Host Resources Research Articles

Short communication: Variation in production parameters among Canadian Holstein cows classified as high, average, and low immune responders

Dairy cattle evaluated for immune responses and identified as high responders are known to have a lower occurrence of economically important diseases, including mastitis, metritis, ketosis, and retained placenta. These high immune responders have also been shown to make more antibody following vaccination and to have improved milk and colostrum quality. Therefore, breeding for improved immune response is expected to have several benefits in the dairy industry. However, a concern of such an approach to improve animal health is the potential cost of lost production due to an allocation of host resources to mount a robust immune response. The objective of this study was to evaluate early- and late-lactation production parameters in cattle classified as having high, average, or low estimated breeding values (EBV) for cell-mediated (CMIR), antibody-mediated (AMIR), and overall immune responses. A total of 561 cows from 6 herds were phenotyped for immune response and ranked based on EBV for CMIR and AMIR. A linear animal model was used to evaluate differences in milk, fat, and protein yields among immune response groups, and a regression analysis was conducted based on immune response EBV. Overall, no difference in production parameters was found based on immune response rank; however, some positive relationships with immune response EBV were found, suggesting that breeding for enhanced immune responsiveness as a prophylactic approach to improve animal health would not come at the cost of lost production.

Enhanced Promoter Activity by Replenishment of Sigma Factor rpoE in Klebsiella pneumoniae.

Plasmid-dependent overexpression of enzyme(s) aims to divert carbon flux toward a desired compound. One drawback of this strategy is compromise of growth due to massive consumption of host resources. Here we show that replenishment of sigma factor rpoE improves the growth of Klebsiella pneumoniae. The gene rpoE was expressed alone or coexpressed with Ald4 (an aldehyde dehydrogenase from Saccharomyces cerevisiae) in K. pneumoniae. We found that the Ald4 activity was higher in the strain coexpressing Ald4 and rpoE (32.3U/mg) than that expressing Ald4 alone (29.9U/mg). Additionally, under shake-flask conditions, the strain coexpressing Ald4 and rpoE produced 0.5g 3-hydroxypropionic acid (3-HP) and 9.8g 1,3-propanediol (1,3-PD) per liter in 24h, which were 1.6- and 0.85-fold enhancement, respectively, compared to those expressing Ald4 alone. Notably, under non-optimized bioreactor conditions, the strain coexpressing Ald4 and rpoE produced 13.5g 3-HP and 37.8g 1,3-PD per liter with glycerol conversion ratio of 0.45mol/mol. These results indicate that replenishment of rpoE enhanced promoter activity and stimulated glycerol consumption.

The 124202 candidate effector of Melampsora larici-populina interacts with membranes in Nicotiana and Arabidopsis

Melampsora larici-populina (Mlp) is a parasitic fungus causing poplar leaf rust, a disease that threatens poplar plantations worldwide. Like other phytopathogens, Mlp translocates specialized proteins, called effectors, into host tissues and cells to eventually divert host resources. 124202 is a hypothetical Mlp effector selected through an in silico secretome analysis. It shares about 30% identity with the M. lini AvrM effector. Using heterologous systems, the objectives of this work were to assess if 124202 could mitigate Arabidopsis defence or potentiate Pseudomonas virulence and investigate its putative interaction partners in plants. Yeast two-hybrid screens identified three potential 124202 interactors in plants: lipoxygenase 2, synaptotagmin A and quinolinate synthase. Expression of a fluorescently tagged 124202 protein in Nicotiana benthamiana and Arabidopsis thaliana showed that it could be associated with membranes but may also be found in the cytoplasm of host cells. Bacterial infection assays in wild-type and 124202-expressing Arabidopsis lines indicate that 124202 does not alter the susceptibility of Arabidopsis to Pseudomonas syringae pv. tomato DC3000. Overall, our results suggest that the function of 124202 might involve vesicle-mediated trafficking but is unlikely to quantifiably contribute to the suppression of plant immunity.

Sequestration of host metabolism by an intracellular pathogen.

For intracellular pathogens, residence in a vacuole provides a shelter against cytosolic host defense to the cost of limited access to nutrients. The human pathogen Chlamydia trachomatis grows in a glycogen-rich vacuole. How this large polymer accumulates there is unknown. We reveal that host glycogen stores shift to the vacuole through two pathways: bulk uptake from the cytoplasmic pool, and de novo synthesis. We provide evidence that bacterial glycogen metabolism enzymes are secreted into the vacuole lumen through type 3 secretion. Our data bring strong support to the following scenario: bacteria co-opt the host transporter SLC35D2 to import UDP-glucose into the vacuole, where it serves as substrate for de novo glycogen synthesis, through a remarkable adaptation of the bacterial glycogen synthase. Based on these findings we propose that parasitophorous vacuoles not only offer protection but also provide a microorganism-controlled metabolically active compartment essential for redirecting host resources to the pathogens.

