Distinct Host Species Research Articles

Host species and geography impact bee-associated RNA virus communities with evidence for isolation by distance in viral populations.

Virus symbionts are important mediators of ecosystem function, yet we know little of their diversity and ecology in natural populations. The alarming decline of pollinating insects in many regions of the globe, especially the European honey bee, Apis mellifera, has been driven in part by worldwide transmission of virus pathogens. Previous work has examined the transmission of known honey bee virus pathogens to wild bee populations, but only a handful of studies have investigated the native viromes associated with wild bees, limiting epidemiological predictors associated with viral pathogenesis. Further, variation among different bee species might have important consequences in the acquisition and maintenance of bee-associated virome diversity. We utilized comparative metatranscriptomics to develop a baseline description of the RNA viromes associated with wild bee pollinators and to document viral diversity, community composition, and structure. Our sampling includes five wild-caught, native bee species that vary in social behavior as well as managed honey bees. We describe 26 putatively new RNA virus species based on RNA-dependent RNA polymerase phylogeny and show that each sampled bee species was associated with a specific virus community composition, even among sympatric populations of distinct host species. From 17 samples of a single host species, we recovered a single virus species despite over 600km of distance between host populations and found strong evidence for isolation by distance in associated viral populations. Our work adds to the small number of studies examining viral prevalence and community composition in wild bees.

The advantage of intergenic regions as genomic features for machine-learning-based host attribution of Salmonella Typhimurium from the USA.

Salmonella enterica is a taxonomically diverse pathogen with over 2600 serovars associated with a wide variety of animal hosts including humans, other mammals, birds and reptiles. Some serovars are host-specific or host-restricted and cause disease in distinct host species, while others, such as serovar S. Typhimurium (STm), are generalists and have the potential to colonize a wide variety of species. However, even within generalist serovars such as STm it is becoming clear that pathovariants exist that differ in tropism and virulence. Identifying the genetic factors underlying host specificity is complex, but the availability of thousands of genome sequences and advances in machine learning have made it possible to build specific host prediction models to aid outbreak control and predict the human pathogenic potential of isolates from animals and other reservoirs. We have advanced this area by building host-association prediction models trained on a wide range of genomic features and compared them with predictions based on nearest-neighbour phylogeny. SNPs, protein variants (PVs), antimicrobial resistance (AMR) profiles and intergenic regions (IGRs) were extracted from 3883 high-quality STm assemblies collected from humans, swine, bovine and poultry in the USA, and used to construct Random Forest (RF) machine learning models. An additional 244 recent STm assemblies from farm animals were used as a test set for further validation. The models based on PVs and IGRs had the best performance in terms of predicting the host of origin of isolates and outperformed nearest-neighbour phylogenetic host prediction as well as models based on SNPs or AMR data. However, the models did not yield reliable predictions when tested with isolates that were phylogenetically distinct from the training set. The IGR and PV models were often able to differentiate human isolates in clusters where the majority of isolates were from a single animal source. Notably, IGRs were the feature with the best performance across multiple models which may be due to IGRs acting as both a representation of their flanking genes, equivalent to PVs, while also capturing genomic regulatory variation, such as altered promoter regions. The IGR and PV models predict that ~45 % of the human infections with STm in the USA originate from bovine, ~40 % from poultry and ~14.5 % from swine, although sequences of isolates from other sources were not used for training. In summary, the research demonstrates a significant gain in accuracy for models with IGRs and PVs as features compared to SNP-based and core genome phylogeny predictions when applied within the existing population structure. This article contains data hosted by Microreact.

Identification and genetic characteristics of tusavirus in fecal samples of patients with chronic diseases in Guangzhou, China.

