Microsporidia
Microsporidia
Taxonomic Classification
Overview
Microsporidia are highly specialized obligate intracellular parasites, once thought to be protists but now recognized as highly derived fungi. These minute organisms (1-40 μm) infect virtually all animal groups and some protists. They possess one of the smallest known eukaryotic genomes and have lost many typical eukaryotic features, including mitochondria. Their unique infection mechanism involves a polar tube that penetrates host cells.
Key Characteristics
- Obligate intracellular parasites
- Extremely reduced genomes and cellular organization
- Lack mitochondria, possess mitosomes
- Unique infection apparatus with polar filament
- Resistant spores as transmission stage
- Minute size (1-40 μm spores)
Ecological Role
Parasites of virtually all animal phyla, with significant impacts on insect populations, fish, and immunocompromised humans. May regulate host populations in natural ecosystems. Used as biological control agents for insect pests. Important pathogens in aquaculture.
Diversity
Over 1,500 described species, likely tens of thousands exist
Reproduction
Asexual reproduction within host cells, producing resistant spores. Sexual reproduction has been documented in some species. Spores germinate by extruding a polar tube that injects sporoplasm into new host cells.
Distribution
Worldwide, found in terrestrial and aquatic environments wherever hosts occur
Notable Features
- Among smallest eukaryotic genomes (2.3-19.5 Mb)
- Unique infection mechanism via polar tube
- Infect all major animal groups
- Cause diseases in immunocompromised humans
- Used in biological control of insect pests
- Represent extreme evolutionary reduction
- Some species transmitted through food and water
Economic Importance
- Significant pathogens in aquaculture (especially fish and shrimp)
- Biological control agents for insect pests
- Opportunistic infections in HIV/AIDS patients
- Economic losses in honeybee populations (Nosema species)
- Contamination concerns in water supplies
- Research models for genome evolution and host-parasite interactions
Example Species
Explore representative species from Microsporidia that demonstrate the diversity and importance of this phylum.
Honeybee Microsporidian
Nosema ceranae
Nosema ceranae is an obligate intracellular parasite of honeybees, causing nosemosis. Originally infecting Asian honeybe...
Human Microsporidian
Enterocytozoon bieneusi
Enterocytozoon bieneusi is the most common microsporidian infecting humans, causing chronic diarrhea particularly in imm...
Rabbit Microsporidian
Encephalitozoon cuniculi
Encephalitozoon cuniculi is a microsporidian parasite primarily affecting rabbits but capable of infecting many mammals ...