Jacques Mahillon

Catholic University of Louvain, Walloon Region, Belgium

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Publications (125)395.43 Total impact

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    ABSTRACT: Cytotoxin K (CytK) produced by Bacillus cereus s.l. has generally been considered to be associated with the foodborne diarrhoeal syndrome. Two distinct variants of CytK have been reported: CytK-1 from Bacillus cytotoxicus and CytK-2 from B. cereus. In order to determine whether CytK plays a significant role in the diarrhoeal disease, the occurrence of cytK genes was assessed among 390 B. cereus isolates with different origins including clinical and food poisoning samples and was found to be 46%. Interestingly, the cytK occurrence was slightly lower in food poisoning and clinical isolates than in environmental samples. Seventy cytK-2 positive strains (including 28 isolates from foodborne outbreaks) were then selected in order to assess their genetic diversity. A genetic dendrogram based on the cytK-2 sequences of these 70 strains and on two cytK-1 sequences from strains NVH 391-98 and 883-00 showed an important diversity. However, no strain clustering according to the origin or source of isolation was observed. These observations were confirmed by Multi-Locus Sequences Typing (MLST) based on five different loci of housekeeping genes (ccpA, recF, sucC, purF and gdpD) for which no grouping of foodborne outbreak strains could be identified. Therefore, the choice of cytK as virulence factor for the diarrhoeal pathotype does not seem to be relevant per se, even though the involvement of CytK in the diarrhoeal syndrome cannot be fully excluded. Potential synergistic effects between CytK and other virulence factors, together with their potential variable expression levels should be further investigated. Copyright © 2015 Elsevier B.V. All rights reserved.
    International journal of food microbiology 06/2015; 211:79-85. DOI:10.1016/j.ijfoodmicro.2015.06.020 · 3.16 Impact Factor
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    ABSTRACT: We tested the hypothesis that changing the gut microbiota using pectic oligosaccharides (POS) or inulin (INU) differently modulates the progression of leukemia and related metabolic disorders. Mice were transplanted with Bcr-Abl-transfected proB lymphocytes mimicking leukemia and received either POS or INU in their diet (5%) for 2 weeks. Combination of pyrosequencing, PCR-DGGE and qPCR analyses of the 16S rRNA gene revealed that POS decreased microbial diversity and richness of caecal microbiota whereas it increased Bifidobacterium spp., Roseburia spp. and Bacteroides spp. (affecting specifically B. dorei) to a higher extent than INU. INU supplementation increased the portal SCFA propionate and butyrate, and decreased cancer cell invasion in the liver. POS treatment did not affect hepatic cancer cell invasion, but was more efficient than INU to decrease the metabolic alterations. Indeed, POS better than INU delayed anorexia linked to cancer progression. In addition, POS treatment increased acetate in the caecal content, changed the fatty acid profile inside adipose tissue and counteracted the induction of markers controlling β-oxidation, thereby hampering fat mass loss. Non digestible carbohydrates with prebiotic properties may constitute a new nutritional strategy to modulate gut microbiota with positive consequences on cancer progression and associated cachexia.
    PLoS ONE 06/2015; 10(6):e0131009. DOI:10.1371/journal.pone.0131009 · 3.23 Impact Factor
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    ABSTRACT: Staphylococcus epidermidis is a world leading pathogen in health-care facilities, mainly causing medical device-associated infections. These nosocomial diseases often result in complications such as bacteremia, fibrosis or peritonitis. The virulence of S. epidermidis relies on its ability to colonize surfaces and develop thereupon in the form of biofilms. Bacterial adherence on biomaterials, usually covered with plasma proteins after implantation, is a critical step leading to biofilm infections. The cell surface protein SdrG mediates adhesion of S. epidermidis to Fibrinogen (Fg) through a specific "dock, lock and latch" mechanism, which results in greatly stabilized protein-ligand complexes. Here, we combine single-molecule, single-cell and whole population assays to investigate the extent to which the surface density of SdrG determines the ability of S. epidermidis clinical strains HB, ATCC 35984 and ATCC 12228 to bind to Fg-coated surfaces. Strains that showed enhanced adhesion on Fg-coated PolyDiMethylSiloxane (PDMS) were characterized by increased amounts of SdrG proteins on the cell surface, as observed by single-molecule analysis. Consistent with previous reports showing increased expression of SdrG following in vivo exposure, this work provides direct evidence that abundance of SdrG on the cell surface of S. epidermidis strains dramatically improves their ability to bind to Fg-coated implanted medical devices.
