Host-specificity of Monoxenous Trypanosomatids: Statistical Analysis of the Distribution and Transmission Patterns of the Parasites from Neotropical Heteroptera

Multiple and frequent trypanosomatid co-infections of insects: the Cuban case study

Trypanosomatids are obligate parasites of animals, predominantly insects and vertebrates, and flowering plants. Monoxenous species, representing the vast majority of trypanosomatid diversity, develop in a single host, whereas dixenous species cycle between two hosts, of which primarily insect serves as a vector. To explore in-depth the diversity of insect trypanosomatids including their co-infections, sequence profiling of their 18S rRNA gene was used for true bugs (Hemiptera; 18% infection rate) and flies (Diptera; 10%) in Cuba. Out of 48 species (molecular operational taxonomic units) belonging to the genera Vickermania (16 spp.), Blastocrithidia (7), Obscuromonas (4), Phytomonas (5), Leptomonas/Crithidia (5), Herpetomonas (5), Wallacemonas (2), Kentomonas (1), Angomonas (1) and two unnamed genera (1 + 1), 38 species have been encountered for the first time. The detected Wallacemonas and Angomonas species constitute the most basal lineages of their respective genera, while Vickermania emerged as the most diverse group. The finding of Leptomonas seymouri, which is known to rarely infect humans, confirms that Dysdercus bugs are its natural hosts. A clear association of Phytomonas with the heteropteran family Pentatomidae hints at its narrow host association with the insect rather than plant hosts. With a focus on multiple infections of a single fly host, using deep Nanopore sequencing of 18S rRNA, we have identified co-infections with up to 8 trypanosomatid species. The fly midgut was usually occupied by several Vickermania species, while Herpetomonas and/or Kentomonas species prevailed in the hindgut. Metabarcoding was instrumental for analysing extensive co-infections and also allowed the identification of trypanosomatid lineages and genera.

Parasites of firebugs in Austria with focus on the "micro"-diversity of the cosmopolitan trypanosomatid Leptomonas pyrrhocoris

In this work, we investigated parasites of the firebug Pyrrhocoris apterus in Austria and demonstrated that in addition to the extensively studied Leptomonas pyrrhocoris, it can also be infected by Blastocrithidia sp. and by a mermithid, which for the first time has been characterized using molecular methods. This diversity can be explained by the gregarious lifestyle, as well as the coprophagous and cannibalistic behavior of the insect hosts that makes them susceptible to various parasites. In addition, we showed no tight association of the L. pyrrhocoris haplotypes and geographical locations (at least, considering the relatively small scale of locations in Austria) implying that the natural populations of L. pyrrhocoris are mixed due to the mobility of their firebug hosts.

Symbiosis: A duplicated host protein controlling a nascent mutualism

Mechanistic studies on how eukaryotes ensure vertical inheritance of beneficial intracellular prokaryotes have focused mostly on highly integrated relationships. A new study by Zakharova, Tashyreva et al. reveals how a duplicated host gene impacts symbiont inheritance in a young mutualism.

First Evidence of Co-Circulation of Emerging Leishmania martiniquensis, Leishmania orientalis, and Crithidia sp. in Culicoides Biting Midges (Diptera: Ceratopogonidae), the Putative Vectors for Autochthonous Transmission in Southern Thailand

