboratory for Cancer Research, Department of Genetics, University of Wisconsin, Madison, WI 53706, USA.

ABSTRACT
Bacterial flagellar motility and chemotaxis help cells to reach the most favorable environments and to successfully compete with other micro-organisms in response to external stimuli. Escherichia coli is a motile gram-negative bacterium, and the flagellar regulon in E. coli is controlled by a master regulator FlhDC as well as a second regulator, flagellum-specific sigma factor, sigma(F). To define the physiological role of these two regulators, we carried out transcription profiling experiments to identify, on a genome-wide basis, genes under the control of these two regulators. In addition, the synchronized pattern of increasing CRP activity causing increasing FlhDC expression with decreasing carbon source quality, together with the apparent coupling of motility activity with the activation of motility and chemotaxis genes in poor quality carbon sources, highlights the importance of CRP activation in allowing E. coli to devote progressively more of its limited reserves to search out better conditions. In adaptation to a variety of carbon sources, the motile bacteria carry out tactical responses by increasing flagellar operation but restricting costly flagellar synthesis, indicating its capability of strategically using the precious energy in nutrient-poor environments for maximizing survival.

Show MeSH
Related in: MedlinePlus