Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailDistribution and evolution of ferripyoverdine receptors in Pseudomonas aeruginosa.
Bodilis, Josselin; Ghysels, Bart ULg; Osayande, Julie et al

in Environmental microbiology (2009), 11(8), 2123-35

Pseudomonas aeruginosa is a ubiquitous gram-negative bacterium, which is also able to cause severe opportunistic infections in humans. The colonization of the host is importantly affected by the ... [more ▼]

Pseudomonas aeruginosa is a ubiquitous gram-negative bacterium, which is also able to cause severe opportunistic infections in humans. The colonization of the host is importantly affected by the production of the high-affinity iron (III) scavenging peptidic siderophore pyoverdine. The species P. aeruginosa can be divided into three subgroups ('siderovars'), each characterized by the production of a specific pyoverdine and receptor (FpvA). We used a multiplex PCR to determine the FpvA siderovar on 345 P. aeruginosa strains from environmental or clinical origin. We found about the same proportion of each type in clinical strains, while FpvA type I was slightly over-represented (49%) in environmental strains. Our multiplex PCR also detected the presence or absence of an additional receptor for type I pyoverdine (FpvB). The fpvB gene was in fact present in the vast majority of P. aeruginosa strains (93%), regardless of their siderovar or their origin. Finally, molecular analyses of fpvA and fpvB genes highlighted a complex evolutionary history, probably linked to the central role of iron acquisition in the ecology and virulence of P. aeruginosa. [less ▲]

Detailed reference viewed: 10 (1 ULg)
Full Text
Peer Reviewed
See detailDistribution and identification of molecular interactions between tomato roots and bacterial biofilms
Debois, Delphine ULg; Jourdan, Emmanuel; Smargiasso, Nicolas ULg et al

Poster (2013, June 12)

Some non-pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in ... [more ▼]

Some non-pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in soil (1). To initiate both phenomena leading to biocontrol activity, microorganisms use plant exudates to grow on roots and to produce in-situ active compounds. In Bacilli, cyclic lipopeptides of the surfactin, iturin and fengycin families represent important antibiotics involved in biocontrol (2). Recent studies in microbiology allowed a better understanding of plant microorganism interactions but few has been done at the molecular level. In this study, MALDI MS imaging has been used to study the nature of the secreted lipopeptide molecules, their relative quantity and their distribution in the root’s environment.Disinfected tomato seeds were first germinated at 28°C in sterile conditions for germination. Seedlings were then placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution containing 1,75% of agar and treated with freshly-grown cells of Bacillus amyloliquefaciens S499. Petri dishes were incubated at 28°C with a 16h photoperiod. Different growth / incubation durations were studied: 10/3; 13/7; 21/14 and 39/32. For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. (HCCA, 5mg/mL in ACN/0.2% TFA 70:30) was used as matrix. UltraFlex II TOF/TOF and Solarix FT-ICR mass spectrometers were used to record molecular cartographies and perform MS/MS experiments for structural analysis purposes. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. The relative intensity of lipopeptides families varied with respect to the age of the root/biofilm system. In the 10/3 system, 3 homologues of surfactins were essentially detected (C13, C14 and C15), with very few iturins and fengycins. Their localizations were identical, whatever the considered homologue. Then the production of iturin and fengycin families increases in older systems (13/7 and 21/14) and a novel homologue of surfactin is detected (C12). Some variations in localizations within families may be observed (around the root or at the close vicinity of it in function of the considered homologue or alkali adduct). Then for the oldest system we studied, iturins and fengycins are not detected anymore and the localization of surfactins is less precise. In the 39/32 system, we also detected unknown compounds at 986.6, 1000.6, 1014.7 and 1028.7 m/z. The mass range of these compounds allied to the mass difference between two consecutive ion peaks let us think that these unknown compounds could be a new lipopeptide family. Tandem mass spectrometry experiments, performed on the dried culture medium, allowed to partially sequence these new lipopeptides. MS/MS results allied to exact mass measurements and isotopic pattern simulation give good confidence in the chemical structure we suggest. Nevertheless, to fully identify these new variants of surfactin, micro-extractions followed by (LC)-nano-ESI-MS/MS using a LESA module are in progress. MALDI Mass Spectrometry Imaging becomes a tool to decipher inter-species molecular communication. [less ▲]

