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The RNA polymerase alternative o factor RpoS in Borrelia burgdorferi (Bb), the Lyme disease pathogen, is responsible for programmatic-positive and -negative gene regulation essential for the spirochete's dual-host enzootic cycle. RpoS is expressed during tick-to-mammal transmission and throughout mammalian infection. Although the mammalian-phase RpoS regulon is well described, its counterpart during the transmission blood meal is unknown. Here, we used Bb- specific transcript enrichment by tick-borne disease capture sequencing (TBDCapSeq) to compare the transcriptomes of WT and [DELTA]rpoSBb in engorged nymphs and following mammalian host-adaptation within dialysis membrane chambers. TBDCapSeq revealed dramatic changes in the contours of the RpoS regulon within ticks and mammals and further confirmed that RpoS-mediated repression is specific to the mammalian-phase of Bb's enzootic cycle. We also provide evidence that RpoS-dependent gene regulation, including repression of tick-phase genes, is required for persistence in mice. Comparative transcriptomics of engineered Bb strains revealed that the Borrelia oxidative stress response regulator (BosR), a noncanonical Fur family member, and the cyclic diguanosine monophosphate (c-di- GMP) effector PlzA reciprocally regulate the function of RNA polymerase complexed with RpoS. BosR is required for RpoS- mediated transcription activation and repression in addition to its well-defined role promoting transcription of rpoS by the RNA polymerase alternative o factor RpoN. During transmission, ligand-bound PlzA antagonizes RpoS-mediated repression, presumably acting through BosR., Introduction Lyme disease (LD) is a multisystem infectious disorder caused by the highly motile, invasive spirochetal pathogen Borrelia burgdorferi (Bb) (1). With an estimated 476,000 cases diagnosed and treated annually, [...]

The dry season is a major challenge for Plasmodium falciparum parasites in many malaria endemic regions, where water availability limits mosquito vectors to only part of the year. How P. falciparum bridges two transmission seasons months apart, without being cleared by the human host or compromising host survival, is poorly understood. Here we show that low levels of P. falciparum parasites persist in the blood of asymptomatic Malian individuals during the 5- to 6-month dry season, rarely causing symptoms and minimally affecting the host immune response. Parasites isolated during the dry season are transcriptionally distinct from those of individuals with febrile malaria in the transmission season, coinciding with longer circulation within each replicative cycle of parasitized erythrocytes without adhering to the vascular endothelium. Low parasite levels during the dry season are not due to impaired replication but rather to increased splenic clearance of longer-circulating infected erythrocytes, which likely maintain parasitemias below clinical and immunological radar. We propose that P. falciparum virulence in areas of seasonal malaria transmission is regulated so that the parasite decreases its endothelial binding capacity, allowing increased splenic clearance and enabling several months of subclinical parasite persistence. Malaria cases are predominant during the rainy seasons in many endemic regions owing to the life cycle of the mosquito vector. How Plasmodium falciparum adapts in humans during the intervening dry season, without causing malaria symptoms or killing the host, offers new insights into its persistence in humans., Author(s): Carolina M. Andrade [sup.1] , Hannah Fleckenstein [sup.1] , Richard Thomson-Luque [sup.1] , Safiatou Doumbo [sup.2] , Nathalia F. Lima [sup.1] , Carrie Anderson [sup.1] , Julia Hibbert [sup.1] [...]

