Biological warfare: Microorganisms as drivers of host-parasite interactions

What shapes a microbiome? Differences in bacterial communities associated with helminth-amphipod interactions

The fast technological advances of molecular tools have enabled us to uncover a new dimension hidden within parasites and their hosts: their microbiomes. Increasingly, parasitologists characterise host microbiome changes in the face of parasitic infections, revealing the potential of these microscopic fast-evolving entities to influence host-parasite interactions. However, most of the changes in host microbiomes seem to depend on the host and parasite species in question. Furthermore, we should understand the relative role of parasitic infections as microbiome modulators when compared with other microbiome-impacting factors (e.g., host size, age, sex). Here, we characterised the microbiome of a single intermediate host species infected by two parasites belonging to different phyla: the acanthocephalan Plagiorhynchus allisonae and a dilepidid cestode, both infecting Transorchestia serrulata amphipods collected simultaneously from the same locality. We used the v4 hypervariable region of the 16S rRNA prokaryotic gene to identify the hemolymph bacterial community of uninfected, acanthocephalan-infected, and cestode-infected amphipods, as well as the bacteria in the amphipods' immediate environment and in the parasites infecting them. Our results show that parasitic infections were more strongly associated with differences in host bacterial community richness than amphipod size, presence of amphipod eggs in female amphipods, and even parasite load. Amphipods infected by acanthocephalans had the most divergent bacterial community, with a marked decrease in alpha diversity compared with cestode-infected and uninfected hosts. In accordance with the species-specific nature of microbiome changes in parasitic infections, we found unique microbial taxa associating with hosts infected by each parasite species, as well as taxa only shared between a parasite species and their infected hosts. However, there were some bacterial taxa detected in all parasitised amphipods (regardless of the parasite species), but not in uninfected amphipods or the environment. We propose that shared bacteria associated with all hosts parasitised by distantly related helminths may be important either in helping host defences or parasites' success, and could thus interact with host-parasite evolution.

Microbial artists: the role of parasite microbiomes in explaining colour polymorphism among amphipods and potential link to host manipulation

Parasite infections are increasingly reported to change the microbiome of the parasitized hosts, while parasites bring their own microbes to what can be a multi-dimensional interaction. For instance, a recent hypothesis suggests that the microbial communities harboured by parasites may play a role in the well-documented ability of many parasites to manipulate host phenotype, and explain why the degree to which host phenotype is altered varies among conspecific parasites. Here, we explored whether the microbiomes of both hosts and parasites are associated with variation in host manipulation by parasites. Using colour quantification methods applied to digital images, we investigated colour variation among uninfected Transorchestia serrulata amphipods, as well as amphipods infected with Plagiorhynchus allisonae acanthocephalans and with a dilepidid cestode. We then characterized the bacteriota of amphipod hosts and of their parasites, looking for correlations between host phenotype and the bacterial taxa associated with hosts and parasites. We found large variation in amphipod colours, and weak support for a direct impact of parasites on the colour of their hosts. Conversely, and most interestingly, the parasite's bacteriota was more strongly correlated with colour variation among their amphipod hosts, with potential impact of amphipod-associated bacteria as well. Some bacterial taxa found associated with amphipods and parasites may have the ability to synthesize pigments, and we propose they may interact with colour determination in the amphipods. This study provides correlational support for an association between the parasite's microbiome and the evolution of host manipulation by parasites and host-parasite interactions more generally.

Preconceptional, pregnant, and postnatal exposure to outdoor air pollution and indoor environmental factors: Effects on childhood parasitic infections

BACKGROUND

Parasitic infections (PIs) are common and pose substantial health hazards in children globally, but the fundamental environmental variables exposure during crucial time window(s) are unclear.

OBJECTIVES

To identify key indoor and outdoor environmental factors leading to childhood PIs throughout critical time window(s).

METHODS

A combined cross-sectional and retrospective cohort study was performed on 8689 children residing in Changsha, China. Data was acquired pertaining to the health status and environmental exposure of the children in their homes. Personal exposure to outdoor air pollutants at the residential address during the preconceptional, perinatal, and postnatal periods was computed using data from ten air quality monitoring stations. An analysis of the relationships between childhood PIs and both indoor and outdoor factors was conducted using a multiple logistic regression model.

RESULTS

Childhood PIs were associated with outdoor CO and ozone (O3) exposure during the 10th-12th months prior to pregnancy, with ORs (95 % CI) of 1.68 (1.24-2.27) and 1.60 (1.15-2.22), respectively; childhood PIs were also associated with CO exposure during one year prior to pregnancy and the first trimester in utero [ORs = 1.57 (1.14-2.15) and 1.52 (1.17-1.97)]. Childhood PIs were found to be associated with PM2.5 exposure during pregnancy and the first year, with odds ratios of 1.51 (1.14-2.00) and 1.95 (1.22-3.12) per IQR increase in pollutant exposure, respectively. Exposures to smoke, renovation-related indoor air pollution (IAP), dampness and plant-related indoor allergens in the early life and past year were all associated with childhood PI, with odds ratios (95 % CI) ranging from 1.40 (1.01-1.95) for environmental tobacco smoke (ETS) during pregnancy to 1.63 (1.12-2.37) for mold/damp stains in the past year. In terms of PI risk, the early life and present periods were critical time windows for outdoor and indoor exposures, respectively. Certain individuals were more vulnerable to the PI risk associated with both indoor and outdoor exposures. Antibiotic use during child's lifetime and early years increased and decreased the PI risk of exposure to outdoor and indoor environments, respectively.

CONCLUSIONS

Exposure to outdoor air pollution in early life and indoor environments in the past year were found to be associated with childhood PI.

In vitro assessment of crude oil degradation by Acinetobacter junii and Alcanivorax xenomutans isolated from the coast of Ghana

This study was aimed at using in vitro microcosm experiments to assess crude oil degradation efficiency of Acinetobacter junii and Alcanivorax xenomutans isolated along Ghana's coast. Uncontaminated seawater from selected locations along the coast was used to isolate bacterial species by employing enrichment culture procedures with crude oil as the only carbon source. The isolates were identified by means of the extended direct colony transfer method of the Matrix Assisted Laser Desorption Ionization Time of Flight Mass Spectroscopy (MALDI-TOF MS), as Acinetobacter junii, and Alcanivorax xenomutans. Remediation tests showed that Acinetobacter junii yielded degradation efficiencies of 27.59 %, 41.38 % and 57.47 %. Whereas efficiencies of 21.14 %, 32.18 % and 43.68 % were recorded by Alcanivorax xenomutans representing 15, 30 and 45 days respectively. Consortia of Acinetobacter junii, and Alcanivorax xenomutans also yielded 32.18 %, 48.28 % and 62.07 % for the selected days respectively. Phylogenetic characterization using ClustalW and BLAST of sequences generated from the Oxford Nanopore Sequencing technique, showed that the Ghanaian isolates clustered with Alcanivorax xenomutans and Acinetobacter junii species respectively. An analysis of the sequenced data for the 1394-bp portion of the 16S rRNA gene of the isolates revealed >99 % sequence identity with the isolates present on the GenBank database. The isolates of closest identity were Alcanivorax xenomutans and Acinetobacter junii with accession numbers, NR_133958.1 and KJ147060.1 respectively. Acinetobacter junii and Alcanivorax xenomutans isolated from Ghana's coast under pristine seawater conditions have therefore demonstrated their capacity to be used for the remediation of crude oil spills.