Detailed reference viewed: 81 (17 ULg)
Peer Reviewed
See detailDistribution and identification of molecular interactions between tomato roots and bacterial biofilms
Debois, Delphine ULg; Jourdan, Emmanuel ULg; Smargiasso, Nicolas ULg et al

Conference (2012, September)

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in ... [more ▼]

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in soil (1). To initiate both phenomena leading to biocontrol activity, microorganisms use plant exudates to grow on roots and to produce in-situ active compounds. In Bacilli, cyclic lipopeptides of the surfactin, iturin and fengycin families represent important antibiotics involved in biocontrol (2). Recent studies in microbiology allowed a better understanding of plant microorganism interactions but few has been done at the molecular level. In this study, MALDI MS imaging has been used to study the nature of the secreted lipopeptide molecules, their relative quantity and their distribution in the root’s environment. Disinfected tomato seeds were first germinated at 28°C in sterile conditions for germination. Seedlings were then placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution (Hoagland) containing 1,75% of agar and treated with freshly-grown cells of Bacillus amyloliquefaciens S499. Petri dishes were finally incubated vertically in phytotron at 28°C with a 16h photoperiod. Different root age / time of incubation were studied: 13 / 3; 13 / 7; 21 / 14 and 39 / 32. Control tomato root (without bacterial treatment) of the same ages were also analyzed (13 / 0; 21 / 0 and 42 / 0. For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. The matrix solution (α-cyano-hydroxycinnamic acid, 5mg/mL in ACN/0.2% TFA 70/30) was applied with an ImagePrep automated sprayer (Bruker Daltonics). An UltraFlex II TOF/TOF and a Solarix FT-ICR mass spectrometers were used to record molecular cartographies. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. The relative intensity of lipopeptides families varied with respect to the age of the root/biofilm system. In the 13/3 system, 3 homologues of surfactins were essentially detected (C13, C14 and C15), with very few iturins and fengycins. Their localizations were identical, whatever the considered homologue. Then the production of iturin and fengycin families increases in older systems (13/7 and 21/14) and a novel homologue of surfactin is detected (C12). Some variations in localizations within families may be observed (around the root or at the close vicinity of it in function of the considered homologue or alkali adduct). Then for the oldest system we studied, iturins and fengycins are not detected anymore and the localization of surfactins is less precise. In the 39/32 system, we also detected unknown compounds at 986.6, 1000.6, 1014.7 and 1028.7 m/z. The mass range of these compounds allied to the mass difference between two consecutive ion peaks let us think that these unknown compounds could be a new lipopeptide family. Investigations are in progress to identify these new secondary metabolites of Bacillus amyloliquefaciens. [less ▲]

Detailed reference viewed: 50 (10 ULg)
Peer Reviewed
See detailDistribution and identification of molecular interactions between tomato roots and bacterial biofilms
Debois, Delphine ULg; Jourdan, Emmanuel ULg; Ongena, Marc ULg et al

Conference (2012, September 05)

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in ... [more ▼]

Some non pathogenic microorganisms evolving in the root micro-environment can trigger a positive effect on plant, increasing host defense against disease or/and directly inhibiting growth of pathogen in soil (1). To initiate both phenomena leading to biocontrol activity, microorganisms use plant exudates to grow on roots and to produce in-situ active compounds. In Bacilli, cyclic lipopeptides of the surfactin, iturin and fengycin families represent important antibiotics involved in biocontrol (2). Recent studies in microbiology allowed a better understanding of plant microorganism interactions but few has been done at the molecular level. In this study, MALDI MS imaging has been used to study the nature of the secreted lipopeptide molecules, their relative quantity and their distribution in the root’s environment. Disinfected tomato seeds were first germinated at 28°C in sterile conditions for germination. Seedlings were then placed in Petri dish on ITO glass slide recovered with a thin layer of plant nutritive solution (Hoagland) containing 1,75% of agar and treated with freshly-grown cells of Bacillus amyloliquefaciens S499. Petri dishes were finally incubated vertically in phytotron at 28°C with a 16h photoperiod. Different root age / time of incubation were studied: 13 / 3; 13 / 7; 21 / 14 and 39 / 32. Control tomato root (without bacterial treatment) of the same ages were also analyzed (13 / 0; 21 / 0 and 42 / 0. For MALDI imaging experiments, the ITO slide was removed from the agar and dried in a dessiccator under vacuum. The matrix solution (α-cyano-hydroxycinnamic acid, 5mg/mL in ACN/0.2% TFA 70/30) was applied with an ImagePrep automated sprayer (Bruker Daltonics). An UltraFlex II TOF/TOF and a Solarix FT-ICR mass spectrometers were used to record molecular cartographies. The average mass spectra recorded around the tomato root (2-3 mm on both sides of the root) showed that lipopeptides were major compounds detected on the agar. The relative intensity of lipopeptides families varied with respect to the age of the root/biofilm system. In the 13/3 system, 3 homologues of surfactins were essentially detected (C13, C14 and C15), with very few iturins and fengycins. Their localizations were identical, whatever the considered homologue. Then the production of iturin and fengycin families increases in older systems (13/7 and 21/14) and a novel homologue of surfactin is detected (C12). Some variations in localizations within families may be observed (around the root or at the close vicinity of it in function of the considered homologue or alkali adduct). Then for the oldest system we studied, iturins and fengycins are not detected anymore and the localization of surfactins is less precise. In the 39/32 system, we also detected unknown compounds at 986.6, 1000.6, 1014.7 and 1028.7 m/z. The mass range of these compounds allied to the mass difference between two consecutive ion peaks let us think that these unknown compounds could be a new lipopeptide family. Investigations are in progress to identify these new secondary metabolites of Bacillus amyloliquefaciens. [less ▲]