Two sides of the same coin: Xyloglucan endotransglucosylases/hydrolases in host infection by the parasitic plant Cuscuta

ABSTRACTThe holoparasitic angiosperm Cuscuta develops haustoria that enable it to feed on other plants. Recent findings corroborate the long-standing theory that cell wall modifications are required in order for the parasite to successfully infect a host, and further suggest that changes to xyloglucan through the activity of xyloglucan endotransglucosylases/hydrolases (XTHs) are essential. On the other hand, XTH expression was also detected in resistant tomato upon an attack by Cuscuta, which suggests that both host and parasite use these enzymes in their “arms race.” Here, we summarize existing data on the cell wall-modifying activities of XTHs during parasitization and present a model suggesting how XTHs might function to make the host's resources accessible to Cuscuta.

Observations of parasitism and aggression by female Enoggera nassaui, an egg parasitoid of the eucalypt pest, Paropsis charybdis

Female parasitoids that display aggressive behaviour towards conspecifics in defence of host resources must make a trade-off between time spent on aggression and time spent on parasitism. Such a trade-off not only affects the fitness of individual females but also may affect the overall rate of parasitism in the host population. Enoggera nassaui is an egg parasitoid of the eucalypt pest, Paropsis charybdis, with females that defend batches of host eggs from conspecific females by chasing, pushing and sometimes biting their opponent. The behaviour of female E. nassaui was observed when alone (solo) and in pairs (owner-intruder) in response to a single batch of P. charybdis eggs. The first female in a pair to contact the host eggs was designated the owner and the second female the intruder. Both parasitism-related behaviour for solo and paired females and aggressive interactions between paired females were described from direct observation. Parasitism rates for solo and paired females were also measured. Solo females had a consistent pattern of parasitism-related behaviour, spending 80 % of their time in contact with the host eggs. Paired females showed a similar pattern of parasitism-related behaviour when not interrupted by their competitor. Owners spent 6 % and intruders spent 17 % of their time on aggressive interactions. Intruders completed parasitism faster than solo females because intruders reduced the duration of specific parasitism-related behaviours. Yet from the host’s perspective, parasitism by solo females (69 %) was similar to that achieved by both owners and intruders together (66 %). By completing parasitism faster in the presence of a competitor, intruder females compensated to some extent for time spent on aggressive interactions. If E. nassaui has a similar response to intraspecific competitors under natural conditions, then aggression between conspecific females is unlikely to harm pest suppression by these parasitoids.

Diversity of parasitic fungi associated with phytoplankton in Hawaiian waters

ABSTRACTParasitic fungi infect large phytoplankton species in freshwater, playing a fundamental role in their host's health and habitat range. However, those associated with the marine phytoplankton community remain largely unknown. This study investigated the infectivity and biodiversity of phytoplanktonic parasitic fungi in three ecosystems of Hawaiian waters, with contrasting trophic statuses – oligotrophic (Waikiki Beach), mesotrophic (Kaneohe Bay) and eutrophic (Ala Wai Canal). The occurrence of fungal parasites (e.g. attached spores) was primarily associated with diatom cells (i.e. the most vulnerable populations) as well as various pelagic fungal forms (i.e. zoosporic, yeast and mycelial), suggesting the coexistence of different fungal lifestyles. Phylogenetic analysis categorized our retrieved fungal sequences from six clone libraries into five taxonomic orders that belonged to the phyla of Ascomycota and Basidiomycota, along with culturable fungal endophytes and pathogens from diverse host resources. The great majority of these sequences (∼93%) were associated with three taxonomic orders of Ascomycota (Pleosporales, Hypocreales and Saccharomycetales). There was greater infectivity and diversity of fungal species in eutrophic (Ala Wai) waters compared with oligotrophic (Waikiki Beach) waters, and both factors were significantly (P < 0.05) correlated to nutrient P levels at the sampling sites. This is the first report of the occurrence and phylogenetic diversity of phytoplankton-associated fungi in Hawaiian waters and may bring new insights into our understanding of marine fungal communities.

WASP-ASSOCIATED FACTORS ACT IN INTERSPECIES COMPETITION DURING MULTIPARASITISM.