Microbial communities are indicators of parasite infection status

Growing evidence suggests that microbiomes have been shaping the evolutionary pathways of macroorganisms for millennia and that these tiny symbionts can influence, and possibly even control, species interactions like host-parasite relationships. Yet, while studies have investigated host-parasites and microbiomes separately, little has been done to understand all three groups synergistically. Here, we collected infected and uninfected Eurypanopeus depressus crab hosts from a coastal North Carolina oyster reef three times over 4 months. Infected crabs demonstrated an external stage of the rhizocephalan parasite, Loxothylacus panopaei. Community analyses revealed that microbial richness and diversity were significantly different among tissue types (uninfected crab, infected crab, parasite externae and parasite larvae) and over time (summer and fall). Specifically, the microbial communities from parasite externae and larvae had similar microbiomes that were consistent through time. Infected crabs demonstrated microbial communities spanning those of their host and parasite, while uninfected crabs showed more distinctive communities with greater variability over time. Microbial communities were also found to be indicators of early-stage infections. Resolving the microbial community composition of a host and its parasite is an important step in understanding the microbiome's role in the host-parasite relationship and determining how this tripartite relationship impacts coevolutionary processes.

Different trematode parasites in the same snail host: Species-specific or shared microbiota?

The concept that microbes associated with macroorganisms evolve as a unit has swept evolutionary ecology. However, this idea is controversial due to factors such as imperfect vertical transmission of microbial lineages and high microbiome variability among conspecific individuals of the same population. Here, we tested several predictions regarding the microbiota of four trematodes (Galactosomum otepotiense, Philophthalmus attenuatus, Acanthoparyphium sp. and Maritrema novaezealandense) that parasitize the same snail host population. We predicted that each parasite species would harbour a distinct microbiota, with microbial composition similarity decreasing with increasing phylogenetic distance among parasite species. We also predicted that trematode species co-infecting the same individual host would influence each other's microbiota. We detected significant differences in alpha and beta diversity, as well as differential abundance, in the microbiota of the four trematode species. We found no evidence that phylogenetically closely related trematodes had more similar microbiota. We also uncovered indicator bacterial taxa that were significantly associated with each trematode species. Trematode species sharing the same snail host showed evidence of mostly one-sided bacterial exchanges, with the microbial community of one species approaching that of the other. We hypothesize that natural selection acting on specific microbial lineages may be important to maintain differences in horizontally acquired microbes, with vertical transmission also playing a role. In particular, one trematode species had a more consistent and diverse bacteriota than the others, potentially a result of stronger stabilizing pressures. We conclude that species-specific processes shape microbial community assembly in different trematodes exploiting the same host population.

Bacterial Communities Are Less Diverse in a Strepsipteran Endoparasitoid than in Its Fruit Fly Hosts and Dominated by Wolbachia

Microbiomes play vital roles in insect fitness and health and can be influenced by interactions between insects and their parasites. Many studies investigate the microbiome of free-living insects, whereas microbiomes of endoparasitoids and their interactions with parasitised insects are less explored. Due to their development in the constrained environment within a host, endoparasitoids are expected to have less diverse yet distinct microbiomes. We used high-throughput 16S rRNA gene amplicon sequencing to characterise the bacterial communities of Dipterophagus daci (Strepsiptera) and seven of its tephritid fruit fly host species. Bacterial communities of D. daci were less diverse and contained fewer taxa relative to the bacterial communities of the tephritid hosts. The strepsipteran's microbiome was dominated by Pseudomonadota (formerly Proteobacteria) (> 96%), mainly attributed to the presence of Wolbachia, with few other bacterial community members, indicative of an overall less diverse microbiome in D. daci. In contrast, a dominance of Wolbachia was not found in flies parasitised by early stages of D. daci nor unparasitised flies. Yet, early stages of D. daci parasitisation resulted in structural changes in the bacterial communities of parasitised flies. Furthermore, parasitisation with early stages of D. daci with Wolbachia was associated with a change in the relative abundance of some bacterial taxa relative to parasitisation with early stages of D. daci lacking Wolbachia. Our study is a first comprehensive characterisation of bacterial communities in a Strepsiptera species together with the more diverse bacterial communities of its hosts and reveals effects of concealed stages of parasitisation on host bacterial communities.

Rickettsia communities and their relationship with tick species within and around the national park of Iguaçu, Brazil

We report Rickettsia species from 2,334 ticks collected from environment (1,939 ticks) and animals (395 ticks) in the largest inland fragment of the Atlantic rainforest of southern Brazil and its fragments. Additionally, the DNA infection rates of Amblyomma ovale tick populations in the Neotropics with Rickettsia bellii and Rickettsia parkeri strain Atlantic rainforest were calculated using data from scientific publications, and their correlation was evaluated. From 11 tick species Rickettsia DNA was detected in seven (Amblyomma brasiliense, Amblyomma coelebs, Amblyomma incisum, Amblyomma longirostre, A. ovale, Haemaphysalis juxtakochi, Ixodes fuscipes) and was not detected in four species (Amblyomma dubitatum, Ixodes loricatus, Rhipicephalus microplus and Rhipicephalus sanguineus sensu lato). DNA of five Rickettsia species was detected (R. bellii, Rickettsia amblyommatis, Rickettsia rhipicephali, Rickettsia felis and Rickettsia sp. Aragaoi). To determine the prevalence of Rickettsia DNA positivity according to vector species, ticks were processed individually or in pools of 2-10 individuals (samples). The most prevalent Rickettsia species was R. bellii, found in 112 samples, followed by R. amblyommatis, R. rhipicephali, R. felis and Rickettsia sp. Aragaoi, found in 16, five, two and one sample, respectively. Rickettsia bellii DNA was found in five tick species with the highest infection rate in A. ovale and A. brasiliense. Absence of R. parkeri strain Atlantic rainforest in A. ovale ticks was an unexpected result. Furthermore, a negative correlation was identified between the infection rates (DNA) of R. bellii and/or R. parkeri strain Atlantic rainforest within A. ovale tick populations in the Neotropics. Putting together current knowledge, it can be proposed that, within natural settings, the diversity of rickettsiae and ticks creates a buffering effect on the overgrowth of rickettsiae and episodes of bacteremia in the hosts.

A Diverse Virome Is Identified in Parasitic Flatworms of Domestic Animals in Xinjiang, China

Parasitic flatworms infect diverse vertebrates and are major threats to animal and even human health; however, little is known about the virome of these lower life forms. Using viral metagenomic sequencing, we characterized the virome of the parasitic flatworms collected from major domestic animals, including Dicrocoelium lanceatum and Taenia hydatigena, Echinococcus granulosus sensu stricto and Echinococcus multilocularis. Seven and three different viruses were discovered from D. lanceatum and T. hydatigena, respectively, and no viral sequences were found in adult tapeworms and protoscoleces of E. granulosus sensu stricto and E. multilocularis. Two out of the five parasitic flatworm species carry viruses, showing a host specificity of these viruses. These viruses belong to the Parvoviridae, Circoviridae, unclassified circular, Rep-encoding single-stranded (CRESS) DNA virus, Rhabdoviridae, Endornaviridae, and unclassified RNA viruses. The presence of multiple highly divergent RNA viruses, especially those that cluster with viruses found in marine animals, implies a deep evolutionary history of parasite-associated viruses. In addition, we found viruses with high identity to common pathogens in dogs, including canine circovirus and canine parvovirus 2. The presence of these viruses in the parasites implies that they may infect parasitic flatworms but does not completely exclude the possibility of contamination from host intestinal contents. Furthermore, we demonstrated that certain viruses, such as CRESS DNA virus may integrate into the genome of their host. Our results expand the knowledge of viral diversity in parasites of important domestic animals, highlighting the need for further investigations of their prevalence among other parasites of key animals. IMPORTANCE Characterizing the virome of parasites is important for unveiling the viral diversity, evolution, and ecology and will help to understand the "Russian doll" pattern among viruses, parasites, and host animals. Our data indicate that diverse viruses are present in specific parasitic flatworms, including viruses that may have an ancient evolutionary history and viruses currently circulating in parasite-infected host animals. These data also raise the question of whether parasitic flatworms acquire and/or carry some viruses that may have transmission potential to animals. In addition, through the study of virus-parasite-host interactions, including the influence of viral infection on the life cycle of the parasite, as well as its fitness and pathogenicity to the host, we could find new strategies to prevent and control parasitic diseases.