Since 1996, autochthonous cases of emerging leishmaniasis caused by Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis have been more frequently reported, especially in the northern and southern parts of Thailand. However, the accurate identification of their natural vectors and reservoirs remains unconfirmed. Previous studies have suggested that these emerging parasites might be transmitted by other non-phlebotomine vectors. Herein, we speculated that Culicoides biting midges might act as the competent vectors responsible for autochthonous leishmaniasis in southern Thailand. In this research, 187 non-engorged, parous and gravid Culicoides females and 47 blood-engorged ones were trapped from the residences of two recently diagnosed visceral leishmaniasis patients in Sadao District and the unaffected site in Rattaphum District, Songkhla Province, southern Thailand. Species diversity and abundance of biting midges varied among the trapping sites. Using ITS1-PCR and BLASTn analysis, L. martiniquensis was predominantly detected in several Culicoides species, including C. peregrinus, C. oxystoma, C. mahasarakhamense, and C. huffi from the vicinity of patients’ houses; and in C. fordae and C. fulvus from the unaffected site. L. orientalis was also co-circulated in C. peregrinus and C. oxystoma caught near the second patient’s house. Additionally, Crithidia sp. were also detected using SSU rRNA-PCR across Culicoides spp. Host blood meal analysis of eight different Culicoides species from the unaffected site also revealed that all trapped Culicoides had fed on cows and goats, indicating the possible role of these mammalian species as reservoir hosts. Essentially, this study is the first entomological investigation, revealing the co-circulation of emerging trypanosomatids among several species of Culicoides biting midges and strongly supporting the potential role of this insect group as the main vectors responsible for the epidemiology of autochthonous leishmaniasis in southern Thailand.

The Roles of Mosquitoes in the Circulation of Monoxenous Trypanosomatids in Temperate Climates

Monoxenous (insect-restricted) trypanosomatids are highly diverse and abundant in nature. While many papers focus on the taxonomy and distribution of these parasites, studies on their biology are still scarce. In particular, this concerns trypanosomatids inhabiting the ubiquitous mosquitoes. To shed light on the circulation of monoxenous trypanosomatids with the participation of mosquitoes, we performed a multifaceted study combining the examination of naturally- and experimentally-infected insects using light and electron microscopy and molecular identification of parasites. Our examination of overwintering mosquitoes (genera Culex and Culiseta) revealed that their guts contained living trypanosomatids, which can be spread during the next season. Experimental infections with Crithidia spp. demonstrated that imagines represent permissive hosts, while larvae are resistant to these parasites. We argue that for the parasites with wide specificity, mosquitoes act as facultative hosts. Other trypanosomatids may have specific adaptations for vertical transmission in these insects at the expense of their potential to infect a wider range of hosts and, consequently, abundance in nature.

The Haptomonad Stage of Crithidia acanthocephali in Apis mellifera Hindgut

Crithidia acanthocephali is a trypanosomatid species that was initially described in the digestive tract of Hemiptera. However, this parasite was recently detected in honey bee colonies in Spain, raising the question as to whether bees can act as true hosts for this species. To address this issue, worker bees were experimentally infected with choanomastigotes from the early stationary growth phase and after 12 days, their hindgut was extracted for analysis by light microscopy and TEM. Although no cellular lesions were observed in the honey bee’s tissue, trypanosomatids had differentiated and adopted a haptomonad morphology, transforming their flagella into an attachment pad. This structure allows the protozoa to remain attached to the gut walls via hemidesmosomes-such as junctions. The impact of this species on honey bee health, as well as the pathogenic mechanisms involved, remains unknown. Nevertheless, these results suggest that insect trypanosomatids may have a broader range of hosts than initially thought.

Trypanosoma Species in Small Nonflying Mammals in an Area With a Single Previous Chagas Disease Case

