M Hébraud - Academia.edu (original) (raw)

Papers by M Hébraud

Research paper thumbnail of Purification and characterization of a dipeptidase from Lactobacillus sake

Applied and Environmental Microbiology, 1995

A dipeptidase was purified from cell extracts of Lactobacillus sake. This compound was a monomer ... more A dipeptidase was purified from cell extracts of Lactobacillus sake. This compound was a monomer having a molecular weight of 50,000 and a pI of 4.7 and exhibited broad specificity against all dipeptides except those with proline or glycine at the N terminus. The enzyme was inhibited by EDTA or 1,10-phenanthroline but could be reactivated with CoCl2 and MnCl2.

Research paper thumbnail of Lactobacillus paracasei subsp. paracasei, an Algerian isolate with antibacterial activity against enteric pathogens and probiotic fitness

Maintenance of the intestinal microbiota is important in preventing diseases by controlling the o... more Maintenance of the intestinal microbiota is important in preventing diseases by controlling the overgrowth of potentially pathogenic bacte-ria. Wide-spread prescription of antibiotics not only has led to an increase in antibiotic-resistant pathogenic strains, but is often associated with the disruption of the protective flora, leading to pre-disposition to infections. For these reasons, the control of infections through a non-antibiotic ap-proach is urgently needed and bacterial replace-ment therapy using non-pathogenic bacteria, from the natural microbiota or probiotics, represents a promising alternative. It is accepted that these bacteria might represent an effective tool for con-trolling the overgrowth of pathogens and main-taining the integrity of the gut mucosal barrier [1]. Lactobacillus and Bifidobacterium, which have a long history of safe use in the manufacture of dairy products, are traditionally included as pro-biotics to protect against intestinal disorders [2]. Both ar...

Research paper thumbnail of Microbial pathogen control in the beef chain: Recent research advances

Meat Science, 2014

Within a recent EU research project (&amp... more Within a recent EU research project ("ProSafeBeef"), research on foodborne pathogens in the beef chain was conducted by using a longitudinally integrated (fork-to-farm) approach. There is not any…

Research paper thumbnail of Kinetic of production and mode of action of the Lactobacillus paracasei subsp. paracasei anti-listerial bacteriocin, an Algerian isolate

LWT - Food Science and Technology, 2008

Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn f... more Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards listerial strains (Listeria innocua CLIP ...

Research paper thumbnail of Protein synthesis inEscherichia coli at 4°C

Electrophoresis, 2000

Two-dimensional electrophoresis technology was used to investigate protein synthesis by the mesop... more Two-dimensional electrophoresis technology was used to investigate protein synthesis by the mesophilic bacterium Escherichia coli at low temperature. It was confirmed that protein synthesis in E. coli decreased strongly after a temperature downshift from 37 to 4 o C. After incubation for 150 min at 4 o C, however, the number of synthesized proteins represented 60% of the overall polypeptide number observed at 37 o C. Furthermore, the analysis of autoradiograms revealed the overexpression of 69 proteins by shocked bacteria, showing that the number of cold-induced proteins has been significantly underestimated so far.

Research paper thumbnail of Cold shock response and low temperature adaptation in psychrotrophic bacteria

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow... more Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic microorganisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been desc...

Research paper thumbnail of DOP49 Quantitative proteomics analysis of macrophages from Crohn’s disease patients and infected with adherent-invasive Escherichia coli

Journal of Crohn's and Colitis

Background Crohn’s disease (CD) is a disabling inflammatory bowel disease. Currently, the availab... more Background Crohn’s disease (CD) is a disabling inflammatory bowel disease. Currently, the available treatments only alleviate the symptoms. The anti-TNFα represent the most efficient therapeutic class, but its mechanisms are poorly known. Experimental data have highlighted the role of intestinal macrophages in the pathogenesis of CD. These macrophages present a defect in the control of CD-associated adherent-invasive E. coli (AIEC) replication, which is linked to altered autophagy. The main aim of this study was to compare the proteomic profile of macrophages from CD patients with and without anti-TNFα treatment, to those from ulcerative colitis (UC) patients or healthy subjects, both at the basal state and after AIEC infection. Methods Peripheral blood monocyte-derived macrophages (MDM) were obtained from 44 CD patients including 22 with and 22 without anti-TNFα treatment, 22 UC patients and 22 healthy subjects. MDM was infected or not with AIEC LF82 reference strain. The numbers o...

