Schistosomes are parasitic blood flukes, responsible for significant human disease in tropical and developing nations. Here we review information on the organization of the cytoskeleton and associated motor proteins of schistosomes, with particular reference to the organization of the syncytial tegument, a unique cellular adaptation of these and other neodermatan flatworms. Extensive EST databases show that the molecular constituents of the cytoskeleton and associated molecular systems are likely to be similar to those of other eukaryotes, although there are potentially some (...) molecules unique to schistosomes and platyhelminths. The biology of some components, particular those contributing to host–parasite interactions as well as chemotherapy and immunotherapy are discussed. Unresolved questions in relation to the structure and function of the tegument relate to dynamic organization of the syncytial layer. BioEssays 26:752–765, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Reorganization of cell organelle‐deprived host red blood cells by the apicomplexan malaria parasite Plasmodium falciparum enables their cytoadherence to endothelial cells that line the microvasculature. This increases the time red blood cells infected with mature developmental stages remain within selected organs such as the brain to avoid the spleen passage, which can lead to severe complications and cumulate in patient death. The Maurer's clefts are a novel secretory organelle of parasite origin established by the parasite in (...) the cytoplasm of the host red blood cell in order to facilitate the establishment of cytoadherence by conducting the trafficking of immunovariant adhesins to the host cell surface. Another important function of the organelle is the sorting of other proteins the parasite traffics into its host cell. Although the organelle is of high importance for the pathology of malaria, additional putative functions, structure, and genesis remain shrouded in mystery more than a century after its discovery. In this review, we highlight our current knowledge about the Maurer's clefts and other novel secretory organelles established within the host cell cytoplasm by human‐pathogenic malaria parasites and other parasites that reside within human red blood cells. (shrink)

A better understanding of how schistosomes exploit host nutrients, neuro‐endocrine hormones and signalling pathways for growth, development and maturation may provide new insights for improved interventions in the control of schistosomiasis. This paper describes recent advances in the identification and characterisation of schistosome tyrosine kinase and signalling pathways. It discusses the potential intervention value of insulin signalling, which may play an important role in glucose uptake and carbohydrate metabolism in schistosomes, providing the nutrients essential for parasite growth, development (...) and, notably, female fecundity. Significant progress has also been made in the characterisation of other schistosome growth factor receptors, such as transforming growth factor beta receptor and epidermal growth factor receptor, and in our understanding of their roles in the host‐parasite molecular dialogue and parasite development. The use of parasite signal transduction components as novel vaccine or drug targets may prove invaluable in prevention, treatment and control strategies to combat schistosomiasis. (shrink)

Study of the multiplicity of interactions between invertebrate hosts and their parasites helps to define the aspects of the host immune systems that have ecological and evolutionary significance. Such study, however, reveals how much is yet unknown. For instance, the costs of mounting an immune response, the nature of the long-lasting protection sometimes attained, and the high degree of specificity observed in certain hosts are phenomena that still await full explanation. An additional puzzle is the high degree of specificity (...) achieved in light of the apparent low degree of specificity in the recognition and effector mechanisms of insect immune systems. Furthermore, while protective immunity is typically associated with vertebrate adaptive immune systems, invertebrates may have analogous capacities, whose nature is still largely unknown. This review will illustrate how the traditional host-centred view of immune defence can be usefully extended by taking account of parasite immune evasion strategies and the variation that such strategies create in the observed outcomes of infection. BioEssays 27:1026–1034, 2005. © 2005 Wiley Peiodicals, Inc. (shrink)

The interest of F. Macfarlane Burnet in host–parasite interactions grew through the 1920s and 1930s, culminating in his book, Biological Aspects of Infectious Disease, often regarded as the founding text of disease ecology. Our knowledge of the influences on Burnet’s ecological thinking is still incomplete. Burnet later attributed much of his conceptual development to his reading of British theoretical biology, especially the work of Julian Huxley and Charles Elton, and regretted he did not study Theobald Smith’s Parasitism and (...) Disease until after he had formulated his ideas. Scholars also have adduced Burnet’s fascination with natural history and the clinical and public health demands on his research effort, among other influences. I want to consider here additional contributions to Burnet’s ecological thinking, focusing on his intellectual milieu, placing his research in a settler society with exceptional expertise in environmental studies and pest management. In part, an ‘‘ecological turn’’ in Australian science in the 1930s, derived to a degree from British colonial scientific investments, shaped Burnet’s conceptual development. This raises the question of whether we might characterize, in postcolonial fashion, disease ecology, and other studies of parasitism, as successful settler colonial or dominion science. (shrink)