The Tunisian stool-associated parvovirus [Tusavirus (TuV)] is a novel member of the genus Protoparvovirus, which may be linked to diarrhea. Herein, we investigated the prevalence of TuV in different populations and analyzed its genetic and bioinformatic characteristics. This study was conducted in a tertiary hospital in Guangzhou (China) from February 2018 to July 2022. Demographic and clinical information and stool samples were collected from individuals who visited the hospital. ProtScale, SwissModel, Datamonkey, and other tools were used to analyze and predict the physicochemical parameters, tertiary structure, selection pressure, and B-cell epitopes of capsid viral protein 2 of TuV (VP2-TuV). A total of 3,837 participants were enrolled, among which two stool samples from patients with chronic illnesses were tested positive for TuV DNA. However, no positive sample was detected among patients with diarrhea. Two near-complete genome sequences were amplified. The genetic analysis revealed the presence of diversity among TuVs isolated from distinct host species. Bioinformatics analysis revealed that VP2-TuV exhibited hydrophilic properties and lacked transmembrane domains and signal peptides. The secondary structure of VP2-TuV was composed mainly of random coils and β-strands. Selective-pressure analysis of the VP2 region suggested that TuV primarily underwent negative selection during evolution. Negatively selected codon sites coincided with residues comprising of B-cell epitopes, suggesting minimal changes in the immunogenicity of TuV over time. TuV was detected in patients with chronic diseases but not in patients with diarrhea. The putative roles of TuV in the pathogenicity of human diseases and zoonotic viruses must be determined by additional studies.

Avian Influenza Virus Tropism in Humans.

An influenza pandemic happens when a novel influenza A virus is able to infect and transmit efficiently to a new, distinct host species. Although the exact timing of pandemics is uncertain, it is known that both viral and host factors play a role in their emergence. Species-specific interactions between the virus and the host cell determine the virus tropism, including binding and entering cells, replicating the viral RNA genome within the host cell nucleus, assembling, maturing and releasing the virus to neighboring cells, tissues or organs before transmitting it between individuals. The influenza A virus has a vast and antigenically varied reservoir. In wild aquatic birds, the infection is typically asymptomatic. Avian influenza virus (AIV) can cross into new species, and occasionally it can acquire the ability to transmit from human to human. A pandemic might occur if a new influenza virus acquires enough adaptive mutations to maintain transmission between people. This review highlights the key determinants AIV must achieve to initiate a human pandemic and describes how AIV mutates to establish tropism and stable human adaptation. Understanding the tropism of AIV may be crucial in preventing virus transmission in humans and may help the design of vaccines, antivirals and therapeutic agents against the virus.

Genotipagem e relações filogenéticas de Giardia duodenalis infectando suínos, caprinos e ovinos no nordeste do Brasil, avaliadas por sequenciamento parcial do gene da β-giardina

ABSTRACT: This study performed a molecular detection and characterization of Giardia duodenalis infecting pigs, goats and sheep in rural and peri-urban communities in the state of Piauí, northeastern Brazil, and proposed phylogenetic relationships among the characterized parasites. We assessed 52 fecal samples from pigs, 13 from goats, and 10 from sheep. A fragment of the β-giardin locus was PCR-amplified and sequenced. Overall, PCR-based G. duodenalis positivity was 11/52 (21.2%) in pigs, 2/13 (15.4%) in goats, and 2/10 (20%) in sheep. Seven out of 15 successfully amplified samples could be sequenced: three from pigs, two from goats, and two from sheep. Parasites from different hosts were found to belong to sub-assemblage AII. The phylogenetic analyses of the original G. duodenalis AII β-giardin sequences obtained from distinct host species and sequences of G. duodenalis recovered from humans available in GenBank suggest that the parasites are genetically related, supporting a local scenario of cross-host transmission.

Multiclonal human origin and global expansion of an endemic bacterial pathogen of livestock.

Most new pathogens of humans and animals arise via switching events from distinct host species. However, our understanding of the evolutionary and ecological drivers of successful host adaptation, expansion, and dissemination are limited. Staphylococcus aureus is a major bacterial pathogen of humans and a leading cause of mastitis in dairy cows worldwide. Here we trace the evolutionary history of bovine S. aureus using a global dataset of 10,254 S. aureus genomes including 1,896 bovine isolates from 32 countries in 6 continents. We identified 7 major contemporary endemic clones of S. aureus causing bovine mastitis around the world and traced them back to 4 independent host-jump events from humans that occurred up to 2,500 y ago. Individual clones emerged and underwent clonal expansion from the mid-19th to late 20th century coinciding with the commercialization and industrialization of dairy farming, and older lineages have become globally distributed via established cattle trade links. Importantly, we identified lineage-dependent differences in the frequency of host transmission events between humans and cows in both directions revealing high risk clones threatening veterinary and human health. Finally, pangenome network analysis revealed that some bovine S. aureus lineages contained distinct sets of bovine-associated genes, consistent with multiple trajectories to host adaptation via gene acquisition. Taken together, we have dissected the evolutionary history of a major endemic pathogen of livestock providing a comprehensive temporal, geographic, and gene-level perspective of its remarkable success.