Adoption of alternative life cycles in a parasitic trematode is linked to microbiome differences

For parasites with complex multi-host life cycles, the facultative truncation of the cycle represents an adaptation to challenging conditions for transmission. However, why certain individuals are capable of abbreviating their life cycle while other conspecifics are not remains poorly understood. Here, we test whether conspecific trematodes that either follow the normal three-host life cycle or skip their final host by reproducing precociously (via progenesis) in an intermediate host differ in the composition of their microbiomes. Characterization of bacterial communities based on sequencing of the V4 hypervariable region of the 16S SSU rRNA gene revealed that the same bacterial taxa occur in both normal and progenetic individuals, independent of host identity and temporal variation. However, all bacterial phyla recorded in our study, and two-thirds of bacterial families, differed in abundance between the two morphs, with some achieving higher abundance in the normal morph and others in the progenetic morph. Although the evidence is purely correlative, our results reveal a weak association between microbiome differences and intraspecific plasticity in life cycle pathways. Advances in functional genomics and experimental microbiome manipulation will allow future tests of the significance of these findings.

Eco-evolutionary implications of helminth microbiomes

The evolution of helminth parasites has long been seen as an interplay between host resistance to infection and the parasite's capacity to bypass such resistance. However, there has recently been an increasing appreciation of the role of symbiotic microbes in the interaction of helminth parasites and their hosts. It is now clear that helminths have a different microbiome from the organisms they parasitize, and sometimes amid large variability, components of the microbiome are shared among different life stages or among populations of the parasite. Helminths have been shown to acquire microbes from their parent generations (vertical transmission) and from their surroundings (horizontal transmission). In this latter case, natural selection has been strongly linked to the fact that helminth-associated microbiota is not simply a random assemblage of the pool of microbes available from their organismal hosts or environments. Indeed, some helminth parasites and specific microbial taxa have evolved complex ecological relationships, ranging from obligate mutualism to reproductive manipulation of the helminth by associated microbes. However, our understanding is still very elementary regarding the net effect of all microbiome components in the eco-evolution of helminths and their interaction with hosts. In this non-exhaustible review, we focus on the bacterial microbiome associated with helminths (as opposed to the microbiome of their hosts) and highlight relevant concepts and key findings in bacterial transmission, ecological associations, and taxonomic and functional diversity of the bacteriome. We integrate the microbiome dimension in a discussion of the evolution of helminth parasites and identify fundamental knowledge gaps, finally suggesting research avenues for understanding the eco-evolutionary impacts of the microbiome in host-parasite interactions in light of new technological developments.

Microsporidian Infection in Mosquitoes (Culicidae) Is Associated with Gut Microbiome Composition and Predicted Gut Microbiome Functional Content

The animal gut microbiota consist of many different microorganisms, mainly bacteria, but archaea, fungi, protozoans, and viruses may also be present. This complex and dynamic community of microorganisms may change during parasitic infection. In the present study, we investigated the effect of the presence of microsporidians on the composition of the mosquito gut microbiota and linked some microbiome taxa and functionalities to infections caused by these parasites. We characterised bacterial communities of 188 mosquito females, of which 108 were positive for microsporidian DNA. To assess how bacterial communities change during microsporidian infection, microbiome structures were identified using 16S rRNA microbial profiling. In total, we identified 46 families and four higher taxa, of which Comamonadaceae, Enterobacteriaceae, Flavobacteriaceae and Pseudomonadaceae were the most abundant mosquito-associated bacterial families. Our data suggest that the mosquito gut microbial composition varies among host species. In addition, we found a correlation between the microbiome composition and the presence of microsporidians. The prediction of metagenome functional content from the 16S rRNA gene sequencing suggests that microsporidian infection is characterised by some bacterial species capable of specific metabolic functions, especially the biosynthesis of ansamycins and vancomycin antibiotics and the pentose phosphate pathway. Moreover, we detected a positive correlation between the presence of microsporidian DNA and bacteria belonging to Spiroplasmataceae and Leuconostocaceae, each represented by a single species, Spiroplasma sp. PL03 and Weissella cf. viridescens, respectively. Additionally, W. cf. viridescens was observed only in microsporidian-infected mosquitoes. More extensive research, including intensive and varied host sampling, as well as determination of metabolic activities based on quantitative methods, should be carried out to confirm our results.

Guts within guts: the microbiome of the intestinal helminth parasite Ascaris suum is derived but distinct from its host

BACKGROUND

Intestinal helminths are extremely prevalent among humans and animals. In particular, intestinal roundworms affect more than 1 billion people around the globe and are a major issue in animal husbandry. These pathogens live in intimate contact with the host gut microbiota and harbor bacteria within their own intestines. Knowledge of the bacterial host microbiome at the site of infection is limited, and data on the parasite microbiome is, to the best of our knowledge, non-existent.

RESULTS

The intestinal microbiome of the natural parasite and zoonotic macropathogen, Ascaris suum was analyzed in contrast to the diversity and composition of the infected host gut. 16S sequencing of the parasite intestine and host intestinal compartments showed that the parasite gut has a significantly less diverse microbiome than its host, and the host gut exhibits a reduced microbiome diversity at the site of parasite infection in the jejunum. While the host's microbiome composition at the site of infection significantly determines the microbiome composition of its parasite, microbial signatures differentiate the nematodes from their hosts as the Ascaris intestine supports the growth of microbes that are otherwise under-represented in the host gut.

CONCLUSION

Our data clearly indicate that a nematode infection reduces the microbiome diversity of the host gut, and that the nematode gut represents a selective bacterial niche harboring bacteria that are derived but distinct from the host gut. Video Abstract.

Environments and Hosts Structure the Bacterial Microbiomes of Fungus-Gardening Ants and their Symbiotic Fungus Gardens

The fungus gardening-ant system is considered a complex, multi-tiered symbiosis, as it is composed of ants, their fungus, and microorganisms associated with either ants or fungus. We examine the bacterial microbiome of Trachymyrmex septentrionalis and Mycetomoellerius turrifex ants and their symbiotic fungus gardens, using 16S rRNA Illumina sequencing, over a region spanning approximately 350 km (east and central Texas). Typically, microorganisms can be acquired from a parent colony (vertical transmission) or from the environment (horizontal transmission). Because the symbiosis is characterized by co-dispersal of the ants and fungus, elements of both ant and fungus garden microbiome could be characterized by vertical transmission. The goals of this study were to explore how both the ant and fungus garden bacterial microbiome are acquired. The main findings were that different mechanisms appear to explain the structure the microbiomes of ants and their symbiotic fungus gardens. Ant associated microbiomes had a strong host ant signature, which could be indicative of vertical inheritance of the ant associated bacterial microbiome or an unknown mechanism of active uptake or screening. On the other hand, the bacterial microbiome of the fungus garden was more complex in that some bacterial taxa appear to be structured by the ant host species, whereas others by fungal lineage or the environment (geographic region). Thus bacteria in fungus gardens appear to be acquired both horizontally and vertically.

Association between parasite microbiomes and caste development and colony structure in a social trematode

Division of labour through the formation of morphologically and functionally distinct castes is a recurring theme in the evolution of animal sociality. The mechanisms driving the differentiation of individuals into distinct castes remain poorly understood, especially for animals forming clonal colonies. We test the association between microbiomes and caste formation within the social trematode Philophthalmus attenuatus, using a metabarcoding approach targeting the bacterial 16S SSU rRNA gene. Clonal colonies of this trematode within snail hosts comprise large reproductive individuals which produce dispersal stages, and small, non-reproducing soldiers which defend the colony against invaders. In colonies extracted directly from field-collected snails, reproductives harboured more diverse bacterial communities than soldiers, and reproductives and soldiers harboured distinct bacterial communities, at all taxonomic levels considered. No single bacterial taxon showed high enough prevalence in either soldiers or reproductives to be singled out as a key driver, indicating that the whole microbial community contributes to these differences. Other colonies were experimentally exposed to antibiotics to alter their bacterial communities, and sampled shortly after treatment and weeks later after allowing for turnover of colony members. At those time points, bacterial communities of the two castes still differed across all antibiotic treatments; however, the caste ratio within colonies changed: after antibiotic disruption and turnover of individuals, new individuals were more likely to become reproductives than in undisturbed control colonies. Our results reveal that each caste has a distinct microbiome; whether the social context affects the microbiota, or whether microbes contribute to modulating the phenotype of individuals, remains to be determined.

