Groupe Bacillus cereus

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Les bactéries du " groupe bacillus cereus " dans les conserves à pH peu acide ( petits pois): détection, caractérisation par méthode probabiliste numérisée, moléculaire et antibiorésistance

Les bactéries du " groupe bacillus cereus " dans les conserves à pH peu acide ( petits pois): détection, caractérisation par méthode probabiliste numérisée, moléculaire et antibiorésistance

Des souches bactériennes appartiendront au même genre si leurs séquences d’ADNr 16S possèdent un degré de similitude supérieur à 97% et à la même espèce si le degré de similitude est de 99% (Drancourt et al., 2000). Alors que la taxonomie traditionnelle présente le groupe Bacillus cereus comme des espèces distinctes, la phylogénie moléculaire nouvelle et le séquençage comparé des génomes sont en faveur de leur classification en une seule espèce (Guinebretière et al., 2008; Schmidt et al., 2011; Tourasse et al., 2011). Le concept de l’espèce unique a déjà été largement proposé notamment pour les trois espèces très proches génétiquement : Bacillus anthracis, Bacillus thuringiensis et Bacillus cereus sensu stricto (Hansen et Hendriksen, 2001 ; Helgason et al., 2004; Priest et al., 2004; Tourasse et al., 2006; Vilas-Boas et al., 2007). La proximité génétique de ces espèces est révélée par la similarité extrêmement élevée (plus de 99%) de leurs chromosomes (Ash et al., 1991; Rasko et al., 2005).
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Détection par PCR en temps réel du groupe Bacillus cereus et identification de Bacillus anthracis dans les produits alimentaires

Détection par PCR en temps réel du groupe Bacillus cereus et identification de Bacillus anthracis dans les produits alimentaires

Malgre la variabilite observee avec la methode de concentration, les deux methodes, directe et avec concentration, ont ete utilisees pour quantifier par PCR en temps reel.. La quantifi[r]

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Etude du système de communication cellulaire NprR-NprX au sein du groupe Bacillus cereus

Etude du système de communication cellulaire NprR-NprX au sein du groupe Bacillus cereus

An extracellular heptapeptide encoded by nprX restores nprA expression in nprX mutant strain We investigated whether the nprX gene product was a cell–cell signalling peptide by co-growin[r]

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The role of active site flexible loops in catalysis and of zinc in conformational stability of Bacillus cereus 569/H/9 beta-lactamase.

The role of active site flexible loops in catalysis and of zinc in conformational stability of Bacillus cereus 569/H/9 beta-lactamase.

However, since the enzyme was not fully unfolded in 10 M urea (note that no significant unfolding could be observed by both intrinsic fluorescence and far-UV CD measur[r]

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Two new secreted proteases generate a casein-derived antimicrobial peptide in $Bacillus\ cereus$ food born isolate leading to bacterial competition in milk

Two new secreted proteases generate a casein-derived antimicrobial peptide in $Bacillus\ cereus$ food born isolate leading to bacterial competition in milk

Thr Tyr 57 Leu 64 B. cereus as a contaminant ( Janštová et al., 2006 ). In general, milk contaminated by B. cereus occurs either at the farm or during processing of final products, such as UHT milk ( Vidal et al., 2016 ). Milk proteins exert a wide range of nutritional, functional, and biological activities. Moreover, many milk proteins possess specific biological properties, which make them potential ingredients of health-promoting foods. Therefore, increased attention is being given to active peptides derived from milk proteins. These peptides are inactive within the sequence of the parent protein molecule and can be liberated by (1) gastrointestinal digestion of milk, (2) fermentation of milk with proteolytic starter cultures, or (3) hydrolysis by proteolytic enzymes ( Korhonen and Pihlanto, 2006 ). Indeed, the ability of B. cereus to degrade milk proteins, particularly casein, has already been reported ( Janštová et al., 2006; Jadhav et al., 2014 ). Another important property of Bacillus spp. is the ability of their vegetative cells to produce thermally stable extracellular enzymes after proliferation ( Meer et al., 1991; Ipsen et al., 2000 ). These enzymes hydrolyze milk proteins, which affect nutritional and sensory properties even if viable bacteria are not present ( Boor et al., 1998 ). Lopez-Fandino et al. (1993) reported that B. cereus enzymes first break down casein before they start breaking down whey proteins ( Lopez-Fandino et al., 1993 ). In addition, Melachouris and Tuckey (1968) reported that β-casein was more readily degraded by B. cereus protease than other casein fractions and total degradation of β-casein was observed after 40 min ( Melachouris and Tuckey, 1968 ). In the present study, we showed that two new proteases from the B. cereus RC6 strain degrade bovine β-casein resulting in the generation of an AMP. This AMP inhibits the growth of various Gram-positive bacteria including B. cereus, B. thuringiensis, and L. monocytogenes. This characteristic is typical of AMPs produced by Gram-positive bacteria which are mostly active against Gram-positive bacteria and are less effective against Gram-negative bacteria ( Gray et al., 2006 ). The AMP was eluted using HPLC with a 29% acetonitrile mobile phase, which indicates a high degree of hydrophobicity. The molecular weight of the peptide obtained by MALDI-TOF was 751 Da and Edman degradation revealed an YPVEPF amino acid sequence. The strong correlation of the
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Antimicrobial and antioxidant activity of Ammi visnaga (L) phenolic extracts and their effects on planktonic and biofilm growth of food spoilage Bacillus cereus