Parasites can be detrimental to the health of wildlife populations and may negatively affect several aspects of the life history of their hosts. Investigating host health, therefore, is key to understanding important mechanisms of the host-parasite interaction at the individual and population levels. Recently, we reported a prevalence of 10% of Trypanosoma evansi Steel, 1884 in a population of capybaras (Hydrochoerus hydrochaeris (L., 1766)) from Esteros del Ibera, Argentina; however, the impact of T. evansi infection on capybaras is unknown. The aim of this study was to explore associations between T. evansi infection and biochemical and physiological parameters in wild capybaras using blood samples (n = 60) from a managed population of free-ranging capybaras from Esteros del Ibera. Infection by T. evansi was negatively associated with body condition, albumin, alpha-2 globulin concentrations, albumin/globulin ratio, and eosinophil counts, and it was positively associated with spleen index and gamma-globulin concentrations. These results suggest that T. evansi infection may pose a significant impact on the health of wild capybaras. Key words: haematology, Hydrochoerus hydrochaeris, serum proteinogram, Trypanosoma evansi. Les parasites peuvent être néfastes pour la santé des populations d'animaux sauvages et avoir une incidence négative sur plusieurs aspects du cycle biologique de leurs hôtes. L'étude de la santé des hôtes revêt donc une importance clé pour la compréhension des mécanismes qui jouent un rôle dans les interactions entre hôtes et parasites à l'échelle de l'individu et de la population. Nous avons récemment fait état d'une prévalence de 10 % de Trypanosoma evansi Steel, 1884 dans une population de capybaras (Hydrochoerus hydrochaeris (L., 1766)) des Esteros del Iberá (Argentine); toutefois, l'impact de l'infection à T. evansi chez les capybaras n'est pas connu. La présente étude visait donc à examiner les associations entre l'infection à T. evansi et des paramètres biochimiques et physiologiques chez les capybaras sauvages en utilisant des échantillons sanguins (n = 60) prélevés dans une population gérée de capybaras en liberté des Esteros del Iberá. L'infection à T. evansi présentait une association négative avec l'embonpoint, les concentrations d'albumine et d'alpha-2 globulines, le rapport albumine/globuline et les comptes d'éosinophiles, et une association positive avec l'indice splénique et les concentrations de gammaglobulines. Ces résultats donnent à penser que l'infection à T. evansi pourrait avoir un impact significatif sur la santé des capybaras sauvages. [Traduit par la Rédaction] Mots-clés : hématologie, Hydrochoerus hydrochaeris, protéinogramme sérique, Trypanosoma evansi., Introduction Parasites can be detrimental to the health of wild mammalian populations and may negatively affect several aspects of the life history of their hosts (Gulland 1995), which may ultimately [...]

Background A very large biomass of intact asexual-stage malaria parasites accumulates in the spleen of asymptomatic human individuals infected with Plasmodium vivax. The mechanisms underlying this intense tropism are not clear. We hypothesised that immature reticulocytes, in which P. vivax develops, may display high densities in the spleen, thereby providing a niche for parasite survival. Methods and findings We examined spleen tissue in 22 mostly untreated individuals naturally exposed to P. vivax and Plasmodium falciparum undergoing splenectomy for any clinical indication in malaria-endemic Papua, Indonesia (2015 to 2017). Infection, parasite and immature reticulocyte density, and splenic distribution were analysed by optical microscopy, flow cytometry, and molecular assays. Nine non-endemic control spleens from individuals undergoing spleno-pancreatectomy in France (2017 to 2020) were also examined for reticulocyte densities. There were no exclusion criteria or sample size considerations in both patient cohorts for this demanding approach. In Indonesia, 95.5% (21/22) of splenectomy patients had asymptomatic splenic Plasmodium infection (7 P. vivax, 13 P. falciparum, and 1 mixed infection). Significant splenic accumulation of immature CD71 intermediate- and high-expressing reticulocytes was seen, with concentrations 11 times greater than in peripheral blood. Accordingly, in France, reticulocyte concentrations in the splenic effluent were higher than in peripheral blood. Greater rigidity of reticulocytes in splenic than in peripheral blood, and their higher densities in splenic cords both suggest a mechanical retention process. Asexual-stage P. vivax-infected erythrocytes of all developmental stages accumulated in the spleen, with non-phagocytosed parasite densities 3,590 times (IQR: 2,600 to 4,130) higher than in circulating blood, and median total splenic parasite loads 81 (IQR: 14 to 205) times greater, accounting for 98.7% (IQR: 95.1% to 98.9%) of the estimated total-body P. vivax biomass. More reticulocytes were in contact with sinus lumen endothelial cells in P. vivax- than in P. falciparum-infected spleens. Histological analyses revealed 96% of P. vivax rings/trophozoites and 46% of schizonts colocalised with 92% of immature reticulocytes in the cords and sinus lumens of the red pulp. Larger splenic cohort studies and similar investigations in untreated symptomatic malaria are warranted. Conclusions Immature CD71.sup.+ reticulocytes and splenic P. vivax-infected erythrocytes of all asexual stages accumulate in the same splenic compartments, suggesting the existence of a cryptic endosplenic lifecycle in chronic P. vivax infection. Findings provide insight into P. vivax-specific adaptions that have evolved to maximise survival and replication in the spleen., Author(s): Steven Kho 1, Labibah Qotrunnada 2, Leo Leonardo 3, Benediktus Andries 3, Putu A. I. Wardani 4, Aurelie Fricot 5, Benoit Henry 5, David Hardy 6, Nur I. Margyaningsih [...]

