An endosymbiont or endobiont is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. This phenomenon is known as endosymbiosis. Examples are nitrogen-fixing bacteria, which live in the root nodules of legumes, single-cell algae inside reef-building corals and bacterial endosymbionts that provide essential nutrients to insects.
Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci, bacilli, or threads. The genus was named after Howard Taylor Ricketts in honor of his pioneering work on tick-borne spotted fever.
Ticks are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by feeding on the blood of mammals, birds, and sometimes reptiles and amphibians. The timing of the origin of ticks is uncertain, though the oldest known tick fossils are from the Cretaceous period, around 100 million years old. Ticks are widely distributed around the world, especially in warm, humid climates.
Tularemia, also known as rabbit fever, is an infectious disease caused by the bacterium Francisella tularensis. Symptoms may include fever, skin ulcers, and enlarged lymph nodes. Occasionally, a form that results in pneumonia or a throat infection may occur.
Wolbachia is a genus of gram-negative bacteria that can either infect many species of arthropod as an intracellular parasite, or act as a mutualistic microbe in filarial nematodes. It is one of the most common parasitic microbes of arthropods, and is possibly the most common reproductive parasite in the biosphere. Its interactions with its hosts are often complex. Some host species cannot reproduce, or even survive, without Wolbachia colonisation. One study concluded that more than 16% of neotropical insect species carry bacteria of this genus, and as many as 25 to 70% of all insect species are estimated to be potential hosts.
Francisella tularensis is a pathogenic species of Gram-negative coccobacillus, an aerobic bacterium. It is nonspore-forming, nonmotile, and the causative agent of tularemia, the pneumonic form of which is often lethal without treatment. It is a fastidious, facultative intracellular bacterium, which requires cysteine for growth. Due to its low infectious dose, ease of spread by aerosol, and high virulence, F. tularensis is classified as a Tier 1 Select Agent by the U.S. government, along with other potential agents of bioterrorism such as Yersinia pestis, Bacillus anthracis, and Ebola virus. When found in nature, Francisella tularensis can survive for several weeks at low temperatures in animal carcasses, soil, and water. In the laboratory, F. tularensis appears as small rods, and is grown best at 35–37 °C.
Coliform bacteria are defined as either motile or non-motile Gram-negative non-spore forming bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35–37 °C. They can be aerobes or facultative aerobes, and are a commonly used indicator of low sanitary quality of foods, milk, and water. Coliforms can be found in the aquatic environment, in soil and on vegetation; they are universally present in large numbers in the feces of warm-blooded animals as they are known to inhabit the gastrointestinal system. While coliform bacteria are not normally causes of serious illness, they are easy to culture, and their presence is used to infer that other pathogenic organisms of fecal origin may be present in a sample, or that said sample is not safe to consume. Such pathogens include disease-causing bacteria, viruses, or protozoa and many multicellular parasites.
Spiroplasma is a genus of Mollicutes, a group of small bacteria without cell walls. Spiroplasma shares the simple metabolism, parasitic lifestyle, fried-egg colony morphology and small genome of other Mollicutes, but has a distinctive helical morphology, unlike Mycoplasma. It has a spiral shape and moves in a corkscrew motion. Many Spiroplasma are found either in the gut or haemolymph of insects where they can act to manipulate host reproduction, or defend the host as endosymbionts. Spiroplasma are also disease-causing agents in the phloem of plants. Spiroplasmas are fastidious organisms, which require a rich culture medium. Typically they grow well at 30 °C, but not at 37 °C. A few species, notably Spiroplasma mirum, grow well at 37 °C, and cause cataracts and neurological damage in suckling mice. The best studied species of spiroplasmas are Spiroplasma poulsonii, a reproductive manipulator and defensive insect symbiont, Spiroplasma citri, the causative agent of citrus stubborn disease, and Spiroplasma kunkelii, the causative agent of corn stunt disease.
"Candidatus Midichloria" is a candidatus genus of Gram-negative, non-endospore-forming bacteria, with a bacillus shape around 0.45 µm in diameter and 1.2 µm in length. First described in 2004 with the temporary name IricES1, "Candidatus Midichloria" species are symbionts of several species of hard ticks. They live in the cells of the ovary of the females of this tick species. These bacteria have been observed in the mitochondria of the host cells, a trait that has never been described in any other symbiont of animals.