Detailed reference viewed: 60 (12 ULg)
Peer Reviewed
See detailDistribution and immunoelectron microscopic localization of laminin, a noncollagenous basement membrane glycoprotein.
Foidart, Jean-Michel ULg; Bere, EW Jr; Yaar, M. et al

in Laboratory Investigation : Journal of Technical Methods & Pathology (1980), 42(3), 336-42

Detailed reference viewed: 11 (1 ULg)
Full Text
Peer Reviewed
See detailDistribution and origin of suspended matter and organic carbon pools in the Tana River Basin, Kenya
Tamooh, F; Van den Meersche, K; Meysman, F et al

in Biogeosciences (2012), 9

We studied patterns in organic carbon pools and their origin in the Tana River Basin (Kenya), in February 2008 (dry season), September–November 2009 (wet season), and June–July 2010 (end of wet season ... [more ▼]

We studied patterns in organic carbon pools and their origin in the Tana River Basin (Kenya), in February 2008 (dry season), September–November 2009 (wet season), and June–July 2010 (end of wet season), covering the full continuum from headwater streams to lowland mainstream sites. A consistent downstream increase in total suspended matter (TSM, 0.6 to 7058 mg l−1) and particulate organic carbon (POC, 0.23 to 119.8 mg l−1) was observed during all three sampling campaigns, particularly pronounced below 1000m above sea level, indicating that most particulate matter exported towards the coastal zone originated from the mid and low altitude zones rather than from headwater regions. This indicates that the cascade of hydroelectrical reservoirs act as an extremely efficient particle trap. Although 7Be / 210Pbxs ratios/age of suspended sediment do not show clear seasonal variation, the gradual downstream increase of suspended matter during end of wet season suggests its origin is caused by inputs of older sediments from bank erosion and/or river sediment resuspension. During wet season, higher TSM concentrations correspond with relatively young suspended matter, suggesting a contribution from recently eroded material.With the exception of reservoir waters, POC was predominantly of terrestrial origin as indicated by generally high POC : chlorophyll a (POC : Chl a) ratios (up to 41 000). Stable isotope signatures of POC ( 13CPOC) ranged between −32 and −20‰and increased downstream, reflecting an increasing contribution of C4-derived carbon in combination with an expected shift in 13C for C3 vegetation towards the more semi-arid lowlands. 13C values in sediments from the main reservoir (−19.5 to −15.7 ‰) were higher than those found in any of the riverine samples, indicating selective retention of particles associated with C4 fraction. Dissolved organic carbon (DOC) concentrations were highest during the end of wet season (2.1 to 6.9 mg l−1), with stable isotope signatures generally between −28 and −22 ‰. A consistent downstream decrease in % organic carbon (%OC) was observed for soils, riverine sediments, and suspended matter. This was likely due to better preservation of the organic fraction in colder high altitude regions, with loss of carbon during downstream spiraling. 13C values for soil and sediment did not exhibit clear altitudinal patterns, but values reflect the full spectrum from C3-dominated to C4-dominated sites. Very low ratios of organic carbon to mineral surface area (OC : SA) were found in reservoir sediments and suspended matter in the lower Tana River, indicating that these are stable OC pools which have undergone extensive degradation. Overall, our study demonstrates that substantial differences occur in both the quantities and origin of suspended sediments and organic carbon along the river profile in this tropical river basin, as well as seasonal differences in the mechanisms causing such variations. [less ▲]

