Michel Hébraud

Publications (52) View all

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  Available from: Michel Hébraud

  Article: Cell immobilization induces changes in the protein response of Escherichia coli K-12 to a cold shock.

  F Perrot, M Hebraud, R Charlionet, G A Junter, T Jouenne
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  ABSTRACT: We have compared the protein expression of gel-entrapped Escherichia coli cells submitted to a cold shock at 4 degrees C with those of exponential- and stationary-phase free-floating counterparts. Autoradiograms of two-dimensional gel electrophoresis patterns of proteins radiolabeled with L-[35S]methionine were compared using computing scanning densitometry. The levels of 203 proteins synthesized during the temperature shift were significantly and reproducibly higher than those corresponding to synthesis at 37 degrees C. A principal component analysis (PCA) was performed on the synthesis levels of these 203 proteins in the different incubation conditions tested. This study showed that the protein response of immobilized cells after the cold shock was significantly different from those of exponential- and stationary-phase free-floating organisms. For instance, protein SSB was specifically overexpressed by shocked immobilized organisms. Such induction of specific molecular mechanisms in immobilized bacteria might explain the high resistance of sessile-like organisms to stresses.
  Electrophoresis 07/2001; 22(10):2110-9. · 3.30 Impact Factor
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  Article: Effects of pH or a(w) stress on growth of Listeria monocytogenes.

  M Cheroutre-Vialette, I Lebert, M Hebraud, J C Labadie, A Lebert
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  ABSTRACT: The growth of three strains of Listeria monocytogenes at 20 degrees C in a meat broth of different pH or water activity was investigated. At inoculation or at the beginning of the exponential phase, cells were exposed to stress by the addition of NaOH or NH4+, acetic acid, NaCl or KCl, in order to reach a pH of either 9.0 or 5.6, or an a(w) of 0.950 or 0.965, respectively. The effects of the exposure to stress on the generation and lag times of each strain were analysed by turbidity measurements for cultures in micro-titer plates. Results were confirmed by conducting the same experiments in a fermentor, except for the maximal population reached. The three strains showed similar behaviour. Cells were able to overcome the alkaline stress rapidly whereas acid and osmotic shocks induced important changes of the growth parameters. Cells exposed to acid or osmotic conditions from the time of inoculation were less affected than cells exposed at the beginning of the mid-exponential phase.
  International Journal of Food Microbiology 07/1998; 42(1-2):71-7. · 3.33 Impact Factor
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  Article: The cold shock response of the psychrotrophic bacterium Pseudomonas fragi involves four low-molecular-mass nucleic acid-binding proteins.

  V Michel, I Lehoux, G Depret, P Anglade, J Labadie, M Hebraud
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  ABSTRACT: The psychrotrophic bacterium Pseudomonas fragi was subjected to cold shocks from 30 or 20 to 5 degrees C. The downshifts were followed by a lag phase before growth resumed at a characteristic 5 degrees C growth rate. The analysis of protein patterns by two-dimentional gel electrophoresis revealed overexpression of 25 or 17 proteins and underexpression of 12 proteins following the 30- or 20-to-5 degrees C shift, respectively. The two downshifts shared similar variations of synthesis of 20 proteins. The kinetic analysis distinguished the induced proteins into cold shock proteins (Csps), which were rapidly but transiently overexpressed, and cold acclimation proteins (Caps), which were more or less rapidly induced but still overexpressed several hours after the downshifts. Among the cold-induced proteins, four low-molecular-mass proteins, two of them previously characterized as Caps (CapA and CapB), and heat acclimation proteins (Haps) as well as heat shock proteins (Hsps) for the two others (TapA and TapB) displayed higher levels of induction. Partial amino acid sequences, obtained by microsequencing, were used to design primers to amplify by PCR the four genes and then determine their nucleotide sequences. A BamHI-EcoRI restriction fragment of 1.9 kb, containing the complete coding sequence for capB, was cloned and sequenced. The four peptides belong to the family of small nucleic acid-binding proteins as CspA, the major Escherichia coli Csp. They are likely to play a major role in the adaptative response of P. fragi to environmental temperature changes.
  Journal of Bacteriology 01/1998; 179(23):7331-42. · 3.83 Impact Factor
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  Article: Effect of growth temperatures on the protein levels in a psychrotrophic bacterium, Pseudomonas fragi.

  M Hebraud, E Dubois, P Potier, J Labadie
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  ABSTRACT: Pseudomonas fragi has the ability to grow between 0 and 35 degrees C and grows optimally at 30 degrees C. Cellular proteins from mid-log-phase cells growing from 4 to 34 degrees C were labeled with L-[35S]methionine during 1 generation time and analyzed by two-dimensional gel electrophoresis. The electrophoretic patterns revealed differences in the patterns of protein synthesis over this temperature span. A qualitative comparison of cellular proteins led to their separation into five thermal classes. The first class contained proteins whose relative rates of synthesis were unaffected by the growth temperature. Three other classes included proteins with optimal expression at 4 to 10, 15 to 20, and 25 to 30 degrees C. A fifth class contained proteins which were more specifically synthesized at a supraoptimal growth temperature (34 degrees C). Two low-molecular-mass proteins, designated C7.0 and C8.0, were highly concentrated at 4 to 10 degrees C, and their relative rates of synthesis steadily increased with decreasing temperature. Polyclonal antibodies were separately raised against these two proteins. Immunological analyses revealed cross-reaction between these two proteins and between two additional low-molecular-mass proteins which were maximally produced at elevated temperatures. Antisera directed against C8.0 recognized the major cold shock protein of Escherichia coli, CspA, indicating the presence of similarities between these proteins.
  Journal of Bacteriology 08/1994; 176(13):4017-24. · 3.83 Impact Factor
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  Article: Molecular cloning of genes from the rumen anaerobic fungus Neocallimastix frontalis: expression during hydrolase induction.

  P Reymond, R Durand, M Hebraud, M Fevre
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  ABSTRACT: Glycoside and polysaccharide hydrolase production by the rumen anaerobic fungus, Neocalimastix frontalis is induced by the presence of crystalline cellulose. A differential screening of a cDNA library was used to isolate DNA sequences transcribed at high levels under growth conditions which induce enzyme production. Seven clones were isolated that preferentially hybridized to the induced cDNA probe versus the non-induced cDNA probe. Southern analysis showed that a cDNA clone (118) hybridized to a DNA probe encoding part of the exo-cellobiohydrolase I (CBH I) gene of Trichoderma reesei. Northern analysis demonstrated that the cDNA 118 was transcribed to yield a 2.1 kb RNA. This transcript was induced in the presence of cellulose.
  FEMS Microbiology Letters 02/1991; 61(1):107-12. · 2.04 Impact Factor