Escherichia coli is by far the most studied prokaryote and an invaluable tool in the laboratory and for biotechnological applications. It is a typical member of the mammalian gut microbiota but it can also exist as six different “pathotypes” that cause serious illness in humans. The sequenced E. coli genomes, from commensal and pathogenic strains, exhibit a “conserved core” genome of approximately 2,200 genes (half of the genome) and a pangenome of over 12,000 genes. The acquisition by horizontal gene transfer of pathogenicity islands, virulence plasmids and other mobile genetic elements allows the genomes of pathogenic E. coli to reshape into new pathotypes. The severe outbreak caused by the E. coli strain of serotype O104:H4 in Germany in May-July 2011, with more than 4,000 cases in 13 European countries and over 50 deaths, is a recent, dramatic example. Instrumental to host gut colonization is the ability of E. coli and other enteropathogenic bacteria to overcome the extremely acidic environment of the host stomach, the major bactericidal barrier of the gastrointestinal tract. In E. coli the glutamate-dependent acid resistance (GDAR) system plays a major role in protection form the extreme acid stress. Structural genes of this system are gadA, gadB and gadC, which encode two glutamate decarboxylase isoforms and a glutamate/γ-aminobutyrate (GABA) antiporter, respectively. Crystallographic studies have elegantly shown that both GadA/B and GadC become active only when the intracellular pH falls below 5.6. Glutamate decarboxylation, with the concomitant consumption of H+, and Glu/GABA electrogenic antiport contribute to protecting the cells from the harmful intracellular levels of H+. Even though the gadA and gadBC genes are 2,1 Mb apart, their transcription is under the control of the same regulators, namely GadE, GadX, GadW, H-NS and RpoS. These regulators also affect the expression of 12 genes located in the acid fitness island (AFI). In the complex regulatory network controlling the expression of the GDAR genes, GadX plays an important role, i.e. it activates the GDAR structural genes in stationary phase both directly and indirectly, via activation of gadE, the gene coding for the central GDAR regulator. In a previous work we identified the GadX binding site, a 42-bp sequence, in the regulatory regions of all the AFI genes and gadBC. More recently, by means of a genome wide approach (ChIP-chip) and in vitro and in vivo studies, we have obtained experimental evidence that GadX affects the expression of many more targets, approx. 100 genes, than previously expected. These are scattered along the genome. Some of them are known to play major roles in important physiological processes, only apparently unrelated to the response to acid stress.
The meeting is focused on microbial stresses, covering experimental approaches from detailed molecular dissection of individual components to understanding stress responses at the whole cell and the whole population levels. It will bring together researchers, both academic and industrial, from all over the world, with a shared interest in all aspects of microbial stresses. This year, the themes will cover both intracellular and environmental stresses, the links between stress responses and energy metabolism, and the impacts of stress on microbial productivity. A must for all microbial physiologists, geneticists, cell biologists, biochemists, and systems biologists! Announced speakers: Theme One: Intracellular and environmental stresses: how cells cope with them Daniela De Biase, Michael Hecker, Frank Madeo, John Morrissey, Aurelio Serrano Theme Two: Cell stress and energy metabolism Eva-Mari Aro, Timothy J. Donohue, Vassily Hatzimanikatis, Luigi Palmieri Theme Three: Cell stress and bio-based microbial productions Eckhard Boles, Pascale Daran-Lapujade, Ryan Gill, Jens Nielsen Scientific Committee Paola Branduardi (chair), Dept of Biotechnology and Biosciences University of Milano-Bicocca (I) Michael Sauer (co-chair), IAM University of Natural Resources and Life Sciences, Wien (A) Peter Lund (co-chair), School of Biosciences, University of Birmingham (UK) Jeff Cole, School of Biosciences, University of Birmingham (UK) Eckhard Boles, Institut für Molekulare Biowissenschaften Goethe-Universität Frankfurt (D) Toni Villaverde, Department of Genetics and Microbiology, Universitat Aut?noma de Barcelona (E) John Morrissey, Microbiology Department Food Science Building University College Cork (Ireland) Industrial Committee Danilo Porro (Committee chair), Dept of Biotechnology and Biosciences University of Milano-Bicocca (I) Jens Nielsen, Dept of Chemical and Biological Engineering, Chalmers University of Technology (S) Laura Ruohonen, VTT Technical Research Centre of Finland, Espoo (F) Gunnar Lidén, Department of Chemical Engineering Lund University (S) Vassily Hatzimanikatis, Laboratory of Computational Systems Biotechnology (LCSB) Ecole Polytechnique Federale de Lausanne (CH) Francesca De Ferra, Eni Refining & Marketing (I) Satoshi Harashima, International Center for Biotechnology Osaka University (Japan) Luis Oriani, Chemtex Italia, Mossi and Ghisolfi Group (I)
Beyond acid resistance: identification of novel targets of the regulators of the gad system in Escherichia coli / DE BIASE, Daniela. - STAMPA. - (2012), pp. 18-19. (Intervento presentato al convegno Microbial stress from Molecules to Systems (2nd International Conference) tenutosi a Belgirate (Italy) nel 10-13 May 2012).
Beyond acid resistance: identification of novel targets of the regulators of the gad system in Escherichia coli
DE BIASE, Daniela
2012
Abstract
Escherichia coli is by far the most studied prokaryote and an invaluable tool in the laboratory and for biotechnological applications. It is a typical member of the mammalian gut microbiota but it can also exist as six different “pathotypes” that cause serious illness in humans. The sequenced E. coli genomes, from commensal and pathogenic strains, exhibit a “conserved core” genome of approximately 2,200 genes (half of the genome) and a pangenome of over 12,000 genes. The acquisition by horizontal gene transfer of pathogenicity islands, virulence plasmids and other mobile genetic elements allows the genomes of pathogenic E. coli to reshape into new pathotypes. The severe outbreak caused by the E. coli strain of serotype O104:H4 in Germany in May-July 2011, with more than 4,000 cases in 13 European countries and over 50 deaths, is a recent, dramatic example. Instrumental to host gut colonization is the ability of E. coli and other enteropathogenic bacteria to overcome the extremely acidic environment of the host stomach, the major bactericidal barrier of the gastrointestinal tract. In E. coli the glutamate-dependent acid resistance (GDAR) system plays a major role in protection form the extreme acid stress. Structural genes of this system are gadA, gadB and gadC, which encode two glutamate decarboxylase isoforms and a glutamate/γ-aminobutyrate (GABA) antiporter, respectively. Crystallographic studies have elegantly shown that both GadA/B and GadC become active only when the intracellular pH falls below 5.6. Glutamate decarboxylation, with the concomitant consumption of H+, and Glu/GABA electrogenic antiport contribute to protecting the cells from the harmful intracellular levels of H+. Even though the gadA and gadBC genes are 2,1 Mb apart, their transcription is under the control of the same regulators, namely GadE, GadX, GadW, H-NS and RpoS. These regulators also affect the expression of 12 genes located in the acid fitness island (AFI). In the complex regulatory network controlling the expression of the GDAR genes, GadX plays an important role, i.e. it activates the GDAR structural genes in stationary phase both directly and indirectly, via activation of gadE, the gene coding for the central GDAR regulator. In a previous work we identified the GadX binding site, a 42-bp sequence, in the regulatory regions of all the AFI genes and gadBC. More recently, by means of a genome wide approach (ChIP-chip) and in vitro and in vivo studies, we have obtained experimental evidence that GadX affects the expression of many more targets, approx. 100 genes, than previously expected. These are scattered along the genome. Some of them are known to play major roles in important physiological processes, only apparently unrelated to the response to acid stress.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