Background Plasmodium vivax has been proposed to infect and replicate in the human spleen and bone marrow. Compared to Plasmodium falciparum, which is known to undergo microvascular tissue sequestration, little is known about the behavior of P. vivax outside of the circulating compartment. This may be due in part to difficulties in studying parasite location and activity in life. Methods and findings To identify organ-specific changes during the early stages of P. vivax infection, we performed 18-F fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) at baseline and just prior to onset of clinical illness in P. vivax experimentally induced blood-stage malaria (IBSM) and compared findings to P. falciparum IBSM. Seven healthy, malaria-naive participants were enrolled from 3 IBSM trials: NCT02867059, ACTRN12616000174482, and ACTRN12619001085167. Imaging took place between 2016 and 2019 at the Herston Imaging Research Facility, Australia. Postinoculation imaging was performed after a median of 9 days in both species (n = 3 P. vivax; n = 4 P. falciparum). All participants were aged between 19 and 23 years, and 6/7 were male. Splenic volume (P. vivax: +28.8% [confidence interval (CI) +10.3% to +57.3%], P. falciparum: +22.9 [CI -15.3% to +61.1%]) and radiotracer uptake (P. vivax: +15.5% [CI -0.7% to +31.7%], P. falciparum: +5.5% [CI +1.4% to +9.6%]) increased following infection with each species, but more so in P. vivax infection (volume: p = 0.72, radiotracer uptake: p = 0.036). There was no change in FDG uptake in the bone marrow (P. vivax: +4.6% [CI -15.9% to +25.0%], P. falciparum: +3.2% [CI -3.2% to +9.6%]) or liver (P. vivax: +6.2% [CI -8.7% to +21.1%], P. falciparum: -1.4% [CI -4.6% to +1.8%]) following infection with either species. In participants with P. vivax, hemoglobin, hematocrit, and platelet count decreased from baseline at the time of postinoculation imaging. Decrements in hemoglobin and hematocrit were significantly greater in participants with P. vivax infection compared to P. falciparum. The main limitations of this study are the small sample size and the inability of this tracer to differentiate between host and parasite metabolic activity. Conclusions PET/MRI indicated greater splenic tropism and metabolic activity in early P. vivax infection compared to P. falciparum, supporting the hypothesis of splenic accumulation of P. vivax very early in infection. The absence of uptake in the bone marrow and liver suggests that, at least in early infection, these tissues do not harbor a large parasite biomass or do not provoke a prominent metabolic response. PET/MRI is a safe and noninvasive method to evaluate infection-associated organ changes in morphology and glucose metabolism., Author(s): John Woodford 1,2,*, Ashley Gillman 3, Peter Jenvey 4, Jennie Roberts 4, Stephen Woolley 1,5, Bridget E. Barber 1,6, Melissa Fernandez 1, Stephen Rose 3, Paul Thomas 7, Nicholas [...]

Ticks are notorious hematophagous ectoparasites and vectors of many deadly pathogens. As an effective vector, ticks must break the strong barrier provided by the skin of their host during feeding, and their saliva contains a complex mixture of bioactive molecules that paralyze host defenses. The receptor for advanced glycation end products (RAGE) mediates immune cell activation at inflammatory sites and is constitutively and highly expressed in skin. Here, we demonstrate that longistatin secreted with saliva of the tick Haemaphysalislongicornis binds RAGE and modulates the host immune response. Similar to other RAGE ligands, longistatin specifically bound the RAGE V domain, and stimulated cultured HUVECs adhered to a longistatin-coated surface; this binding was dramatically inhibited by soluble RAGE or RAGE siRNA. Treatment of HUVECs with longistatin prior to stimulation substantially attenuated cellular oxidative stress and prevented NF-κB translocation, thereby reducing adhesion molecule and cytokine production. Recombinant longistatin inhibited RAGE-mediated migration of mouse peritoneal resident cells (mPRCs) and ameliorated inflammation in mouse footpad edema and pneumonia models. Importantly, tick bite upregulated RAGE ligands in skin, and endogenous longistatin attenuated RAGE-mediated inflammation during tick feeding. Our results suggest that longistatin is a RAGE antagonist that suppresses tick bite-associated inflammation, allowing successful blood-meal acquisition from hosts., Introduction Ticks are notorious blood-sucking ectoparasites, and about 1,000 tick species are distributed throughout the world. They have immense vector potential and serve as a unique vector of various deadly [...]