Research paper thumbnail of How different is the proteome of the extended spectrum β-lactamase producing Escherichia coli strains from seagulls of the Berlengas natural reserve of Portugal?

Research paper thumbnail of Combined effects of NaCl, NaOH, and biocides (monolaurin or lauric acid) on inactivation of Listeria monocytogenes and Pseudomonas spp

Journal of food protection, 2001

This study highlighted combinations of chemical stresses that could decrease or eliminate Listeri... more This study highlighted combinations of chemical stresses that could decrease or eliminate Listeria monocytogenes and Pseudomonas spp. surviving in food processing plants. Strains of L. monocytogenes, Pseudomonas fragi, and Pseudomonas fluorescens isolated from processing environments (meat and milk) were grown at 20 degrees C up to the early stationary phase. The strains were then subjected to 30 min of physicochemical treatments. These treatments included individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (fatty acids) challenges. Survival of the strains was studied after individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (monolaurin, lauric acid) challenges. Individual pH shocks had lower efficiencies than those used in combinations with other parameters. The treatment pH 5.4 followed by pH 10.5 had a low efficiency against L. monocytogenes. The opposite combination, pH 10.5 followed by pH 5.4, led to a 3-...

Research paper thumbnail of Cold shock response and low temperature adaptation in psychrotrophic bacteria

Journal of molecular microbiology and biotechnology, 1999

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow... more Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic microorganisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been desc...

Research paper thumbnail of Production et purification des glycosidases sécrétées par le champignon Neocallimastix frontalis

Reproduction Nutrition Développement, 1988

Research paper thumbnail of Outer membrane translocation: numerical protein secretion nomenclature in question in mycobacteria

Trends in Microbiology, 2009

Research paper thumbnail of The proteomic approach for better understanding the physiology of bacteria adaptation to food plant environments

Sciences des Aliments, 2003

Research paper thumbnail of Growth of Listeria monocytogenes in biofilm according to the surface and the temperature and effects of different treatments on its survival

Sciences des Aliments, 2003

Research paper thumbnail of Chitin Synthase Activity from Neocallimastix frontalis, an Anaerobic Rumen Fungus

Microbiology, 1989

Chitin synthase activity was detected in actively growing mycelium of Neocallimastix frontalis af... more Chitin synthase activity was detected in actively growing mycelium of Neocallimastix frontalis after mechanical disruption of the cells. Chitin formation in fungal extracts at 32 "C was linear with respect to time for at least 60min, and with respect to protein concentration up to 750 pg ml-l. The optimum pH for enzyme activity was 8.5 using 10 mM-Tris/HCl buffer. Mg2+ was necessary for maximum activity and 10 mM-MgC1, was routinely used during the assays. The apparent K, for the substrate UDP-GlcNAc was 2 m~. Polyoxin D was a competitive inhibitor of chitin synthesis with an apparent Ki of 4 p~. Following treatment with trypsin (12.5 pg ml-I), the chitin synthase activity of the fungal extract increased by six-fold, indicating that most of the chitin synthase activity was zymogenic. The reaction product was insoluble in 1 M-KOH or 1 M-acetic acid, but it was solubilized by heating in 6 M-HC~ at 120 "C for 2.5 h and was hydrolysed by chitinase into diacetylchitobiose.

Research paper thumbnail of Adapted tolerance to benzalkonium chloride in Escherichia coli K-12 studied by transcriptome and proteome analyses

Microbiology, 2007

Benzalkonium chloride (BC) is a commonly used disinfectant and preservative. This study describes... more Benzalkonium chloride (BC) is a commonly used disinfectant and preservative. This study describes changes in expression level at the transcriptomic and proteomic level for Escherichia coli K-12 gradually adapted to a tolerance level to BC of 7-8 times the initial MIC. Results from DNA arrays and two-dimensional gel electrophoresis for global gene and protein expression studies were confirmed by real-time quantitative PCR. Peptide mass fingerprinting by MALDI-TOF MS was used to identify differentially expressed proteins. Changes in expression level in adapted cells were shown for porins, drug transporters, glycolytic enzymes, ribosomal subunits and several genes and proteins involved in protection against oxidative stress and antibiotics. Adapted strains showed increased tolerance to several antibiotics. In conclusion, E. coli K-12 adapted to higher tolerance to BC acquired several general resistance mechanisms, including responses normally related to the multiple antibiotic resistance (Mar) regulon and protection against oxidative stress. The results revealed that BC treatment might result in superoxide stress in E. coli.

Research paper thumbnail of Attachment and biofilm formation by foodborne bacteria in meat processing environments: Causes, implications, role of bacterial interactions and control by alternative novel methods

Meat Science, 2014

Attachment of potential spoilage and pathogenic bacteria to food contact surfaces and the subsequ... more Attachment of potential spoilage and pathogenic bacteria to food contact surfaces and the subsequent biofilm formation represent serious challenges to the meat industry, since these may lead to cross-contamination of the products, resulting in lowered-shelf life and transmission of diseases. In meat processing environments, microorganisms are sometimes associated to surfaces in complex multispecies communities, while bacterial interactions have been shown to play a key role in cell attachment and detachment from biofilms, as well as in the resistance of biofilm community members against antimicrobial treatments. Disinfection of food contact surfaces in such environments is a challenging task, aggravated by the great antimicrobial resistance of biofilm associated bacteria. In recent years, several alternative novel methods, such as essential oils and bacteriophages, have been successfully tested as an alternative means for the disinfection of microbial-contaminated food contact surfaces. In this review, all these aspects of biofilm formation in meat processing environments are discussed from a microbial meat-quality and safety perspective.

Research paper thumbnail of Assessment of Hierarchical Clustering Methodologies for Proteomic Data Mining

Journal of Proteome Research, 2007

Research paper thumbnail of Purification and characterization of a collagenolytic enzyme produced by Rathayibacter sp. strains isolated from cultures of Clavibacter michiganensis subsp. michiganensis

Journal of Applied Microbiology, 1997

Collagenase from the internal organs of a mackerel was purified using acetone precipitation, ion-... more Collagenase from the internal organs of a mackerel was purified using acetone precipitation, ion-exchange chromatography on a DEAE-Sephadex A-50, gel filtration chromatography on a Sephadex G-100, ion-exchange chromatography on DEAE-Sephacel, and gel filtration chromatography on a Sephadex G-75 column. The molecular mass of the purified enzyme was estimated to be 14.8 kDa by gel filtration and SDS-PAGE. The purification and yield were 39.5-fold and 0.1% when compared to those in the starting-crude extract. The optimum pH and temperature for the enzyme activity were around pH 7.5 and 55 o C, respectively. The K m and V max of the enzyme for collagen Type I were approximately 1.1 mM and 2,343 U, respectively. The purified enzyme was strongly inhibited by Hg 2+ , Zn 2+ , PMSF, TLCK, and the soybean-trypsin inhibitor.

Research paper thumbnail of Effect of osmotic, alkaline, acid or thermal stresses on the growth and inhibition of Listeria monocytogenes

Journal of Applied Microbiology, 1999

Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have be... more Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have been subjected to different osmotic, alkaline, acid or thermal stresses. The effects of these treatments on lag-phase (L) and growth rate (mu) of cells in mid-log phase have been followed using an automated optical density monitoring system. Increasing the osmotic pressure by the addition of different amounts of NaCl increased the lag phase and decreased the growth rate. The same phenomena were observed after decreasing the pH of the medium to 5.8, 5.6 or 5.4 by addition of acetic, lactic or hydrochloric acids. The inhibitory effect was: acetic acid > lactic acid > hydrochloric acid. The addition of NaOH to attain pH values of 9.5, 10.0, 10.5 or 11.0 in the medium produced a dramatic increase of the lag phase at pH 10.5 and 11. Growth rates were also decreased while the maximal population increased with high pH values. These effects varied according to strains. Strains d and e were the most resistant to acidic and alkaline stresses, and e was the most affected by the addition of NaCl. A cold shock of 30 min at 0 degree C had limited effects on growth parameters. On the other hand, hyperthermal shocks (55 or 63 degrees C, 30 min) led to similar increased lag phases and to significant increases of the maximal population in all five strains.

Research paper thumbnail of Purification and characterization of a dipeptidase from Lactobacillus sake

Applied and Environmental Microbiology, 1995

A dipeptidase was purified from cell extracts of Lactobacillus sake. This compound was a monomer ... more A dipeptidase was purified from cell extracts of Lactobacillus sake. This compound was a monomer having a molecular weight of 50,000 and a pI of 4.7 and exhibited broad specificity against all dipeptides except those with proline or glycine at the N terminus. The enzyme was inhibited by EDTA or 1,10-phenanthroline but could be reactivated with CoCl2 and MnCl2.