When parasites have different interests in regard to how their host should behave this can result in a conflict over host manipulation, i.e. parasite induced changes in host behaviour that enhance parasite fitness. Such a conflict can result in the alteration, or even complete suppression, of one parasite's host manipulation. Many parasites, and probably also symbionts and commensals, have the ability to manipulate the behaviour of their host. Non‐manipulating parasites should also have (...) an interest in host behaviour. Given the frequency of multiple parasite infections in nature, potential conflicts of interest over host behaviour and manipulation may be common. This review summarizes the evidence on how parasites can alter other parasite's host manipulation. Host manipulation can have important ecological and medical consequences. I speculate on how a conflict over host manipulation could alter these consequences and potentially offer a new avenue of research to ameliorate harmful consequences of host manipulation. (shrink)

Fast and effective detection of the causative agent of malaria in humans, protozoan Plasmodium parasites, is of crucial importance for increasing the effectiveness of treatment and to control a devastating disease that affects millions of people living in endemic areas. The microscopic examination of Giemsa‐stained blood films still remains the gold‐standard in Plasmodium detection today. However, there is a high demand for alternative diagnostic methods that are simple, fast, highly sensitive, ideally do not rely on blood‐drawing and can potentially be (...) conducted by the patients themselves. Here, the history of Plasmodium detection is discussed, and advantages and disadvantages of diagnostic methods that are currently being applied are assessed. (shrink)

Entamoeba histolytica is a protozoan parasite of humans, and the causitive agent of intestinal amebiasis. The disease‐causing stage of the parasite is an osmotically sensitive ameboid form, which differentiates into a thick‐walled cyst for transmission from person to person. The conditions within the human intestine that induce encystment of the amoeba are unknown, but studies using an amoebic parasite of reptiles are now yielding information about the molecules and host:parasite interactions involved in the process. An (...) understanding of the amoeba's obligatory encystment pathway should provide an approach for interrupting the transmission of this parasite, for which there is currently no vaccine. (shrink)

This essay considers biotrophic cyst and root‐knot nematodes in relation to their biology, host–parasite interactions and molecular genetics. These nematodes have to face the biological consequences of the physical constraints imposed by the soil environment in which they live while their hosts inhabit both above and below ground environments. The two groups of nematodes appear to have adopted radically different solutions to these problems with the result that one group is a host specialist and reproduces sexually while (...) the other has an enormous host range and reproduces by mitotic parthenogenesis. We consider what is known about the modes of parasitism used by these nematodes and how it relates to their host range, including the surprising finding that parasitism genes in both nematode groups have been recruited from bacteria. The nuclear and mitochondrial genomes of these two nematode groups are very different and we consider how these findings relate to the biology of the organisms. BioEssays 30:249–259, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Schistosomes are intravascular parasitic helminths (blood flukes) that infect more than 200 million people globally. Proteomic analysis of the tegument (skin) of these worms has revealed the surprising presence of glycolytic enzymes on the parasite's external surface. Immunolocalization data as well as enzyme activity displayed by live worms confirm that functional glycolytic enzymes are indeed expressed at the host–parasite interface. Since these enzymes are traditionally considered to function intracellularly to drive glycolysis, in an extracellular location they are (...) hypothesized to engage in novel “moonlighting” functions such as immune modulation and blood clot dissolution that promote parasite survival. For instance, several glycolytic enzymes can interact with plasminogen and promote its activation to the thrombolytic plasmin; some can inhibit complement function; some induce B cell proliferation or macrophage apoptosis. Several pathogenic bacteria and protists also express glycolytic enzymes externally, suggesting that moonlighting functions of extracellular glycolytic enzymes can contribute broadly to pathogen virulence. Also see the video abstract here https://youtu.be/njtWZ2y3k_I. (shrink)