Regulation of amino acid metabolism in Aphis gossypii parasitized by Binodoxys communis

The vast majority of parasitoids are capable of precise and meticulous regulation of nutrition and metabolism within the host. An important building block of life, amino acids are critical to the development of parasitoids. To date, research on how parasitoids regulate host amino acid metabolism remains limited. In this study, Aphis gossypii and its dominant parasitoid Binodoxys communis were used as a study system to explore how parasitism may change the regulation of amino acids in A. gossypii with UHPLC-MS/MS and RT-qPCR techniques. Here, for the first 8 h of parasitism the abundance of almost all amino acids in cotton aphids increased, and after 16 h most of the amino acids decreased. An amino acid of parasitic syndrome, the content of Tyr increased gradually after being parasitized. The expression of genes related to amino acid metabolism increased significantly in early stages of parasitism and then significantly decreased gradually. At the same time, the abundance of Buchnera, a cotton aphid specific symbiont increased significantly. Our comprehensive analyses reveal impacts of B. communis on the amino acid regulatory network in cotton aphid from three aspects: amino acid metabolism, gene expression, and bacterial symbionts. Therefore, this research provides an important theoretical basis for parasitoid nutritional regulation in host, which is highly significant as it may inform the artificial reproduction of parasitoids and the biological control of insect pests.

Inter-individual variation in parasite manipulation of host phenotype: A role for parasite microbiomes?

Alterations in host phenotype induced by metazoan parasites are widespread in nature, yet the underlying mechanisms and the sources of intraspecific variation in the extent of those alterations remain poorly understood. In light of the microbiome revolution sweeping through ecology and evolutionary biology, we hypothesise that the composition of symbiotic microbial communities living within individual parasites influences the nature and extent of their effect on host phenotype. The interests of both the parasite and its symbionts are aligned through the latter's vertical transmission, favouring joint contributions to the manipulation of host phenotype. Our hypothesis can explain the variation in the extent to which parasites alter host phenotype, as microbiome composition varies among individual parasites. We propose two non-exclusive approaches to test the hypothesis, furthering the integration of microbiomes into studies of host-parasite interactions.

Consistency of Bacterial Communities in a Parasitic Worm: Variation Throughout the Life Cycle and Across Geographic Space

Microbial communities within metazoans are increasingly linked with development, health and behaviour, possibly functioning as integrated evolutionary units with the animal in which they live. This would require microbial communities to show some consistency both ontogenetically (across life stages) and geographically (among populations). We characterise the bacteriome of the parasitic trematode Philophthalmus attenuatus, which undergoes major life cycle transitions, and test whether its bacteriome remains consistent on developmental and spatial scales. Based on sequencing the prokaryotic 16S SSU rRNA gene, we compared the parasite bacteriome (i) across three life stages (rediae in snails, cercariae exiting snails, adults in birds) in one locality and (ii) among three geographic localities for rediae only. We found that each life stage harbours a bacteriome different from that of its host (except the adult stage) and the external environment. Very few bacterial taxa were shared among life stages, suggesting substantial ontogenetic turnover in bacteriome composition. Rediae from the three different localities also had different bacteriomes, with dissimilarities increasing with geographical distance. However, rediae from different localities nevertheless shared more bacterial taxa than did different life stages from the same locality. Changes in the bacteriome along the parasite's developmental history but some degree of geographical stability within a given life stage point toward non-random, stage-specific acquisition, selection and/or propagation of bacteria.

MIxS-SA: a MIxS extension defining the minimum information standard for sequence data from symbiont-associated micro-organisms

The symbiont-associated (SA) environmental package is a new extension to the minimum information about any (x) sequence (MIxS) standards, established by the Parasite Microbiome Project (PMP) consortium, in collaboration with the Genomics Standard Consortium. The SA was built upon the host-associated MIxS standard, but reflects the nestedness of symbiont-associated microbiota within and across host-symbiont-microbe interactions. This package is designed to facilitate the collection and reporting of a broad range of metadata information that apply to symbionts such as life history traits, association with one or multiple host organisms, or the nature of host-symbiont interactions along the mutualism-parasitism continuum. To better reflect the inherent nestedness of all biological systems, we present a novel feature that allows users to co-localize samples, to nest a package within another package, and to identify replicates. Adoption of the MIxS-SA and of the new terms will facilitate reports of complex sampling design from a myriad of environments.

Bacterial community dynamics following antibiotic exposure in a trematode parasite

Parasites harbour rich microbial communities that may play a role in host-parasite interactions, from influencing the parasite's infectivity to modulating its virulence. Experimental manipulation of a parasite's microbes would be essential, however, in order to establish their causal role. Here, we tested whether indirect exposure of a trematode parasite within its snail intermediate host to a variety of antibiotics could alter its bacterial community. Based on sequencing the prokaryotic 16S ssrRNA gene, we characterised and compared the bacterial community of the trematode Philophthalmus attenuatus before, shortly after, and weeks after exposure to different antibiotics (penicillin, colistin, gentamicin) with distinct activity spectra. Our findings revealed that indirectly treating the parasites by exposing their snail host to antibiotics resulted in changes to their bacterial communities, measured as their diversity, taxonomic composition, and/or the relative abundance of certain taxa. However, alterations to the parasite's bacterial community were not always as predicted from the activity spectrum of the antibiotic used. Furthermore, the bacterial communities of the parasites followed significantly divergent trajectories in the days post-exposure to antibiotics, but later converged toward a new state, i.e. a new bacterial community structure different from that pre-exposure. Our results confirm that a trematode's microbial community can be experimentally altered by antibiotic exposure while within its snail host, with the dynamic nature of the bacterial assemblage driving it to a new state over time after the perturbation. This research opens new possibilities for future experimental investigations of the functional roles of microbes in host-parasite interactions.

Investigation and molecular identification of Eimeria sp. sampled from captive forest musk deer

Forest musk deer (Moschus berezovskii) is an endangered, protected species in China. Intestinal coccidiosis is a significant problem for captive forest musk deer. However, there are few reports on the prevalence and molecular characteristics of Eimeria sp. in forest musk deer. We sought to investigate the prevalence of Eimeria sp. in forest musk deer in the Sichuan and Shaanxi provinces in China. We also investigated the molecular characteristics of Eimeria sp. by analyzing the 18S rRNA gene. We collected a total of 328 fecal samples from forest musk deer on seven farms throughout the Sichuan and Shaanxi provinces. We extracted this parasite’s DNA and used this as a template for nested PCR amplification. The 18S rRNA gene fragment was associated with the plasmid vector, and these products were introduced into Escherichia coli (DH5α). The cultured bacterial solution was used as a PCR reaction template for identification purposes. We collected 328 fecal samples from forest musk deer in Lixian (n = 54), Maoxian (n = 52), Ma’erkang (n = 49), Dujiangyan (n = 55), Hanyuan (n = 41), Luding (n = 36) and Weinan (n = 41). One hundred ninety-eight (60.37%) fecal samples tested positive for Eimeria sp. . In our analysis of the 18S rRNA gene we found 34 types of Eimeria sp. with a similarity of 90.5–100%. We constructed a phylogenetic tree based on the parasite’s 18S rRNA gene sequence. Our findings indicated that the Eimeria sp. that parasitized the intestinal tract of forest musk deer was closely related to Eimeria alabamensis from Bos taurus and Eimeria ahsata from Ovis aries. To the best of our knowledge, ours was the first investigation and molecular identification of Eimeria sp. sampled from captive forest musk deer in China. Our results provide epidemiological data for the monitoring and prevention of Eimeria sp. in captive forest musk deer.

The rise of ecological parasitology: twelve landmark advances that changed its history

In the five decades since the first publication of the International Journal for Parasitology, ecological parasitology has grown from modest beginnings to become a modern discipline with a strong theoretical foundation, a diverse toolkit, and a multidisciplinary approach. In this review, I highlight 12 advances in the field that have spurred its growth over the past 50 years. Where relevant, I identify pivotal contributions that have altered the course of research, as well as the influence of developments in other fields such as mainstream ecology and molecular biology. The 12 key advances discussed are in areas including parasite population dynamics and community assembly, the regulation of host population abundance and food web structure, parasites as agents of natural selection, the impacts of biodiversity and anthropogenic changes on host-parasite interactions, the biogeography of parasite diversity, and the evolutionary genetics of parasites. I conclude by identifying some challenges and opportunities lying ahead, which need to be met for the future growth of ecological research on host-parasite interactions.

Characterization and comparison of the bacterial microbiota of Lysiphlebia japonica parasitioid wasps and their aphid host Aphis gosypii

BACKGROUND

Endosymbiotic bacteria have been reported to mediate interactions between parasitoids and their insect hosts. How parasitic wasps influence changes in host microbial communities and the relationship between them are of great importance to the study of host-parasitoid co-evolutionary and ecological interactions. However, these interactions remain largely unreported for interactions between Aphis gossypii and Lysiphlebia japonica.

RESULTS

In this study, we characterize the bacterial microbiota of L. japonica wasps at different developmental stages and monitor changes over time in the bacterial microbiota of their parasitized and nonparasitized aphid hosts, using metagenomic analysis of 16S rDNA sequencing data. Proteobacteria, Firmicutes, and Actinobacteria were the three most abundant bacterial phyla identified in L. japonica. We found that parasitism was associated with an increased abundance of Buchnera nutritional endosymbionts, but decreased abundance of Acinetobacter, Arsenophonus, Candidatus_Hamiltonella, and Pseudomonas facultative symbionts in aphid hosts. Functional analysis of enriched pathways of parasitized aphids showed significant differences in the 'transport and metabolism of carbohydrates' and 'amino acid, lipid, and coenzyme biosynthesis' pathways. Notably, the composition of symbiotic bacteria in wasp larvae was highly similar to that of their aphid hosts, especially the high abundance of Buchnera.

CONCLUSION

The results provide a conceptual framework for L. japonica interactions with A. gossypii in which the exchange of symbiotic microbes provides a means by which microbiota can potentially serve as evolutionary drivers of complex, multilevel interactions underlying the ecology and co-evolution of these hosts and parasites. © 2021 Society of Chemical Industry.

As vicissitudes do matar. Conflitos ontológicos em um estudo sobre leishmaniose tegumentar americana na TI Wajãpi

Resumo A partir de uma pesquisa sobre os padrões epidemiológicos de leishmaniose tegumentar americana na Terra Indígena Wajãpi (AP), tomo como ponto de partida as perspectivas de alguns Wajãpi e de cientistas para explorar aspectos das ontologias em disputas nesse contexto. Oscilando entre os diferentes sujeitos dessa pesquisa, pretendo refletir e descrever como cada um deles compreende questões comuns como: a matabilidade de alguns seres, as relações com diferentes níveis de alteridade e as perspectivas das relações interespecíficas.

Synthesized OH-radical rich bacteria cellulosic pockets with photodynamic bacteria inactivation properties against S. ureus and E. coli

Inulin as an external carbon source was used as the fructose substitute to Gluconacetobacter xylinus (ATCC 10245) bacterial strain in a successful synthesis of cellulosic pockets to be used in drug delivery and storage. It was observed that inulobiose trans conformation was in agreement with ϕ = Ψ = ω = 180° and angular rotation of ϴ (C1-C2-0-CI''), ϴ (C2-0-C 1'-C2') and ϴ (0-C1'-C2'-0') respectively. A bacterial susceptibility test revealed a successful inactivation of Staphylococcus aureus and Escherichia coli in the presence of photons. Fourier Transform Infrared Spectroscopy analysis confirmed an OH absorption was verified at 3423 cm^-1. Pocket drug uptake test revealed a highly absorbent structure with the thermal stability directly proportional to the increase in drug uptake, while the increase in the degree of polymerization resulted in the increase in antioxidant activity and rate of bacterial inactivation. HYPOTHESIS: Inulin as an inert polysaccharide is neutral to cellular activity, therefore, could not be an agent for bacteria inactivation.

The role of innate immunity in the protection conferred by a bacterial infection against cancer: study of an invertebrate model

All multicellular organisms are exposed to a diversity of infectious agents and to the emergence and proliferation of malignant cells. The protection conferred by some infections against cancer has been recently linked to the production of acquired immunity effectors such as antibodies. However, the evolution of innate immunity as a mechanism to prevent cancer and how it is jeopardized by infections remain poorly investigated. Here, we explored this question by performing experimental infections in two genetically modified invertebrate models (Drosophila melanogaster) that develop invasive or non-invasive neoplastic brain tumors. After quantifying tumor size and antimicrobial peptide gene expression, we found that Drosophila larvae infected with a naturally occurring bacterium had smaller tumors compared to controls and to fungus-infected larvae. This was associated with the upregulation of genes encoding two antimicrobial peptides-diptericin and drosomycin-that are known to be important mediators of tumor cell death. We further confirmed that tumor regression upon infection was associated with an increase in tumor cell death. Thus, our study suggests that infection could have a protective role through the production of antimicrobial peptides that increase tumor cell death. Finally, our study highlights the need to understand the role of innate immune effectors in the complex interactions between infections and cancer cell communities in order to develop innovative cancer treatment strategies.

Insights into the Natural Defenses of a Coral Reef Fish Against Gill Ectoparasites: Integrated Metabolome and Microbiome Approach

Understanding natural defense mechanisms against parasites can be a valuable tool for the development of innovative therapies. We have previously identified a butterflyfish species (Chaetodon lunulatus) that avoids gill monogenean parasites while living amongst closely related parasitized species. The metabolome and microbiome of several sympatric butterflyfish species from the island of Moorea (French Polynesia) were previously described. In this study, we used the previously generated datasets in an attempt to identify metabolites and bacteria potentially involved in parasite defense mechanisms. We investigated the interplay between the gill mucus metabolome and microbiome of the non-susceptible C. lunulatus versus sympatric butterflyfish species that were always found parasitized in the Central and Eastern Indo-Pacific. After observing significant differences between the metabolome and bacteria of susceptible versus non-susceptible fish, we obtained the discriminant metabolites and operational taxonomic units (OTUs) using a supervised analysis. Some of the most important discriminant metabolites were identified as peptides, and three new peptides derived from β-subunit hemoglobin from C. lunulatus (CLHbβ-1, CLHbβ-2, and CLHbβ-3) were purified, characterized and synthesized to confirm their structures. We also identified specific bacterial families and OTUs typical from low-oxygen habitats in C. lunulatus gill mucus. By using a correlation network between the two datasets, we found a Fusobacteriaceae strain exclusively present in C. lunulatus and highly correlated to the peptides. Finally, we discuss the possible involvement of these peptides and Fusobacteriaceae in monogenean avoidance by this fish species.