Characterization of a Pseudokeronopsis Strain (Ciliophora, Urostylida) and Its Bacterial Endosymbiont “Candidatus Trichorickettsia” (Alphaproteobacteria, Rickettsiales)

Symbiotic associations between bacteria and ciliate protists are rather common. In particular, several cases were reported involving bacteria of the alphaproteobacterial lineage Rickettsiales, but the diversity, features, and interactions in these associations are still poorly understood. In this work, we characterized a novel ciliate protist strain originating from Brazil and its associated Rickettsiales endosymbiont by means of live and ultrastructural observations, as well as molecular phylogeny. Though with few morphological peculiarities, the ciliate was found to be phylogenetically affiliated with Pseudokeronopsis erythrina, a euryhaline species, which is consistent with its origin from a lagoon with significant spatial and seasonal salinity variations. The bacterial symbiont was assigned to “Candidatus Trichorickettsia mobilis subsp. hyperinfectiva”, being the first documented case of a Rickettsiales associated with urostylid ciliates. It resided in the host cytoplasm and bore flagella, similarly to many, but not all, conspecifics in other host species. These findings highlight the ability of “Candidatus Trichorickettsia” to infect multiple distinct host species and underline the importance of further studies on this system, in particular on flagella and their regulation, from a functional and also an evolutionary perspective, considering the phylogenetic proximity with the well-studied and non-flagellated Rickettsia.

Detection of human feces pecovirus in newly diagnosed HIV patients in Brazil.

Circular single stranded DNA viruses (CRESS DNA) encoding a homologous replication-associated protein (REP) have been identified in most of eukaryotic groups. It is not clear yet the role in human diseases or details of the life cycle of these viruses. Recently, much interest has been raised in the evolutionary history of CRESS DNA owing to the increasing number of new sequences obtained by Next-Generation Sequencing (NGS) in distinct host species. In this study we describe two full-length CRESS DNA genomes obtained of two newly diagnosed HIV patients from São Paulo State, Brazil. The initial BLASTx search indicated that both sequences (named SP-FFB/2020 and SP-MJMS/2020) are highly similar (98%) to a previous CRESS DNA sequence detected in human fecal sample from Peru in 2016 and designated as pecovirus (Peruvian stool-associated circo-like virus). This study reported for the first time the Human feces pecovirus in the feces of two newly diagnosed HIV patients in Brazil. Our comparative analysis showed that although pecoviruses in South America share an identical genome structure they diverge and form distinct clades. Thus, we suggest the circulation of different species of pecoviruses in Latin America. Nevertheless, further studies must be done to examine the pathogenicity of this virus.

Characterization of triatomine bloodmeal sources using direct Sanger sequencing and amplicon deep sequencing methods

Knowledge of host associations of blood-feeding vectors may afford insights into managing disease systems and protecting public health. However, the ability of methods to distinguish bloodmeal sources varies widely. We used two methods—Sanger sequencing and amplicon deep sequencing—to target a 228 bp region of the vertebrate Cytochrome b gene and determine hosts fed upon by triatomines (n = 115) collected primarily in Texas, USA. Direct Sanger sequencing of PCR amplicons was successful for 36 samples (31%). Sanger sequencing revealed 15 distinct host species, which included humans, domestic animals (Canis lupus familiaris, Ovis aries, Gallus gallus, Bos taurus, Felis catus, and Capra hircus), wildlife (Rattus rattus, Incilius nebulifer, Sciurus carolinensis, Sciurus niger, and Odocoileus virginianus), and captive animals (Panthera tigris, Colobus spp., and Chelonoidis carbonaria). Samples sequenced by the Sanger method were also subjected to Illumina MiSeq amplicon deep sequencing. The amplicon deep sequencing results (average of 302,080 usable reads per sample) replicated the host community revealed using Sanger sequencing, and detected additional hosts in five triatomines (13.9%), including two additional blood sources (Procyon lotor and Bassariscus astutus). Up to four bloodmeal sources were detected in a single triatomine (I. nebulifer, Homo sapiens, C. lupus familiaris, and S. carolinensis). Enhanced understanding of vector-host-parasite networks may allow for integrated vector management programs focusing on highly-utilized and highly-infected host species.