Detailed reference viewed: 21 (2 ULg)
Full Text
See detailDistribution and quantification of tension wood in poplar shoote
Jourez, Benoît ULg; Leclercq, André

Conference (1996)

Detailed reference viewed: 15 (4 ULg)
Full Text
Peer Reviewed
See detailDistribution and Regulation of Estrogen-2-Hydroxylase in the Quail Brain
Balthazart, Jacques ULg; Stoop, R.; Foidart, Agnès ULg et al

in Brain Research Bulletin (1994), 35(4), 339-45

The anatomical distribution and endocrine regulation of the estrogen-2-hydroxylase activity were investigated in the brain of adult male and female Japanese quail. Significant levels of enzymatic activity ... [more ▼]

The anatomical distribution and endocrine regulation of the estrogen-2-hydroxylase activity were investigated in the brain of adult male and female Japanese quail. Significant levels of enzymatic activity were detected in all brain regions that were studied, but the highest levels were observed in preoptic and hypothalamic brain nuclei that are known to contain high levels of aromatase activity. These data are consistent with previous results suggesting that the placental aromatase is also responsible for the estrogen-2-hydroxylase activity. However, there is a marked sex difference and a control by T of aromatase activity in the quail brain, and no such difference in 2-hydroxylase activity could generally be detected except in the VMN. Further studies will be needed to know whether the previously published conclusions concerning the human placenta also apply to the brain. The present data are consistent with the idea that estrogens formed locally in the brain by testosterone aromatization could affect reproduction by interfering with the catecholaminergic transmission after being metabolized into catechol-estrogens. [less ▲]

Detailed reference viewed: 12 (0 ULg)
Full Text
See detailDistribution and robustness of a distance-based multivariate coefficient of variation
Aerts, Stéphanie ULg

Poster (2014, November)

When one wants to compare the homogeneity of a characteristic in several popula- tions that have di erent means, the advocated statistic is the univariate coe cient of variation. However, in the ... [more ▼]

When one wants to compare the homogeneity of a characteristic in several popula- tions that have di erent means, the advocated statistic is the univariate coe cient of variation. However, in the multivariate setting, comparing marginal coe cients may be inconclusive. Therefore, several extensions that summarize multivariate relative dispersion in one single in- dex have been proposed in the literature (see Albert & Zhang, 2010, for a review). In this poster, focus is on a particular extension, due to Voinov & Nikulin (1996), based on the Mahalanobis distance between the mean and the origin of the design space. Some arguments are outlined for justifying this choice. Then, properties of its sample version under elliptical symmetry are discussed. Under normality, this estimator is shown to be biased at nite samples. In order to overcome this drawback, two bias corrections are proposed. Moreover, the empirical estimator also su ers from a lack of robustness, which is illustrated by means of in uence functions. A robust counterpart based on the Minimum Covariance Determinant estimator is advocated. [less ▲]

Detailed reference viewed: 29 (8 ULg)
See detailDistribution and variations of pCO2 in subantarctic waters of the Kerguelen Archipelago
Delille, Bruno ULg; Delille, D.; Fiala, M. et al

Poster (2000, July)

Detailed reference viewed: 9 (0 ULg)
Full Text
See detailDistribution assessment of endangered Lepilemur in northwestern Madagascar
Wilmet, Leslie ULg; Vermeulen, Cédric ULg; Beudels-Jamar, Roseline

Scientific conference (2013, October 21)

Detailed reference viewed: 21 (3 ULg)
Full Text
Peer Reviewed
See detailDistribution d’adhésines potentielles au sein de souches d’Escherichia coli entérohémorragiques de sérogroupes O26
Bardiau, Marjorie ULg; Labrozzo, Sabrina; Mainil, Jacques

Poster (2008, September)

Detailed reference viewed: 4 (0 ULg)
Full Text
Peer Reviewed
See detailDistribution de 8 espèces végétales endémiques du Katanga (R.D.Congo) le long d'un gradient de cuivre et de cobalt
Boisson, Sylvain ULg; Lebrun, Julie ULg; Mahy, Grégory ULg

Poster (2013, November 06)