    Langmuir 03/2015; 31(16). DOI:10.1021/acs.langmuir.5b00360 · 4.46 Impact Factor
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    Lionel Makart · Annika Gillis · Jacques Mahillon
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    ABSTRACT: Bacillus thuringiensis strains usually harbor large sets of plasmids, some of which carrying the entomopathogenic δ-endotoxins. B. thuringiensis serovar israelensis, active on Dipteran larvae, carries the very large conjugative plasmid pXO16 (350 kb). pXO16 displays a macroscopic aggregation phenotype when liquid cultures of conjugative partners are mixed. Its conjugative apparatus is able of transferring itself and other non-conjugative and non-mobilizable plasmids in a fast and very efficient manner. Even though its conjugative kinetics and capabilities have been extensively studied, the genetic bases for this unique transfer system remain largely unknown. In this work, the sequence of pXO16 has been identified in the existing sequenced genome of B. thuringiensis sv. israelensis HD-789 as corresponding to the p01 plasmid. Despite pXO16 sequence being highly coding, few CDS possess homologues in the databases. However, potential regions responsible for the aggregation phenotype and the plasmid replication have been highlighted. The common orientation of all CDS and the presence of a high number of potential paralogues suggested a phage-like nature. Concerning conjugative functions, no significant type IV secretion system homologues have been found, indicating that pXO16 encodes an unforeseen conjugative system. Copyright © 2015 Elsevier Inc. All rights reserved.
    Plasmid 03/2015; 80. DOI:10.1016/j.plasmid.2015.03.002 · 1.76 Impact Factor
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    ABSTRACT: Fifty-nine monophasic Salmonella Typhimurium isolates, collected in Belgium during the period 2008-2011, have been serotyped as 4,[5]:i:- while harboring a fljB coding sequence. The genetic differences between these strains and phenotypically biphasic Salmonella Typhimurium were therefore analyzed through PCR and DNA sequencing. Genetic alterations in the fljB promoter region affecting expression of the phase-2 flagellin were observed in 53 isolates. Other genetic events in the invertible region carrying the fljB promoter were observed in 2 isolates. For the remaining 4 isolates, no molecular differences with a reference biphasic Salmonella Typhimurium strain could be observed. Next generation sequencing of one representative isolate affected in the fljB promoter region revealed a 26-kb IS26 composite transposon insertion along with a local genomic rearrangement. Several other IS26 element-mediated alterations of this genomic region were observed. This group of monophasic Salmonella Typhimurium was genetically heterogeneous as revealed by Multiple Locus Variable Number of Tandem repeats Analysis (MLVA), PCR and sequencing. Pig and pork represented a major source of such monophasic isolates in Belgium, as reported in other countries. Three out of 5 isolates of human origin presented identical genetic profiles compared to food isolates, demonstrating pathogenic potential of the newly characterized variants and potential dissemination along the food chain. This study highlighted the key role played by IS26 insertions in the loss of phase-2 flagellin expression and the subsequent generation of multiple monophasic variant lineages from biphasic Salmonella Typhimurium ancestors. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Applied and Environmental Microbiology 02/2015; 81(9). DOI:10.1128/AEM.00270-15 · 3.95 Impact Factor