Identification and genome analysis of a novel picornavirus from captive belugas (Delphinapterus leucas) in China

The discovery of new viruses is important for predicting their potential threats to the health of humans and other animals. A novel picornavirus was identified from oral, throat, and anal swab samples collected from belugas (Delphinapterus leucas), from Dalian Sun Asia Tourism Holding Co., China, between January and December 2018, using a metagenomics approach. The genome of this novel PicoV-HMU-1 strain was 8197 nucleotides (nt) in length, with a open reading frame (from 1091 to 8074 nt) that encoded a polyprotein precursor of 2328 amino acids. Moreover, the genomic length and GC content of PicoV-HMU-1 were within the ranges found in other picornaviruses, and the genome organization was also similar. Nevertheless, PicoV-HMU-1 had a lower amino acid identity and distinct host species compared with other members of the Picornaviridae family. Phylogenetic trees were constructed based on the P1 and 3D amino acid sequences of PicoV-HMU-1 along with representative members of the Picornaviridae family, which showed that PicoV-HMU-1 was related to unclassified bat picornaviruses groups. These findings suggest that the PicoV-HMU-1 strain represents a potentially novel genus of picornavirus. These data can enhance our understanding of the picornavirus genetic diversity and evolution.

Trends in Molecular Diagnosis and Diversity Studies for Phytosanitary Regulated Xanthomonas.

Bacteria in the genus Xanthomonas infect a wide range of crops and wild plants, with most species responsible for plant diseases that have a global economic and environmental impact on the seed, plant, and food trade. Infections by Xanthomonas spp. cause a wide variety of non-specific symptoms, making their identification difficult. The coexistence of phylogenetically close strains, but drastically different in their phenotype, poses an added challenge to diagnosis. Data on future climate change scenarios predict an increase in the severity of epidemics and a geographical expansion of pathogens, increasing pressure on plant health services. In this context, the effectiveness of integrated disease management strategies strongly depends on the availability of rapid, sensitive, and specific diagnostic methods. The accumulation of genomic information in recent years has facilitated the identification of new DNA markers, a cornerstone for the development of more sensitive and specific methods. Nevertheless, the challenges that the taxonomic complexity of this genus represents in terms of diagnosis together with the fact that within the same bacterial species, groups of strains may interact with distinct host species demonstrate that there is still a long way to go. In this review, we describe and discuss the current molecular-based methods for the diagnosis and detection of regulated Xanthomonas, taxonomic and diversity studies in Xanthomonas and genomic approaches for molecular diagnosis.

Morphological and molecular description of a distinct population of Echinorhynchus gadi Zoega in Müller, 1776 (Paleacanthocephala: Echinorhynchidae) from the pacific halibut Hippoglossus stenolepis Schmidt in Alaska.

Echinorhynchus gadi is one of the most widely distributed and commonly described acanthocephalans in marine fishes throughout the world. We provide a detailed morphometric and molecular description of a distinct Alaska population collected from the Pacific halibut Hippoglossus stenolepis Schmidt (Pleuronectidae) compared to those from other hosts and regions, illustrating new features never previously reported. We described new specimens by microscopical studies, augmented by SEM, Energy Dispersive x-ray and molecular analyses, and histopathology. Specimens from Alaska were distinguished from those collected from the other geographical areas in proboscis size and its armature, especially number of hook rows and hooks per row, and length of hooks. The size of the receptacle, lemnisci, and reproductive structures in some other collections also varied from the Alaska material. X-ray scans of the gallium cut hooks depict prominent layering with high Sulfur content for tip cuts and increased calcium and phosphorus content in the base area of the hook. Sections of E. gadi specimens in the host tissue show prominent hook entanglement with subsequent connective tissue invasion also depicting the internal anatomy of certain worm structures not readily seen by other means. Molecular analyses clearly confirmed the identity of our E. gadi sequences. Our Alaska population of the E. gadi complex appears to represent a novel population distinguishable by its distinct morphometrics, geography and host species. We further establish new information on the Energy Dispersive X-ray analysis in our Alaska material for future comparisons with the other siblings and explore genetic relationships among echinorhynchid genera and species.