Trypanosomatids are hemoflagellate parasites that even though they have been increasingly studied, many aspects of their biology and taxonomy remain unknown. The aim of this study was to investigate the Trypanosoma sp. transmission cycle in nonflying small mammals in an area where a case of acute Chagas disease occurred in Mangaratiba municipality, Rio de Janeiro state. Three expeditions were conducted in the area: the first in 2012, soon after the human case, and two others in 2015. Sylvatic mammals were captured and submitted to blood collection for trypanosomatid parasitological and serological exams. Dogs from the surrounding areas where the sylvatic mammals were captured were also tested for T. cruzi infection. DNA samples were extracted from blood clots and positive hemocultures, submitted to polymerase chain reaction targeting SSU rDNA and gGAPDH genes, sequenced and phylogenetic analysed. Twenty-one wild mammals were captured in 2012, mainly rodents, and 17 mammals, mainly marsupials, were captured in the two expeditions conducted in 2015. Only four rodents demonstrated borderline serological T. cruzi test (IFAT), two in 2012 and two in 2015. Trypanosoma janseni was the main Trypanosoma species identified, and isolates were obtained solely from Didelphis aurita. In addition to biological differences, molecular differences are suggestive of genetic diversity in this flagellate species. Trypanosoma sp. DID was identified in blood clots from D. aurita in single and mixed infections with T. janseni. Concerning dogs, 12 presented mostly borderline serological titers for T. cruzi and no positive hemoculture. In blood clots from 11 dogs, T. cruzi DNA was detected and characterized as TcI (n = 9) or TcII (n = 2). Infections by Trypanosoma rangeli lineage E (n = 2) and, for the first time, Trypanosoma caninum, Trypanosoma dionisii, and Crithidia mellificae (n = 1 each) were also detected in dogs. We concluded that despite the low mammalian species richness and degraded environment, a high Trypanosoma species richness species was being transmitted with the predominance of T. janseni and not T. cruzi, as would be expected in a locality of an acute case of Chagas disease.

Crithidia mellificae infection in different mammalian species in Brazil

Crithidia mellificae, a monoxenous trypanosomatid considered restricted to insects, was recently reported to infect a bat. Herein, C. mellificae has been demonstrated to have a wider range of vertebrate hosts and distribution in Brazilian biomes than once thought. Parasites isolated from haemocultures were characterized using V7V8 SSU rDNA and glyceraldehyde 3-phosphate dehydrogenase genes. Coatis (Nasua nasua) in the Cerrado; marmosets (Callithrix sp.) and bats (Carollia perspicillata, Myotis lavali, M. izecksohni, Artibeus lituratus) in the Atlantic Forest; crab-eating foxes (Cerdocyon thous) and ocelot (Leopardus pardalis) in the Pantanal biomes were infected by trypanosomatids that displayed choanomastigote forms in haemoculture in Giemsa-stained slide smears. Molecular characterization and phylogenetic inference confirmed the infection of C. mellificae in these animals. Moreover, slight differences in C. mellificae sequences were observed. Crithidia mellificae growth curves were counted at 27°C, 36°C and 37°C, and the morphotypes were able to grow and survive for up to 16 days. Serological titers for C. mellificae were observed in nonhuman primates, demonstrating that this parasite is able to induce a humoral immune response in an infected mammal. These results showed that host specificity in trypanosomatids is complex and far from understood.

Development of Monoxenous Trypanosomatids and Phytomonads in Insects

In this review, we summarize the current data on development of monoxenous trypanosomatids and phytomonads in various insects. Of these, Diptera and Hemiptera are the main host groups, and, consequently, most available information concerns their parasites. Within the insect body, the midgut and hindgut are the predominant colonization sites; in addition, some trypanosomatids can invade the foregut, Malpighian tubules, hemolymph, and/or salivary glands. Differences in the intestinal structure and biology of the host determine the variety of parasites' developmental and transmission strategies. Meanwhile, similar mechanisms are used by unrelated trypanosomatids, reflecting the limited range of options to achieve the same goal.

Species-level identification of trypanosomes infecting Australian wildlife by High-Resolution Melting - Real Time Quantitative Polymerase Chain Reaction (HRM-qPCR)

