Partial vinylphenol reductase purification and characterization from Brettanomyces bruxellensis
International audience; Brettanomyces is the major microbial cause for wine spoilage worldwide and causes significant economic losses. The reasons are the production of ethylphenols that lead to an unpleasant taint described as 'phenolic odour'. Despite its economic importance, Brettanomyces has remained poorly studied at the metabolic level. The origin of the ethylphenol results from the conversion of vinylphenols in ethylphenol by Brettanomyces hydroxycinnamate decarboxylase. However, no information is available on the vinylphenol reductase responsible for the conversion of vinylphenols in ethylphenols. In this study, a vinylphenol reductase was partially purified from Brettanomyces bruxe…
Investigation of root-associated biofilms of the human pathogenic bacterium Listeria monocytogenes
EAMERSCT1EJ2; International audience; No abstract
Assessment of the roles of LuxS, Autoinducer 2 and its precursor S-Ribosyl Homocysteine, in cell attachment during biofilm formation by Listeria monocytogenes EGD-e
No abstract
Impact of temperature and soil type on Mycobacterium bovis survival in the environment
Mycobacterium bovis, the causative agent of the bovine tuberculosis (bTB), mainly affects cattle, its natural reservoir, but also a wide range of domestic and wild mammals. Besides direct transmission via contaminated aerosols, indirect transmission of the M. bovis between wildlife and livestock might occur by inhalation or ingestion of environmental substrates contaminated through infected animal shedding. We monitored the survival of M. bovis in two soil samples chosen for their contrasted physical and-chemical properties (i.e. pH, clay content). The population of M. bovis spiked in sterile soils was enumerated by a culture-based method after 14, 30, 60, 90, 120 and 150 days of incubation…
LisRK is required for optimal fitness ofListeria monocytogenesin soil
ABSTRACTListeria monocytogenes is a food-borne pathogen responsible for the disease listeriosis. It is ubiquitously found in the environment and soil is one of its natural habitats. Listeria monocytogenes is highly capable of coping with various stressful conditions. We hypothesized that stress-responsive two-component systems such as LisRK might contribute to the adaptation of L. monocytogenes to the soil environment. Indeed, investigations of the population dynamics of wild-type and mutant strains suggest an important role of LisRK for optimal fitness of L. monocytogenes in sterile soil. Results from non-sterile soil showed that the parental strain was capable of surviving longer than mut…
Development of phylogroup-specific taqman real-time assays for identification of members of klebsiella pneumoniae complex
International audience; • Klebsiella Klebsiellapneumoniae pneumoniae pneumoniae (Kp )represents agrowinggrowing public publichealth concern due to the emergence emergence of multidrug multidrug multidrug resistance resistance and andhypervirulence hypervirulence . • The Kp species complex complex includes includes 7closely related related phylogroups :Klebsiella Klebsiellapneumoniae (phylogroup (phylogroup Kp 1), K.quasipneumoniae quasipneumoniae quasipneumoniae subsp .quasipneumoniae quasipneumoniae (Kp 2)and subsp .similipneumoniae similipneumoniae similipneumoniae similipneumoniae similipneumoniae (Kp 4), K.variicola variicola subsp .variicola variicola variicola(Kp 3)and subsp .tropical…
Communication and Autoinduction in the species Listeria monocytogenes
International audience; In order to withstand changes in their environment, bacteria have evolved mechanisms to sense the surrounding environment, integrate these signals and adapt their physiology to thrive under fluctuating conditions. Among these mechanisms, the ability of bacteria to exchange information between cells has become a dynamic field of interest for microbiologists over the past four decades. First described by Nelson et al.,1 this phenomenon often referred as either cell-cell communication, Quorum Sensing and/or AutoInduction involves the synthesis of small signal molecules called autoinducers. These signal molecules may be sensed by the bacterial population in the vicinity …
The Agr communication system provides a benefit to the populations of Listeria monocytogenes in soil
International audience; In this study, we investigated whether the Agr communication system of the pathogenic bacterium Listeria monocytogenes was involved in adaptation and competitiveness in soil. Alteration of the ability to communicate, either by deletion of the gene coding the response regulator AgrA (response-negative mutant) or the signal pro-peptide AgrD (signal-negative mutant), did not affect population dynamics in soil that had been sterilized but survival was altered in biotic soil suggesting that the Agr system of L. monocytogenes was involved to face the complex soil biotic environment. This was confirmed by a set of co-incubation experiments. The fitness of the response-negat…
Evidence of autoinduction heterogeneity via expression of the agr system of listeria monocytogenes at the single-cell level
ABSTRACT To investigate if the primary function of the Agr system of Listeria monocytogenes is to monitor cell density, we followed Agr expression in batch cultures, in which the autoinducer concentration was uniform, and in biofilms. Expression was heterogeneous, suggesting that the primary function of Agr is not to monitor population density.
A small HSP, Lo18, interacts with the cell membrane and modulates lipid physical state under heat shock conditions in a lactic acid bacterium
International audience; The small heat shock proteins (sHSP) are characterized by a chaperone activity to prevent irreversible protein denaturation. This study deals with the sHSP Lo18 induced by multiple stresses in Oenococcus oeni, a lactic acid bacterium. Using in situ immunocytochemistry and cellular fractionation experiments, we demonstrated the association of Lo18 with the membrane in O. oeni cells submitted to heat shock. The same result was obtained after exposure of cells to ethanol or benzyl alcohol, agents known to have an influence on membranes. For the different stresses, the protein was located on the periphery of the cell at membrane level and was also found within the cytopl…
Investigation of rhizosphere as a niche for Listeria monocytogenes
EAUBAGROSUPBIOME; International audience; No abstract
Effects of yeast proteolytic activity on Oenococcus oeni and malolactic fermentation
International audience; Alcoholic fermentation of synthetic must was performed using either Saccharomyces cerevisiae or a mutant Delta pep4, which is deleted for the proteinase A gene. Fermentation with the mutant Delta pep4 resulted in 61% lower levels of free amino acids, and in 62% lower peptide concentrations at the end of alcoholic fermentation than in the control. Qualitative differences in amino acid composition were observed. Changes observed in amino acids in peptides were mainly quantitative. After alcoholic fermentation each medium was inoculated with Oenococcus oeni. Malolactic fermentation in the medium with the Delta pep4 strain took 10 days longer than the control. This diffe…
Single cell analysis evidence Heterogeneous expression of the Agr communication system of Listeria monocytogenes
http://prodinra.inra.fr/record/271694EAMERSCT3 EJ3; Communication, often referred as Quorum Sensing, is involved in the adaptation of most bacteria to their environment. In the genus Listeria, the agr communication system affects the biology of Listeria monocytogenes during saprophytic life (biofilm formation) and during infection. In the present study, we investigated in situ agr expression of six isolates of L. monocytogenes by combining gfp reporters, flow cytometry and fluorescent microscopy during plantonic growth and dynamic flow cell biofilm set ups. Unexpectedly, during growth in TSB homogenised liquid cultures incubated at 25°C, while auto-inducer concentration was uniform, statist…
σB and agrA regulation in Listeria monocytogenes: Effect on survival in soil/rhizosphere under biotic and abiotic conditions
International audience; Abstract -250 words Backgrounds: Listeria monocytogenes is the agent of listeriosis, a life-threatening condition in at-risk people. Complex transmission routes between outdoor environments and the food chain result in foodstuff contamination. Sensing of environmental changes can trigger regulation of gene expression, allowing bacteria to adapt their physiology and survive. The Agr cell-cell communication system transcription regulator AgrA is triggered during several environmental conditions including soil, an important reservoir of L. monocytogenes. The RNA polymerase σB factor aids survival in several stress conditions and may be required for L. monocytogenes surv…
Techniques d'études de la formation des biofilms. Retour d'expérience issu du domaine "agro-alimentaire" et du domaine "environnemental"
No abstract
Survival of Listeria monocytogenes in Soil Requires AgrA-Mediated Regulation
ABSTRACT In a recent paper, we demonstrated that inactivation of the Agr system affects the patterns of survival of Listeria monocytogenes (A.-L. Vivant, D. Garmyn, L. Gal, and P. Piveteau, Front Cell Infect Microbiol 4:160, http://dx.doi.org/10.3389/fcimb.2014.00160 ). In this study, we investigated whether the Agr-mediated response is triggered during adaptation in soil, and we compared survival patterns in a set of 10 soils. The fate of the parental strain L. monocytogenes L9 (a rifampin-resistant mutant of L. monocytogenes EGD-e) and that of a Δ agrA deletion mutant were compared in a collection of 10 soil microcosms. The Δ agrA mutant displayed significantly reduced survival in these b…
Investigation of the roles of AgrA and σB regulators in Listeria monocytogenes adaptation to roots and soil
ABSTRACT Little is known about the regulatory mechanisms that ensure the survival of the food-borne bacterial pathogen Listeria monocytogenes in the telluric environment and on roots. Earlier studies have suggested a regulatory overlap between the Agr cell–cell communication system and the general stress response regulator σB. Here, we investigated the contribution of these two systems to root colonisation and survival in sterilised and biotic soil. The ability to colonise the roots of the grass Festuca arundinacea was significantly compromised in the double mutant (∆agrA∆sigB). In sterile soil at 25°C, a significant defect was observed in the double mutant, suggesting some synergy between …
Listeria monocytogenes Differential Transcriptome Analysis Reveals Temperature-Dependent Agr Regulation and Suggests Overlaps with Other Regulons
Listeria monocytogenes is a ubiquitous, opportunistic pathogenic organism. Environmental adaptation requires constant regulation of gene expression. Among transcriptional regulators, AgrA is part of an auto-induction system. Temperature is an environmental cue critical for in vivo adaptation. In order to investigate how temperature may affect AgrA-dependent transcription, we compared the transcriptomes of the parental strain L. monocytogenes EGD-e and its Delta agrA mutant at the saprophytic temperature of 25 degrees C and in vivo temperature of 37 degrees C. Variations of transcriptome were higher at 37 degrees C than at 25 degrees C. Results suggested that AgrA may be involved in the regu…
Biofilm-detached cells, a transition from a sessile to a planktonic phenotype: a comparative study of adhesion and physiological characteristics in Pseudomonas aeruginosa
Pseudomonas aeruginosa is a pathogenic bacterium widely investigated for its high incidence in clinical environments and its ability to form strong biofilms. During biofilm development, sessile cells acquire physiological characteristics differentiating them from planktonic cells. But after treatment with disinfectants, or to ensure survival of the species in hostile environments, biofilm cells can detach. This complicates disinfection procedures. This study aimed to physiologically characterize cells detached from a P. aeruginosa biofilm and to compare them with their sessile and planktonic counterparts. We first tested planktonic growth kinetics and capacities to form new biofilms. Then w…