Antimicrobial and antioxidant activity of Ammi visnaga (L) phenolic extracts and their effects on planktonic and biofilm growth of food spoilage Bacillus cereus

http://dx.doi.org/10.12692/ijb/9.4.32-47 Article published on October 11, 2016 Abstract Ammi visnaga (L) is a species from Apiaceae family (Umbelliferae), it is widely used in Algeria. It is supposed to be an interesting source of phenolic compounds which can be used against biofilm growth of bacteria. Bacillus cereus, a crucial pathogenic bacterium that causes food poisoning, is known as a producer of gastrointestinal diseases. In the present work we used water, acetone, ethanol and methanol to extract phenolic compound from the plant Ammi visnaga (L). The extracts were evaluated for their antioxidant activity and their effects on planktonic cells, swarming motility and biofilm growth of Bacillus cereus isolates. The results indicate that 70% methanolic extract represent the highest amount of total phenols (176mg GAE/g), and the lowest amount was obtained with acetone extract (18, 66mg GAE/g). Flavonoids extractability was found to be highest with ethanolic extract (22mg QE/g). Among all the extracts of A. visnaga (L), methanolic extract 70% showed the most potent radical scavenging ability (IC 50: 1, 46mg/ml) and the highest reducing power values from 1,129 to 1,974 at 700nm. DPPH assay of plant extracts was well correlated with FRAP assay (R 2 =0, 7018) and a good
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The Role of Active Site Flexible Loops in Catalysis and of Zinc in Conformational Stability of Bacillus cereus 569/H/9 β-Lactamase

The Role of Active Site Flexible Loops in Catalysis and of Zinc in Conformational Stability of Bacillus cereus 569/H/9 β-Lactamase

AtUCP1 and AtUCP2 share a number of similar transport properties; for example, both proteins catalyze a highly efficient counterexchange of substrates; do not transport mono- and tricarb[r]

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Expanding the known repertoire of virulence factors produced by <em>Bacillus cereus</em> through early secretome profiling in three redox conditions

Expanding the known repertoire of virulence factors produced by <em>Bacillus cereus</em> through early secretome profiling in three redox conditions

RESULTS Shotgun Proteomics Analysis of Early Growth B. cereus Cells The early secretomes of B. cereus ATCC 14579 grown in pH-regulated batch cultures on glucose-containing MOD me- dium were analyzed in duplicate under low ORP anaerobiosis (ORP ⫽ ⫺410 mV, pO 2 ⫽ 0%), high ORP anaerobiosis (ORP ⫽ ⫺10 mV, pO 2 ⫽ 0%), and full aerobiosis (ORP ⫽ ⫹140 mV, pO 2 ⫽ 100%). For each of the six biological sam- ples, the extracellular proteins were extracted twice to vali- date our technical procedure. For each technical duplicate, we performed two analytical nano-LC-MS/MS analyses. The full recorded data set for the resulting 24 nano-LC-MS/MS runs corresponds to 107,090 MS/MS spectra. One-third of these spectra were assigned to specific B. cereus peptides. A total of 1,018 different peptides were confidently listed (see supplemental Table 2 ). They made it possible to validate the presence of 133 proteins (see supplemental Table 3). The number of MS/MS spectra assigned to each polypeptide de- tected in the 24 nano-LC-MS/MS runs and normalized using the dry weight of considered biological replicates is reported in supplemental Table 3. We evaluated the analytical, techni- cal, and biological variances in our data. The total numbers of proteins detected per nano-LC-MS/MS are quite similar. Standard deviations and mean coefficients of variation were determined for all replicates. Mean coefficient of variation values were below 0.18, 0.18, and 0.32 for analytical, techni- cal, and biological replicates, respectively. The detected pro- teins were cataloged into five groups according to function: 1) toxins or putative toxins, 2) degradative enzymes and ad- hesins, 3) flagella components, 4) metabolism, and 5) others (see supplemental Table 3). Fig. 1 shows the distribution of proteins among the five functional groups in the three different growth conditions, taking into account their quantities. The results indicate that potential virulence factors, including tox- ins, degradative enzymes and adhesins, and flagella compo- nents (groups 1–3), represented 85.7 ⫾ 6.1, 91.5 ⫾ 3.6, and 87.3 ⫾ 1.7% of extracellular proteins under fully oxic, high ORP anoxic, and low ORP anoxic conditions, respectively. For fully oxic, high ORP anoxic, and low ORP anoxic condi- tions, respectively, 33.4 ⫾ 1.3, 38.8 ⫾ 2.8, and 32.4 ⫾ 4.8% of MS/MS spectra were assigned to toxins and putative tox- ins, but the level of toxins that accumulated in the supernatant was slightly higher in high ORP anaerobic conditions. These
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Bacillus anthracis