Coxiella refers to a genus of Gram-negative bacteria in the family Coxiellaceae. It is named after Herald Rea Cox (1907–1986), an American bacteriologist. It is one of the Gammaproteobacteria.
Blattabacterium is a genus of obligate mutualistic endosymbiont bacteria that are believed to inhabit all species of cockroach studied to date, with the exception of the genus Nocticola. The genus' presence in the termite Mastotermes darwiniensis led to speculation, later confirmed, that termites and cockroaches are evolutionarily linked.
Arsenophonus nasoniae is a species of bacterium which was previously isolated from Nasonia vitripennis, a species of parasitoid wasp. These wasps are generalists which afflict the larvae of parasitic carrion flies such as blowflies, houseflies and flesh flies. A. nasoniae belongs to the phylum Pseudomonadota and family Morganellaceae. The genus Arsenophonus, has a close relationship to the Proteus (bacterium) rather than to that of Salmonella and Escherichia. The genus is composed of gammaproteobacterial, secondary-endosymbionts which are gram-negative. Cells are non-flagellated, non-motile, non-spore forming and form long to highly filamentous rods. Cellular division is exhibited through septation. The name 'Arsenophonus nasoniae gen. nov., sp. nov.' was therefore proposed for the discovered bacterium due to its characteristics and its microbial interaction with N. vitripennis. The type strain of A. nasoniae is Strain SKI4.
Francisella novicida is a bacterium of the Francisellaceae family, which consist of Gram-negative pathogenic bacteria. These bacteria vary from small cocci to rod-shaped, and are most known for their intracellular parasitic capabilities. In this family, six species have been identified; however, the species F. novicida is under intense scrutiny. Though some believe it should be classified with its own species designation, others argue it should be reclassified as a subspecies under F. tularensis. If it were to be classified as a subspecies, F. novicida would join the other known subspecies including F. t. tularensis and F. t. holarctica. Biochemical assays for identifying F. tularensis subtypes and strains are not ideal because the results are often non-definitive and subject to variation, therefore these assays should only be considered as supplementary tests for identification of Francisella species and subspecies. Several strains of F. novicida or F. novicida-like bacteria have been described, and these strains may be resolved by PCR-based methods.
Aspergillus restrictus is a species of fungus in the genus Aspergillus. It is from the Restricti section. The species was first described in 1931. It is xerophilic, frequently found in house dust. Studies have suggested that it is an allergen implicated in asthma. In 2016, the genome of A. restrictus was sequenced as a part of the Aspergillus whole-genome sequencing project - a project dedicated to performing whole-genome sequencing of all members of the genus Aspergillus. The genome assembly size was 23.26 Mbp.
Arsenophonus is a genus of Morganellaceae, of the Gammaproteobacteria. Members of the Arsenophonus genus are increasingly discovered bacterial symbionts of arthropods that are estimated to infect over 5% of arthropod species globally and form a variety of relationships with hosts across the mutualism parasitism continuum. Arsenophonus bacteria have been identified in a diversity of insect taxa, including economically important species such as the Western honey bee and the rice pest Nilaparvata lugens.
Bacteroides dorei is a species of bacteria within the genus Bacteroides, first isolated in 2006. It is found in the intestinal systems of humans and animals. Research is being conducted to better understand the relationship Bacteroides dorei has on the human intestinal system and the autoimmune disease, Type 1 Diabetes (T1D).
Several small RNAs have been identified in Francisella tularensis, pathogenic bacterium that causes the disease tularaemia. Very little is known about Francisella's regulatory networks that allow this bacterium to survive in many environments.
Aspergillus chevalieri is a species of fungus in the genus Aspergillus. It is from the Aspergillus section. The fungi in the Aspergillus section are known for their ability to grow at extremely low water activities. The species was first described in 1926. It has since been reported as an opportunistic pathogen causing skin infections.
Aspergillus spinulosporus is a species of fungus in the genus Aspergillus. It is from the Nidulantes section. It was first described in 2016. It has been reported to produce asperthecin, echinocandin B1, desferritriacetylfusigen, and sterigmatocystin.
Paramecium biaurelia is a species of unicellular ciliates under the genus Paramecium, and one of the cryptic species of Paramecium aurelia. It is a free-living protist in water bodies and harbours several different bacteria as endosymbionts. Although the bacteria are parasites by definition, they also exhibit mutual relationship with the protist by providing survival benefits. It is used as an organism model in the study of the effects of gravitational forces in different environments.