Conventional nested PCR and Sanger sequencing methods are currently the gold standards for detecting trypanosomes in wildlife. However, these techniques are time-consuming and can often overlook mixed infections. True trypanosome prevalence can thus be underrepresented. Here, we designed an 18S rDNA-based real-time quantitative PCR (qPCR) assay coupled with High-Resolution Melting Analysis (HRMA) to detect and discriminate three Trypanosoma species (T. copemani, T. noyesi, and T. vegrandis) commonly infecting Australian marsupials. A total of 68 genetically characterised samples from blood and tissue were used to validate the High-Resolution Melting - Real Time Quantitative Polymerase Chain Reaction (HRM-qPCR) assay. A further 87 marsupial samples consisting of blood, tissue and in vitro cultures derived from wildlife blood samples, were screened for the first time using this assay, and species identity confirmed using conventional PCR and Sanger sequencing. All three Trypanosoma species were successfully detected in pure cultures using the HRM-qPCR assay, and in samples containing mixed trypanosome infections. Of the 87 marsupial samples screened using the HRM-qPCR assay, 93.1% were positive for trypanosomes, and 8.0% contained more than one trypanosome species. In addition to the three targeted Trypanosoma species, this assay was also able to detect and identify other native and exotic trypanosomes. The turnaround time for this assay, from sample preparation to obtaining results, was less than 2 h, with a detection limit of 10 copies of the amplicon in a reaction for each of the targeted trypanosome species. This more rapid and sensitive diagnostic tool provides a high throughput platform for the detection, identification and quantification of trypanosome infections. It will also improve understanding of host diversity and parasite relationships and facilitate conservation management decisions.

Cross-infectivity of honey and bumble bee-associated parasites across three bee families

Recent declines of wild pollinators and infections in honey, bumble and other bee species have raised concerns about pathogen spillover from managed honey and bumble bees to other pollinators. Parasites of honey and bumble bees include trypanosomatids and microsporidia that often exhibit low host specificity, suggesting potential for spillover to co-occurring bees via shared floral resources. However, experimental tests of trypanosomatid and microsporidial cross-infectivity outside of managed honey and bumble bees are scarce. To characterize potential cross-infectivity of honey and bumble bee-associated parasites, we inoculated three trypanosomatids and one microsporidian into five potential hosts – including four managed species – from the apid, halictid and megachilid bee families. We found evidence of cross-infection by the trypanosomatids Crithidia bombi and C. mellificae, with evidence for replication in 3/5 and 3/4 host species, respectively. These include the first reports of experimental C. bombi infection in Megachile rotundata and Osmia lignaria, and C. mellificae infection in O. lignaria and Halictus ligatus. Although inability to control amounts inoculated in O. lignaria and H. ligatus hindered estimates of parasite replication, our findings suggest a broad host range in these trypanosomatids, and underscore the need to quantify disease-mediated threats of managed social bees to sympatric pollinators.

A novel endosymbiont-containing trypanosomatid Phytomonas borealis sp. n. from the predatory bug Picromerus bidens (Heteroptera: Pentatomidae)

Here we describe the new trypanosomatid, Phytomonas borealis sp. n., from the midgut of the spiked shieldbugs, Picromerus bidens (Linnaeus), collected in two locations, Novgorod and Pskov Oblasts of Russia. The phylogenetic analyses, based on the 18S rRNA gene, demonstrated that this flagellate is a sister species to the secondary monoxenous Phytomonas nordicus Frolov et Malysheva, 1993, which was concurrently documented in the same host species in Pskov Oblast. Unlike P. nordicus, which can complete its development (including exit to haemolymph and penetration into salivary glands) in Picromerus bidens, the new species did not form any extraintestinal stages in the host. It also did not produce endomastigotes, indispensable for transmission in other Phytomonas spp. These observations, along with the fact that P. bidens overwinters at the egg stage, led us to the conclusion that the examined infections with P. borealis were non-specific. Strikingly, the flagellates from the Novgorod population contained prokaryotic endosymbionts, whereas the parasites from the second locality were endosymbiont-free. This is a first case documenting presence of intracellular symbiotic bacteria in Phytomonas spp. We suggest that this novel endosymbiotic association arose very recently and did not become obligate yet. Further investigation of P. borealis and its intracellular bacteria may shed light on the origin and early evolution of endosymbiosis in trypanosomatids.