Tobacco Necrosis Virus-AC Single Coat Protein Amino Acid Substitutions Determine Host-Specific Systemic Infections of Nicotiana benthamiana and Soybean.

Plant viruses often infect several distinct host species. Sometimes, viruses can systemically infect a specific host whereas, in other cases, only local infections occur in other species. How viral and host factors interact to determine systemic infections among different hosts is largely unknown, particularly for icosahedral positive-stranded RNA viruses. The Tobacco necrosis virus-A Chinese isolate belongs to the genus Alphanecrovirus in the family Tombusviridae. In this study, we investigated variations in systemic infections of tobacco necrosis virus-AC (TNV-AC) in Nicotiana benthamiana and Glycine max (soybean) by alanine-scanning mutagenesis of the viral coat protein (CP), which is essential for systemic movement of TNV-AC. We found that three amino acids, R169, K177, and Q233, are key residues that mediate varying degrees of systemic infections of N. benthamiana and soybean. Further analysis revealed that variations in systemic trafficking of TNV-AC CP mutants in N. benthamiana and soybean are associated with virion assembly and stability. The CP amino acids K177 and Q233 are highly conserved among all TNV-A isolates and are replaced by Q and K in the TNV-D isolates. We demonstrated that systemic infectivity of either TNV-AC K177A and Q233A or K177Q and Q233K mutants are correlated with the binding affinity of the mutated CPs to the host-specific Hsc70-2 protein. These results expand our understanding of host-dependent long-distance movement of icosahedral viruses in plants.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Saprolegnia parasitica zoospore activity and host survival indicates isolate variation in host preference

The ubiquitous freshwater pathogen Saprolegnia parasitica has long been considered a true generalist, capable of infecting a wide range of fish species. It remains unclear, however, whether different isolates of this pathogen, obtained from distinct geographic locations and host species, display differences in host preference. To assess this, the current study examined the induced zoospore encystment responses of four S. parasitica isolates towards the skin of four fish species. While three of the isolates displayed ‘specialist’ responses, one appeared to be more of a ‘generalist’. In vivo challenge infections involving salmon and sea trout with the ‘generalist’ (salmon isolate EA001) and a ‘specialist’ (sea trout isolate EA016) pathogen, however, did not support the in vitro findings, with no apparent host preference reflected in infection outcomes. Survival of sea trout and salmon though was significantly different following a challenge infection with the sea trout (EA016) isolate. These results indicate that while S. parasitica isolates can be considered true generalists, they may target hosts to which they have been more frequently exposed (potential local adaptation). Understanding host preference of this pathogen could aid our understanding of infection epidemics and help with the development of fish management procedures.

Identification of Zoonotic Tick-Borne Pathogens from Korean Water Deer (Hydropotes inermis argyropus).