Two ill-explored hypotheses might explain host castration by parasitic pea crabs. The 'energy drain' hypothesis states that castration is caused by host-derived nutrient consumption of parasites that ultimately diminishes host-energy intake. The 'steric interference' hypothesis states that castration occurs when parasites physically inhibit host reproduction. This study evaluated whether Calyptraeotheres garthi, a pea crab from the southwestern Atlantic, is a parasitic castrator and explored whether the two hypotheses above explain castration in the limpet Crepidula cachimilla. None of three studied limpet species brooded embryos during the reproductive season when infested by mature female pea crabs. Also, limpets of C. cachimilla infested by C. garthi did not reproduce during a 90-day experimental period while crab-free limpets did spawn embryos during this period. Limpets resumed reproduction soon after pea crabs were experimentally removed from their brooding chamber. Thus, C. garthi does castrate limpets, and castration is reversible. Pea crabs 'steal' food from limpets, and infested limpets did not modify their feeding behavior to counteract nutrient loss. Thus, infested limpets are expected to ingest less food which provides partial support for the 'energy drain' hypothesis. However, the limpet's body condition increased or was not affected by pea crabs during the breeding season which argues against the same hypothesis. Furthermore, that limpets promptly recovered reproductive activity once pea crabs were experimentally removed, that castration was not induced by the smallest pea crabs in the population (that fill only partially the brooding chamber), and that parasitized limpets did exhibit fully mature ovaries, support the 'steric interference' hypothesis explaining parasitic castration., Introduction Parasitic associations are pervasive in both aquatic and terrestrial ecosystems and involve many levels of biological organization (Margulis and Fester 1991). Among parasites, species of 'parasitic castrators' are known [...]

It has been hypothesized that endolithic photoautotrophs inside the skeleton of cold-water corals may have a mutualistic relationship with the coral host positively affecting coral calcification. This study investigated the effect of endolithic photo-autotrophs on the apical septal extension of the cold-water coral Desmophyllum dianthus at Fjord Comau, southern Chile (42.41[degrees]-42.15[degrees]S, 72.5[degrees]W). The fluorescent staining agent calcein was used to document the linear apical extension of septae for a period of one and a half years between 2006 and 2007. The results showed a severe reduction in extension rates associated with the presence of endolithic photo-autotrophs. Infested individuals grew about half as fast as non-infested polyps with a median value of 1.18 [micro]m [day.sup.-1] compared to 2.76 [micro]m [day.sup.-1]. Contrary to the initial hypothesis, these results point toward a parasitic relationship between D. dianthus and its endolithic photo-autotrophs potentially impairing coral fitness. However, further data on physiological parameters and other aspects of the calcification process are necessary to confirm these findings., Introduction Endolithic photo-autotrophs are common in skeletons of live corals in tropical as well as temperate and cold-water regions (Highsmith 1981; Le Campion-Alsumard et al. 1995b; Schlichter et al. 1997;Forsterra [...]