Bacillus anthracis

1. BREF APERCU HISTORIQUE : La maladie du Charbon, ou anthrax, « murrain », « woolsorter’s disease », ou encore « sang de rate » est une maladie bien plus ancienne qu’on ne le pense… La première mention faite à propos d’une infection apparentée à celle provoquée par Bacillus anthracis date de l’Antiquité, lorsque Moïse menaça les Egyptiens d’une 5 ème Plaie envoyée par Dieu et qui devait décimer les troupeaux et les humains dans d’atroces mais rapides souffrances.

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Deciphering the interactions between the <em>Bacillus cereus</em> linear plasmid, pBClin15, and its host by high-throughput comparative proteomics

Deciphering the interactions between the <em>Bacillus cereus</em> linear plasmid, pBClin15, and its host by high-throughput comparative proteomics

1. Introduction Members of the Bacillus cereus sensu lato group are found in diverse environments and include eight closely related species – Bacillus cereus sensu stricto, Bacillus anthracis, Bacillus thuringiensis, Bacillus weihenstephanensis, Bacillus mycoides, Bacillus pseudomycoides, Bacillus cytotoxicus, and Bacillus toyonensis [1,2] . The plasmids in this group dis- play a strain-dependent distribution, with some strains containing no plasmid, whereas others have many. Some of these plasmids have a small genome size, only 2 kb, whereas others are very large, up to 600 kb [3] . Large plasmids are key components in de fining the pheno- typic traits associated with pathogenesis [4] . For example, emetic syn- drome, which is associated with B. cereus sensu stricto, is caused by cereulide. The cereulide synthetase gene cluster, which encodes the en- zymatic machinery required for the biosynthesis of cereulide, is located on a 208 kb megaplasmid [5] . As a mammalian pathogen, the ability of B. anthracis to cause anthrax originates from two large plasmids: pXO1
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Methionine Residues in Exoproteins and Their Recycling by Methionine Sulfoxide Reductase AB Serve as an Antioxidant Strategy in Bacillus cereus

Methionine Residues in Exoproteins and Their Recycling by Methionine Sulfoxide Reductase AB Serve as an Antioxidant Strategy in Bacillus cereus

phase ( Madeira et al., 2015 ). Insofar as there is no ROS source and no Msr to reduce Met(O) back to Met in the extracellular milieu, we assumed that the time dynamic of protein-bound Met(O) in the B. cereus exoproteome could reflect the growth phase-dependent activity of an intracellular Msr. Here, we show that B. cereus encodes a functional MsrAB methionine sulfoxide reductase that is responsible for the decrease of the Met(O) content of the B. cereus exoproteome during aerobic respiratory growth. In addition, our results provide evidence that Met residues in exoproteins, especially enterotoxins, and their recycling by MsrAB, can serve as an antioxidant system that could trap ROS and maintain redox homeostasis in cells.
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Bacillus cereus Decreases NHE and CLO Exotoxin Synthesis to Maintain Appropriate Proteome Dynamics During Growth at Low Temperature

Bacillus cereus Decreases NHE and CLO Exotoxin Synthesis to Maintain Appropriate Proteome Dynamics During Growth at Low Temperature

Pathogenicity depends on the accumulation of toxins and other virulence factors in the extracellular medium, and thus in the exoproteome. To accumulate in the exoproteome, proteins must be synthesized within the cells, secreted by appropriate pathways, and/or be resistant to proteolysis. Our results indicated that the toxin content in the B. cereus exoproteome decreased when cells were grown at low temperature compared to high temperature; in addition, abundance levels were lower for cells in the S-phase compared to the log-phase of growth, whatever the culture temperature. Cellular proteome analysis revealed that the abundance of AcpP and other cell-surface components was reduced at low- compared to high-temperature, suggesting alterations to membrane fluidity, active transport, and thus secretory capacity [ 47 ]. Analysis of exoproteome data indicated that proteolysis, possibly mediated by the highly-abundant extracellular protease B7HVA4, could play a role in the temperature- and growth-phase-dependent decrease in toxin abundance levels. Finally, the toxin-depletion observed in the low-temperature exoproteome could be the result of decreased toxin synthesis due to catabolite repression combined with an altered secretory capacity and a higher rate of proteolysis.
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The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold

The 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold

The structure was solved by the multiple isomorphous replacement method, with density modification and phase combination, using X-ray data collected from the native.. protein and the T97[r]

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Identifcation of new hosts-dependants factors in Bacillus cereus Molecular and functional characterization of IlsA, a surface protein essential for iron acquisition during infection

Identifcation of new hosts-dependants factors in Bacillus cereus Molecular and functional characterization of IlsA, a surface protein essential for iron acquisition during infection

Fig. 7. Effect of ilsA mutation on virulence against the insect G. mellonella. Twenty last-instar larvae were force fed with 3 mg of Cry1C toxin associated with spores (from 5 ¥ 10 3 to 5 ¥ 10 6 ). Dose-mortality responses were observed 24 h after ingestion of B. cereus ATCC14579 (bold line, +) and B. cereus ATCC14579 DilsA (dotted line, 䉫) and analysed by Probit. Experiments were repeated at least three times. No mortality was obtained in the control (NaPi buffer alone).

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Extraction et caractérisations (structurale et physico-chimique) de polysaccharides hydrosolubles issus de cladoces de Cereus triangularis

Extraction et caractérisations (structurale et physico-chimique) de polysaccharides hydrosolubles issus de cladoces de Cereus triangularis

8 1.2.2. Multiplication et plantation des espèces appartenant au genre Cereus La multiplication des espèces appartenant au genre Cereus peut être réalisée par bouturage ou par semis de graines (Barbeau, 1990; Fouqué, 1969). Le bouturage est une méthode efficace et préférable car il permet de multiplier fidèlement la variété. De plus, la mise à fruits est rapide et survient moins d’un an après le bouturage contre trois ans pour les plantes issues de semis. Enfin, la rusticité des espèces de Cereus permet de réaliser un bouturage directement au champ à condition de prendre des boutures en repos végétatif d’au moins 50-70 cm de longueur (Nguyen, 1996). Il est également nécessaire d’assurer un arrosage régulier afin de permettre l’enracinement. Toutes ces conditions conduisent à des taux de reprise de l’ordre de 90 % (Le Belle et Judith, 1999). Les distances de plantation recommandées dépendent du type de tuteur choisi. En palissage verticale, des espacements de 2 à 3 m sur la ligne de plantation et de 4 à 5 m entre deux lignes sont requis (soit entre 2000 et 3750 boutures par ha, à raison de 3 boutures par tuteur) (Barbeau, 1990; Nguyen, 1996). Les densités sur palissage horizontal et sur plan incliné sont beaucoup plus élevées puisque les boutures sont implantées tous les 50-75 cm autour de la table de production qui est la parcelle de terrain destinée à la plantation (6500 boutures par ha) ou tout du long du plan incliné (5000 boutures par ha) (Le Bellec et Judith, 1999).
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Chromosome partitioning in Bacillus subtilis

Chromosome partitioning in Bacillus subtilis

Origin localization in wild type and spoOj cells, and the effects of inserting multiple parS partitioning sites into the terminus region of Bacillus subtilis.. Discussion.[r]

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Pépite | Caractérisation des propriétés de Bacillus amyloliquefaciens FZB42 et Bacillus subtilis BBG131 responsables de leur capacité à coloniser la rhizosphère de tomate

Pépite | Caractérisation des propriétés de Bacillus amyloliquefaciens FZB42 et Bacillus subtilis BBG131 responsables de leur capacité à coloniser la rhizosphère de tomate

2 Résumé Les bactéries qui promeuvent la croissance de plantes (PGPR) constituent une partie indispensable du biote de la rhizosphère et lorsqu’elles sont cultivées en association avec les plantes hôtes elles peuvent stimuler la croissance de ces dernières. Les PGPR favorisent la croissance de plantes directement soit en facilitant l’acquisition de ressources (azote, phosphore et des éléments essentiels) soit en modulant le niveau d’hormone de plante, ou indirectement en diminuant les effets inhibiteurs de différents agents pathogènes sur la croissance des plantes. Plusieurs espèces de Bacillus appartiennent aux PGPR et ont la capacité de produire des lipopeptides cycliques d’origine non ribosomique tels que la surfactine, la fengycine et la bacillomycine. Les lipopeptides cycliques peuvent être produits in vitro et in vivo, tels que dans la rhizosphère. La production de ces lipopeptides dans la rhizosphère joue un rôle important pour réprimer les agents pathogènes des plantes et améliorer la relation entre PGPR et plantes hôtes. La rhizosphère est la région complexe en contact étroit avec les racines des plantes. Les principaux partenaires biologiques de la rhizosphère sont la plante hôte, les microorganismes délétères et les microorganismes bénéfiques. Dans cette région, la colonisation représente le critère le plus important pour les facteurs biotiques en particulier pour les agents de biocontrôle. Plusieurs propriétés des microorganismes peuvent influencer leur potentialité à coloniser la rhizosphère comme leurs capacités de formation de biofilm et de production de lipopeptides. Ces deux propriétés peuvent, elles-mêmes être modulées par la composition des exudats racinaires. Dans cette étude, nous avons décidé d’étudier ces trois paramètres avec différentes souches de Bacillus sp. en relation avec la rhizosphère de la tomate.
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Bacillus subtilis and Bacillus velezensis population dynamic and quantification of spores after inoculation on ornamental plants

Bacillus subtilis and Bacillus velezensis population dynamic and quantification of spores after inoculation on ornamental plants

225 Taken together, our results show that, following application on plants, spores of 226 both B. subtilis NCIB3610 and B. velezensis QST713 are rapidly differentiating into 227 metabolically active cells in the rhizosphere, while those on the leaves and in the 228 soil were more likely to stay as spores or to sporulate again after a short phase of 229 germination. Thus, plant sites are clearly different in their impact on the proportions 230 of dormant Bacillus in the population. Bacteria colonizing roots are significantly 231 more active, strongly pointing toward the rhizosphere as being a key site for the 232 establishment of a durable relationship between B. subtilis and/or B. velezensis 233 and plants. These observations challenge the relevance of inoculating Bacillus- 234 based biofertilizers on leaves since these spores do not appear to gain activities 235 on this plant site. Inoculation directly into the soil, at root crown, or irrigation for the 236 penetrance of bacteria will favor a better colonization of roots and the germination 237 of spores into metabolically active cells. Understanding dynamics of the life cycle 238 of Bacillus species used in commercial products in relation with crops for which 239 they are used will allow us to improve how we use them. Such optimization should 240 lead to an increase in the efficacy and reliability of various biofungicides and 241 biopesticides used in organic agriculture.
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Bacillus pumilus et Bacillus subtilis pour lutter contre la pourriture grise chez la tomate et le concombre de serre

Bacillus pumilus et Bacillus subtilis pour lutter contre la pourriture grise chez la tomate et le concombre de serre

on tomato) to 100% (PTB180 on cucumber). Highest survival rates were observed for both PTB180 (100%) and PTB185 (71%) on cucumber plants. Previous work with Bacillus thuringiensis on rice leaves and with B. amyloliquefaciens on tomato leaves have associated the ability of Bacillus to colonize and to survive on the phyllosphere with an increase in control of gray mold (Salvatierra‐Martinez et al., 2018; Wang et al., 2014; Zeriouh et al., 2014). In these studies, the Bacillus used, mostly B. subtilis, remained able to control gray mold, with a survival rate of 10% (21 days after Bacillus inoculation). The high survival rate of the PTB strains for a period as long as 21 days also suggests that the frequency of their application to control foliar pathogens could be reduced to a minimum interval of 21 days between applications instead of a minimum interval of 5 days between applications, as recommended by the manufacturer of Rhapsody®, for the treatment of greenhouse tomato and cucumber plants against gray mold. In addition, compatibility was observed between the two PTB strains when applied as a mixture. The combination of the two strains does not seem to affect their survival on the leaves. Furthermore, neither of the two bacteria seems to take over the other, even 21 days following their inoculation. Further investigation would be necessary however to determine the ability of the strains to survive with the presence of B.
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Travail de groupe

Travail de groupe

• Les phrases importantes ou les définitions seront faciles à repérer (couleur). • On introduira au minimum deux exercices corrigés dans le cours (exercices d’applications) que l’on pourra rendre sur une feuille séparée du cours, leur numéro sera noté à la bonne place dans le cours. • Chaque membre du groupe « évaluera » ses camarades grâce à ce tableau :

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