Au sud de la province du Katanga (R.D.Congo), se développe une végétation unique sur des sols recouvrant une centaine d’affleurements de cuivre et de cobalt parmi les plus importants au monde (Arc ... [more ▼]

Au sud de la province du Katanga (R.D.Congo), se développe une végétation unique sur des sols recouvrant une centaine d’affleurements de cuivre et de cobalt parmi les plus importants au monde (Arc cuprifère katangais). Le paysage de cette région est composé de collines isolées les unes des autres et présentant des communautés végétales distinctes selon la concentration en éléments traces métalliques du sol. Les savanes steppiques se retrouvent sur des sols faiblement contaminés tandis que les pelouses sont inféodées aux sols pouvant être contaminés à des teneurs avoisinant les 10 000 mg.kg-1 de cuivre et 1000 mg.kg-1 de cobalt. Plus de 600 espèces d’angiospermes métallophytes y sont retrouvées dont 32 vivant exclusivement sur des sols contaminés (endémiques strictes). Ces espèces présentent des adaptations physiologiques et biologiques leur permettant de tolérer les concentrations exceptionnelles dans le sol. Certaines d’entre-elles ont d’ailleurs été identifiées comme des hyperaccumulatrices de cuivre et/ou de cobalt. Le caractère unique de la plupart des espèces endémiques de cette flore est aujourd’hui menacé par les activités minières intenses dans la province. Ces espèces représentent pourtant des ressources génétiques de grands intérêts pour développer des stratégies de restauration et de remédiation des sites pollués par leur rôle potentiel en phytostabilisation des sols. L’objectif de l’étude est de caractériser la niche écologique réalisée de 8 espèces endémiques le long du gradient de cuivre et cobalt en vue d’adapter les stratégies de conservation et de restauration des espèces. Les espèces étudiées sont Triumfetta likasiensis, Lopholaena deltombei, Tinnea coerulea var. obovata, Sopubia neptunii, Basananthe kisimbae, Barleria lobelioides, Commelina zigzag, Euphorbia cupricola. Pour chaque espèce, 3 sites ont été prospectés en faisant un transect de 2 m de large le long des gradients métalliques et en identifiant tous les individus de l’espèce. Ensuite, 5 individus ont été sélectionnés parmi le nombre total d’individus comptés : 2 extrêmes, 1er quartile, 1 médian, 3ème quartile. Pour chacun d’eux, un quadrat d’un mètre carré y a été centré au sol et le nombre d’individus de l’espèce dénombrés. Un échantillon de sol composite a ensuite été prélevé entre 0 et 15 cm de profondeur afin de déterminer les teneurs en cuivre et cobalt par une spectrométrie d’absorption atomique dans la flamme à partir de l’extrait NH4-Acétate-EDTA du sol. Les niches écologiques réalisées ont été modélisées pour chaque métal par la méthode d’estimation des noyaux avec le logiciel R 3.0.1 (package ‘vioplot’). Les résultats montrent que les niches écologiques de ces espèces endémiques se répartissent entre 50 et 11 000 mg.kg-1 de sol pour le cuivre et 4 et 1500 mg.kg-1 de sol pour le cobalt. Six espèces se situent dans des concentrations inférieures à 100 mg.kg-1 le long du gradient de cobalt. Le long du gradient de cuivre, deux espèces ont des optima écologiques supérieurs à 3000 mg.kg-1. La niche écologique de B. kisimbae est la plus étroite avec un optimum environnant les 200 mg Cu.kg-1 et 50 mg Co.kg-1. L’espèce S. neptunii est présente sur l’entièreté du gradient de cobalt et est retrouvée dans les concentrations élevées. La variation des niches écologiques le long des gradients métalliques indique que les stratégies de conservation doivent être adaptées selon les espèces à conserver. Dans cette étude, 4 des 8 espèces pourraient être conservées sur un sol contaminé à 500 mg Cu.kg-1 et 30 mg Co.kg-1. Pour les autres, il est indispensable de mettre en place les stratégies de conservation en considérant, dans un premier temps, les espèces au cas par cas. [less ▲]

Detailed reference viewed: 48 (7 ULg)
Full Text
See detailDistribution des cas européens de myopathie atypique de 2003 à 2013 : maladie endémique ou émergente Pratique vétérinaire équine
Patarin, Florence; Pitel, Christel; Votion, Dominique ULg

in Pratique Vétérinaire Equine (2014), 46(182), 6-10

Detailed reference viewed: 6 (0 ULg)