In this paper, we revisit a host–parasite system with multiple parasite strains and superinfection proposed by Nowak and May :81–89, 1994), and study its global dynamics when we relax the two strict conditions assumed therein. As for system with two parasite strains, we derive that the basic reproduction number $$R_0$$ is the threshold condition for parasite extinction and the invasion reproduction number $$R_i^j\ $$ is the subthreshold condition for coexistence of two parasite strains. As (...) for system with three parasite strains, we are surprised to discover the global stability of parasite-free and coexistence equilibrium, which is distinct from the previous result. Furthermore, for system with n strains, we obtain the global asymptotical stability of the parasite-free equilibrium, conjecture a general result on the global stability of coexistence equilibrium and provide two numerical examples to testify our conjecture. (shrink)

All the conserved detailed results of evolution stored in DNA must be read, transcribed, and translated via an RNAmediated process. This is required for the development and growth of each individual cell. Thus, all known living organisms fundamentally depend on these RNA-mediated processes. In most cases, they are interconnected with other RNAs and their associated protein complexes and function in a strictly coordinated hierarchy of temporal and spatial steps (i.e., an RNA network). Clearly, all cellular life as we know it (...) could not function without these key agents of DNA replication, namely rRNA, tRNA, and mRNA. Thus, any definition of life that lacks RNA functions and their networks misses an essential requirement for RNA agents that inherently regulate and coordinate (communicate to) cells, tissues, organs, and organisms. The precellular evolution of RNAs occurred at the core of the emergence of cellular life and the question remained of how both precellular and cellular levels are interconnected historically and functionally. RNA-networks andRNA-communication can interconnect these levels.With the reemergence of virology in evolution, it became clear that communicating viruses and subviral infectious genetic parasites are bridging these two levels by invading, integrating, coadapting, exapting, and recombining constituent parts in host genomes for cellular requirements in gene regulation and coordination aims. Therefore, a 21st century understanding of life is of an inherently social process based on communicating RNA networks, in which viruses and cells continuously interact. (shrink)

The question asked in this article is: what is a parasite?. Defining a parasite requires defining its host at the same time. A difficult question therefore arises about host-parasite relationships. The object of general parasitology is in fact to study the relationship between a host and its parasite. The initial question what is a parasite? has to be reformulated within a conceptual framework, that of relationship. This article is an attempt to transpose (...) into parasitology some concepts which have been profitable in the fields of physics and chemistry. The studies of R. Thom about the individual are also used. Concepts like that of field and principles like that of minimization are probably operational on a high level of organization. The description of host-parasite relationships could benefit from these concepts. (shrink)

Zonulin is a physiological modulator of intercellular tight junctions, which upregulation is involved in several diseases like celiac disease (CeD). The polyQ gliadin fragment binds to the CXCR3 chemokine receptor that activates zonulin upregulation, leading to increased intestinal permeability in humans. Here, we report a general hypothesis based on the structural connection between the polyQ sequence of the immunogenic CeD protein, gliadin, and enteric coccidian parasites proteins. Firstly, a novel interaction pathway between the parasites and the host is (...) described based on the structural similarities between polyQ gliadin fragments and the parasite proteins. Secondly, a potential connection between coccidial infections as a novel environmental trigger of CeD is hypothesized. Therefore, this report represents a promising breakthrough for coccidian research and points out the potential role of coccidian parasites as a novel trigger of CeD that might define a preventive strategy for gluten‐related disorders in general. Also see the video abstract here: https://youtu.be/oMaQasStcFI. (shrink)

The morbidity of tick‐borne encephalitis (TBE) varies yearly by as much as 10‐fold among the people of Western Siberia. This long‐term variation is dependent on many factors such as the density of the tick populations, the prevalence of TBE virus (TBEV) among sub‐adult ticks, the yearly virulence of the TBEV, and prophylactic measures. Here we highlight the role of small mammal hosts in the circulation of TBEV through the ecosystem. Refining classical models of non‐viremic horizontal transmission, we emphasize the recently (...) understood fact that the physiological and immunological status of the small mammal hosts affects the tick and virus‐host interactions. In addition to its theoretical interest, our approach may lead to some practical improvements in the precision of epidemiological forecasts and perhaps in forestalling the severity of outbreaks of TBE, or, at least, in forewarning medical authorities and the general public of impending TBE outbreaks. (shrink)