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    ABSTRACT: Bacillus cereus, the Gram-positive and spore-forming ubiquitous bacterium, may cause emesis as the result of food intoxication with cereulide, a heat stable emetic toxin. Rapid determination of cereulide-positive B. cereus isolates is of highest importance due to consequences of this intoxication for human health and life. Here we present a one-day pulsed-field gel electrophoresis for emetic B. cereus isolates, which allows rapid and efficient determination of their genomic relatedness and helps determining the source of intoxication in case of outbreaks caused by these bacilli.This article is protected by copyright. All rights reserved
    Electrophoresis 01/2015; 36(7-8). DOI:10.1002/elps.201400552 · 3.16 Impact Factor
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    ABSTRACT: In this study, the complete CoSYPS Path Food workflow including all steps, namely swab sample enrichment, SYBR®Green qPCR detection of Salmonella spp. and Listeria spp., isolation and confirmation of the detected strain, was validated on beef carcass swabs. To perform the validation, the results of the complete workflow were compared, according to the ISO 16140:2003, with the ISO reference methods for detection, isolation and confirmation of Listeria monocytogenes and Salmonella spp. The results showed that the relative level of detection and the limit of detection of the complete workflow and ISO reference methods are in a range from 2 to 16 CFU/swab for both bacteria. The relative specificity, sensitivity and accuracy identified during this validation were all 100% since the results obtained with the complete CoSYPS Path Food workflow and the ISO reference methods were identical (Cohen's kappa index = 1.00). In addition the complete CoSYPS Path Food workflow is able to provide detection results (negative or presumptive positive) in half the time needed as for the ISO reference methods. These results demonstrate that the performance of the complete CoSYPS Path Food workflow is not only comparable to the ISO reference methods but also provides a faster response for the verification of beef carcasses before commercial distribution.
    International Journal of Food Microbiology 01/2015; 192:103–110. DOI:10.1016/j.ijfoodmicro.2014.09.018 · 3.16 Impact Factor
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    Winfab Day 2014; 10/2014
  • Annika Gillis · Jacques Mahillon
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    ABSTRACT: Bacillus thuringiensis is an entomopathogenic bacterium that has been used as an efficient biopesticide worldwide. Despite the fact that this bacterium is usually described as an insect pathogen, its life cycle in the environment is still largely unknown. B. thuringiensis belongs to the Bacillus cereus group of bacteria, which has been associated with many mobile genetic elements, such as species-specific temperate or virulent bacteriophages (phages). Temperate (lysogenic) phages are able to establish a long-term relationship with their host, providing, in some cases, novel ecological traits to the bacterial lysogens. Therefore, this work focuses on evaluating the potential influence of temperate tectiviruses GIL01 and GIL16 on the development of different life traits of B. thuringiensis. For this purpose, a B. thuringiensis serovar israelensis plasmid-cured (nonlysogenic) strain was used to establish bacterial lysogens for phages GIL01 and GIL16, and, subsequently, the following life traits were compared among the strains: kinetics of growth, metabolic profiles, antibiotics susceptibility, biofilm formation, swarming motility, and sporulation. The results revealed that GIL01 and GIL16 lysogeny has a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of B. thuringiensis. No changes in metabolic profiles or antibiotic susceptibilities were detected. These findings provide evidence that tectiviruses have a putative role in the B. thuringiensis life cycle as adapters of life traits with ecological advantages.
    Applied and Environmental Microbiology 09/2014; 80(24):7620-7630. DOI:10.1128/AEM.01869-14 · 3.95 Impact Factor
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    ABSTRACT: Bacillus cereus is ubiquitous and is commonly found in a wide range of environments, including food. In this study, we analyzed 114 foodborne B. cereus strains isolated mainly from starchy and dairy products in order to investigate their phenotypic diversity (API system), antimicrobial resistance and toxigenic profiles (hblA, nheA, hlyII, cereolysin O, cytK2, cytK1 and EM1 genes). All isolates were confirmed as B. cereus using their 16-23S ribosomal DNA intergenic transcribed spacer (ITS) signature, and were shown to be Gram-positive, catalase and caseinase positive, hemolytic (97 %), and positive for lecithin hydrolysis and motility (97 and 87 %, respectively). PCR detection of B. cereus-specific toxin genes revealed occurrence rates of 100 % for cereolysin O, 98 % for nheA, 74 % for cytk2, 52 % for hblA, 28 % for hlyII, and the absence of cytK1. Only two strains (2 %), isolated from intestine of boar and pheasant, carried the emetic toxin genetic determinants (ces). The antimicrobial susceptibility of isolates was tested towards 15 different antimicrobial agents. We detected susceptibility of all strains to most antibiotics, intermediate resistance to clindamycin, and resistance to β-lactam antibiotics with 83 % of the resistant isolates producing β-lactamase enzyme. This large phenotypic diversity, combined with the toxigenic traits and antibiotic resistance, emphasize the high potential risk of food poisoning of B. cereus isolates. Additionally, a clear correlation between the metabolic features and the origin of isolation was shown. Most starchy isolates were able to hydrolyze starch while dairy strains were not able to produce amylases. Overall, our results reveal that metabolic flexibility and toxigenic potential represent the main drivers for B. cereus ubiquity and adaptation in a given ecological niche.
    Annals of Microbiology 09/2014; 65(2). DOI:10.1007/s13213-014-0941-9 · 1.04 Impact Factor
  • Annika Gillis · Jacques Mahillon
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    ABSTRACT: A simple method to isolate, screen and select phage-resistant mutants of Bacillus thuringiensis was developed. The traditional double-layer agar method was improved by a combination of the spotting assay using a lytic phage, to generate the bacterial-resistant mutants, with an inverted spotting assay (ISA), to rapidly screen the candidate-resistant mutants.
    Journal of Microbiological Methods 08/2014; 106:101–103. DOI:10.1016/j.mimet.2014.08.012 · 2.10 Impact Factor
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    ABSTRACT: Salting is one of the oldest means of food preservation: adding salt decreases water activity and inhibits microbial development. However, salt is also a source of living bacteria and archaea. The occurrence and diversity of viable archaea in this extreme environment were assessed in 26 food-grade salts from worldwide origin by cultivation on four culture media. Additionally, metagenomic analysis of 16S rRNA gene was performed on nine salts. Viable archaea were observed in 14 salts and colony counts reached more than 10(5)CFU per gram in three salts. All archaeal isolates identified by 16S rRNA gene sequencing belonged to the Halobacteriaceae family and were related to 17 distinct genera among which Haloarcula, Halobacterium and Halorubrum were the most represented. High-throughput sequencing generated extremely different profiles for each salt. Four of them contained a single major genus (Halorubrum, Halonotius or Haloarcula) while the others had three or more genera of similar occurrence. The number of distinct genera per salt ranged from 21 to 27. Halorubrum had a significant contribution to the archaeal diversity in seven salts; this correlates with its frequent occurrence in crystallization ponds. On the contrary, Haloquadratum walsbyi, the halophilic archaea most commonly found in solar salterns, was a minor actor of the food-grade salt diversity. Our results indicate that the occurrence and diversity of viable halophilic archaea in salt can be important, while their fate in the gastrointestinal tract after ingestion remains largely unknown.
    International Journal of Food Microbiology 08/2014; 191C:36-44. DOI:10.1016/j.ijfoodmicro.2014.08.019 · 3.16 Impact Factor
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    ABSTRACT: Point-of-care (PoC) diagnostics for bacterial detection offer tremendous prospects for public health care improvement. However, such tools require the complex combination of the following performances: rapidity, selectivity, sensitivity, miniaturization and affordability. To meet these specifications, this paper presents a new selectivity method involving lysostaphin together with a CMOS-compatible impedance sensor for genus-specific bacterial detection. The method enables the sample matrix to be directly flown on the polydopamine-covered sensor surface without any pre-treatment, and considerably reduces the background noise. Experimental proof-of-concept, explored by simulations and confirmed through a setup combining simultaneous optical and electrical real-time monitoring, illustrates the selective and capacitive detection of Staphylococcus epidermidis in synthetic urine also containing Enterococcus faecium. While providing capabilities for miniaturization and system integration thanks to CMOS compatibility, the sensors show a detection limit of ca. 108 (CFU/mL).min in a 1.5 μL microfluidic chamber with an additional setup time of 50 min. The potentials, advantages and limitations of the method are also discussed.
    Biosensors & Bioelectronics 08/2014; 67. DOI:10.1016/j.bios.2014.07.084 · 6.45 Impact Factor
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    Annika Gillis · Jacques Mahillon
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    ABSTRACT: Many bacteriophages (phages) have been widely studied due to their major role in virulence evolution of bacterial pathogens. However, less attention has been paid to phages preying on bacteria from the Bacillus cereus group and their contribution to the bacterial genetic pool has been disregarded. Therefore, this review brings together the main information for the B. cereus group phages, from their discovery to their modern biotechnological applications. A special focus is given to phages infecting Bacillus anthracis, B. cereus and Bacillus thuringiensis. These phages belong to the Myoviridae, Siphoviridae, Podoviridae and Tectiviridae families. For the sake of clarity, several phage categories have been made according to significant characteristics such as lifestyles and lysogenic states. The main categories comprise the transducing phages, phages with a chromosomal or plasmidial prophage state, γ-like phages and jumbo-phages. The current genomic characterization of some of these phages is also addressed throughout this work and some promising applications are discussed here.
    Viruses 07/2014; 6(7):2623-2672. DOI:10.3390/v6072623 · 3.28 Impact Factor
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    ABSTRACT: The propidium monoazide (PMA) coupled with PCR (viability PCR) is used in foodborne pathogen detection in order to detect only viable bacteria. Originally presented to fully remove the signal of dead bacteria, the limits of the viability PCR rapidly came out in the literature. In this study, the use of PMA in a viability-qPCR (v-qPCR) was assessed on viable and dead cells of Salmonella enterica subsp. enterica serovar Enteritidis. The PMA treatment protocol was modified (dark incubation duration, concentration of PMA) to evaluate if a complete negative signal of dead Salmonella was possible. However, none of these modifications was found to improve the removal of the remaining qPCR signal observed in the presence of dead bacteria. The present research also underlines that PMA may unexpectedly decrease the qPCR signal observed on living S. Enteritidis at low concentration. Finally, the use of S. Enteritidis cells killed by processes altering, or not, the cell-wall/membrane gives us a clue to answering the question about the non-total extinction of the signal of dead cells sample in the v-qPCR assay. Indeed, the data strongly indicate that the remaining qPCR signal observed in non-culturable cells does not only depend on the cell-wall/membrane integrity of the bacteria. According to these results, the authors suggest that for a rapid and reliable foodborne bacteria detection system, an enrichment followed by a qPCR analysis should be preferred to a v-qPCR.
    Journal of Microbiological Methods 06/2014; 103. DOI:10.1016/j.mimet.2014.06.003 · 2.10 Impact Factor
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    Xiaofen Mei · Kai Xu · Lingling Yang · Zhiming Yuan · Jacques Mahillon · Xiaomin Hu
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    ABSTRACT: Background Cereulide is a cyclic dodecadepsipeptide ionophore, produced via non-ribosomal peptide synthetases (NRPS), which in rare cases can lead to human death. Early studies had shown that emetic toxin formation belongs to a homogeneous group of Bacillus cereus sensu stricto and the genetic determinants of cereulide (a 24-kb gene cluster of cesHPTABCD) are located on a 270-kb plasmid related to the Bacillus anthracis virulence plasmid pXO1. Results The whole genome sequences from seven emetic isolates, including two B. cereus sensu stricto and five Bacillus weihenstephanensis strains, were compared, and their inside and adjacent DNA sequences of the cereulide biosynthesis gene clusters were analyzed. The sequence diversity was observed, which classified the seven emetic isolates into three clades. Different genomic locations of the cereulide biosynthesis gene clusters, plasmid-borne and chromosome-borne, were also found. Potential mobile genetic elements (MGEs) were identified in the flanking sequences of the ces gene cluster in all three types. The most striking observation was the identification of a putative composite transposon, Tnces, consisting of two copies of ISces element (belonging to IS6 family) in opposite orientations flanking the ces gene cluster in emetic B. weihenstephanensis. The mobility of this element was tested by replacing the ces gene cluster by a KmR gene marker and performing mating-out transposition assays in Escherichia coli. The results showed that Tnces::km transposes efficiently (1.04 × 10-3 T/R) and produces 8-bp direct repeat (DR) at the insertion sites. Conclusions Cereulide biosynthesis gene clusters display sequence diversity, different genomic locations and association with MGEs, in which the transposition capacity of a resistant derivative of the composite transposon Tnces in E. coli was demonstrated. Further study is needed to look for appropriate genetic tools to analysis the transposition of Tnces in Bacillus spp. and the dynamics of other MGEs flanking the ces gene clusters.
