A Microbial Biorealm page on the genus Coccidioides immitis
Higher order taxa(1)
cellular organisms; Eukaryota; Fungi/Metazoa group; Fungi; Dikarya; Ascomycota; Pezizomycotina; Eurotiomycetes; Eurotiomycetidae; Onygenales; mitosporic Onygenales; Coccidioides
Description and significance
Coccidioides immitis is a dimorphic fungus (existing in two distinct forms) with a unique life cycle. In the soil, the organism exists as a mold with septated hyphae resembling a shape of a barrel. When entering a host, the arthroconidia (spores) break off from the hyphae and evolve into round structures called spherules. Then when inside the host, spherules grows and undergo internal division, forming smaller structures called endospores. Large spherules can rupture to release packets of endospores, resulting in new foci of infection within the host (2). Coccidioides immitis main habitat is in soil, geographically limited to California's San Joaquin valley region, and in the desert southwest and Mexico, where it co exists with its closest relative, Coccidioides posadasii.
Formal description of C. immitis was performed by Rixford and Gilchrist from a case observed in California in 1986 (3). However, the parasite was then still thought to be a protozoan. The correct taxonomic status of C. immitis as an ascomycete fungus was demonstrated by Ophuls and Moffit in 1900 (4) by culture on artificial of the fungal mycelia using arthrospores isolated from laboratory infections of guinea pigs. It is important to have its genome sequences because Coccidioides immitis, along with its relative Coccidioides posadasii, can cause a disease called Coccidioidomycosis (Valley Fever), and it is a rare cause of meningitis, mostly in immunocompromised persons, and the disease can be fatal. Persons afflicted with HIV/AIDS are highly susceptible to Coccidioidomycosis and suffer a high mortality rate from the disease. (5).
The current total unique contig length of Coccidioides immitis genome is 28,876,843 bp (base pairs); the estimated genome size is 29 Mb. Also, Coccidioides immitis strain RS was sequenced by way of sequencing each end of plasmids and Fosmids from libraries containing randomly sheared fragments of 4 kb, 10 kb, and 40 kb average size respectively. Coccidioides immitis strains contain either a MAT1-1 or a MAT1-2 idiomorph, which is 8.1 or 9 kb in length, respectively, the longest reported for any ascomycete species. MAT1-1 and MAT1-2 contain four or five genes, respectively, more than are present in the MAT loci of most ascomycetes. Along with their cDNA structures, all genes in the MAT loci are transcribed (6). An analysis of 436 Coccidioides isolates from patients and the environment indicates that in both Coccidioides immitis and C. posadasii, there is a 1:1 distribution of MAT loci, as would be expected for sexually reproducing species. The current assembly contains 50 sequence contigs in 7 supercontigs (scaffolds).(7)
Coccidioides immitis SOWgp gene was also isolated; SOWgp encodes an immunodominant, spherule outer wall glycoprotein that is presented as a component of a parasitic phase-specific, membranous layer at the cell surface. SOGwgp translates a 422-amino-acid (aa) polypeptide that contains 6 copies of a 41- to 47-residue tandem repeat enriched in proline (20.4 mol%) and aspartate (19.7%). Two additional isolates of C. immitis produce SOWgps of different molecular sizes (328 and 375 aa) and show a corresponding difference in the number of tandem repeats (four and five, respectively)(8). The recombinant polypeptide (rSOWp) was shown to bind to mammalian extracellular matrix (ECM) proteins in an in vitro assay, suggesting that the parasitic cell surface antigen may function as an adhesion. Deletion of the SOWgp gene by using a targeted gene replacement strategy resulted in partial loss of the ability of intact spherules to bind to ECM proteins and a significant reduction in virulence of the mutant strain. The parasitic cell surface glycoprotein encoded by the SOWgp gene appears to function as an adhesion and contributes to the virulence of C. immitis.(8)
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.
Edited by student of Rachel Larsen
2. Drutz, D. J., and M. Huppert. 1983. Coccidioidomycosis: factors affecting the host-parasite interaction. J. Infect. Dis. 147: 372-390
3. Rixford E, Gilchrist TC., 1896 Two cases of protozoan (coccidioidal) infection of the skin and other organs Johns Hopkins Hosp Rep1:209-268.
4. Ophuls, W. and H. Moffitt. 1900. A new pathogenic mould. Philadelphia Med. J. 5: 1471-1472.
5. Ampel, N. M., K. J. Ryan, P. J. Carry, M. A. Wieden, and R. B. Schifman. 1986. Fungemia due to Coccidioides immitis. Medicine. 65:312-321