Detrimental effects of parasitism on host fitness are frequently attributed to parasite-associated perturbations to host energy budgets. It has therefore been widely hypothesized that energetic costs of infection may be manifest as changes in host resting metabolic rate (RMR). Attempts to quantify these effects have yielded contradictory results across host--parasite systems. We used a meta-analysis of the literature to test the effects of parasites on mass-specific (n = 22) and whole-body (n = 15) host RMR. Parasites resulted in a qualitative increase in host RMR in the majority of studies; however, the overall effect of parasites on host RMR was small and statistically nonsignificant. Additionally, substantial among-study variation in host RMR could not be explained by any of the tested covariates. We conclude that the lack of an overall effect of parasites on host metabolism reflects inconsistent directionality and varying magnitudes of parasite- associated effects across studies, rather than an absence of system-specific effects. We contend that a general understanding of parasite effects on host energetics may be best achieved through identifying mechanisms underlying among-system variance in parasite effects on host RMR and relating parasite-associated perturbations of host energy budgets to robust estimates of host fitness. On attribue frequemment les effets nefastes du parasitisme sur la fitness de l'hote aux perturbations des bilans energetiques de l'hote associees au parasite. On emet donc souvent l'hypothese qui veut que les couts energetiques de l'infection peuvent se manifester comme des modifications du taux metabolique au repos (RMR) de l'hote. Les tentatives pour mesurer ces effets ont donne des resultats contradictoires dans l'ensemble des systemes hotes-parasites. Nous entreprenons une meta-analyse de la litterature afin de verifier les effets des parasites sur le RMR specifique a la masse (n = 22) et le RMR du corps entier (n = 15) chez les hotes. Dans la plupart des etudes, les parasites causent une augmentation qualitative du RMR de l'hote, mais l'effet global des parasites sur le RMR des hotes est faible et statistiquement non significatif. De plus, il n'a pas ete possible d'expliquer l'importante variation dans le MRM des hotes entre les etudes par les covariables testees. Nous concluons que l' absence d' effet global des parasites sur le metabolisme des hotes demontre une direction inconstante et des ordres de grandeur variables des effets associes aux parasites dans l'ensemble des etudes, plutot qu'une absence d'effets specifiques au systeme. Nous croyons qu'une comprehension generale des effets des parasites sur le systeme energetique des hotes pourra etre obtenue le plus efficacement en identifiant les mecanismes sous-jacents a la variance des effets des parasites sur le RMR des hotes entre les systemes et en mettant en relation les perturbations des bilans energetiques associees aux parasites et des estimations robustes de la fitness des hotes. [Traduit par la Redaction], Introduction While contemporary theory recognizes the deleterious impacts of parasitism on host fitness (see Gulland 1995; Tompkins et al. 2002), our understanding of parasite virulence and pathogenicity remains in its [...]

The fungal cell wall plays a crucial role in host-pathogen interactions. Its formation is the result of the coordinated activity of several extracellutar enzymes, which assemble the constituents, and remodel and hydrolyse them in the extracellular space. Canclida albicans Phrl and Phr2 proteins belong to family GH72 of the [beta]-(1,)-glucanosyltransferases and play a crucial role in cell wall assembly. PHR1 and PHR2, homologues of Saccharomyces cerevisiae GAS1, are differently regulated by extracellular pH. PHR1 is expressed when ambient pH is 5.5 or higher, whereas PHR2 has the reverse expression pattern. Their deletion causes a pH-conditional defect in morphogenesis and virulence. In this work we explored whether PHR1 deletion affects the ability of C. albicans to adhere to and invade human epithelia. PHR1 null mutants exhibited a marked reduction in adhesion to both abiotic surfaces and epithelial cell monolayers. In addition, the mutant was unable to penetrate and invade reconstituted human epithelia. Transcription profiling of selected hyphal-specific and adhesin-encoding genes indicated that in the PHR1 null mutant, HWP1 and ECE1 transcript levels were similarly reduced in both adhesion and suspension conditions. These results, combined with microscopy analysis of the septum position, suggest that PHR1 is not required for the induction of hyphal development but plays a key role in the maintenance of hyphal growth. Thus, the [beta]-(1,)-glucan processing catalysed by Phrl p is of fundamental importance in the maintenance of the morphological state on which the adhesive and invasive properties of C. albicans greatly depend. DOI 10.1099/mic.0.038000-0

Mycorrhizal status of the host plant is often ignored in studies on plant--herbivore interactions, but mycorrhizal colonization is known to induce many morphological, physiological, and biochemical changes in host plants, which in turn may alter plant quality as a host for insect herbivores. Both positive and negative effects of mycorrhizal colonization of the host plant on performance and density of insect herbivores have been reported in previous studies. We have conducted a meta-analysis of 34 published and unpublished studies on this topic in order to find out the sources of variation in mycorrhizae effects on insect herbivores. Effects of mycorrhizae on chewing insects depended upon the parameter measured and the degree of herbivore feeding specialization. Density and consumption of chewing insects were higher on mycorrhizal plants, but this did not lead to greater plant damage, presumably because herbivore survival tended to be lower on mycorrhizal plants. Mono-and oligophagous chewers benefited from mycorrhizal colonization of their host plants, whereas performance of polyphagous chewers was reduced on mycorrhizal plants. Among sucking insects, phloem feeders benefited from mycorrhizal infection, but performance of mesophyll feeders was lower on mycorrhizal plants. The type of mycorrhiza was not important for chewing insects, but performance of sucking insects was increased more by arbuscular mycorrhizal fungi (AM) than by ectomycorrhizae (ECM). Among AM inoculation studies, the most commonly used fungal species, Glomus intraradices, tended to have a negative effect on chewer performance, whereas all other fungal species tended to have a positive effect. There was no significant difference in results between studies using inoculation and fungicides, field and laboratory studies, and published and unpublished studies. Mycorrhizal status of the host plant thus influences insect herbivore performance, but the magnitude and direction of the effect depend upon the feeding mode and diet breadth of the insect and the identity of fungi. Key words: arbuscular mycorrhizae; ectomycorrhizae; feeding guilds; insect herbivores; meta-analysis; multitrophic interactions.