Persistence of a Core Microbiome Through the Ontogeny of a Multi-Host Parasite

Animal microbiomes influence their development, behavior and interactions with other organisms. Parasitic metazoans also harbor microbial communities; although they are likely to modulate host-parasite interactions, little is known about parasite microbiomes. The persistence of microbial communities throughout the life of a parasite is particularly challenging for helminths with complex life cycles. These parasites undergo major morphological changes during their life, and parasitize host species that are immunologically, physiologically, and phylogenetically very different. Here, using 16S amplicon sequencing, we characterize the microbiome of the trematode Coitocaecum parvum across four of its life stages: sporocysts, metacercariae and adults inhabiting (respectively) snails, crustaceans and fish, as well as free-living cercariae. Our results demonstrate that, at each life stage, the parasite possesses a phylogenetically diverse microbiome, distinct from that of its hosts or the external environment. The parasite's microbiome comprises bacterial taxa specific to each life stage in different hosts, as well as a small core set of taxa that persists across the parasite's whole life. The apparent existence of an ontogenetically and vertically transmitted core microbiome is supported by the findings that the diversity and taxonomic composition of the microbiome does not vary significantly among life stages, and that the main source of microbial taxa at any life stage is the previous life stage. Our results suggest that microbes are an integrated component of the trematode, possibly shaping its phenotype and host-parasite interactions.

Characterization of viruses in a tapeworm: phylogenetic position, vertical transmission, and transmission to the parasitized host

Parasitic flatworms (Neodermata) infect all vertebrates and represent a significant health and economic burden worldwide due to the debilitating diseases they cause. This study sheds light for the first time into the virome of a tapeworm by describing six novel RNA virus candidate species associated with Schistocephalus solidus, including three negative-strand RNA viruses (order Jingchuvirales, Mononegavirales, and Bunyavirales) and three double-stranded RNA viruses. Using in vitro culture of S. solidus, controlled experimental infections and field sampling, we demonstrate that five of these viruses are vertically transmitted, and persist throughout the S. solidus complex life cycle. Moreover, we show that one of the viruses, named Schistocephalus solidus rhabdovirus (SsRV1), is excreted by the parasite and transmitted to parasitized hosts indicating that it may impact S. solidus-host interactions. In addition, SsRV1 has a basal phylogenetic position relative to vertebrate rhabdoviruses suggesting that parasitic flatworms could have contributed to virus emergence. Viruses similar to four of the S. solidus viruses identified here were found in geographically distant S. solidus populations through data mining. Further studies are necessary to determine if flatworm viruses can replicate in parasitized hosts, how they contribute to parasite infection dynamics and if these viruses could be targeted for treatment of parasitic disease.

Unique bacterial assembly, composition, and interactions in a parasitic plant and its host

How plant-associated microbiota are shaped by, and potentially contribute to, the unique ecology and heterotrophic life history of parasitic plants is relatively unknown. Here, we investigate the leaf and root bacterial communities of the root holoparasite Orobanche hederae and its host Hedera spp. from natural populations. Root bacteria inhabiting Orobanche were less diverse, had fewer co-associations, and displayed increased compositional similarity to leaf bacteria relative to Hedera. Overall, Orobanche bacteria exhibited significant congruency with Hedera root bacteria across sites, but not the surrounding soil. Infection had localized and systemic effects on Hedera bacteria, which included effects on the abundance of individual taxa and root network properties. Collectively, our results indicate that the parasitic plant microbiome is derived but distinct from the host plant microbiota, exhibits increased homogenization between shoot and root tissues, and displays far fewer co-associations among individual bacterial members. Host plant infection is accompanied by modest changes of associated microbiota at both local and systemic scales compared with uninfected individuals. Our results are a first step towards extending the growing insight into the assembly and function of the plant microbiome to include the ecologically unique but often overlooked guild of heterotrophic plants.

The state of fish parasite discovery and taxonomy: a critical assessment and a look forward

Efforts to find and characterise new parasite species in fish hosts are crucial not just to complete our inventory of Earth's biodiversity, but also to monitor and mitigate disease threats in fisheries and aquaculture in the face of global climate change. Here, we review recent quantitative assessments of research efforts into fish parasite discovery and taxonomy. We address broad questions including: Are efforts aimed at finding new parasite species targeted at geographical hotspots of fish biodiversity, where there should be more parasite species to be found? Is the application of molecular tools to study parasite genetic diversity deployed strategically across regions of the world, or focused disproportionately on certain areas? How well coordinated is the search for new parasite species of fish among workers specialising on different higher helminth taxa? Are parasite discovery efforts in any geographical area consistent over time, or subject to idiosyncrasies due to the waxing and waning of highly prolific research careers? Is the quality of taxonomic descriptions of new species improving over time, with the incorporation of new tools to characterise species? Are taxonomic descriptions moving away from a focus on the adult stage only toward attempts to characterise the full life cycle of newly-discovered helminth species? By using empirical evidence to answer these questions, we assess the current state of research into fish parasite discovery and taxonomy. We also explore the far-reaching implications of recent research on parasite microbiomes for parasite taxonomy. We end with recommendations aimed at maximising the knowledge gained per fish sacrificed, and per dollar and time invested into research on fish parasite biodiversity.

Parasites modulate the gut-microbiome in insects: A proof-of-concept study

Host-parasite interactions may be modulated by host- or parasite-associated microbes, but the role of these are often overlooked. Particularly for parasites with intestinal stages (either larval or adult), the host gut microbiome may play a key role for parasite establishment; moreover, the microbiome may change in response to invading parasites. Hypothesis testing at the organismal level may be hampered, particularly in mammalian definitive hosts, by ethical, logistical, and economical restrictions. Thus, invertebrates naturally serving as intermediate hosts to parasites with complex life cycles may inform the development of mammalian models as an early-stage host-parasite model. In addition, several important pathogens are vectored by insects, and insect gut microbiome-pathogen interactions may provide essential base-line knowledge, which may be used to control vectorborne pathogens. Here, we used the grain beetle, Tenebrio molitor, a host of the tapeworm Hymenolepis diminuta, to explore interactions between infection status and resident gut microbiota at two pre-determined time points (day two and seven) post infection. Using 16S/18S microbial profiling, we measured key parameters of the composition, relative abundance, and diversity of the host gut bacteriome and mycobiome. In addition, we quantified the systemic beetle immune response to infection by Phenoloxidase activity and hemocyte abundance. We found significant changes in the gut bacteriome and mycobiome in relation to infection status and beetle age. Thus, the relative abundance of Proteobacteria was significantly higher in the gut of infected beetles and driven mostly by an increased abundance of Acinetobacter. In addition, the mycobiome was less abundant in infected beetles but maintained higher Shannon diversity in infected compared with non-infected beetles. Beetles treated with a broad-spectrum antibiotic (Tetracycline) exhibited significantly reduced parasite establishment compared with the untreated control group, indicating that the host microbiome may greatly influence hatching of eggs and subsequent establishment of H. diminuta larvae. Our results suggest that experimental work using invertebrates may provide a platform for explorative studies of host-parasite-microbe interactions and their underlying mechanisms.

Amphibian Host and Skin Microbiota Response to a Common Agricultural Antimicrobial and Internal Parasite

Holistic approaches that simultaneously characterize responses of both microbial symbionts and their hosts to environmental shifts are imperative to understanding the role of microbiotas on host health. Using the northern leopard frog (Lithobates pipiens) as our model, we investigated the effects of a common trematode (family Echinostomatidae), a common agricultural antimicrobial (Sulfadimethoxine; SDM), and their interaction on amphibian skin microbiota and amphibian health (growth metrics and susceptibility to parasites). In the trematode-exposed individuals, we noted an increase in alpha diversity and a shift in microbial communities. In the SDM-treated individuals, we found a change in the composition of the skin microbiota similar to those induced by the trematode treatment. Groups treated with SDM, echinostomes, or a combination of SDM and echinostomes, had higher relative abundances of OTUs assigned to Flavobacterium and Acinetobacter. Both of these genera have been associated with infectious disease in amphibians and the production of anti-pathogen metabolites. Similar changes in microbial community composition between SDM and trematode exposed individuals may have resulted from stress-related disruption of host immunity. Despite changes in the microbiota, we found no effect of echinostomes and SDM on host health. Given the current disease- and pollution-related threats facing amphibians, our study highlights the need to continue to evaluate the influence of natural and anthropogenic stressors on host-associated microbial communities.