Reflecting on his scientific career toward the end of his life, the French-educated medical researcher René Dubos presented his flowering as an ecological thinker as a story of linear progression—the inevitable product of the intellectual seeds planted in his youth. But how much store should we set by Dubos’s account of his ecological journey? Resisting retrospective biographical readings, this paper seeks to relate the development of Dubos’s ecological ideas to his experimental practices and his career as a laboratory researcher. In (...) particular, I focus on Dubos’s studies of tuberculosis at the Rockefeller Institute in the period 1944–1956—studies which began with an inquiry into the tubercle bacillus and the physiochemical determinants of virulence, but which soon encompassed a wider investigation of the influence of environmental forces and host–parasite interactions on susceptibility and resistance to infection in animal models. At the same time, through a close reading of Dubos’s scientific papers and correspondence, I show how he both drew on and distinguished his ecological ideas from those of other medical researchers such as Theobald Smith, Frank Macfarlane Burnet, and Frank Fenner. However, whereas Burnet and Fenner tended to view ecological interactions at the level of populations, Dubos focused on the interface of hosts and parasites in the physiological environments of individuals. The result was that although Dubos never fully engaged with the science of ecology, he was able to incorporate ecological ideas into his thought and practices, and relate them to his holistic views on health and the natural harmony of man and his environment. (shrink)

Frederick Griffith was an English bacteriologist at the Pathological Laboratory of the Ministry of Health in London who believed that progress in the epidemiology and control of infectious diseases would come only with more precise knowledge of the identity of the causative microorganisms. Over the years, Griffith developed and expanded a serological technique for identifying pathogenic microorganisms, which allowed the tracing of the sources of infectious disease outbreaks: slide agglutination. Yet Griffith is not remembered for his contributions to the biology (...) and epidemiology of infectious diseases so much as for discovering the phenomenon known as ‘transformation’. Griffith’s discovery, for many, was a pure case of serendipity whose biological relevance had also largely escaped him. In this paper, I argue that the key to understanding the significance of bacterial transformation – and the scientific legacy of Fred Griffith – rests not only on it initiating a cascade of events leading to molecular genetics but also on its implications for epidemiology based on the biology of host–parasite interactions. Looking at Griffith’s entire career, instead of focusing only on the transformation study, we can better appreciate the place of the latter within Griffith’s overall contributions. Presented in this way, Griffith’s experiment on bacterial transformation also ceases to appear as an anomaly, which in turn leads us to rethink some of the most prevalent historical conceptions about his work. (shrink)

COVID-19 often manifests with different outcomes in different patients, highlighting the complexity of the host-pathogen interactions involved in manifestations of the disease at the molecular and cellular levels. In this paper, we propose a set of postulates and a framework for systematically understanding complex molecular host-pathogen interaction networks. Specifically, we first propose four host-pathogen interaction (HPI) postulates as the basis for understanding molecular and cellular host-pathogen interactions and their relations to disease outcomes. These four (...) postulates cover the evolutionary dispositions involved in HPIs, the dynamic nature of HPI outcomes, roles that HPI components may occupy leading to such outcomes, and HPI checkpoints that are critical for specific disease outcomes. Based on these postulates, an HPI Postulate and Ontology (HPIPO) framework is proposed to apply interoperable ontologies to systematically model and represent various granular details and knowledge within the scope of the HPI postulates, in a way that will support AI-ready data standardization, sharing, integration, and analysis. As a demonstration, the HPI postulates and the HPIPO framework were applied to study COVID-19 with the Coronavirus Infectious Disease Ontology (CIDO), leading to a novel approach to rational design of drug/vaccine cocktails aimed at interrupting processes occurring at critical host-coronavirus interaction checkpoints. Furthermore, the host-coronavirus protein-protein interactions (PPIs) relevant to COVID-19 were predicted and evaluated based on prior knowledge of curated PPIs and domain-domain interactions, and how such studies can be further explored with the HPI postulates and the HPIPO framework is discussed. (shrink)

Host-microbiome interactions (HMIs) are critical for the modulation of biological processes and are associated with several diseases, and extensive HMI studies have generated large amounts of data. We propose that the logical representation of the knowledge derived from these data and the standardized representation of experimental variables and processes can foster integration of data and reproducibility of experiments and thereby further HMI knowledge discovery. A community-based Ontology of Host-Microbiome Interactions (OHMI) was developed following the OBO Foundry principles. OHMI (...) leverages established ontologies to create logically structured representations of microbiomes, microbial taxonomy, host species, host anatomical entities, and HMIs under different conditions and associated study protocols and types of data analysis and experimental results. (shrink)

