Fixation of microsporidian spores for electron microscopy

J I Ronny Larsson1

  • 1Department of Cell and Organism Biology, University of Lund, Helgonavagen 3, S-223 62 Lund, Sweden. ronny.larsson@cob.lu.se

Insights

Fixation methods for Nosema spores were evaluated. Paraformaldehyde and formaldehyde proved effective, with higher temperatures improving fixation for terrestrial host spores, and freezing preserved spore cytology.

Area of Science:

  • Microbiology
  • Parasitology
  • Cell Biology

Background:

  • Nosema species are important microsporidian parasites affecting various hosts.
  • Effective fixation of spores is crucial for accurate microscopic examination and research.
  • Previous fixation protocols may not be optimal for all Nosema species or sample types.

Purpose of the Study:

  • To compare the efficacy of different fixatives and conditions for Nosema apis and Nosema bombi spores.
  • To determine the impact of temperature and freezing on spore fixation quality.
  • To identify optimal fixation parameters for reliable cytological studies.

Main Methods:

  • Spores of Nosema apis and Nosema bombi (fresh and frozen) were subjected to fixation.
  • Various fixatives including paraformaldehyde, technical formaldehyde, and glutaraldehyde were tested.
  • Fixation was performed at different temperatures and time points.
  • The cytology of fixed spores was examined microscopically.

Main Results:

  • Paraformaldehyde and technical formaldehyde yielded fixation results comparable or superior to glutaraldehyde.
  • Increased fixation temperatures enhanced the quality of spore fixation, particularly for terrestrial host-derived spores.
  • Freezing of spores did not compromise their cellular structure or cytology.

Conclusions:

  • Paraformaldehyde and technical formaldehyde are effective alternatives to glutaraldehyde for Nosema spore fixation.
  • Optimizing fixation temperature is important for achieving high-quality results with spores from terrestrial hosts.
  • Freezing is a viable method for preserving Nosema spores for subsequent cytological analysis, without loss of structural integrity.

Related Concept Videos

Preparation of Samples for Electron Microscopy01:20

Preparation of Samples for Electron Microscopy

To be visualized by an electron microscope, either transmission or scanning, biological samples need to be fixed (stabilized) so the electron beam does not destroy them and dried thoroughly (desiccated/dehydrated) so the vacuum does not affect them. Fixation needs to be done as quickly as possible because the sample properties will start changing as soon as it is removed from its natural environment. For example, in a tissue sample, the oxygen levels begin decreasing, causing an altered...
Fixation and Sectioning01:03

Fixation and Sectioning

Two basic types of preparation are used to visualize specimens with a light microscope: wet mounts and fixed specimens.
The simplest type of preparation is the wet mount, in which the specimen is placed in a drop of liquid on the slide. A liquid specimen can be directly deposited on the slide using a dropper. Solid specimens, such as skin scraping, can be placed on the slide before adding a drop of liquid to prepare the wet mount. Sometimes the liquid is simply water, but stains are often added...
Fungal Phylum Microsporidia01:28

Fungal Phylum Microsporidia

Microsporidia are a group of obligate intracellular fungi that were initially classified as protists but were later reclassified based on phylogenetic, molecular, and structural evidence linking them to the Chytridiomycota. These unicellular, non-motile organisms are highly specialized parasites that infect a wide range of animal hosts, including humans. They have evolved extensive genomic and metabolic reductions, making them highly dependent on their hosts for survival.Morphology and Genomic...