Category Archives: microspordia

Postdoctoral Position in Bioinformatics – University of Ottawa

The Corradi Lab is currently seeking a postdoctoral fellow in Bioinformatics to work on projects related to Comparative and Population Genomics. The research will be led by Dr. Nicolas Corradi and carried out in a CIFAR (Canadian Institute for Advanced Research) – affiliated laboratory located in the Department of Biology of the University of Ottawa, Canada.

Website: http://corradilab.weebly.com/

The position is initially funded for one year, with the possibility of renewal for up to three years, depending on performance. The candidate is expected to work on two ongoing lab projects:

  1. Populations genomics of global samples of the bee-pathogen Nosema ceranae

    The recent decline in global populations of honey-bees has been attributed to a many factors, including infections from the microsporidian pathogen Nosema ceranae. Despite the potential threat that this parasite may have on global bee populations, the basic biology of this species is not well understood.
    The present project aims to increase our knowledge of the N. ceranae’s biology by exploring the extent, nature and function of genome diversity that exist both within and between dozens of parasite samples isolated globally (i.e. Spain, France, Turkey, Thailand, USA..etc…).
  2. Population genomics of global isolates of the model plant symbiont, Rhizophagus irregularis

    The Arbuscular Mycorrhizal Fungi (AMF) are ubiquitous plant symbionts that improve the ability of roots to uptake nutrients from soil and provide protection against plant pathogens. These organisms are intriguing as they harbor many nuclei within one cytoplasm throughout their entire life cycle. The genetic organization of these nuclei has been debated for years, but recent genome analyses in our lab are providing essential insights to this debate.

    The proposed projects aims to increase our knowledge of biology and evolution of these curious fungi and critical symbionts by investigating the genome diversity within and across different strains of the model AMF R. irregularis sampled globally.

For specific enquiries please contactDr. Nicolas Corradi (ncorradi@uottawa.ca).

Applicants are expected to have a strong background in either comparative genomics or populations genomics. Experience in either population genetics, environmental genomics, metagenomics, or ab-initio gene annotation and programming will be seen as an asset for the final selection of the candidate. Some basic training in bioinformatics (Perl, Python, or R) is desired.

A complete application package includes a CV, a one-page description of past research accomplishments and future goals, and the names and e-mail addresses of at least 2 references. The position opens immediately, and evaluation of applications will continue until a suitable candidate is found.

The University of Ottawa is a large, research-intensive university, hosting over 40,000 students and located in the downtown core area of Canada’s capital city. Ottawa is a vibrant, multicultural city with a very high quality of life.

Applications can be sent to Dr. Nicolas Corradi (ncorradi@uottawa.ca).

Representative publications:

  • Pelin A., Selman M., Laurent Farinelli, Aris-Brosou S. and N. Corradi. 2015. Genome analyses suggest the presence of polyploidy and recent human-driven expansions in eight global populations of the honeybee pathogen Nosema ceranae. Environmental Microbiology
  • Ropars J. and N. Corradi. 2015. Heterokaryotic vs Homokaryotic Mycelium in the Arbuscular Mycorrhizal Fungi: Different Techniques, Different Results? New Phytologist
  • Corradi, N. 2015. Microsporidians: Intracellular Parasites Shaped by Gene Loss and Horizontal Gene Transfer. Annual Review of Microbiology
  • Riley R., Charron P., Idnurm A., Farinelli F., Yolande D. , Martin F. and N. Corradi. 2014. Extreme diversification of the mating type–high?mobility group (MATA?HMG) gene family in a plant?associated arbuscular mycorrhizal fungus. New Phytologist
  • Tisserant E., Malbreil M. et al. 2013. Genome of an arbuscular mycorrhizal fungus provides insight into the oldest plant symbiosis. PNAS

Recent animal-associated fungal genome papers

The genomes of five dermatophyte fungi were sequenced and the analyses of their lifestyles presented in a new paper out in mBio in Martinez et al. 2012. The authors were able to identify gene family changes that associate with lifestyle changes including proteases that can degrade keratin suggesting how these species have adapted to obtaining nutrients from an animal host. The continued finding of fungal-specific kinase families in these fungi, extending the observations from previous studies in Coprinopsis and Paracoccidioides on the FunK1 kinase family, makes me hope we will some day get some molecular information on the specificity of these families in addition to these copy number observations.
Another paper published in Genome Research this summer from Emily Troemel‘s lab and the Broad Institute describes the sequencing of two microsporidia species that are natural parasites of Caenorhabditis.The paper reveals some suprising things about Microsporidia evolution including the presence of a clade-specific nucleoside H+ symporter which is only found in bacteria and some eukaryotes and not in any Fungi. The phyletic distribution suggested it was acquired more recently and couple from lateral gene transfer. This acquisition likely helps the microsporidia cells obtain nucleosides from the host since the parasite cannot synthesize these. There is also evidence of evolution of microsporidia-specific secretion signals in the hexokinases which may be a mechanism for delivery of these enzymes into host cells to catalyze rapid growth once inside the host. Many more gems in this paper including phylogenetic placement of the microsporidia from phylogenomic approaches (also see related recent work from Toni Gabaldon‘s lab).