Reflecting on his scientific career toward the end of his life, the French-educated medical researcher René Dubos presented his flowering as an ecological thinker as a story of linear progression—the inevitable product of the intellectual seeds planted in his youth. But how much store should we set by Dubos’s account of his ecological journey? Resisting retrospective biographical readings, this paper seeks to relate the development of Dubos’s ecological ideas to his experimental practices and his career as a laboratory researcher. In (...) particular, I focus on Dubos’s studies of tuberculosis at the Rockefeller Institute in the period 1944–1956—studies which began with an inquiry into the tubercle bacillus and the physiochemical determinants of virulence, but which soon encompassed a wider investigation of the influence of environmental forces and host–parasite interactions on susceptibility and resistance to infection in animal models. At the same time, through a close reading of Dubos’s scientific papers and correspondence, I show how he both drew on and distinguished his ecological ideas from those of other medical researchers such as Theobald Smith, Frank Macfarlane Burnet, and Frank Fenner. However, whereas Burnet and Fenner tended to view ecological interactions at the level of populations, Dubos focused on the interface of hosts and parasites in the physiological environments of individuals. The result was that although Dubos never fully engaged with the science of ecology, he was able to incorporate ecological ideas into his thought and practices, and relate them to his holistic views on health and the natural harmony of man and his environment. (shrink)

Giardia lamblia, a protozoan parasite that causes widespread diarrheal disease, expresses a surface membrane associated lectin, taglin, which is specifically activated by limited proteolysis with trypsin, a protease that is present in abundance at the site of infection. When activated, taglin agglutinates enterocytes which are the cells to which the parasite adheres in vivo, and in addition, binds to isolated brush border membranes of these cells. These findings suggest that this lectin may be involved in the host‐ (...) class='Hi'>parasite interaction. Taglin is most specific for terminal phosphomannosyl residues and its binding to red cells is mediated by cell surface phosphate residues. Hemagglutinating activity induced by taglin is most active at pH6.5 and is dependent on divalent cations. A monoclonal antibody to taglin reacts with the surface membrane of live trophozoites and recognizes a protein of 28/30 kDa in lysates of Giardia trophozoites, by immunoblotting. This finding is confirmed by direct demonstration of lectin activity by erythrocyte binding to proteins electroblotted to nitrocellulose, which revealed specific red cell binding to giardial protein bands in the same molecular weight range as those recognized by the monoclonal antibody. (shrink)

Current work in experimental biology revolves around a handful of animal species. Studying only a few organisms limits science to the answers that those organisms can provide. Nature has given us an overwhelming diversity of animals to study, and recent technological advances have greatly accelerated the ability to generate genetic and genomic tools to develop model organisms for research on host–microbe interactions. With the help of such models the authors therefore hope to construct a more complete picture of the (...) mechanisms that underlie crucial interactions in a given metaorganism (entity consisting of a eukaryotic host with all its associated microbial partners). As reviewed here, new knowledge of the diversity of host–microbe interactions found across the animal kingdom will provide new insights into how animals develop, evolve, and succumb to the disease. (shrink)

Successful therapies to combat microbial diseases and cancers require incorporating ecological and evolutionary principles. Drawing upon the fields of ecology and evolutionary biology, we present a systems‐based approach in which host and disease‐causing factors are considered as part of a complex network of interactions, analogous to studies of “classical” ecosystems. Centering this approach around empirical examples of disease treatment, we present evidence that successful therapies invariably engage multiple interactions with other components of the host ecosystem. Many of these (...) factors interact nonlinearly to yield synergistic benefits and curative outcomes. We argue that these synergies and nonlinear feedbacks must be leveraged to improve the study of pathogenesis in situ and to develop more effective therapies. An eco‐evolutionary systems perspective has surprising and important consequences, and we use it to articulate areas of high research priority for improving treatment strategies. (shrink)