The recognition and binding of pathogens to extracellular matrix glycoproteins may determine the outcome of infective processes. The interaction between the bovine urogenital parasite Tritrichomonas foetus and the major basal membrane glycoprotein laminin-1 (LMN-1) was investigated. The chemical nature of parasite molecules involved in the attachment of T. foetus to immobilized LMN-1 and the influence of LMN-1 in the toxicity exerted by the parasite to HeLa cells was studied. Attachment of T. foetus to LMN-1 resulted in notable morphological alterations of the parasite, which became amoeboid. T. foetus recognized LMN-1 through specific amino acid sequences (AG73, C16, A208 and A13) in the LMN-1 molecule, and the protein nature of the parasite molecules involved in the recognition was demonstrated by dot-blot analyses. Such molecular recognition was cation-dependent and five LMN-l-binding molecules (220, 200, 130, 125 and 80 kDa) were identified in T. foetus. Binding of T. foetus to LMN-1 rendered the parasite toxic to HeLa cell monolayers. Thus, LMN-1 appears to provide signalling cues that mediate important cell functions in T. foetus concerning its interaction with host cells.

Abstract: The physiological consequences of 'premature migratory return' to freshwater for wild sea-run brown trout (Salmo trutta) smolts infested with sea lice (Lepeophtheirus salmonis) were investigated in the laboratory. Osmoregulatory, [...]

The production of antimicrobial compounds known as colicins has been shown to be an important mediator of competitive interactions among Escherichia coli genotypes. There is some understanding of the forces responsible for determining the frequency of colicin production in E. coli populations; however, this understanding cannot explain all of the observed variation. A survey of colicin production in E. coli isolated from native Australian mammals revealed that the frequency of colicin production in strains isolated from carnivores was significantly lower than the frequency of production in strains recovered from herbivores or omnivores. The intestine of Australian carnivores is tube-like and gut turnover rates are rapid compared with the turnover rates of the intestinal tracts of herbivores and omnivores, all of which possess a hindgut fermentation chamber. A mathematical model was developed in order to determine if variation in gut turnover rates could determine if a host was more likely to harbour a colicin-producing strain or a non-producer. The model predicted that a colicin producer was more likely to dominate in the gut of a host with lower gut turnover rates, and a non-producer to dominate in hosts with rapid gut turnover rates.

Parasites often play an important role in modifying the physiology and behavior of their hosts and may, consequently, mediate the influence hosts have on other components of an ecological community. Along the northern Atlantic coast of North America, the dominant herbivorous snail Littorina littorea structures rocky intertidal communities through strong grazing pressure and is frequently parasitized by the digenean trematode Cryptocotyle lingua. We hypothesized that the effects of parasitism on host physiology would induce behavioral changes in L. littorea, which in turn would modulate L. littorea's influence on intertidal community composition. Specifically, we hypothesized that C. lingua infection would alter the grazing rate of L. littorea and, consequently, macroalgal communities would develop differently in the presence of infected versus uninfected snails. Our results show that uninfected snails consumed 40% more ephemeral macroalgal biomass than infected snails in the laboratory, probably because the digestive system of infected snails is compromised by C. lingua infection. In the field, this weaker grazing by infected snails resulted in significantly greater expansion of ephemeral macroalgal cover relative to grazing by uninfected snails. By decreasing the per-capita grazing rate of the dominant herbivore, C. lingua indirectly affects the composition of the macroalgal community and may in turn affect other species that depend on macroalgae for resources or habitat structure. In light of the abundance of parasites across systems, we suggest that, through trait-mediated indirect effects, parasites may be a common determinant of structure in ecological communities. behavior modification | ecosystem functioning | herbivory | intertidal zone | trait-mediated indirect interactions

A previously undetected domain, named CW for its conserved cysteine and tryptophan residues, appears to be a four-cysteine zinc-finger motif found exclusively in vertebrates, vertebrate-infecting parasites and higher plants. Of the twelve distinct nuclear protein families that comprise the CW domain-containing superfamily, only the microrchida (MORC) family has begun to be characterized. However, several families contain other domains suggesting a relationship between the CW domain and either chromatin methylation status or early embryonic development.