Microsporidia genomes on the way

New genomes from Microsporidia are on the way from the Broad Institute and other groups, and will be a boon to those working on these fascinating creatures. Microsporidia are obligate intracellular parasites of eukaryotic cells and many can cause serious disease in humans. Some parasitize worms and insects too. The evolutionary placement of these species in the fungi is still debated with recent evidence placing them as derived members of the Mucormycotina based on shared synteny (conserved gene order), in particular around the mating type locus.  There is still some debate as to where this group belongs in the Fungal kingdom, with their highly derived characteristics and long branches they are still make them hard to place.  The synteny-based evidence was another way to find a phylogenetic placement for them but it would be helpful to have additional support in the form of additional shared derived characteristics that group Mucormycotina and Microsporidia. There is hope that increased number of genome sequences and phylogenomic approaches can help resolve the placement and more further understand the evolution of the group.

For data analysis, a new genome database for comparing these genomes is online called MicrosporidiaDB. This project has begun incorporating the available genomes and providing a data mining interface that extends from the EuPathDB project.

a mushroom and a microsporidia walk into a bar

These papers got lost in my drafts of things to write about.  Grants and overdue manuscripts are keeping me away from the blog.

  • Published work from Gary Foster’s lab in Applied Env Micro show progress on genetic engineering tools to express introduced genes in the basidiomycete mushroom system Clitopilus passeckerianus. C. passeckarianus produces an antibiotic, pleuromutilin, an important antibiotic. Cover photo [Press] They also showed the  5′ intron is important for efficient expression, something that has been shown several times in fungi and provides more evidence for the role of introns in promoting or regulating an aspect of gene expression or translation. Perhaps by splicing-dependent export.
  • Corradi et al – the genome of the microsporidia parasite of Daphnia (water flea). It’s as big as a fungal genome at 24Mb (S.cerevisiae is about 12Mb, Neurospora crassa about 40Mb) but only has about 2,100 genes (S.cerevisiae has ~6,000, N.crassa ~ 10,000). DOI: 10.1186/gb-2009-10-10-r106

Multiple Losses of sex within Microsporidia

Blogging about Peer-Reviewed ResearchA recent paper I found interesting (and I am sure was interesting to Dr Logsdon) about Multiple losses of sex within a single genus of Microsporidia. In the paper Joseph Ironside describes multiple instances of loss of sex within the Nosema/Vairimorpha group testing the hypothesis that the ancestral lineage was asexual. The group of species are undergoing rapid evolution where changes in lifestyle/lifecycle can occur even among very closely related lineages. In order to do test a formal hypothesis about whether the ancestor was asexual or sexual this the author had to improve the resolution of the phylogenetic relationships of these species and deal with some technical problems due to mutational biases in the rDNA sequences. The result he found was that the ancestral lineage was sexual and that asexuality arose multiple times among these species. He also provides a caution:

“The rapid evolution of microsporidian life cycles indicated by this study also suggests that even closely related microsporidia cannot be assumed to have similar life cycles and the life cycle of each newly discovered species must therefore be completely described.”

Something one has to be careful about in comparative studies of these species.

Continue reading Multiple Losses of sex within Microsporidia

Where’d the bees go? Ask a fungus

I don’t know if you’ve heard, but bee colonies are disappearing! Colony collapse disorder, as this phenomenon is better known, worries bee-keepers, agriculturalists and insect admirers all over: over 25% of the commerical bee colonies have disappeared since last fall. Normally, when a commerical hive collapses, honey is left behind in the box and wild bees set up shop on top of this free resource. But it seems that wild bees are also suffering, as honey filled boxes remain bee-less.

Researchers are scrambling to determine the cause of this bee die-off. Given the agricultural implications of losing one of nature’s best pollinators, time is of the essence. All sorts of hypotheses have been suggested, from pesticides or pathogens to solar flares and cell phones, but little evidence has been accumulated (mostly due to the fact that bee bodies are rarely found).

Fortunately, a recent breakthrough occured at UCSF. Joe DiRisi’s group found, in collaboration with other researchers, that Nosema ceranae (a microsporidian) had invaded several dead bees that had been found in the wild. There are several bee pathogens in the fungi (e.g. Ascosphera apis, whose genome was recently sequenced), but the discovery of Nosema infection is notable given that Nosema apis was the cause of widespread colony collapse disorder in Spain during the mid-nineties.

So is this pathogen the cause of the widespread colony die off? The jury is still out. But this represents some of the best evidence to date that fungi may be playing a role in this unfortunate event.