Korean water deer (Hydropotes inermis argyropus) are widespread in the Republic of Korea (ROK). Mostly, Korean water deer are essential hosts for maintaining ticks and tick-borne diseases (TBDs). Here, we investigated the prevalence of tick-borne pathogens (TBPs) among rescued Korean water deer. Anaplasma phagocytophilum (21.4%, 6/28), Anaplasma capra (14.3%, 4/28), Babesia capreoli (3.6%, 1/28), and Coxiella burnetii (3.6%, 1/28) were detected, but Borrelia burgdorferi, Ehrlichia, Rickettsia, and Theileria infections were not found. A. phagocytophilum was the most commonly detected pathogen, and co-infection with A. capra and B. capreoli was also noted in one Korean water deer. To our knowledge, this is the first article of B. capreoli infection in Korean water deer in the ROK. The infecting isolate of A. phagocytophilum was genetically characterized by 16S ribosomal RNA (rRNA) gene and ankyrin-related protein (ankA) gene. Although the 16S rRNA gene alone may not be informative enough to delineate distinct host species, ankA-based phylogeny revealed a high identity of Korean water deer sequences with those of the causative agent of human granulocytic anaplasmosis. A. capra was detected by using citrate synthase gene (gltA), heat-shock protein (groEL), and major surface protein 4 (msp4) genes. Phylogenetic tree based on these gene markers revealed that there were at least two distinct variants within A. capra circulating in the ROK. One variant originated from different hosts including humans, ticks, goats, and sheep, whereas the other variant was reported recently in Korean water deer in the ROK. Consequently, these sequences were identified to belong to a zoonotic species. Sequencing analysis of the 18S rRNA gene revealed that our isolate belonged to B. capreoli and was distinct from Babesia divergens and Babesia venatorum. Moreover, our isolate showed 92.2% homology with B. capreoli sequences, indicating that these differences may be attributed to the different tick species that transmit B. capreoli or to different host species. Genotyping and phylogenetic analysis of C. burnetii based on 16S rRNA and IS1111 genes revealed that our isolate was grouped with several strains of C. burnetii and was genetically distant from Coxiella-like bacteria isolates. The present results highlight that Korean water deer act as potential reservoir hosts for zoonotic TBPs, and thus play an important role in the transmission of TBDs in humans, animals, and livestock.

Molecular phylogeny based on six nuclear genes suggests that Echinococcus granulosus sensu lato genotypes G6/G7 and G8/G10 can be regarded as two distinct species.

Tapeworms of the species complex of Echinococcus granulosus sensu lato (s. l.) are the cause of a severe zoonotic disease - cystic echinococcosis, which is listed among the most severe parasitic diseases in humans and is prioritized by the World Health Organization. A stable taxonomy of E. granulosus s. l. is essential to the medical and veterinary communities for accurate and effective communication of the role of different species in this complex on human and animal health. E. granulosus s. l. displays high genetic diversity and has been divided into different species and genotypes. Despite several decades of research, the taxonomy of E. granulosus s. l. has remained controversial, especially the species status of genotypes G6-G10. Here the Bayesian phylogeny based on six nuclear loci (7387 bp in total) demonstrated, with very high support, the clustering of G6/G7 and G8/G10 into two separate clades. According to the evolutionary species concept, G6/G7 and G8/G10 can be regarded as two distinct species. Species differentiation can be attributed to the association with distinct host species, largely separate geographical distribution and low level of cross-fertilization. These factors have limited the gene flow between genotypic groups G6/G7 and G8/G10, resulting in the formation of distinct species. We discuss ecological and epidemiological differences that support the validity of these species.

Incomplete Co-cladogenesis Between Zootermopsis Termites and Their Associated Protists.

Coevolution is a major driver of speciation in many host-associated symbionts. In the termite-protist digestive symbiosis, the protists are vertically inherited by anal feeding among nest mates. Lower termites (all termite families except Termitidae) and their symbionts have broadly co-diversified over ~170 million yr. However, this inference is based mainly on the restricted distribution of certain protist genera to certain termite families. With the exception of one study, which demonstrated congruent phylogenies for the protist Pseudotrichonympha and its Rhinotermitidae hosts, coevolution in this symbiosis has not been investigated with molecular methods. Here we have characterized the hindgut symbiotic protists (Phylum Parabasalia) across the genus Zootermopsis (Archotermopsidae) using single cell isolation, molecular phylogenetics, and high-throughput amplicon sequencing. We report that the deepest divergence in the Zootermopsis phylogeny (Zootermopsis laticeps [Banks; Isoptera: Termopsidae]) corresponds with a divergence in three of the hindgut protist species. However, the crown Zootermopsis taxa (Zootermopsis angusticollis [Hagen; Isoptera: Termopsidae], Z. nevadensis nevadensis [Hagen; Isoptera: Termopsidae], and Z. nevadensis nuttingi [Haverty & Thorne; Isoptera: Termopsidae]) share the same protist species, with no evidence of co-speciation under our methods. We interpret this pattern as incomplete co-cladogenesis, though the possibility of symbiont exchange cannot be entirely ruled out. This is the first molecular evidence that identical communities of termite-associated protist species can inhabit multiple distinct host species.