Cognitive biases can lead to misinterpretations of human and non-human biology and behavior. The concept of the Umwelt describes phylogenetic contrasts in the sensory realms of different species and has important implications for evolutionary studies of cognition (including biases) and social behavior. It has recently been suggested that the microbiome (the diverse network of microorganisms in a given environment, including those within a host organism such as humans) has an influential role in host behavior and health. In this (...) paper, we discuss the host’s microbiome in relation to cognitive biases and the concept of the Umwelt. Failing to consider the role of host–microbiome (collectively termed a “holobiont”) interactions in a given behavior, may underpin a potentially important cognitive bias – which we refer to as the Holobiont Blindspot. We also suggest that microbially mediated behavioral responses could augment our understanding of the Umwelt. For example, the potential role of the microbiome in perception and action could be an important component of the system that gives rise to the Umwelt. We also discuss whether microbial symbionts could be considered in System 1 thinking – that is, decisions driven by perception, intuition and associative memory. Recognizing Holobiont Blindspots and considering the microbiome as a key factor in the Umwelt and System 1 thinking has the potential to advance studies of cognition. Furthermore, investigating Holobiont Blindspots could have important implications for our understanding of social behaviors and mental health. Indeed, the way we think about how we think may need to be revisited. (shrink)

The expression of products encoded by the major histocompatibility complex (MHC) on tumor cells has recently been studied extensively. It has been found that many malignant tumor cells have their MHC antigens ‘switched‐off’ but that these antigens are re‐expressed following DNA‐mediated gene transfer, with increased tumor immunogenicity as a result and the consequence that these ‘transformed’ tumor cells are rejected in vivo.: This review will discuss approaches that have been taken to induce strong tumor‐specific immunity by the manipulation of MHC (...) expression on tumor cells. (shrink)

Accumulating data suggest that the eukaryotic cell originated from a merger of two prokaryotes, an archaeal host and a bacterial endosymbiont. However, since prokaryotes are unable to perform phagocytosis, the means by which the endosymbiont entered its host is an enigma. We suggest that a predatory or parasitic interaction between prokaryotes provides a reasonable explanation for this conundrum. According to the model presented here, the host in this interaction was an anaerobic archaeon with a periplasm‐like (...) space. The predator was a small (facultative) aerobic α‐proteobacterium, which penetrated and replicated within the host periplasm, and later became the mitochondria. Plausible conditions under which this interaction took place and circumstances that may have led to the contemporary complex eukaryotic cell are discussed. (shrink)

Coral reefs have been challenged by the current rate and severity of environmental change that might outpace their ability to adapt and survive. Current research focuses on understanding how microbial communities and epigenetic changes separately affect phenotypes and gene expression of corals. Here, we provide the hypothesis that coral‐associated microorganisms may directly or indirectly affect the coral's phenotypic response through the modulation of its epigenome. Homologs of ankyrin‐repeat protein A and internalin B, which indirectly cause histone modifications in humans, as (...) well as Rv1988 histone methyltransferase, and the DNA methyltransferases Rv2966c, Mhy1, Mhy2, and Mhy3 found in coral‐associated bacteria indicate that there are potential host epigenome‐modifying proteins in the coral microbiome. With the ideas presented here, we suggest that microbiome manipulation may be a means to alter a coral's epigenome, which could aid the current efforts to protect coral reefs. Also see the video abstract here: https://youtu.be/CW9GbChjKM4. (shrink)

Host‐pathogen arms race is a universal, central aspect of the evolution of life. Most organisms evolved several distinct yet interacting strategies of anti‐pathogen defense including resistance to parasite invasion, innate and adaptive immunity, and programmed cell death (PCD). The PCD is the means of last resort, a suicidal response to infection that is activated when resistance and immunity fail. An infected cell faces a decision between active defense and altruistic suicide or dormancy induction, depending on whether immunity is (...) “deemed” capable of preventing parasite reproduction and consequent infection of other cells. In bacteria and archaea, immunity genes typically colocalize with PCD modules, such as toxins‐antitoxins, suggestive of immunity‐PCD coupling, likely mediated by shared proteins that sense damage and “predict” the outcome of infections. In type VI CRISPR‐Cas systems, the same enzyme that inactivates the target RNA might execute cell suicide, in a case of ultimate integration of immunity and PCD. (shrink)

Interactions between the host and its associated microbiota differ spatially and the local cross talk determines organ function and physiology. Animals and their organs are not uniform but contain several functional and cellular compartments and gradients. In the intestinal tract, different parts of the gut carry out different functions, tissue structure varies accordingly, epithelial cells are differentially distributed and gradients exist for several physicochemical parameters such as nutrients, pH, or oxygen. Consequently, the microbiota composition also differs along the length (...) of the gut, but also between lumen and mucosa of the same intestinal segment, and even along the crypt‐villus axis in the epithelium. Thus, host‐microbiota interactions are highly site‐specific and the local cross talk determines intestinal function and physiology. Here we review recent advances in our understanding of site‐specific host‐microbiota interactions and discuss their functional relevance for host physiology. (shrink)