The First Non-LRV RNA Virus in Leishmania

In this work, we describe the first Leishmania-infecting leishbunyavirus-the first virus other than Leishmania RNA virus (LRV) found in trypanosomatid parasites. Its host is Leishmania martiniquensis, a human pathogen causing infections with a wide range of manifestations from asymptomatic to severe visceral disease. This virus (LmarLBV1) possesses many characteristic features of leishbunyaviruses, such as tripartite organization of its RNA genome, with ORFs encoding RNA-dependent RNA polymerase, surface glycoprotein, and nucleoprotein on L, M, and S segments, respectively. Our phylogenetic analyses suggest that LmarLBV1 originated from leishbunyaviruses of monoxenous trypanosomatids and, probably, is a result of genomic re-assortment. The LmarLBV1 facilitates parasites' infectivity in vitro in primary murine macrophages model. The discovery of a virus in L. martiniquensis poses the question of whether it influences pathogenicity of this parasite in vivo, similarly to the LRV in other Leishmania species.

Insect trypanosomatids in Papua New Guinea: high endemism and diversity

The extreme biological diversity of Oceanian archipelagos has long stimulated research in ecology and evolution. However, parasitic protists in this geographic area remained neglected and no molecular analyses have been carried out to understand the evolutionary patterns and relationships with their hosts. Papua New Guinea (PNG) is a biodiversity hotspot containing over 5% of the world's biodiversity in less than 0.5% of the total land area. In the current work, we examined insect heteropteran hosts collected in PNG for the presence of trypanosomatid parasites. The diversity of insect flagellates was analysed, to our knowledge for the first time, east of Wallace's Line, one of the most distinct biogeographic boundaries of the world. Out of 907 investigated specimens from 138 species and 23 families of the true bugs collected in eight localities, 135 (15%) were infected by at least one trypanosomatid species. High species diversity of captured hosts correlated with high diversity of detected trypanosomatids. Of 46 trypanosomatid Typing Units documented in PNG, only eight were known from other geographic locations, while 38 TUs (~83%) have not been previously encountered. The widespread trypanosomatid TUs were found in both widely distributed and endemic/sub-endemic insects. Approximately one-third of the endemic trypanosomatid TUs were found in widely distributed hosts, while the remaining species were confined to endemic and sub-endemic insects. The TUs from PNG form clades with conspicuous host-parasite coevolutionary patterns, as well as those with a remarkable lack of this trait. In addition, our analysis revealed new members of the subfamilies Leishmaniinae and Strigomonadinae, potentially representing new genera of trypanosomatids.

RNA Viruses in Blechomonas (Trypanosomatidae) and Evolution of Leishmaniavirus

In this work, we analyzed viral prevalence in trypanosomatid parasites (Blechomonas spp.) infecting Siphonaptera and discovered nine species of viruses from three different groups (leishbunyaviruses, narnaviruses, and leishmaniaviruses). Most of the flagellate isolates bore two or three viral types (mixed infections). Although no new viral groups were documented in Blechomonas spp., our findings are important for the comprehension of viral evolution. The discovery of bunyaviruses in blechomonads was anticipated, since these viruses have envelopes facilitating their interspecific transmission and have already been found in various trypanosomatids and metatranscriptomes with trypanosomatid signatures. In this work, we also provided evidence that even representatives of the family Narnaviridae are capable of host switching and evidently have accomplished switches multiple times in the course of their evolution. The most unexpected finding was the presence of leishmaniaviruses, a group previously solely confined to the human pathogens Leishmania spp. From phylogenetic inferences and analyses of the life cycles of Leishmania and Blechomonas, we concluded that a common ancestor of leishmaniaviruses most likely infected Leishmania first and was acquired by Blechomonas by horizontal transfer. Our findings demonstrate that evolution of leishmaniaviruses is more complex than previously thought and includes occasional host switching.IMPORTANCE Flagellates belonging to the genus Leishmania are important human parasites. Some strains of different Leishmania species harbor viruses (leishmaniaviruses), which facilitate metastatic spread of the parasites, thus aggravating the disease. Up until now, these viruses were known to be hosted only by Leishmania Here, we analyzed viral distribution in Blechomonas, a related group of flagellates parasitizing fleas, and revealed that they also bear leishmaniaviruses. Our findings shed light on the entangled evolution of these viruses. In addition, we documented that Blechomonas can be also infected by leishbunyaviruses and narnaviruses, viral groups known from other insects' flagellates.

