Candida albicans causes common yeast infections. Saccharomyces are Ascomycota yeast forms that help to brew beer. The basidiomycetes or Basidiomycota have club-shaped structures called basidia that make basidiospores through the budding process and have basidiocarps, which are fruiting bodies. These participate in decomposition. The main clinical organism is Cryptococcus neoformans, which causes lung diseases in the immunosuppressed human. Some poisonous mushrooms are in this category as well. The Microsporidia are strictly unicellular and must replicate inside a host cell. They do not have peroxisomes, centrioles, or mitochondria so they are obligate intracellular pathogens. They do have spores that have a polar tubule, which can pierce the host cell membrane so the fungus can get into the cell. There is one species that will infect the gallbladder, GI tract, and lungs.
HELMINTHS Helminths do not have to be parasitic and are generally not microscopic but their larvae and eggs will be microscopic. The two main classifications are Nematodes, which are roundworms, and Platyhelminthes, which are flatworms. Most have very complex life cycles with the ability to infect more than one host. Those that are monoecious have both male and female reproductive organs, while others are considered dioecious because they are either male or female but not both in the same organism. Nematodes are the roundworms, containing about 15,000 different species. They do not have segments. The largest nematode is Ascaris lumbricoides, which can be a meter in total length. It is more common in developing countries. The most common roundworm infection is Enterobius vermicularis or pinworms. Toxocariasis is a rarer infection that can be gotten from cats or dogs. Hookworm infections are also rare. Each of these primarily infects the GI tract. Trichinellosis or trichinosis is a nematode infection from Trichinella spiralis. It is notable because, when gotten into the system through undercooked meat, the infectious organisms in larval form can form cysts in the muscles as well as the GI tract.
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