Coexistence or displacement of parasitoids in hosts during intrinsic competitive interactions between different parasitoid species (multiparasitism) may depend on their life history traits and behavior. Intense competition for possession of hosts may lead to the elimination of the inferior competitor through physical attack and/or physiological suppression. However, the mechanisms of physiological suppression during multiparasitism remain unclear. Previous work has shown that first instar larvae of the solitary endoparasitoid Meteorus pulchricornis possess well-developed mandibles that are used to kill competitors. Two gregarious endoparasitoids, Cotesia kariyai and C. rufricus, share host resources especially when the time gap of oviposition is short. Here, we investigated the physiological influence of wasp-regulatory factors of the three endoparasitoids, M. pulchricornis, C. kariyai, and C. ruficrus, in their common host Mythimna separata. We found that MpVLP alone (or with venom) deleteriously affected the development of the two gregarious species. Similarly, CkPDV plus venom had toxic effect on M. pulchricornis eggs and immature larvae, although they were not harmful to immature stages of C. ruficrus. Cotesia kariyai and C. ruficrus were able to coexist mainly through the expression of regulatory factors and both could successfully emerge from a multiparasitized host. The injection of CkPDV plus venom after oviposition in L5 host larvae facilitated C. ruficrus development and increased the rate of successful parasitism from 9% to 62%. This suggests that the two gregarious parasitoid wasps exhibit strong phylogenetic affinity, favoring their coexistence and success in multiparasitized hosts.

Effects of Intrinsic and Extrinsic Host Mortality on Disease Spread.

The virulent effects of a pathogen on host fecundity and mortality (both intrinsic and extrinsic mortality due to predation) often increase with the age of infection. Age of infection often is also correlated with parasite fitness, in terms of the number of both infective propagules produced and the between-host transmission rate. We introduce a four-population partial differential equations (PDE) model to investigate the invasibility and prevalence of an obligately killing fungal parasite in a zooplankton host as they are embedded in an ecological network of predators and resources. Our results provide key insights into the role of ecological interactions that vary with the age of infection. First, selective predation, which is known both theoretically and empirically to reduce disease prevalence, does not always limit disease spread. This condition dependency relies on the timing and intensity of selective predation and how that interacts with the direct effects of the parasite on host mortality. Second, low host resources and intense predation can prevent disease spread, but once conditions allow the invasion of the parasite, the qualitative dynamics of the system do not depend on the intensity of the selective predation. Third, a comparison of the PDE model with a model based on ordinary differential equations (ODE model) reveals a parametrization for the ODE version that yields an endemic steady state and basic reproductive ratio that are identical to those in the PDE model. Our results highlight the complexity of resource-host-parasite-predator interactions and suggest the need for additional data-theory coupling exploring how community ecology influences the spread of infectious diseases.

Asymmetric effects of adult nutrition on reproductive success of male and female Diaeretiella rapae (Hymenoptera: Aphidiidae)

AbstractThe role of diet supplements (honey, water or no supplements) on egg maturation, oviposition strategy and longevity of the parasitic wasp Diaeretiella rapae McIntosh (Hymenoptera: Aphidiidae) is investigated. Parasitoids feed as larvae on hosts to acquire nutrition for growth and development, and further gain additional resources during their adult stage by feeding on either host or nonhost resources. The additional resources acquired by adults can help them to increase their reproductive activity or life expectancy, or both. Diaeretiella rapae females emerge with some developed eggs and no additional resources are required for egg maturation or successful oviposition. Females are able to oviposit and produce viable offspring immediately after emergence, and the number of eggs left in the ovaries of females decreases with subsequent oviposition, suggesting that ovigeny index of D. rapae is inclined towards pro‐ovigenic status. When unmated males and females are offered honey solution, females are attracted to it, whereas males display courtship and make mating attempts but then feed on honey after mating. The oviposition efficiency of female D. rapae increases by 30% when they feed on honey compared with when starved. Honey‐fed D. rapae adults live significantly longer (almost twice as long) than starved adults. Honey‐fed females deprived of hosts live longer than those offered hosts regularly. The positive effects of honey‐feeding on longevity are greater in females than in males. Taken together, the results of the present study suggest that the provision of additional resources to adult D. rapae parasitoids could enhance their life expectancy and parasitism efficiency in biological control programmes.

Entomopathogenic Fungi: New Insights into Host-Pathogen Interactions.

Although many insects successfully live in dangerous environments exposed to diverse communities of microbes, they are often exploited and killed by specialist pathogens. Studies of host-pathogen interactions (HPI) provide valuable insights into the dynamics of the highly aggressive coevolutionary arms race between entomopathogenic fungi (EPF) and their arthropod hosts. The host defenses are designed to exclude the pathogen or mitigate the damage inflicted while the pathogen responds with immune evasion and utilization of host resources. EPF neutralize their immediate surroundings on the insect integument and benefit from the physiochemical properties of the cuticle and its compounds that exclude competing microbes. EPF also exhibit adaptations aimed at minimizing trauma that can be deleterious to both host and pathogen (eg, melanization of hemolymph), form narrow penetration pegs that alleviate host dehydration and produce blastospores that lack immunogenic sugars/enzymes but facilitate rapid assimilation of hemolymph nutrients. In response, insects deploy an extensive armory of hemocytes and macromolecules, such as lectins and phenoloxidase, that repel, immobilize, and kill EPF. New evidence suggests that immune bioactives work synergistically (eg, lysozyme with antimicrobial peptides) to combat infections. