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Ghosh A.,Laboratory of Food Microbiology | Passaris I.,Laboratory of Food Microbiology | Mebrhatu M.T.,Laboratory of Food Microbiology | Vanoirbeek K.,Laboratory of Food Microbiology | Aertsen A.,Laboratory of Food Microbiology
Nucleic Acids Research | Year: 2014

In this study, we examined the intracellular whereabouts of Mrr, a cryptic type IV restriction endonuclease of Escherichia coli K12, in response to different conditions. In absence of stimuli triggering its activity, Mrr was found to be strongly associated with the nucleoid as a number of discrete foci, suggesting the presence of Mrr hotspots on the chromosome. Previously established elicitors of Mrr activity, such as exposure to high (hydrostatic) pressure (HP) or expression of the HhaII methyltransferase, both caused nucleoid condensation and an unexpected coalescence of Mrr foci. However, although the resulting Mrr/nucleoid complex was stable when triggered with HhaII, it tended to be only short-lived when elicited with HP. Moreover, HP-mediated activation of Mrr typically led to cellular blebbing, suggesting a link between chromosome and cellular integrity. Interestingly, Mrr variants could be isolated that were specifically compromised in either HhaII- or HP-dependent activation, underscoring a mechanistic difference in the way both triggers activate Mrr. In general, our results reveal that Mrr can take part in complex spatial distributions on the nucleoid and can be engaged in distinct modes of activity. © The Author(s) 2013. Published by Oxford University Press.


Kayode A.P.P.,University Abomey Calavi | Nout M.J.R.,Laboratory of Food Microbiology | Linnemann A.R.,Wageningen University | Hounhouigan J.D.,University Abomey Calavi | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2011

Extracts from leaf sheaths of farmers varieties of dye sorghum cultivated and used in Benin as a source of biocolorings were analyzed for their anthocyanidin and phenolic contents, as well as their antioxidant capacity. The aim was to identify and quantify the types of anthocyanin and phenolic acids. The total anthocyanin content of the leaf sheaths ranged from 13.7 to 35.5 mg of cyanidin 3-glucoside equivalent/g of dry matter (DM), with an average of 27.0 mg/g. The total anthocyanin content is 90 times higher than levels usually reported in fruits and vegetables. Anthocyanin consisted essentially of apigeninidin and luteolinidin, two 3-deoxyanthocyanidins with many applications in food, beverage, and pharmaceutical industries. The apigeninidin content of the leaf sheaths was 30 times higher than that in cereal bran and ranged from 14.7 to 45.8 mg/g, with an average of 31.3 mg/g. The amount of luteolinidin ranged from 0.4 to 2.4 mg/g, with a mean of 1.2 mg/g. The total phenolic content expressed as gallic acid equivalent averaged 95.5 mg/g. The free phenolic acids identified were benzoic acid, p-coumaric acid, and o-coumaric acid at amounts of 801.4, 681.6, and 67.9 μg/g, respectively. The leaf sheaths of dye sorghum have an antioxidant capacity [3.8-5.6 mmol of Trolox equivalent (TE)/g of DM] much higher than that reported for cereal bran and fruits and vegetables. © 2011 American Chemical Society.


PubMed | Laboratory of Gene Technology and Laboratory of Food Microbiology
Type: | Journal: Frontiers in microbiology | Year: 2015

The functional elucidation of small unknown phage proteins (ORFans) presents itself as one of the major challenges of bacteriophage molecular biology. In this work, we mined the Pseudomonas aeruginosa-infecting phage LUZ24 proteome for antibacterial and antibiofilm proteins against its host. Subsequently, their putative host target was identified. In one example, we observed an interaction between LUZ24 gp4 and the host transcriptional regulator MvaT. The polymerization of MvaT across AT-rich DNA strands permits gene silencing of foreign DNA, thereby limiting any potentially adverse effects of such DNA. Gel shift assays proved the inhibitory effect of LUZ24 gp4 on MvaT DNA binding activity. Therefore, we termed this gene product as Mip, the MvaT inhibiting protein. We hypothesize Mip prevents the AT-rich LUZ24 DNA from being physically blocked by MvaT oligomers right after its injection in the host cell, thereby allowing phage transcription and thus completion of the phage infection cycle.


Van Der Veen S.,Top Institute Food and Nutrition TIFN | Van Der Veen S.,Wageningen University | Van Der Veen S.,Laboratory of Food Microbiology | Abee T.,Top Institute Food and Nutrition TIFN | Abee T.,Wageningen University
Applied and Environmental Microbiology | Year: 2010

Listeria monocytogenes is a food-borne pathogen that is able to form biofilms in food processing facilities. Biofilms are generally more resistant to antimicrobial agents, making it difficult to eradicate them during cleanup procedures. So far, little is known about the function of stress resistance mechanisms in biofilm formation and their resistance to disinfectants. In this study, we investigated the role of sigB, which encodes a major transcriptional regulator of stress response genes, in L. monocytogenes static and continuous-flow biofilm formation and its function in the resistance of biofilm cells to the disinfectants benzalkonium chloride and peracetic acid. Quantitative real-time PCR and promoter reporter studies showed that sigB is activated in static and continuous-flow biofilms. Biofilm formation studies using an in-frame sigB deletion mutant and complementation mutant showed that the presence of SigB is required to obtain wild-type levels of both static and continuous-flow biofilms. Finally, disinfection treatments of planktonically grown cells and cells dispersed from static and continuous-flow biofilms showed that SigB is involved in the resistance of both planktonic cells and biofilms to the disinfectants benzalkonium chloride and peracetic acid. Copyright © 2010, American Society for Microbiology.


Vercammen A.,Laboratory of Food Microbiology | Vanoirbeek K.G.A.,Laboratory of Food Microbiology | Lemmens L.,Catholic University of Leuven | Lurquin I.,Laboratory of Food Microbiology | And 2 more authors.
Innovative Food Science and Emerging Technologies | Year: 2012

The inactivation of Candida lipolytica LMM02.68 and Escherichia coli LMM1010 on 1-cm apple cubes in acidified glucose solution (12.5 or 25.0% d-glucose) by high pressure treatment at 200-650 MPa for 10 min at 25 or 40°C was investigated. At 25°C and in all solutions, a 6-log reduction of C. lipolytica and E. coli was achieved at 400 and 600 MPa, respectively. Subsequently the shelf-life of HP-treated packaged apple pieces in 25.0% acidified glucose solution was studied during refrigerated storage (7°C) in a pilot-scale study with 306 packages containing 200 g of product. The microbiological shelf-life of the product, defined as the time when the aerobic mesophilic plate count or mold and yeast count first exceeded 7 log CFU/g, was extended from 15 days at 7°C for the untreated product to at least 90 days after treatment at 450 MPa at 10°C for 10 min. HP treatment had no measurable effect on the hardness of the apple pieces, but to prevent browning during the entire storage period, addition of sodium metabisulfite was necessary. This work demonstrates that HP treatment is well suited to preserve fruit pieces in syrup for extended periods with maximal quality retention. Industrial relevance: HP-treated products are increasingly finding their way to the market. There is however a need of integrated studies that translate fundamental scientific findings from laboratory-scale model systems to the complexity and scale of real food production. In this study, the processing conditions required for the inactivation of relevant spoilage and pathogenic organisms by HP on apple pieces in glucose solution were defined. Subsequently, the shelf-life was determined in a large scale pilot experiment comprising 306 packages each containing 200 g of apple pieces in glucose solution, by evaluating both the microbiological quality and safety and color and texture during refrigerated storage after HP treatment. © 2012 Elsevier Ltd.


Mebrhatu M.T.,Laboratory of Food Microbiology | Cenens W.,Laboratory of Food Microbiology | Aertsen A.,Laboratory of Food Microbiology
Critical Reviews in Microbiology | Year: 2014

Salmonella spp. are accountable for a large fraction of the global infectious disease burden, with most of their infections being food- or water-borne. The phenotypic features and adaptive potential of Salmonella spp. appear to be driven to a large extent by mobile or laterally acquired genetic elements. A better understanding of the conduct and diversification of these important pathogens consequently requires a more profound insight into the different mechanisms by which these pivotal elements establish themselves in the cell and affect its behavior. This review, therefore, provides an overview of the physiological impact and domestication of the Salmonella mobilome. © 2014 Informa Healthcare USA, Inc. All rights reserved: reproduction in whole or part not permitted.


Messelhausser U.,Laboratory of Food Microbiology | Kampf P.,Laboratory of Food Microbiology | Colditz J.,Laboratory of Food Microbiology | Bauer H.,Laboratory of Food Microbiology | And 3 more authors.
Foodborne Pathogens and Disease | Year: 2011

Yersinia enterocolitica is a major foodborne pathogen and the third most important bacteriological cause of diarrhea in Germany. However, studies investigating the occurrence of human pathogenic Y. enterocolitica in food at the retail level are very rare. Most of the studies published so far show qualitative but not quantitative data concerning the prevalence of this human pathogen. In this study the qualitative and quantitative assessment of human pathogenic Y. enterocolitica in different food matrices was investigated. For the qualitative analysis we used an enrichment method according to the International Organisation of Standardization (ISO) standard in combination with a real-time polymerase chain reaction (PCR) method detecting the ail gene of Y. enterocolitica. After detecting Y. enterocolitica in a sample, a quantitative investigation on Cefsulodin-Irgasan-Novobiocin (CIN) Agar was done to get information about the contamination level of the different samples. During the years 2008 and 2009, 446 samples of pork and pork products, 51 samples of game meat, and 61 raw milk samples were investigated for the presence of human pathogenic Y. enterocolitica. The samples were collected at the retail level in Bavaria. From the pork samples investigated, 81 samples (18%) were positive for the ail gene by real-time PCR, but human pathogenic Y. enterocolitica O:3 were found only in 46 (10%) pork samples by culture; the concentration in the samples ranged between 0.04 cfu/g and 2.30 × 105 cfu/g. Three game meat samples were positive by real-time PCR, but not by the cultural detection. All raw milk samples were negative by real-time PCR and culture. © 2011, Mary Ann Liebert, Inc.


Govers S.K.,Laboratory of Food Microbiology | Gayan E.,Laboratory of Food Microbiology | Aertsen A.,Laboratory of Food Microbiology
Environmental Microbiology | Year: 2016

Inactivation of bacterial pathogens is of critical importance in fields ranging from antimicrobial therapy to food preservation. The efficacy of an antimicrobial treatment is often experimentally determined through viable plate counts that inherently provide a poor focus on the mechanisms and distribution of (sub)lethal injury and subsequent inactivation or resuscitation behavior of the stressed cells, which are increasingly important features for the proper understanding and design of inactivation strategies. In this report, we employ a live cell biology approach focusing on the energy-dependent motion of intracellular protein aggregates to investigate the heterogeneity within heat stressed Escherichia coli populations. As such, we were able to identify differential dynamics of cellular resuscitation and inactivation that are impossible to distinguish using more traditional approaches. Moreover, our data indicate the existence of late-resuscitating cells that remain physiologically active and are able to persist in the presence of antibiotics before resuscitation. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.


PubMed | Laboratory of Food Microbiology
Type: Journal Article | Journal: Foodborne pathogens and disease | Year: 2011

Yersinia enterocolitica is a major foodborne pathogen and the third most important bacteriological cause of diarrhea in Germany. However, studies investigating the occurrence of human pathogenic Y. enterocolitica in food at the retail level are very rare. Most of the studies published so far show qualitative but not quantitative data concerning the prevalence of this human pathogen. In this study the qualitative and quantitative assessment of human pathogenic Y. enterocolitica in different food matrices was investigated. For the qualitative analysis we used an enrichment method according to the International Organisation of Standardization (ISO) standard in combination with a real-time polymerase chain reaction (PCR) method detecting the ail gene of Y. enterocolitica. After detecting Y. enterocolitica in a sample, a quantitative investigation on Cefsulodin-Irgasan-Novobiocin (CIN) Agar was done to get information about the contamination level of the different samples. During the years 2008 and 2009, 446 samples of pork and pork products, 51 samples of game meat, and 61 raw milk samples were investigated for the presence of human pathogenic Y. enterocolitica. The samples were collected at the retail level in Bavaria. From the pork samples investigated, 81 samples (18%) were positive for the ail gene by real-time PCR, but human pathogenic Y. enterocolitica O:3 were found only in 46 (10%) pork samples by culture; the concentration in the samples ranged between 0.04 cfu/g and 2.3010(5) cfu/g. Three game meat samples were positive by real-time PCR, but not by the cultural detection. All raw milk samples were negative by real-time PCR and culture.


PubMed | Laboratory of Food Microbiology
Type: | Journal: Frontiers in microbiology | Year: 2016

The survival of some pathotypes of

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