Coccidioides posadasii

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Coccidioides posadasii


Higher order taxa

Eukaryota; Fungi/Metazoa group; Fungi; Dikarya; Ascomycota; Pezizomycotina; Eurotiomycetes; Eurotiomycetidae; Onygenales; mitosporic Onygenales; Coccidioides [Others may be used. Use NCBI link to find]


NCBI: Taxonomy

Coccidioides posadasii

Description and significance

C. posadasii is a pathogenic fungus found in the alkaline rich soil of arid/semiarid regions in Texas, Arizona, Mexico, and South America [12]. It was formally known as the non-California C. immitis because it was morphologically identical to this species. But after comparison of RFLPs of 10 DNA loci from clinical isolates of C. immitis from California, Arizona, and Texas, a significant difference among the allele frequencies was found, thus, suggesting that C. immitis consisted of two different species: C. immitis and C. posadasii [6].

C. posadasii grows in the soil as infectious cells called arthroconidia which are dispersed into the air. And when inhaled by a host, the arthroconidia mature and divide into endospores 60 to >100 micrometers in size in the host lung [3] causing a respiratory disease called coccidioidomycosis. 

The characterization of phenotypic differences in this pathogen is the key toward understanding its immune response and disease causing capabilities [6].

Genome structure

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?

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?

Current Research

1. In the article, “Evolution of the Mating Type Locus: Insights Gained from the Dimorphic Primary Fungal Pathogens Histoplasma capsulatum, Coccidioides immitis, and Coccidioides posadasii,” genomic analysis, dirt sequencing, and bioinformatics was used to determine that the mating type (MAT) locus of three species named. It was found that the MAT loci of H. capsulatum, C. immitis, and C. posadasii contained alleles that encoded either an α-box protein or an HMG domain protein which is in accordance to a heterothallic sexual cycle. These MAT sequences also led to the creation of a PCR test that allowed mating type to be determined rapidly.

2. In the study, “Detection of Coccidioides Species in Clinical Specimens by Real-time PCR,” researchers developed a real-time PCR assay able to rapidly and safely diagnose coccidiomycosis from clinical specimens. The ITS2 region of Coccidioides was selected as the target for PCR assay, and after the testing of various specimens and comparison of results was completed, it was determined that the real-time PCR assay was an effective method for diagnosing coccidiomycosis, but lacked the ability to distinguish between the two species of Coccidioides: C. immitis and C. posadasii.


[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