Proteromonas is a genus of single-celled biflagellated microbial eukaryotes belonging to the superphylum Stramenopiles which are characterized by the presence of tripartite, hair-like structures on the anteriorly-directed larger of the two flagella. Proteromonas on the other hand are notable by having tripartite hairs called somatonemes not on the flagella but on the posterior of the cell. Proteromonas are closely related to Karotomorpha and Blastocystis, which belong to the Opalines group. Many species of Proteromonas are anaerobic and parasitic and can be found in the intestines of amphibians, reptiles, and mammals. The exact habitat and distribution of Proteromonas may vary depending on the species, but they are generally found as intestinal parasites in small animals. The most common and well-researched species is Proteromonas lacertae, which is a very common parasite found in the rectums of reptiles, mostly lizards.
Etymology It is unclear where the word "Proteromonas" first emerged, many of the earlier references to this genus are in French and Spanish. In the case of Proteromonas, the name of the genus likely refers to the position of the organism since they were discovered in the rectal entrance of lizards. The word "monas" comes from the Greek word "μονάς" which means "unit" or "single". The term "monas" is commonly used in scientific terminology as a suffix to denote a single-celled organism or a small, simple organism. The term was first introduced by Ernst Haeckel in 1866, who used the term "monera" to describe the simplest organisms that he believed represented the most primitive form of life. Today, the term "monera" is no longer used as a formal taxonomic group, but the suffix "-monas" is still used to describe certain single-celled organisms, such as bacteria and some protists. Therefore, the name Proteromonas may reflect the organism's location "in front of" other parasitic organisms found deeper within the intestines of hosts, with the suffix "-monas", which denotes the organism's single-celled nature.
Type species Proteromonas lacertae
History of knowledge One of the first mentions of Proteromonads was by Künstler in 1883, though none of his original publications are available online. Before him, the first Proteromonad was described by Grasse in 1879 who named the species Proteromonas lacertae and categorized it under a different genus: Monocercomonas. Then the species was redescribed in 1904 by Prowazek to belong to the genus Bodo. Finally, Alexeieff found a similar species to Proteromonas lacertae in the intestines of Urodeles and united them both under the Genus Hetermita in 1911. Alexeieff then published a complete overhaul of the taxonomy of many protists and finally described Proteromonas as its own genus with species under it in 1912, and in 1946 published a new species P. brevifilia and properly described the genus which allowed for further taxonomic classifications under the Proteromonas genus. Proteromonas were also once included in the Kinetoplastids groups since they shared many similarities such as a transitional helix, tubular cristae and a rhizoplast that passes from the flagella, through the Golgi and to the nucleus, and mastigonemes (which were later found to be somatonemes). Kinetoplatids are also commonly parasites as well, so Proteromonas was morphologically and characteristically really similar to that group. Genetic sequencing of subunit ribosomal RNA (SSU rRNA) proved that Proteromonas are descended from the first tubulocristae eukaryote and are also the descendants of some of the most ancestral Stramenopiles. Proteromonas was also largely debated over being included with Stramenopiles due to its lack of tripartite hairs on flagella and instead on the posterior part of the cell body. Proteromonas was also used as a comparison to add Blastocystis to the Stramenopiles since Blastocystis shares very little morphological similarities with Stramenoiples but is very closely related to Proteromonas.
Habitat and ecology Most species of Proteromonas are parasitic and can be found in the intestines of amphibians, reptiles, and mammals. When Proteromonas infects a reptile, it lives in the gut, where it feeds on the host's nutrients. Whether this actually causes any disease or health effects on the animal has not been determined though some sources say that the intestines of the lizard hosts containing these parasites had their folds destroyed and eroded to the outer wall of the intestine. Not much research has been done on the global effects of this parasite on animal health and population. Proteromonas is transmitted from one host to another through the blood and feces of infected reptiles, which can contaminate the environment and infect other animals. The genus is found in many different countries and was found to inhabit many different species of animals. Some countries where Proteromonas was found include Hungary Poland, Romania, Slovakia, India, the United States, Australia, Mexico, and many others. Since Proteromonas is found on virtually all continents, and in many species of animals, it is assumed they are ecologically diverse. The lizard family Lacertidae, in which P. lacertae are commonly found, are diverse all over Afro-Eurasia and live in all sorts of environments. Since Proteromonas are usually found in lizards, their populations are most common in non-polar climates where lizards can survive. Examples of Proteromonas species and their known hosts:
P. lacertae in rectum of frog (F. limnocharis). P. lacertae in blood of lizards (Acantho-dactylus erythrurus, Darevskia armeniaca, Pristurus carteri) but also many other lizards all over the world. P. grassei in the gut of a lizard (Hemidactylus prashadi). P. lacertae-viridis also in lizard intestine (Eumeces fasciaius, Phyronosoma cornutum, Scincella laterale, Sceloporus undulius, and Cnemidophorus sexlineatus). P. rattusi in rats. Also mentions in pigs, porcupines, and many rodents.
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