Accurate identification of Anopheles gambiae Giles trophic preferences by MALDI-TOF MS

The determination of the trophic preferences of the Anopheles gambiae Giles (Diptera: Culicidae) is a decisive parameter for the monitoring and the prevention of malaria risk transmission. Currently, arthropod blood feeding sources are identified using immunological or molecular biology traditional techniques. Despite the effectiveness of these methods, they present several limitations, and notably, they are time-consuming and costly techniques. A recent study demonstrated that MALDI-TOF MS could be a useful tool for the identification of blood meal origins in freshly engorged mosquitoes. However, the limited number of blood vertebrate species tested to date, did not allow an assessment of the efficiency of MALDI-TOF MS in distinguishing blood MS spectra among close host species, such as humans versus primates. Therefore, in the present study, blood from ten distinct vertebrate host species, including four domestic species, four wild species, and two primates, was selected to control the reliability of MALDI-TOF MS based identification. Host blood species-specific MS profiles, up to 24h post-feeding in engorged Anopheles abdomens, were confirmed. Blind tests underlined the high specificity of MS spectra for the recognition of each host species, preventing misidentification. Nevertheless, an accurate analysis of the results from MS spectra queried against the MS database revealed that the reliability of identification is directly linked to the comprehensiveness of the MS reference database. Finally, the rapidity, the low-cost reagents, the simplicity of data analysis, and the accuracy of the tool for blood origin determination, make this proteomic strategy a promising complementary method for the elucidation of host/vector interactions.

Analysis of Cryptic, Systemic Botrytis Infections in Symptomless Hosts.

Botrytis species are generally considered to be aggressive, necrotrophic plant pathogens. By contrast to this general perception, however, Botrytis species could frequently be isolated from the interior of multiple tissues in apparently healthy hosts of many species. Infection frequencies reached 50% of samples or more, but were commonly less, and cryptic infections were rare or absent in some plant species. Prevalence varied substantially from year to year and from tissue to tissue, but some host species routinely had high prevalence. The same genotype was found to occur throughout a host, representing mycelial spread. Botrytis cinerea and Botrytis pseudocinerea are the species that most commonly occur as cryptic infections, but phylogenetically distant isolates of Botrytis were also detected, one of which does not correspond to previously described species. Sporulation and visible damage occurred only when infected tissues were stressed, or became mature or senescent. There was no evidence of cryptic infection having a deleterious effect on growth of the host, and prevalence was probably greater in plants grown in high light conditions. Isolates from cryptic infections were often capable of causing disease (to varying extents) when spore suspensions were inoculated onto their own host as well as on distinct host species, arguing against co-adaptation between cryptic isolates and their hosts. These data collectively suggest that several Botrytis species, including the most notorious pathogenic species, exist frequently in cryptic form to an extent that has thus far largely been neglected, and do not need to cause disease on healthy hosts in order to complete their life-cycles.

Evidence for suppression of immunity as a driver for genomic introgressions and host range expansion in races of Albugo candida, a generalist parasite.

How generalist parasites with wide host ranges can evolve is a central question in parasite evolution. Albugo candida is an obligate biotrophic parasite that consists of many physiological races that each specialize on distinct Brassicaceae host species. By analyzing genome sequence assemblies of five isolates, we show they represent three races that are genetically diverged by ∼1%. Despite this divergence, their genomes are mosaic-like, with ∼25% being introgressed from other races. Sequential infection experiments show that infection by adapted races enables subsequent infection of hosts by normally non-infecting races. This facilitates introgression and the exchange of effector repertoires, and may enable the evolution of novel races that can undergo clonal population expansion on new hosts. We discuss recent studies on hybridization in other eukaryotes such as yeast, Heliconius butterflies, Darwin's finches, sunflowers and cichlid fishes, and the implications of introgression for pathogen evolution in an agro-ecological environment.