    BMC Microbiology 06/2014; 14(1):149. DOI:10.1186/1471-2180-14-149 · 2.98 Impact Factor
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    ABSTRACT: Background & Aim Inulin-type fructans (ITF) prebiotics promote changes in the composition and activity of the gut microbiota. The aim of this study was to to determine variations on fecal short chain fatty acids (SCFA) concentration in obese women treated with ITF and to explore associations between Bifidobacterium species, SCFA and host biological markers of metabolism. Methods Samples were obtained in a randomized, double blind, parallel, placebo-controlled trial, with 30 obese women randomly assigned to groups that received either 16 g/day ITF (n=15) or maltodextrin (n=15) for 3 months. The qualitative and quantitative analysis of Bifidobacterium spp. was performed in feces by PCR-DGGE and q-PCR, and SCFA profile was analyzed by gas chromatography. Spearman correlation analysis was performed between the different variables analyzed. Results The species Bifidobacterium longum, Bifidobacterium pseudocatenulatum and Bifidobacterium adolescentis were significantly increased at the end of the treatment in the prebiotic group (p <0.01) being B. longum negatively correlated with serum lipopolysaccharide (LPS) endotoxin (p< 0.01). Total SCFA, acetate and propionate, that positively correlated BMI, fasting insulinemia and homeostasis model assessment (HOMA) (p< 0.05), were significantly lower in prebiotic than in placebo group after the treatment Conclusions ITF consumption selectively modulates Bifidobacterium spp. and decreases fecal SCFA concentration in obese women. ITF could lessen metabolic risk factors associated with higher fecal SCFA concentration in obese individuals.
    Clinical Nutrition 06/2014; 34(3). DOI:10.1016/j.clnu.2014.06.001 · 3.94 Impact Factor
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    ABSTRACT: Achieving fast, sensitive and selective detection of bacteria in liquid samples is a major challenge for public healthcare. Unlike conventional methods, CMOS chips with sensing parts provide tremendous benefits in term of portability, system integration and reduced cost. CMOS-compatible microelectrodes were shown to selectively detect whole-cell Staphylococci after drying the sensor surface1. Here, we extend the use of these microelectrodes to bacteria detection in continuous flow for microfluidic applications.
    Biosensors 2014, Melbourne, Australia; 05/2014

Publication Stats

4k Citations
395.43 Total Impact Points

Institutions

  • 1984–2015
    • Catholic University of Louvain
      • • Earth and Life Institute
      • • Institute of Life Sciences
      Walloon Region, Belgium
  • 2011
    • Belgian Scientific Institute for Public Health
      Bruxelles, Brussels Capital Region, Belgium
    • University of Jyväskylä
      • Department of Biological and Environmental Science
      Jyväskylä, Province of Western Finland, Finland
  • 2009
    • Lawrence Berkeley National Laboratory
      • Biological Data Management and Technology Center (BDMTC)
      Berkeley, California, United States
  • 1989–1999
    • Ghent University
      • Laboratory of Microbiology
      Gand, Flemish, Belgium
  • 1992
    • Harvard University
      • Department of Chemistry and Chemical Biology
      Cambridge, Massachusetts, United States