DNA transfer directly from cell to cell (conjugation) is common among prokaryotes, particularly Gram‐negative bacteria like Escherichia coli. The phenomenon invariably requires a set of plasmid genes in the DNA donor cell. In addition, E. coli itself makes limited and specific contributions to the donor activity of strains carrying the conjugative plasmid F. These contributions have yet to be defined biochemically, but it is already clear that the cell envelope is an importan nexus between plasmid‐ and chromosome‐encoded proteins required for (...) the establishment and maintenance of DNA donor activity. (shrink)

Influential philosopher Michel Serres’s foundational work uses fable to explore how human relations are identical to that of the parasite to the host body. Among Serres’s arguments is that by being pests, minor groups can become major players in public dialogue—creating diversity and complexity vital to human life and thought. Michel Serres is professor in history of science at the Sorbonne, professor of Romance languages at Stanford University, and author of several books, including _Genesis._ Lawrence R. Schehr is (...) professor of French at the University of Illinois, Urbana-Champaign. Cary Wolfe is Bruce and Elizabeth Dunlevie Professor of English at Rice University. His books include _Zoontologies: The Question of the Animal _. (shrink)

This paper compares the heuristic potential of three metaphorical paired concepts used in the relevant literature to characterise global relationships between the anthroposphere and the ecosphere. Methodologically, the guiding question is whether and to what extent metaphorical theses can support an arrival at hypotheses which accurately reflect reality and possess explanatory force. The predator-prey model implies that the populations of two species in such a relationship in principle exhibit coupled oscillations, giving prey populations the possibility of periodic regeneration. For some (...) time, however, the most important indicators of human destruction of nature have been showing a relentless upward trend which appears to render the tumour-host metaphor more appropriate. Another fact which favours this analogy is that a tumour develops within its host and from its host's normal cells, in a similar way to the emergence of the anthroposphere from within the biosphere. But the parasite-host analogy also allows the formulation of fruitful hypotheses, since ecological parasitology is equally familiar with varieties of autoaggressive interaction and provides a means of focusing particularly on the adelphoparasitic hierarchy within the anthroposphere. (shrink)

Are there any such things as mind viruses? By analogy with biological parasites, such cultural items are supposed to subvert or harm the interests of their host. Most popularly, this notion has been associated with Richard Dawkins’ concept of the “selfish meme”. To unpack this claim, we first clear some conceptual ground around the notions of cultural adaptation and units of culture. We then formulate Millikan’s challenge: how can cultural items develop novel purposes of their own, cross-cutting or subverting (...) human purposes? If this central challenge is not met, talk of cultural ‘parasites’ or ‘selfish memes’ will be vacuous or superfluous. First, we discuss why other attempts to answer Millikan’s challenge have failed. In particular, we put to rest the claims of panmemetics, a somewhat sinister worldview according to which human culture is nothing more than a swarm of selfish agents, plotting and scheming behind the scenes. Next, we reject a more reasonable, but still overly permissive approach to mind parasites, which equates them with biologically maladaptive culture. Finally, we present our own answer to Millikan’s challenge: certain systems of misbelief can be fruitfully treated as selfish agents developing novel purposes of their own. In fact, we venture that this is the only way to properly understand them. Systems of misbelief are designed to spread in a viral-like manner, without any regard to the interests of their human hosts, and with possibly harmful consequences. As a proof of concept, we discuss witchcraft beliefs in early modern Europe. In this particular case, treating cultural representations as “parasites” – i.e. adopting the meme’s eye view – promises to shed new light on a mystery that historians and social scientists have been wrestling with for decades. (shrink)

What is the origin of individual differences in ideology and personality? According to the parasite stress hypothesis, the structure of a society and the values of individuals within it are both influenced by the prevalence of infectious disease within the society's geographical region. High levels of infection threat are associated with more ethnocentric and collectivist social structures and greater adherence to social norms, as well as with socially conservative political ideology and less open but more conscientious personalities. Here we (...) use an agent-based model to explore a specific opportunities-parasites trade-off hypothesis, according to which utility-maximizing agents place themselves at an optimal point on a trade-off between the gains that may be achieved through accessing the resources of geographically or socially distant out-group members through openness to out-group interaction, and the losses arising due to consequently increased risks of exotic infection to which immunity has not been developed. We examine the evolution of cooperation and the formation of social groups within social networks, and we show that the groups that spontaneously form exhibit greater local rather than global cooperative networks when levels of infection are high. It is suggested that the OPTO model offers a first step toward understanding the specific mechanisms through which environmental conditions may influence cognition, ideology, personality, and social organization. (shrink)

