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Pathogenic fungi are fungi that cause disease in humans or other organisms. Although fungi are eukaryotic , many pathogenic fungi are microorganisms . [ 1 ] Approximately 300 fungi are known to be pathogenic to humans; [ 2 ] their study is called " medical mycology ".
They were once considered protozoans or protists, but are now known to be fungi, [8] or a sister group to true fungi. [9] These fungal microbes are obligate eukaryotic parasites that use a unique mechanism to infect host cells. [7] They have recently been discovered in a 2017 Cornell study to infect Coleoptera on a large scale.
Examples exist in the mushroom genera Armillaria and Xerula, both in the Physalacriaceae. Occasionally, basidiospores are not formed and parts of the "basidia" act as the dispersal agents, e.g. the peculiar mycoparasitic jelly fungus, Tetragoniomyces or the entire "basidium" acts as a "spore", e.g. in some false puffballs (Scleroderma).
Archaea were initially classified as bacteria, receiving the name archaebacteria (/ ˌ ɑːr k i b æ k ˈ t ɪər i ə /, in the Archaebacteria kingdom), but this term has fallen out of use. [5] Archaeal cells have unique properties separating them from Bacteria and Eukaryota. Archaea are further divided into multiple recognized phyla.
The tree of life. Two domains of life are Bacteria (top branches) and Archaea (bottom branches, including eukaryotes). The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea.
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
Archaea share this defining feature with the bacteria with which they were once grouped. In 1990 the microbiologist Woese proposed the three-domain system that divided living things into bacteria, archaea and eukaryotes, [42] and thereby split the prokaryote domain. Archaea differ from bacteria in both their genetics and biochemistry.
Fungi are everywhere, but only some cause disease. [13] Fungal infection occurs after spores are either breathed in, come into contact with skin or enter the body through the skin such as via a cut, wound or injection. [3] It is more likely to occur in people with a weak immune system. [14]