Research paper thumbnail of Lactobacillus paracasei subsp. paracasei, an Algerian isolate with antibacterial activity against enteric pathogens and probiotic fitness

Maintenance of the intestinal microbiota is important in preventing diseases by controlling the o... more Maintenance of the intestinal microbiota is important in preventing diseases by controlling the overgrowth of potentially pathogenic bacte-ria. Wide-spread prescription of antibiotics not only has led to an increase in antibiotic-resistant pathogenic strains, but is often associated with the disruption of the protective flora, leading to pre-disposition to infections. For these reasons, the control of infections through a non-antibiotic ap-proach is urgently needed and bacterial replace-ment therapy using non-pathogenic bacteria, from the natural microbiota or probiotics, represents a promising alternative. It is accepted that these bacteria might represent an effective tool for con-trolling the overgrowth of pathogens and main-taining the integrity of the gut mucosal barrier [1]. Lactobacillus and Bifidobacterium, which have a long history of safe use in the manufacture of dairy products, are traditionally included as pro-biotics to protect against intestinal disorders [2]. Both ar...

Research paper thumbnail of Microbial pathogen control in the beef chain: Recent research advances

Meat Science, 2014

Within a recent EU research project (&amp... more Within a recent EU research project ("ProSafeBeef"), research on foodborne pathogens in the beef chain was conducted by using a longitudinally integrated (fork-to-farm) approach. There is not any…

Research paper thumbnail of Kinetic of production and mode of action of the Lactobacillus paracasei subsp. paracasei anti-listerial bacteriocin, an Algerian isolate

LWT - Food Science and Technology, 2008

Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn f... more Lactobacillus paracasei subsp. paracasei was isolated in our laboratory from breast-fed newborn faeces and identified phenotypically and genotypically. The strain was able to produce a bacteriocin-like substance active towards listerial strains (Listeria innocua CLIP ...

Research paper thumbnail of Protein synthesis inEscherichia coli at 4°C

Electrophoresis, 2000

Two-dimensional electrophoresis technology was used to investigate protein synthesis by the mesop... more Two-dimensional electrophoresis technology was used to investigate protein synthesis by the mesophilic bacterium Escherichia coli at low temperature. It was confirmed that protein synthesis in E. coli decreased strongly after a temperature downshift from 37 to 4 o C. After incubation for 150 min at 4 o C, however, the number of synthesized proteins represented 60% of the overall polypeptide number observed at 37 o C. Furthermore, the analysis of autoradiograms revealed the overexpression of 69 proteins by shocked bacteria, showing that the number of cold-induced proteins has been significantly underestimated so far.

Research paper thumbnail of Cold shock response and low temperature adaptation in psychrotrophic bacteria

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow... more Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic microorganisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been desc...

Research paper thumbnail of DOP49 Quantitative proteomics analysis of macrophages from Crohn’s disease patients and infected with adherent-invasive Escherichia coli

Journal of Crohn's and Colitis

Background Crohn’s disease (CD) is a disabling inflammatory bowel disease. Currently, the availab... more Background Crohn’s disease (CD) is a disabling inflammatory bowel disease. Currently, the available treatments only alleviate the symptoms. The anti-TNFα represent the most efficient therapeutic class, but its mechanisms are poorly known. Experimental data have highlighted the role of intestinal macrophages in the pathogenesis of CD. These macrophages present a defect in the control of CD-associated adherent-invasive E. coli (AIEC) replication, which is linked to altered autophagy. The main aim of this study was to compare the proteomic profile of macrophages from CD patients with and without anti-TNFα treatment, to those from ulcerative colitis (UC) patients or healthy subjects, both at the basal state and after AIEC infection. Methods Peripheral blood monocyte-derived macrophages (MDM) were obtained from 44 CD patients including 22 with and 22 without anti-TNFα treatment, 22 UC patients and 22 healthy subjects. MDM was infected or not with AIEC LF82 reference strain. The numbers o...

Research paper thumbnail of How different is the proteome of the extended spectrum β-lactamase producing Escherichia coli strains from seagulls of the Berlengas natural reserve of Portugal?

