Biology 625
Fall semester lecture note outline

Updated: 24 February 2004

The text below simply represents a crude lecture outline of one of the topics covered in class. It is not meant to substitute for attending lectures or ignoring the textbook. Additional material, including line drawings, kodachromes, and more extensive information on life-cycles and basic biology, will be supplied in the lectures.

TOPIC 36. The Phylum Microspora

  1. about 1000 described species to date; many more to be described
  2. most species infect invertebrates, especially arthropods. However, some vertebrate hosts also known
  3. all species parasitic and with intracellular development
  4. all species produce spores
    1. spheroid, ovoid, ellipsoid, or cylindroid
    2. trilaminar wall
    3. spores usually small, highly refractile, 2-6 micrometers in length; few species with spores up to 20 micrometers in length
    4. spores contain an infective sporoplasm that may be uninucleate or binucleate; most sporoplasms lie within coils of polar tube; mitochondria absent
    5. spores without a suture or obvious pore
    6. contain an extrusion apparatus termed a polar tube; coiled within the spore
    7. each spore contains a vacuolar-like organelle termed a polaroplast; this structure is composed of stacks of mebranous tubules
    8. polar cap covering attached end of polar tube at one pole of spore
    9. posterior vacuole at end opposite the polaroplast
  5. life-cycle
    1. spores ingested
    2. polar tube explosively expelled turning inside out; pierces host cell. the polaroplast becomes incorporated as part of polar tube, allowing the polar tube to become considerably larger than in its dormant state
    3. sporoplasm rapidly flows through polar tube, effectively injected into a host cell
    4. multiple karyokinesis so that large, multinucleate plasmodium formed (asexual reproduction)
    5. cytokinesis to form "trophozoites" or "merozoites," analogous to merogony in the Apicomplexa. Essentially, multiple fission
      1. some species undergo asexual reproduction more than once
      2. some species have 2 closely associated nuclei in each trophozoite; termed diplokarya
    6. eventually, formation of multinucelate sporoplasm with nuclei destined to produce spores
    7. some, but not all, species have nuclei that undergo meiosis so that haploid nuceli are produced and spores with haploid nuclei. These spores not directly infective for hosts, so a second host is involved where syngamy occurs and other spores produced. Typical genera here include Amblyospora which alternates between mosquitos and copepods (1992, Dis Aquat Org 13: 17-28).
    8. most species have nuclei that remain diploid. Multinucleate (sporogonial) plasmodia formed. This can either involve internal spore formation where areas of cytoplasm become segregated around nuclei, or formation of external pansporoblasts (i.e. budding) that give rise to developing spores separate from main plasmodium.
  6. representative species
    1. Amblyospora californica (Culex tarsalis/Macrocyclops albidus)
    2. Ameson michaelis (blue crabs)
    3. Encephalitozoon cuniculi (kidneys of rabbits and tissues of other mammals)
    4. Glugea stephani (flatfish, including flounder)
    5. Nolleria pulicis (cat fleas, Ctenocephalides felis)
    6. Nosema apis (honeybees)
    7. Nosema bombycis (silk moth larvae)
    8. Nosema whitei (flour beetles)
    9. Pleistophora typicalis (sculpin)
    10. Vairimorpha invictae (fire ants)
  7. Species known to infect humans (adapted from Costa and Weiss, 2000, Drug Resistance Updates, 3: 384-399)
    1. Encephalitozoon cuniculi (disseminates and infects a wide range of host cell types; hepatitis, keratoconjunctivitis, peritonitis, sinusitis, renal failure, encephalitis etc.; treated with albendazole)
    2. Encephalitozoon hellem (disseminates and infects a wide range of host cell types; renal failure, keratoconjunctivitis, pneumonia, etc.; treated with albendazole)
    3. Encephalitozoon intestinalis (syn. Septata intestinalis) (disseminates and infects a wide range of host cell types; intestinal involvement, keratoconjunctivitis, sinusitis, osteomyelitis, etc.; treated with albendazole)
    4. Enterocytozoon bieneusi (intestinal infection; most common of all microsporidia in humans; no effective treatment although fumagillin analogs show promise; some reports suggest albendazole may have some effect)
    5. Trachipleistophora hominis (disseminated; myositis, keratoconjunctivitis, encephalitis, etc.; treated with albendazole)
    6. Trachipleistophora anthropopthera (disseminated; myositis)
    7. Pleistophora spp. (myositis)
    8. Vittaforma corneae (syn. Nosema corneae) (necrotizing keratitis and/or corneal ulcers)
    9. Nosema ocularum (necrotizing keratitis and/or corneal ulcers)
    10. Brachiola connori (syn. Nosema connori) (myositis)
    11. Brachiola vesiculatum (myositis; treated with albendazole and itraconazole)
    12. Brachiola algerae (syn. Noesema algerae) (myositis, dermal involvement)
    13. Microsporidium africanum
    14. Microsporidium celonensis

Take me home

Home | Search | What's New | Help | Comments
Kansas State University | Biology Division