Bachewich Research, Dept Biology, Concordia University

Candida albicans is a commensal fungus of the gasterointestinal and genitourinary tract. In healthy individuals it seldom causes diseases more serious than diaper rash or vaginal yeast infections. However, it has the capacity to cause serious to life-threatening diseases such as candidaisis and candidaemia, particularly in immune-compromised individuals. C. albicans has three types of cells—yeasts, pseudo-hyphae, and true hyphae (see image). The ability to switch between these morphologies is important for virulence. Hyphae of C. albicans can penetrate and destroy cells in tissue culture (see movie). The movie images were collected over 13 h by Dr. Anne Marcil in Dr. Malcolm Whiteway's research group at BRI-NRC, Montreal PQ. We are investigating the role of the hypA morphogenesis gene in these processes.

Permission to copy this movie must be obtained from Dr. Anne Marcil or Dr. Malcolm Whiteway, NRC-BRI. Clickto play the movie (13 MB).

Chivers Lab, Dept Biology, U Saskatchewan

We are studying the relationship between fish health and their ability to respond effectively to pathogens including the oomycete (water mold), Saprolegnia. The wild-caught fathead minnow from Pike Lake SK pictured below is infected with an oomycete, which has produced the filaments (hyphae) extending from it. The living Saprolgnia ferax hypha is stained with three fluorescent endomembrane probes. The growth rate of the hypha in the movie was 6.6 µm/min over 548 sec.

Student researchers: Colin Halbgewachs () and Robyn Pollock ().

The fluorescent image was taken by Michelle Hubbard; the fish image by Dennis Dyck. Clickbelow to play the movie (13 MB).

Dahms Lab, Dept Chemistry and Biochemistry, U Regina

Maturation of the hyphal wall of Aspergillus nidulans using atomic force microscopy (AFM) and cryo-scanning electron microscopy (cryoSEM eg.). These complementary methods image cell surfaces in frozen hydrated (cryoSEM) or vapour-fixed critical point dried samples (SEM and AFM). AFM has superb xyz resolution. CryoSEM preserves lifelike spatial relationships and has excellent xy resolution. We are now using AFM to image the surface of growing hyphae.

This AFM image was collected by Ms. Hui Ma:

This cryoSEM was taken with the assistance of George Braybrook, Scanning Electron Microscope Lab, Dept Earth & Atmospheric Sciences, U Alberta:

Gough Lab, Dept Chemistry, U Manitoba

Molecules can be identified by their energy absorption characteristics. Infrared wavelengths can be used for in situ chemical analysis based on their interactions with specific chemical bonds. We are using synchrotron FTIR spectroscopy to characterize maturation-related changes in Aspergillus nidulans hyphae at NSLS (Brookhaven, NY), SRC (U Wisconsin-Madison) and CLS (U Saskatchewan).

Photomicrographs and FTIR spectra acquired along hyphae of permissive (a) and restrictive (b) A. nidulans hypA1 phenotypes. Scale bars 50 µm. This image is from Szeghalmi, Kaminskyj and Gough, A synchrotron FTIR microspectroscopy investigation of fungal hyphae grown under optimal and stressed conditions Analytical and Bioanalytical Chemistry DOI 10.1007/s00216-006-0850-2

The image below was collected at NSLS.

Pictured below, from left to right, are Dr. Susan Kaminskyj, Dr. Kathy Gough, and Konstantin Jilkine at CLS 01B1-1 (Mid IR) beam line, August 2007:

Sanders Lab, Dept Chemistry, U Saskatchewan

We are studying the role of an enzyme, UDP-Galactopyranose mutase, in a simple eukaryotic model system. Mutase catalyzes the interconversion of 5- and 6-membered forms of galactose prior to its incorporation into the cell wall or the extracellular matrix, depending on the organism. The structure of mutase was first determined for prokaryotes including E. coli (below, left). Genomics projects have revealed similar sequences in eukaryotes including Leishmania major (below, right). We will be characterizing the Aspergillus nidulans mutase homologue.

Dr. Karin von Straaten ()

The images:

• on the left, mutase from Eschericia coli (Sanders et al 2001 Nature Structural Biology 8: 858-63), with three domains shown in different colours.; and
  
  
• on the right, proposed structure of mutase from Leishmania major shown in blue, threaded onto the E. coli structure shown in red using Modeller.
  
  

Wei Lab, Dept Biology, U Saskatchewan

Host-pathogen interactions between an obligate biotrophic pathogen, the powdery mildew Blumeria graminis tritici, and susceptible and resistant strains of wheat. This image shows a scanning electron micrograph (SEM) of a Blumeria spore(s) that has produced a germtube (gt) and appressorium (app). This specimen was rapidly frozen and freeze dried. We are combining SEM imaging with energy dispersive spectroscopy to study events critical to host penetration.

This image was collected by Brandon van Leer, FEI, Hillsboro OR, on uncoated material, using a Nova NanoLab 600 Dual Beam that uses a Sirion FEG electron column and is equipped with EDS chemical analysis.

Pictured: spore, germ tube and appressorium