Research paper thumbnail of Combined effects of NaCl, NaOH, and biocides (monolaurin or lauric acid) on inactivation of Listeria monocytogenes and Pseudomonas spp

Journal of food protection, 2001

This study highlighted combinations of chemical stresses that could decrease or eliminate Listeri... more This study highlighted combinations of chemical stresses that could decrease or eliminate Listeria monocytogenes and Pseudomonas spp. surviving in food processing plants. Strains of L. monocytogenes, Pseudomonas fragi, and Pseudomonas fluorescens isolated from processing environments (meat and milk) were grown at 20 degrees C up to the early stationary phase. The strains were then subjected to 30 min of physicochemical treatments. These treatments included individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (fatty acids) challenges. Survival of the strains was studied after individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (monolaurin, lauric acid) challenges. Individual pH shocks had lower efficiencies than those used in combinations with other parameters. The treatment pH 5.4 followed by pH 10.5 had a low efficiency against L. monocytogenes. The opposite combination, pH 10.5 followed by pH 5.4, led to a 3-...

Research paper thumbnail of Cold shock response and low temperature adaptation in psychrotrophic bacteria

Journal of molecular microbiology and biotechnology, 1999

Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow... more Psychrotrophic bacteria are capable of developing over a wide temperature range and they can grow at temperatures close to or below freezing. This ability requires specific adaptative strategies in order to maintain membrane fluidity, the continuance of their metabolic activities, and protein synthesis at low temperature. A cold-shock response has been described in several psychrotrophic bacteria, which is somewhat different from that in mesophilic microorganisms: (i) the synthesis of housekeeping proteins is not repressed following temperature downshift and they are similarly expressed at optimal and low temperatures (ii) cold-shock proteins or Csps are synthesized, the number of which increases with the severity of the shock (iii) a second group of cold-induced proteins, i.e. the cold acclimation proteins or Caps, comparable with Csps are continuously synthesized during prolonged growth at low temperature. Homologues to CspA, the major cold-shock protein in E. coli, have been desc...

Research paper thumbnail of Production et purification des glycosidases sécrétées par le champignon Neocallimastix frontalis

Reproduction Nutrition Développement, 1988

Research paper thumbnail of Outer membrane translocation: numerical protein secretion nomenclature in question in mycobacteria

Trends in Microbiology, 2009

Research paper thumbnail of The proteomic approach for better understanding the physiology of bacteria adaptation to food plant environments

Sciences des Aliments, 2003

Research paper thumbnail of Growth of Listeria monocytogenes in biofilm according to the surface and the temperature and effects of different treatments on its survival

Sciences des Aliments, 2003

Research paper thumbnail of Chitin Synthase Activity from Neocallimastix frontalis, an Anaerobic Rumen Fungus

Microbiology, 1989

Chitin synthase activity was detected in actively growing mycelium of Neocallimastix frontalis af... more Chitin synthase activity was detected in actively growing mycelium of Neocallimastix frontalis after mechanical disruption of the cells. Chitin formation in fungal extracts at 32 "C was linear with respect to time for at least 60min, and with respect to protein concentration up to 750 pg ml-l. The optimum pH for enzyme activity was 8.5 using 10 mM-Tris/HCl buffer. Mg2+ was necessary for maximum activity and 10 mM-MgC1, was routinely used during the assays. The apparent K, for the substrate UDP-GlcNAc was 2 m~. Polyoxin D was a competitive inhibitor of chitin synthesis with an apparent Ki of 4 p~. Following treatment with trypsin (12.5 pg ml-I), the chitin synthase activity of the fungal extract increased by six-fold, indicating that most of the chitin synthase activity was zymogenic. The reaction product was insoluble in 1 M-KOH or 1 M-acetic acid, but it was solubilized by heating in 6 M-HC~ at 120 "C for 2.5 h and was hydrolysed by chitinase into diacetylchitobiose.

Research paper thumbnail of Adapted tolerance to benzalkonium chloride in Escherichia coli K-12 studied by transcriptome and proteome analyses

Microbiology, 2007

Benzalkonium chloride (BC) is a commonly used disinfectant and preservative. This study describes... more Benzalkonium chloride (BC) is a commonly used disinfectant and preservative. This study describes changes in expression level at the transcriptomic and proteomic level for Escherichia coli K-12 gradually adapted to a tolerance level to BC of 7-8 times the initial MIC. Results from DNA arrays and two-dimensional gel electrophoresis for global gene and protein expression studies were confirmed by real-time quantitative PCR. Peptide mass fingerprinting by MALDI-TOF MS was used to identify differentially expressed proteins. Changes in expression level in adapted cells were shown for porins, drug transporters, glycolytic enzymes, ribosomal subunits and several genes and proteins involved in protection against oxidative stress and antibiotics. Adapted strains showed increased tolerance to several antibiotics. In conclusion, E. coli K-12 adapted to higher tolerance to BC acquired several general resistance mechanisms, including responses normally related to the multiple antibiotic resistance (Mar) regulon and protection against oxidative stress. The results revealed that BC treatment might result in superoxide stress in E. coli.

