Microsporidia

Tiny living things called microsporidia live inside animals. They are very small. Some are even smaller than other tiny life forms.

These microbes use a special tool to live in hosts. They have a tiny tube that works like a needle. This tube pops out to get inside a cell.

They can live in many different animals. Most live in bugs, but they also live in fish. Some can even live in people.

These tiny things can stay safe for a long time. Their hard shells let them live outside a host for years. They can even live inside other tiny parasites!

Scientists study them to learn more about life. They are very interesting to find.

Microsporidia are tiny living things called fungi. They are parasites. This means they live inside other living things to survive. They are some of the smallest eukaryotes, which are complex cells.

Their spores are very small, between 1 and 12 micrometers.

Microsporidia use a clever way to enter a host. They make a tough spore with a hard wall. Inside, they have a coiled tube called a polar filament. When the spore is in a host's gut, it builds up pressure. The wall breaks, and the tube shoots out like a needle. This needle pierces the host's cells so the parasite can get inside.

These microbes live in many animals. Most infect insects, but they also live in fish and crabs. Some can even infect humans. Some species are so strong they take over a host cell completely. They make a large mass called a xenoma.

Scientists even study them to help control pests. They are looking at ways to use them to stop malaria. This could help keep mosquitoes from spreading the disease.

Microsporidia are a group of tiny living things known as fungi. They are parasites, which means they must live inside a host to survive. These microbes are some of the smallest eukaryotes, which are complex cells.

Their spores are very small, measuring only 1 to 12 micrometers. Most species are oval or pear-shaped, but some look like rods or spheres. They are very tough and can survive outside a host for several years. These tiny organisms are found in almost all major groups of animals.

To infect a host, microsporidia use a very clever mechanism. The spore has a thick wall made of three layers. Inside the spore, a long, thread-like tube called a polar filament is coiled up. When the spore reaches a host's gut, it builds up internal pressure. The rigid wall eventually ruptures at its thinnest point. This pressure forces the polar filament to shoot out like a needle. The tube pierces the host's cell so the parasite can enter. Once inside, the parasite grows and eventually makes new spores.

Scientists have spent a long time learning about these microbes. In 1884, a researcher named Balbiani used the name Microsporidium. For a long time, people thought they were protozoans or protists. Later, they were grouped with other organisms called Archezoa. However, modern research has changed these ideas. We now know they are specialized fungi or a sister group to fungi. This is because they have lost certain parts, like mitochondria, to live as parasites. They use small structures called mitosomes instead.

There are many different types of microsporidia in the world. Scientists have named about 1,500 species, but there may be over one million. About 10 percent of these known species infect vertebrates, which are animals like fish or humans. Some species, like Trachipleistophora hominis, can cause a disease in humans called microsporidiosis.

They also infect insects, crustaceans, and fish. Some are even hyperparasites, which means they are parasites that live inside other parasites. For example, some infect tiny flatworms that are already inside a fish.

Microsporidia can change how a host lives and grows. In insects, they can cause things like gigantism or change the host's sex. In extreme cases, the parasite takes over a cell to form a large mass called a xenoma.

Scientists are even looking for ways to use them for good. They are studying how certain species can stop mosquitoes from spreading malaria. By infecting mosquitoes, the parasites can shorten the mosquito's life. This might help stop the disease from reaching more people. It is a way to use one tiny living thing to help others.

Microsporidia are a group of spore-forming, unicellular parasitic fungi. They are obligate eukaryotic parasites, meaning they must live inside a host cell to survive. These microbes are among the smallest eukaryotes in existence. Their spores typically measure between 1 and 12 micrometers. Microsporidia that infect mammals are even smaller, ranging from 1.0 to 4.0 micrometers. Because they live as parasites, they have evolved to have the smallest eukaryotic genomes.

The infection process relies on a highly specialized mechanism. The spore is protected by a three-layered wall. This wall includes an outer electron-dense exospore, a middle endospore containing chitin, and a thin internal plasma membrane. Inside the spore, a long, thread-like polar filament is coiled in the posterior half. The anterior half contains a harpoon-like apparatus and a polaroplast, which is a membrane structure. When the spore enters a host's gut, it builds up osmotic pressure. This pressure causes the rigid wall to rupture at its thinnest point, the apex. The posterior vacuole then swells, forcing the polar filament to eject rapidly. This filament acts like a hypodermic needle to penetrate the host's gut epithelium. Once inside the cytoplasm, a sporoplasm grows and eventually produces new spores.

Microsporidia affect a wide variety of hosts. They are restricted to animal hosts, and all major animal groups host them. Most species infect insects, but they also cause diseases in fish and crustaceans. Approximately 10 percent of known species infect vertebrates. Some species can even infect humans, causing a disease called microsporidiosis. At least 14 species across eight genera are recognized as human pathogens, such as Trachipleistophora hominis. Some microsporidia are even hyperparasites. This means they are parasites that live inside other parasites. For example, the species Nosema podocotyloidis infects a digenean flatworm, which is itself a parasite of a fish.

These parasites can significantly alter their hosts. In insects, they can cause parasitic castration, gigantism, or changes in the host's sex. In extreme cases, the microsporidium takes complete control of the host cell's metabolism and reproduction. This results in the formation of a large mass called a xenoma.

Some species are lethal, while others are used for the biological control of insect pests. Microsporidia can also be passed from parent to offspring through vertical transmission. In insects, this often happens through transovarial transmission, where parasites move from a female's ovaries into her eggs. This allows the infection to multiply within the larvae.

Our understanding of microsporidia has changed significantly over time. In 1884, G. Balbiani used the name Microsporidium. For a long time, scientists thought these organisms were primitive protozoans or protists. They were even placed in a group called Archezoa. However, modern research has proven this theory wrong. We now know they are highly developed and specialized fungi or a sister group to fungi. They did not stay primitive; instead, they dispensed with functions like mitochondria because the host provides them. Instead of mitochondria, they possess smaller structures called mitosomes. They also lack motile structures like flagella.

Recent studies have highlighted the massive scale of these microbes. While about 1,500 species have been named, there are likely more than one million species in existence. A 2017 Cornell study discovered that they infect beetles, known as Coleoptera, on a large scale. Their genomes are remarkably small, ranging from 2.5 to 11.6 Mb. This size is similar to many bacteria. These small genomes encode between 1,848 and 3,266 proteins. Their genomic architecture varies, with differences in gene location and methylation levels. Some species even show evidence of horizontal gene transfer, gaining genes from animals, bacteria, or other fungi.

Microsporidia may actually help humans fight disease. Scientists are exploring the use of certain species to control malaria. For example, the species Vavraia culicis infects mosquitoes. Infection in Anopheles gambiae reduces the transmission of malaria and shortens the mosquito's lifespan. In 2020, researchers found that Microsporidia MB in An. arabiensis significantly impaired the transmission of Plasmodium falciparum. Because many malaria-infected mosquitoes die before the parasite is mature, increasing mosquito mortality could reduce malaria transmission to humans. This makes these tiny parasites a potential tool for long-term disease control.