Obligate development of Blastocrithidia papi (Trypanosomatidae) in the Malpighian tubules of Pyrrhocoris apterus (Hemiptera) and coordination of host-parasite life cycles

Blastocrithidia papi is a unique trypanosomatid in that its life cycle is synchronized with that of its host, and includes an obligate stage of development in Malpighian tubules (MTs). This occurs in firebugs, which exited the winter diapause. In the short period, preceding the mating of overwintered insects, the flagellates penetrate MTs of the host, multiply attached to the epithelial surface with their flagella, and start forming cyst-like amastigotes (CLAs) in large agglomerates. By the moment of oviposition, a large number of CLAs are already available in the rectum. They are discharged on the eggs' surface with feces, used for transmission of bugs' symbiotic bacteria, which are compulsorily engulfed by the newly hatched nymphs along with the CLAs. The obligate development of B. papi in MTs is definitely linked to the life cycle synchronization. The absence of peristalsis allow the trypanosomatids to accumulate and form dense CLA-forming subpopulations, whereas the lack of peritrophic structures facilitates the extensive discharge of CLAs directly into the hindgut lumen. The massive release of CLAs associated with oviposition is indispensable for maximization of the infection efficiency at the most favorable time point.

Trypanosomatid parasites in Austrian mosquitoes

Trypanosomatid flagellates have not been studied in Austria in any detail. In this study, specific nested PCR, targeted on the ribosomal small subunit, was used to determine the occurrence and diversity of trypanosomatids in wild-caught mosquitoes sampled across Eastern Austria in the years 2014−2015. We collected a total of 29,975 mosquitoes of 19 species divided in 1680 pools. Of these, 298 (17.7%), representing 12 different mosquito species, were positive for trypanosomatid DNA. In total, seven trypanosomatid spp. were identified (three Trypanosoma, three Crithidia and one Herpetomonas species), with the highest parasite species diversity found in the mosquito host Coquillettidia richiardii. The most frequent parasite species belonged to the mammalian Trypanosoma theileri/cervi species complex (found in 105 pools; 6.3%). The avian species T. culicavium (found in 69 pools; 4.1%) was only detected in mosquitoes of the genus Culex, which corresponds to their preference for avian hosts. Monoxenous trypanosomatids of the genus Crithidia and Herpetomonas were found in 20 (1.3%) mosquito pools. One third (n = 98) of the trypanosomatid positive mosquito pools carried more than one parasite species. This is the first large scale study of trypanosomatid parasites in Austrian mosquitoes and our results are valuable in providing an overview of the diversity of these parasites in Austria.

Trypanosomatids Are Much More than Just Trypanosomes: Clues from the Expanded Family Tree

Trypanosomes and leishmanias are widely known parasites of humans. However, they are just two out of several phylogenetic lineages that constitute the family Trypanosomatidae. Although dixeny - the ability to infect two hosts - is a derived trait of vertebrate-infecting parasites, the majority of trypanosomatids are monoxenous. Like their common ancestor, the monoxenous Trypanosomatidae are mostly parasites or commensals of insects. This review covers recent advances in the study of insect trypanosomatids, highlighting their diversity as well as genetic, morphological and biochemical complexity, which, until recently, was underappreciated. The investigation of insect trypanosomatids is providing an important foundation for understanding the origin and evolution of parasitism, including colonization of vertebrates and the appearance of human pathogens.

