Cryptococcus gattii

This student page has not been curated.

Classification

"Cryptococcus gattii"

Eukaryota; Fungi; Basidiomycota; Tremellomycetes; Tremellales; Cryptococcaceae; Cryptococcus [1].

Introduction

Cryptococcus gattii is a fungal pathogen originating in Australian eucalyptus and almond trees [2]. that has been known to cause respiratory failure and serious central nervous system complications when infecting a human host [3]. Although the pathogenicity of C. gattii has in large part already been investigated, the global distribution of the microbe is unclear because strains of the fungus have only been found in places where samples are tested - areas of high-incidence [4]. This yeast is endemic in parts of Australia, and is normally found in tropical and subtropical areas. However, it has recently been identified as the cause of a cryptococcosis outbreak in British Columbia and parts of the American Pacific Northwest [2]. C. gattii is a leading cause of pulmonary cryptococcosis, basal meningitis, and cerebral cryptococcomas whose emergence, it has been suggested, is a result of changing climate conditions [5].

Genome structure

C. gattii has four main genetic groups (VGI, VGII, VGIII, VGIV); each of these genetic groups has 14 distinct chromosomes. Among these four genetic groups, the majority of genes are collinear, meaning that the same genes are found in the same locations on each of the chromosomes [2]. Amongst these four main groups, there is no evidence of any nuclear exchange. This is indicative of three separate but related species [6]. Sequencing of the mitochondrial genomes of VGI and VGII show adequate sequence similarity to suggest uniparental mitochondrial inheritance, but evidence of virulent traits between these distinct species in laboratory settings indicates that the transfer of mitochondrial genomes between species is possible [6]. 58 different genes located on 68 loci have been identified as showing divergent patterns of copy number variation amongst these 4 genetic groups [7]. The genome contains the CAP59 gene, which encodes the polysaccharide capsule, the LAC1 gene, which is involved in melanin synthesis, and the PLB1 gene, which encodes proteins that allow the yeast to invade host cells, among other proteins [2].

Cell structure

The cell diameter of most C. gattii cells typically ranges from 3-5 micrometers [3]. Most cells are roughly circular in shape, although it is capable of changing the size and shape of its capsule to avoid an immune response. C. gattii has a polysaccharide capsule, which is its main virulence factor [3]. C. gattii is typically found in the yeast form. It typically reproduces through asexual budding in both the environment and inside human hosts once an infection has occurred [2]. It is possible for sexual reproduction to occur. Cells can also undergo a dimorphic transition to hyphae to create a mycelium and generate basidiospores [2].

Ecology

Originally, C. gattii was only found in tropical and subtropical areas, like Australia and Southern California [3]. However, it has recently been found elsewhere, including the Pacific Northwest of the United States and Vancouver, Canada [9]. The fungus’ preferred environment changes depending on where it is found, which is how it has been found to survive in both tropical and temperate locations. It has been isolated in many places, including soil and man-made objects, like tires [9]. It can also live in seawater or freshwater for up to a year [9]. Plant material can promote the yeast’s fertility and possibly make it more pathogenic. The yeast are normally confined to individual trees because it has limited dispersal [2].

Other

2000-2001 Outbreak: Between January 1999 and December 2001, an outbreak of cryptococcosis occurred in British Columbia [12]. Approximately 38 cases of human cryptococcosis were recorded; all were caused by C. gattii. 95.2% of these human cases were identified as the VGII strain, and the remaining case was identified as VGI [12]. All isolates from environmental samples were identified as the VGII strain, which was determined to have caused this outbreak in British Columbia. British Columbia and the Pacific Northwest are both new locations for this microbe; C. gattii was previously found only in tropical and subtropical locations [12].

References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.

[1] Cryptococcus gattii VGI. Retrieved October 21st, 2016