Petroleum Hydrocarbon Contamination in Terrestrial Ecosystems-Fate and Microbial Responses

Petroleum hydrocarbons represent the most frequent environmental contaminant. The introduction of petroleum hydrocarbons into a pristine environment immediately changes the nature of that environment, resulting in reduced ecosystem functionality. Natural attenuation represents the single, most important biological process which removes petroleum hydrocarbons from the environment. It is a process where microorganisms present at the site degrade the organic contaminants without the input of external bioremediation enhancers (i.e., electron donors, electron acceptors, other microorganisms or nutrients). So successful is this natural attenuation process that in environmental biotechnology, bioremediation has developed steadily over the past 50 years based on this natural biodegradation process. Bioremediation is recognized as the most environmentally friendly remediation approach for the removal of petroleum hydrocarbons from an environment as it does not require intensive chemical, mechanical, and costly interventions. However, it is under-utilized as a commercial remediation strategy due to incomplete hydrocarbon catabolism and lengthy remediation times when compared with rival technologies. This review aims to describe the fate of petroleum hydrocarbons in the environment and discuss their interactions with abiotic and biotic components of the environment under both aerobic and anaerobic conditions. Furthermore, the mechanisms for dealing with petroleum hydrocarbon contamination in the environment will be examined. When petroleum hydrocarbons contaminate land, they start to interact with its surrounding, including physical (dispersion), physiochemical (evaporation, dissolution, sorption), chemical (photo-oxidation, auto-oxidation), and biological (plant and microbial catabolism of hydrocarbons) interactions. As microorganism (including bacteria and fungi) play an important role in the degradation of petroleum hydrocarbons, investigations into the microbial communities within contaminated soils is essential for any bioremediation project. This review highlights the fate of petroleum hydrocarbons in tertial environments, as well as the contributions of different microbial consortia for optimum petroleum hydrocarbon bioremediation potential. The impact of high-throughput metagenomic sequencing in determining the underlying degradation mechanisms is also discussed. This knowledge will aid the development of more efficient, cost-effective commercial bioremediation technologies.

Chemical language and warfare of bacterial natural products in bacteria-nematode-insect interactions

Covering: up to November 2017 Organismic interaction is one of the fundamental principles for survival in any ecosystem. Today, numerous examples show the interaction between microorganisms like bacteria and higher eukaryotes that can be anything between mutualistic to parasitic/pathogenic symbioses. There is also increasing evidence that microorganisms are used by higher eukaryotes not only for the supply of essential factors like vitamins but also as biological weapons to protect themselves or to kill other organisms. Excellent examples for such systems are entomopathogenic nematodes of the genera Heterorhabditis and Steinernema that live in mutualistic symbiosis with bacteria of the genera Photorhabdus and Xenorhabdus, respectively. Although these systems have been used successfully in organic farming on an industrial scale, it was only shown during the last 15 years that several different natural products (NPs) produced by the bacteria play key roles in the complex life cycle of the bacterial symbionts, the nematode host and the insect prey that is killed by and provides nutrients for the nematode-bacteria pair. Since the bacteria can switch from mutualistic to pathogenic lifestyle, interacting with two different types of higher eukaryotes, and since the full system with all players can be established in the lab, they are promising model systems to elucidate the natural function of microbial NPs. This review summarizes the current knowledge as well as open questions for NPs from Photorhabdus and Xenorhabdus and tries to assign their roles in the tritrophic relationship.

What's gotten into you?: a review of recent research on parasitoid manipulation of host behavior

Some parasitoids modify the behavior of their hosts, benefiting themselves at the host's expense. This phenomenon is called 'manipulation', and current research on parasitoid manipulation of host behavior tends to fall into one of three categories. First, the frequency of manipulation and the magnitude of its benefits to the parasitoid remains unclear. Basic documentation of manipulations is thus a major research focus, with especially valuable recent data coming from spiders manipulated by Polysphincta wasps. Second, for a handful of systems, we now have sufficient phylogenetic and behavioral data to begin asking questions about how manipulation evolved. Finally, the field continues to probe the mechanisms through which parasitoids manipulate host behavior, and now examines the role of parasitoid symbionts in this interaction.

Dissecting the Heterogeneous Population Genetic Structure of Candida albicans: Limitations and Constraints of the Multilocus Sequence Typing Scheme

Candida albicans is a fungal opportunistic pathogen of significant public health importance mainly due to the recent emergence of strains with increased aggressiveness and antifungal resistance. Here, we aimed to describe the epidemiological profiles and approximate the population structure of C. albicans by analyzing the C. albicans multilocus sequence typing (MLST) database (Calb-MLST-DB), which contains the largest publically available dataset for this species. Based on 4,318 database isolates, we confirmed the ubiquitous nature of C. albicans including a group of diploid sequence types (DSTs) obtained from Healthy individuals exclusively (taken as an indicator of lack of association with illnesses in its host), until isolates established from Non-Healthy individuals (potentially associated with pathogenic processes) and other DSTs reported in both types (Healthy and Non-Healthy). The highest number of reported DSTs was related to blood, oral and vaginal swabs (32.4, 20.5, and 13.8%, respectively). High genetic diversity was observed in the seven housekeeping genes included in the MLST scheme, with a diverse population structure (154 clonal complexes, CCs; and a high number of singletons, n = 1,074). Phylogenetic reconstruction on the concatenated alignment of these housekeeping genes for all the reported DSTs (n = 3,483) was partially concordant with the CC assignment, however, an absence of bootstrap threshold supported nodes or p-distance, and the lack of association with the other epidemiological variables, evidenced the limitations of the MLST scheme. Marked genetic admixture signals were identified by STRUCTURE, with the majority being attributable to recombination events according to the RDP program results, although another type of exchange event cannot be ruled out. Our results reaffirm the genetic diversity inherent in the genes used for the MLST scheme, which are associated with the chromosomal remodeling already proposed for C. albicans. This was also corroborated with an internal validation at a micro geographical scale. Despite these results are biased due to the unavailability of considering the broad global spectrum of C. albicans isolates around the world. This suggests that the strategy used to population type this pathogen should be reevaluated to improve epidemiological monitoring of its health impact.

Parasite Microbiome Project: Systematic Investigation of Microbiome Dynamics within and across Parasite-Host Interactions

Understanding how microbiomes affect host resistance, parasite virulence, and parasite-associated diseases requires a collaborative effort between parasitologists, microbial ecologists, virologists, and immunologists. We hereby propose the Parasite Microbiome Project to bring together researchers with complementary expertise and to study the role of microbes in host-parasite interactions.

Understanding how microbiomes affect host resistance, parasite virulence, and parasite-associated diseases requires a collaborative effort between parasitologists, microbial ecologists, virologists, and immunologists. We hereby propose the Parasite Microbiome Project to bring together researchers with complementary expertise and to study the role of microbes in host-parasite interactions. Data from the Parasite Microbiome Project will help identify the mechanisms driving microbiome variation in parasites and infected hosts and how that variation is associated with the ecology and evolution of parasites and their disease outcomes. This is a call to arms to prevent fragmented research endeavors, encourage best practices in experimental approaches, and allow reliable comparative analyses across model systems. It is also an invitation to foundations and national funding agencies to propel the field of parasitology into the microbiome/metagenomic era.