Leptomonas pyrrhocoris: Genomic insight into Parasite's Physiology

BACKGROUND

Leptomonas pyrrhocoris is a parasite of the firebug Pyrrhocoris apterus. This flagellate has been recently proposed as a model species for studying different aspects of the biology of monoxenous trypanosomatids, including host - parasite interactions. During its life cycle L. pyrrhocoris never tightly attaches to the epithelium of the insect gut. In contrast, its dixenous relatives (Leishmania spp.) establish a stable infection via attachment to the intestinal walls of their insect hosts.

MATERIAL AND METHODS

This process is mediated by chemical modifications of the cell surface lipophosphoglycans. In our study we tested whether the inability of L. pyrrhocoris to attach to the firebug's midgut is associated with the absence of these glycoconjugates. We also analyzed evolution of the proteins involved in proper lipophosphoglycan assembly, cell attachment and establishment of a stable infection in L. pyrrhocoris, L. seymouri, and Leishmania spp. Our comparative analysis demonstrated differences in SCG/L/R repertoire between the two parasite subgenera, Leishmania and Viannia, which may be related to distinct life strategies in various Leishmania spp. The genome of L. pyrrhocoris encodes 6 SCG genes, all of which are quite divergent from their orthologs in the genus Leishmania. Using direct probing with an antibody recognizing the β-Gal side chains of lipophosphoglycans, we confirmed that these structures are not synthesized in L. pyrrhocoris.

CONCLUSION

We conclude that either the SCG enzymes are not active in this species (similarly to SCG5/7 in L. major), or they possess a different biochemical activity.

Revised classification of the subfamily Leishmaniinae (Trypanosomatidae)

In the present study, we critically revised the recently proposed classification of the subfamily Leishmaniinae Maslov et Lukeš in Jirků et al., 2012. Agreeing with erection of the genus Zelonia Shaw, Camargo et Teixeira in Espinosa et al., 2017 and the subgenus Mundinia Shaw, Camargo et Teixeira in Espinosa et al., 2017 within the genus Leishmania Ross, 1908, we argue that other changes are not well justified. We propose to: (i) raise Paraleishmania Cupolillo, Medina-Acosta, Noyes, Momen et Grimaldi, 2000 to generic rank; (ii) create a new genus Borovskyia gen. n. to accommodate the former Leptomonas barvae Maslov et Lukeš, 2010 as its type and only species; (iii) leave the subfamily Leishmaniinae as originally defined, but establish two infrafamilies within it: Leishmaniatae infrafam. n. and Crithidiatae infrafam. n.

The evolution of trypanosomatid taxonomy

Trypanosomatids are protozoan parasites of the class Kinetoplastida predominately restricted to invertebrate hosts (i.e. possess a monoxenous life-cycle). However, several genera are pathogenic to humans, animals and plants, and have an invertebrate vector that facilitates their transmission (i.e. possess a dixenous life-cycle). Phytomonas is one dixenous genus that includes several plant pathogens transmitted by phytophagous insects. Trypanosoma and Leishmania are dixenous genera that infect vertebrates, including humans, and are transmitted by hematophagous invertebrates. Traditionally, monoxenous trypanosomatids such as Leptomonas were distinguished from morphologically similar dixenous species based on their restriction to an invertebrate host. Nonetheless, this criterion is somewhat flawed as exemplified by Leptomonas seymouri which reportedly infects vertebrates opportunistically. Similarly, Novymonas and Zelonia are presumably monoxenous genera yet sit comfortably in the dixenous clade occupied by Leishmania. The isolation of Leishmania macropodum from a biting midge (Forcipomyia spp.) rather than a phlebotomine sand fly calls into question the exclusivity of the Leishmania-sand fly relationship, and its suitability for defining the Leishmania genus. It is now accepted that classic genus-defining characteristics based on parasite morphology and host range are insufficient to form the sole basis of trypanosomatid taxonomy as this has led to several instances of paraphyly. While improvements have been made, resolution of evolutionary relationships within the Trypanosomatidae is confounded by our incomplete knowledge of its true diversity. The known trypanosomatids probably represent a fraction of those that exist and isolation of new species will help resolve relationships in this group with greater accuracy. This review incites a dialogue on how our understanding of the relationships between certain trypanosomatids has shifted, and discusses new knowledge that informs the present taxonomy of these important parasites.