In the last few years, annexins have been discovered in several nematodes and other parasites, and distinct differences between the parasite annexins and those of the hosts make them potentially attractive targets for anti‐parasite therapeutics. Annexins are ubiquitous proteins found in almost all organisms across all kingdoms. Here, we present an overview of novel annexins from parasitic organisms, and summarize their phylogenetic and biochemical properties, with a view to using them as drug or vaccine targets. Building on structural (...) and biological information that has been accumulated for mammalian and plant annexins, we describe a predicted additional secondary structure element found in many parasite annexins that may confer unique functional properties, and present a specific antigenic epitope for use as a vaccine. (shrink)

Animals exist as biodiverse composite organisms that include microbial residents, eukaryotic cells, and organs that collectively form a human being. Through an interdependent relationship and an inherent ability to transmit and reciprocate stimuli in a bidirectional way, a human body or the holobiont secures growth, health, and reproduction. As such, the survival of a holobiont is dependent on the maintenance of biological order including metabolic homeostasis by tight regulation of the communication between its eukaryotic and prokaryotic residents. In this review (...) an overview and perspective are provided on the bidirectional communication between microbes and their host in mutually nurturing biochemical, biological, and social interconnected relationships between the components of the holobiont. An emphasis is placed on exemplifying microbiome‐mediated effects on host functions—aiming to integrate microbiome functionality to host physiology, be it health or disease. Nutrition, immunology, and sexual dimorphism have been traversed extensively to reflect on health and mind states, social interactions, and urbanization defects/effects. Finally, examples of molecular mechanisms potentially orchestrating these complex transkingdom interactions are provided. (shrink)

Similar to parasites, cancer cells depend on their hosts for sustenance, proliferation and reproduction, exploiting the hosts for energy and resources, and thereby impairing their health and fitness. Because of this lifestyle similarity, it is predicted that cancer cells could, like numerous parasitic organisms, evolve the capacity to manipulate the phenotype of their hosts to increase their own fitness. We claim that the extent of this phenomenon and its therapeutic implications are, however, underappreciated. Here, we review and discuss what can (...) be regarded as cases of host manipulation in the context of cancer development and progression. We elaborate on how acknowledging the applicability of these principles can offer novel therapeutic and preventive strategies. The manipulation of host phenotype by cancer cells is one more reason to adopt a Darwinian approach in cancer research. -/- . (shrink)

Investigation into the impact of the stages of a radio call on host–caller interaction has traditionally been conducted in single host scenarios, whereby one host interacts with one caller. Further, this analysis has often been done in the context of talk radio that is designed to promote a sense of conflict in order to entertain its audience. However, what of dual or multi-host scenarios, where a number of hosts are co-participants when interacting with callers? This (...) article considers a talkback segment within a chat-based program in which two studio-based hosts are involved in conversation with callers. It considers previous research into call sequence as applied to this scenario and reveals that rather than working to challenge the caller, the hosts work together to enable the callers to challenge the hosts but in a way that orients to sociability rather than conflict. (shrink)

The host actin nucleation machinery is subverted by many bacterial pathogens to facilitate their entry, motility, replication, and survival. The majority of research conducted in the past primarily focused on exploitation of a host actin nucleator, the Arp2/3 complex, by bacterial pathogens. Recently, new studies have begun to explore the role of formins, another family of host actin nucleators, in bacterial pathogenesis. This review provides an overview of recent advances in the study of the exploitation of the (...) Arp2/3 complex and formins by bacterial pathogens. Secreted bacterial effector proteins seem to manipulate the regulation of these actin nucleators or functionally mimic them to drive bacterial entry, motility and survival within host cells. An enhanced understanding of how formins are exploited will provide us with greater insight into how a fundamental eurkaryotic cellular process is utilized by bacteria and will also advance our knowledge of host‐pathogen interactions. (shrink)