The biotransformation of the phytoanticipins, 2-benzoxazolinone and 2-hydroxy-1,4-benzoxazin-3-one, by Aphelandra tetragona endophytes is described. Results reveal products of oxidation, reduction, hydrolysis, acetylation, and nitration as the biotransformation products mediated by the endophytic fungi.

The author reviews the results of the Molecular Genetics of Bacteria and Phages annual meeting held in Madison at the University of Wisconsin in 2001. The topics discussed at the meeting include host-pathogen interactions, cell surface, secretion and import, DNA replication and repair, posttranscriptional control, cell division and development and bacterial genome and its structure, recombination and transposition.

The factors that control replication rate of the intracellular bacterium Wolbachia pipientis in its insect hosts are unknown and difficult to explore, given the complex interaction of symbiont and host genotypes. Using a strain of Wolbachia that is known to over-replicate and shorten the lifespan of its Drosophila melanogaster host, we have tracked the evolution of replication control in both somatic and reproductive tissues in a novel host/Wolbachia association. After transinfection (the transfer of a Wolbachia strain into a different species) of the over-replicating Wolbachia popcorn strain from D. melanogaster to Drosophila simulans, we demonstrated that initial high densities in the ovaries were in excess of what was required for perfect maternal transmission, and were likely causing reductions in reproductive fitness. Both densities and fitness costs associated with ovary infection rapidly declined in the generations after transinfection. The early death effect in D. simulans attenuated only slightly and was comparable to that induced in D. melanogaster. This study reveals a strong host involvement in Wolbachia replication rates, the independence of density control responses in different tissues, and the strength of natural selection acting on reproductive fitness.

Research on host-parasite interactions in Peruvian birds and bird lice species indicates that mean louse abundance is positively correlated with species richness and host body mass. Louse abundance, however, was negatively linked to the upper mandible size of the host bird's bill, suggesting a preening factor in morphology in addition to feeding.

Research demonstrates that for mutualism, pathogenesis, or both, gram-negative bacteria require the rpoS gene encoded sigma(sup)S transcription factor for mutualism but not for pathogenesis as shown by the rpoS mutant's inability to colonize nematode intestines.

Research shows that autolysin-negative mutants of virulent pneumococcus WU2 type 3 as well as virulent cells grown in broth containing 2% choline chloride do not indicate that autolysin is involved in the release of pneumolysin in steptococcus pneumoniae.

Results demonstrate that compound I of human eosinophil peroxidase can be synthesized by the addition of 1 equivalence of hydrogen peroxide to the native enzyme. Comparative analyses of the enzyme with homologous myeloperoxidase and lactoperoxidase for elucidating its role in the host defence and tissue injury are presented.

Results indicate that Mycobacterium tuberculosis adaptation to long-term survival in asymptomatic patients is mediated by hyperphosphorylated guanine controlling gene expresson. Data further point out that rel(sub)Mtb protein generates the hyperphosphorylated guanine species under nutrient starvation conditions.

Evolution of sex and the coevolution of parasites with host-acquired immunity is discussed. In the system coevolutionary oscillations can be maintained. A deterministic model has been developed. The model describes the coevolution of parasites with the acquired immune responses of hosts, but can be compared with other host-parasite models more traditionally used to investigate Red Queen theories of evolution of sex. Whether sexual reproduction can be advantageous over asexuality and reasons are discussed. The infection of rats by the intestinal nematode Strongyloides ratti is considered.

Evolutionary and ecological physiology are discussed in this review article as they relate to heat-shock proteins (Hsps), the stress response and molecular chaperones. Hsps are responses to natural stress in various organisms at various stages of evolution and in assorted environments. They have consequences for fitness and vary with evolution and with encoding genes. The article seeks to redirect the aims of evolutionary and ecological research in this area beyond the established conclusions.

The interactions between worm expulsion and altered intestinal muscle contractility was analyzed in NIH Swiss mice and B10-BR mice infected with Trichinella spiralis. The nematode-infected mice exhibited increased intestinal contractility in response to Trichinella spiralis infestation. The eviction of the nematode from the rodent gut was mediated by changes in enteric muscle function and increased propulsive forces.

The invasion by tryptosomes of host cells depends upon the availability of peripheral lysosomes and an intact microtubule/kinesin-mediated transport system. Exposure of L6E9 rat myoblasts and normal rat kidney fibroblasts to Tryptosoma cruzi results in the mobilization of peripheral lysosomes toward the parasite attachment site. However, disruption of the microtubule stability and the kinesin function using drugs significantly inhibits the entry of the parasite into the host cell.

The interactions between mushroom-breeding Drosophila species and their nematode parasite Howardula aoronymphium were studied to see how parasite infestation affects the population dynamics of the host organism. The results showed that the prevalence of infection can be very high and that H. aoronymphium reduces the fertility of female flies by 50% to 100%, depending on the species. These interactions can have significant effects on host-parasite population dynamics and may have important consequences for the evolution of both parasite and host species.

Coevolutionary arms races between brood parasites and hosts involve genetic adaptations and counter-adaptations. However, hosts sometimes acquire defenses too rapidly to reflect genetic change. Our field experiments show that observation of cuckoo (Cuculus canorus) mobbing by neighbors on adjacent territories induced reed warblers (Acrocepholus scirpaceus) to increase the mobbing of cuckoos but not of parrots (a harmless control) on their own territory. In contrast, observation of neighbors mobbing parrots had no effect on reed warblers' responses to either cuckoos or parrots. These results indicate that social learning provides a mechanism by which hosts rapidly increase their nest defense against brood parasites. Such enemy-specific social transmission enables hosts to track fine-scare spatiotemporal variation in parasitism and may influence the coevolutionary trajectories and population dynamics of brood parasites and hosts.

Secondary sexual characters may have evolved because they allow females to assess the ability of conspecific males to resist parasites. In this study the prediction that the song output of swallow, Hirundo rustica, males will reflect their parasite load was tested. Male swallows sang more if they nested in colonies and were reproducing early during the season, and if their nests held few or no haematophagous tropical fowl mites, Ornithonyssus bursa. In one experiment the mite loads of swallow nests during the laying of the first clutch were manipulated and the song output of males during the fertile period of their mates prior to both the first and the second clutch was recorded. Song output did not differ between parasite treatments for first clutches (i.e. before treatment), but did so for second clutches, song output being inversely related to parasite abundance. In another experiment both mite loads of swallow nests and clutch sizes were manipulated simultaneously during the laying of the first clutch. There were no differences in song output between experimental groups for the first clutch, but mite load and the clutch size-mite load interaction affected song output during second clutches. It is likely that song output was reduced by the mites because, as a result of the anaemia they cause, they will reduce the working capacity of their hosts.

Research on Petrochelidon pyrrhonota populations in southwestern Nebraska shows that corticosterone concentrations are linked to nesting stage and food scarcity after bad-weather events, in addition to the presence of ectoparasites. Concentrations were not related to body weight, sex, testosterone levels, or age.

Crystal structure of the glutathione S-transferase, with or without glutathione from Schistosoma haematobium is described. It is a 28 kilodalton multifunctional enzyme involved in host-parasite relationships. Data indicate that glutathione is a tightly bound cofactor and mediates the catalytic mechanism for prostaglandin D(sub)2 synthase activity.

Research has been conducted on virulence in host-parasite interactions. The authors have infected Drosophila species with sympatric and allopatric nematodes in the Howardula aoronymphium species complex in the effort to investigate the effect of parasite infection on host fitness components, and they suggest that the changes in virulence sterility component are caused by host evolution.

The authors have investigated the parasites' horizontal and vertical transmissions. The hypothesis that the parasite can switch from horisontal to vertical transmission under environmental conditions favorable for host replication has been tested, and the details are reported.

The authors discuss the study of virulence. The authors describe the development of epidemiological model where the infections are the dynamic processes, where these dynamics generate a trade-off between emerging epidemiological parameters, and where the host's immune strength modifies the trade-off.

Research indicates that Glomus intraradices protects the carrot roots against Pratylenchus coffeae via suppression of nematode production in the roots. Data show that the presence of nematodes does not influence internal and external mycorrhizal development.