Molecular mechanisms of thermal resistance of the insect trypanosomatid Crithidia thermophila

In the present work, we investigated molecular mechanisms governing thermal resistance of a monoxenous trypanosomatid Crithidia luciliae thermophila, which we reclassified as a separate species C. thermophila. We analyzed morphology, growth kinetics, and transcriptomic profiles of flagellates cultivated at low (23°C) and elevated (34°C) temperature. When maintained at high temperature, they grew significantly faster, became shorter, with genes involved in sugar metabolism and mitochondrial stress protection significantly upregulated. Comparison with another thermoresistant monoxenous trypanosomatid, Leptomonas seymouri, revealed dramatic differences in transcription profiles of the two species with only few genes showing the same expression pattern. This disparity illustrates differences in the biology of these two parasites and distinct mechanisms of their thermotolerance, a prerequisite for living in warm-blooded vertebrates.

Phytomonas (Euglenozoa: Trypanosomatidae): Phylogenetic analyses support infrageneric lineages and a new species transmitted to Solanaceae fruits by a pentatomid hemipteran

The genus Phytomonas includes trypanosomatids transmitted to the fruits, latex, and phloem of vascular plants by hemipterans. We inferred the phylogenetic relationships of plant and insect isolates assigned to the previously defined genetic groups A-F and H of Phytomonas, particularly those from groups A, C and E comprising flagellates of Solanaceae fruits. Phylogenetic analyses using glycosomal Glyceraldehyde Phosphate Dehydrogenase (gGAPDH) and Small Subunit rRNA (SSU rRNA) genes strongly supported the monophyly of the genus Phytomonas and its division into seven main infrageneric phylogenetic lineages (Phy clades). Isolates from fruit or latex do not constitute monophyletic assemblages but disperse through more than one lineages. In this study, fruit flagellates were distributed in three clades: PhyA, formed by isolates from Solanaceae and phytophagous hemipterans; PhyC comprising flagellates from four plant families; and PhyE, which contains 15 fruit isolates from seven species of Solanaceae. The flagellates of PhyE are described as Phytomonas dolleti n. sp. according to their positioning in phylogenetic trees, complemented by data about their life cycle, and developmental and morphological characteristics in cultures, fruits of Solanum spp., and salivary glands of the vector, the phytophagous hemipteran Arvelius albopunctatus (Pentatomidae).

Novel Trypanosomatid-Bacterium Association: Evolution of Endosymbiosis in Action

We describe a novel symbiotic association between a kinetoplastid protist, Novymonas esmeraldas gen. nov., sp. nov., and an intracytoplasmic bacterium, “Candidatus Pandoraea novymonadis” sp. nov., discovered as a result of a broad-scale survey of insect trypanosomatid biodiversity in Ecuador. We characterize this association by describing the morphology of both organisms, as well as their interactions, and by establishing their phylogenetic affinities. Importantly, neither partner is closely related to other known organisms previously implicated in eukaryote-bacterial symbiosis. This symbiotic association seems to be relatively recent, as the host does not exert a stringent control over the number of bacteria harbored in its cytoplasm. We argue that this unique relationship may represent a suitable model for studying the initial stages of establishment of endosymbiosis between a single-cellular eukaryote and a prokaryote. Based on phylogenetic analyses, Novymonas could be considered a proxy for the insect-only ancestor of the dixenous genus Leishmania and shed light on the origin of the two-host life cycle within the subfamily Leishmaniinae.

The parasitic trypanosomatid protist Novymonas esmeraldas gen. nov., sp. nov. entered into endosymbiosis with the bacterium “Ca. Pandoraea novymonadis” sp. nov. This novel and rather unstable interaction shows several signs of relatively recent establishment, qualifying it as a potentially unique transient stage in the increasingly complex range of eukaryotic-prokaryotic relationships.