Immune response and gut microbial community structure in bumblebees after microbiota transplants

Microbial communities are a key component of host health. As the microbiota is initially 'foreign' to a host, the host's immune system should respond to its acquisition. Such variation in the response should relate not only to host genetic background, but also to differences in the beneficial properties of the microbiota. However, little is known about such interactions. Here, we investigate the gut microbiota of the bumblebee, Bombus terrestris, which has a protective function against the bee's natural trypanosome gut parasite, Crithidia bombi We transplanted 'resistant' and 'susceptible' microbiota into 'resistant' and 'susceptible' host backgrounds, and studied the activity of the host immune system. We found that bees from different resistance backgrounds receiving a microbiota differed in aspects of their immune response. At the same time, the elicited immune response also depended on the received microbiota's resistance phenotype. Furthermore, the microbial community composition differed between microbiota resistance phenotypes (resistant versus susceptible). Our results underline the complex feedback between the host's ability to potentially exert selection on the establishment of a microbial community and the influence of the microbial community on the host immune response in turn.

Parasitoid wasp usurps its host to guard its pupa against hyperparasitoids and induces rapid behavioral changes in the parasitized host

Some parasites have an ability to fabricate the behavior of their host and impel the host to guard parasites' offspring, which is popularly called as bodyguard manipulation. Psalis pennatula larva parasitized by a braconid parasitoid wasp Microplitis pennatula exhibits some behavioral changes including the guarding of the parasitoid pupa from its natural enemies. We hypothesized that these behavioral change exhibited by the parasitized host larva are induced by the parasitoid and can be considered as an example of bodyguard manipulation. Even though hyperparasitoids are the more specialized natural enemy of parasitoids than predators, very few studies tested the success of guarding parasitoid pupa against hyperparasitoids. This study analyzed the success of guarding behavior of the parasitized host against hyperparasitoids. The onsets of parasite-induced phenotypic alterations (PIPAs) in the parasitized host were inspected to analyze whether these behavioral changes in the host larva manifests gradually or abruptly. The study concludes that parasitized host larva defends the parasitoid pupa from hyperparasitoids and the PIPAs in the parasitized host develops abruptly only after the egression of parasitoid prepupa.

Experimental Models to Study the Role of Microbes in Host-Parasite Interactions

Until recently, parasitic infections have been primarily studied as interactions between the parasite and the host, leaving out crucial players: microbes. The recent realization that microbes play key roles in the biology of all living organisms is not only challenging our understanding of host-parasite evolution, but it also provides new clues to develop new therapies and remediation strategies. In this paper we provide a review of promising and advanced experimental organismal systems to examine the dynamic of host-parasite-microbe interactions. We address the benefits of developing new experimental models appropriate to this new research area and identify systems that offer the best promises considering the nature of the interactions among hosts, parasites, and microbes. Based on these systems, we identify key criteria for selecting experimental models to elucidate the fundamental principles of these complex webs of interactions. It appears that no model is ideal and that complementary studies should be performed on different systems in order to understand the driving roles of microbes in host and parasite evolution.

The role of hyperparasitism in microbial pathogen ecology and evolution

Many micro-organisms employ a parasitic lifestyle and, through their antagonistic interactions with host populations, have major impacts on human, agricultural and natural ecosystems. Most pathogens are likely to host parasites of their own, that is, hyperparasites, but how nested chains of parasites impact on disease dynamics is grossly neglected in the ecological and evolutionary literature. In this minireview we argue that the diversity and dynamics of micro-hyperparasites are an important component of natural host-pathogen systems. We use the current literature from a handful of key systems to show that observed patterns of pathogen virulence and disease dynamics may well be influenced by hyperparasites. Exploring these factors will shed light on many aspects of microbial ecology and disease biology, including resistance-virulence evolution, apparent competition, epidemiology and ecosystem stability. Considering the importance of hyperparasites in natural populations will have applied consequences for the field of biological control and therapeutic science, where hyperparastism is employed as a control mechanism but not necessarily ecologically understood.

Detection of the bacterial endosymbiont Neorickettsia in a New Zealand digenean

Neorickettsia are endosymbiotic bacteria that infect digeneans (Trematoda). These bacteria are of interest worldwide because of their ability to move from the parasite to its host, where they can cause serious diseases of humans and animals. While several disease-forming species of Neorickettsia have been well studied, and numerous Neorickettsia types have been identified in regions such as North America and parts of Asia, records from other locations are sparse. To date, there have been no reports of Neorickettsia from New Zealand. We screened ten species of digeneans infecting seven native gastropod species (both marine and freshwater) found near Dunedin, New Zealand, for the presence of neorickettsial infections. A >1300 bp long section of 16S rRNA belonging to a Neorickettsia bacterium was isolated from opecoelid digeneans of two individuals of the mudflat topshell snail Diloma subrostrata. These sequences represent the first evidence of neorickettsial infection in native New Zealand animals and are also the first Neorickettsia found in digeneans of the family Opecoelidae.

Neuromodulatory effects and targets of the SCFAs and gasotransmitters produced by the human symbiotic microbiota

The symbiotic gut microbiota plays an important role in the development and homeostasis of the host organism. Its physiological, biochemical, behavioral, and communicative effects are mediated by multiple low molecular weight compounds. Recent data on small molecules produced by gut microbiota in mammalian organisms demonstrate the paramount importance of these biologically active molecules in terms of biology and medicine. Many of these molecules are pleiotropic mediators exerting effects on various tissues and organs. This review is focused on the functional roles of gaseous molecules that perform neuromediator and/or endocrine functions. The molecular mechanisms that underlie the effects of microbial fermentation-derived gaseous metabolites are not well understood. It is possible that these metabolites produce their effects via immunological, biochemical, and neuroendocrine mechanisms that involve endogenous and microbial modulators and transmitters; of considerable importance are also changes in epigenetic transcriptional factors, protein post-translational modification, lipid and mitochondrial metabolism, redox signaling, and ion channel/gap junction/transporter regulation. Recent findings have revealed that interactivity among such modulators/transmitters is a prerequisite for the ongoing dialog between microbial cells and host cells, including neurons. Using simple reliable methods for the detection and measurement of short-chain fatty acids (SCFAs) and small gaseous molecules in eukaryotic tissues and prokaryotic cells, selective inhibitors of enzymes that participate in their synthesis, as well as safe chemical and microbial donors of pleiotropic mediators and modulators of host intestinal microbial ecology, should enable us to apply these chemicals as novel therapeutics and medical research tools.

The bacterial community of entomophilic nematodes and host beetles

Insects form the most species-rich lineage of Eukaryotes and each is a potential host for organisms from multiple phyla, including fungi, protozoa, mites, bacteria and nematodes. In particular, beetles are known to be associated with distinct bacterial communities and entomophilic nematodes. While entomopathogenic nematodes require symbiotic bacteria to kill and reproduce inside their insect hosts, the microbial ecology that facilitates other types of nematode-insect associations is largely unknown. To illuminate detailed patterns of the tritrophic beetle-nematode-bacteria relationship, we surveyed the nematode infestation profiles of scarab beetles in the greater Los Angeles area over a five-year period and found distinct nematode infestation patterns for certain beetle hosts. Over a single season, we characterized the bacterial communities of beetles and their associated nematodes using high-throughput sequencing of the 16S rRNA gene. We found significant differences in bacterial community composition among the five prevalent beetle host species, independent of geographical origin. Anaerobes Synergistaceae and sulphate-reducing Desulfovibrionaceae were most abundant in Amblonoxia beetles, while Enterobacteriaceae and Lachnospiraceae were common in Cyclocephala beetles. Unlike entomopathogenic nematodes that carry bacterial symbionts, insect-associated nematodes do not alter the beetles' native bacterial communities, nor do their microbiomes differ according to nematode or beetle host species. The conservation of Diplogastrid nematodes associations with Melolonthinae beetles and sulphate-reducing bacteria suggests a possible link between beetle-bacterial communities and their associated nematodes. Our results establish a starting point towards understanding the dynamic interactions between soil macroinvertebrates and their microbiota in a highly accessible urban environment.