Angomonas deanei

Novymonas esmeraldas, Diplonema japonicum and Diplonema aggregatum are considered as good models for the understanding of the evolution of eukaryotes from prokaryotes,^[3][4][5] and on the origin of cell organelles (i.e. symbiogenesis).^[6][7]

phylogenetic analysis in 2011 revealed that it belongs to the genus Angomonas, thereby becoming Angomonas deanei. The symbiotic bacterium is a member of the β-proteobacterium that descended from the common ancestor with the genus Bordetella,^[1] or more likely, Taylorella.^[8] The two organisms have depended on each other so much that the bacterium cannot reproduce and the protozoan can no longer infect insects when they are isolated.^[9][10]

Universidade de Brasilia reported the biochemical properties and structural details based on transmission electron microscopy. They discovered that it harbours an endosymbiont, describing it as "probably bacterial" that provided the "trypanosomatid essential nutrients."^[13] The bacterial nature of the endosymbiont was confirmed in 1977 when it was shown that it could be killed by treating with an antibiotic chloramphenicol,^[14] and that it helps the host in synthesising the amino acid arginine from ornithine.^[15]

Instituto Oswaldo Cruz proposed a new genus Angomonas for the species.^[16][17] Phylogenetic study by Marta M.G. Teixeira and Erney P. Camargo at the University of São Paulo with their collaborators in 2011 validated the new species name A. deanei along with a description of a new related species A. ambiguus, which also contains the same bacterial endosymbiont.^[1]

β-barrel porin, which is a characteristic protein of Gram-negative bacteria, and unusual of eukaryotes.^[18] In addition it contains cardiolipin and phosphatidylcholine as the major phospholipids, while sterols are absent.^[19] Cardiolipin is a typical lipid of bacterial membranes; phosphatidylcholine, on the other hand, is mostly present in symbiotic prokaryotes of eukaryotic cells. For symbiotic adaptation, the protozoan host has undergone alterations such as reduced paraflagellar rod, which is required for full motility of the bacterial flagella. Yet the paraflagellar rod gene PFR1 is fully functional.^[20] It also lacks introns and transcription of long polycistronic mRNAs required by other eukaryotes for complex gene activities.^[21] Its entire genome is distributed in 29 chromosomes and contains 10,365 protein-coding genes, 59 transfer RNAs, 26 ribosomal RNAs, and 62 noncoding RNAs.^[22]

electron transport system for the production of cellular energy, the ATP molecules are produced through its glycosomes.^[9] The bacterium is known to provide essential nutrients to the host. It synthesises amino acids,^[23] vitamins,^[24] nitrogenous bases and haem^[25] for the protozoan. Haem is necessary for the growth and development of the protozoan.^[21] The bacterium also provides the enzymes for urea cycle which are absent in the host. In return the protozoan offers its enzymes for the complete metabolic pathways for the biosynthesis of amino acids, lipids and nucleotides, that are absent in the bacterium.^[26] The bacterium has highly reduced genome compared to its related bacterial species, lacking many genes essential for its survival.^[21] Phosphatidylinositol, a membrane lipid required for cell-cell interaction in the bacteria is also synthesised by the protozoan.^[27] The bacterium also depends on the host for ATP molecules for its energetic functions. Thus, the two organisms intimately share and exchange their metabolic systems.^[9]

antibiotics, the protozoan can no longer infect insects,^[10] due to the altered glycosylphosphatidylinositol (gp63) in the protozoan flagellum.^[28] A bacterium-less protozoan exhibits reduced gene activities; particularly those involved in oxidation-reduction process, ATP hydrolysis-coupled proton transport and glycolysis are stopped.^[29] The structural components are also altered including cell surface, carbohydrate composition, paraflagellar rod and kinetoplast.^[30]