Research paper thumbnail of Attachment and biofilm formation by foodborne bacteria in meat processing environments: Causes, implications, role of bacterial interactions and control by alternative novel methods

Meat Science, 2014

Attachment of potential spoilage and pathogenic bacteria to food contact surfaces and the subsequ... more Attachment of potential spoilage and pathogenic bacteria to food contact surfaces and the subsequent biofilm formation represent serious challenges to the meat industry, since these may lead to cross-contamination of the products, resulting in lowered-shelf life and transmission of diseases. In meat processing environments, microorganisms are sometimes associated to surfaces in complex multispecies communities, while bacterial interactions have been shown to play a key role in cell attachment and detachment from biofilms, as well as in the resistance of biofilm community members against antimicrobial treatments. Disinfection of food contact surfaces in such environments is a challenging task, aggravated by the great antimicrobial resistance of biofilm associated bacteria. In recent years, several alternative novel methods, such as essential oils and bacteriophages, have been successfully tested as an alternative means for the disinfection of microbial-contaminated food contact surfaces. In this review, all these aspects of biofilm formation in meat processing environments are discussed from a microbial meat-quality and safety perspective.

Research paper thumbnail of Assessment of Hierarchical Clustering Methodologies for Proteomic Data Mining

Journal of Proteome Research, 2007

Research paper thumbnail of Purification and characterization of a collagenolytic enzyme produced by Rathayibacter sp. strains isolated from cultures of Clavibacter michiganensis subsp. michiganensis

Journal of Applied Microbiology, 1997

Collagenase from the internal organs of a mackerel was purified using acetone precipitation, ion-... more Collagenase from the internal organs of a mackerel was purified using acetone precipitation, ion-exchange chromatography on a DEAE-Sephadex A-50, gel filtration chromatography on a Sephadex G-100, ion-exchange chromatography on DEAE-Sephacel, and gel filtration chromatography on a Sephadex G-75 column. The molecular mass of the purified enzyme was estimated to be 14.8 kDa by gel filtration and SDS-PAGE. The purification and yield were 39.5-fold and 0.1% when compared to those in the starting-crude extract. The optimum pH and temperature for the enzyme activity were around pH 7.5 and 55 o C, respectively. The K m and V max of the enzyme for collagen Type I were approximately 1.1 mM and 2,343 U, respectively. The purified enzyme was strongly inhibited by Hg 2+ , Zn 2+ , PMSF, TLCK, and the soybean-trypsin inhibitor.

Research paper thumbnail of Effect of osmotic, alkaline, acid or thermal stresses on the growth and inhibition of Listeria monocytogenes

Journal of Applied Microbiology, 1999

Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have be... more Five strains of Listeria monocytogenes (a, b, c, d and e) isolated from industrial plants have been subjected to different osmotic, alkaline, acid or thermal stresses. The effects of these treatments on lag-phase (L) and growth rate (mu) of cells in mid-log phase have been followed using an automated optical density monitoring system. Increasing the osmotic pressure by the addition of different amounts of NaCl increased the lag phase and decreased the growth rate. The same phenomena were observed after decreasing the pH of the medium to 5.8, 5.6 or 5.4 by addition of acetic, lactic or hydrochloric acids. The inhibitory effect was: acetic acid > lactic acid > hydrochloric acid. The addition of NaOH to attain pH values of 9.5, 10.0, 10.5 or 11.0 in the medium produced a dramatic increase of the lag phase at pH 10.5 and 11. Growth rates were also decreased while the maximal population increased with high pH values. These effects varied according to strains. Strains d and e were the most resistant to acidic and alkaline stresses, and e was the most affected by the addition of NaCl. A cold shock of 30 min at 0 degree C had limited effects on growth parameters. On the other hand, hyperthermal shocks (55 or 63 degrees C, 30 min) led to similar increased lag phases and to significant increases of the maximal population in all five strains.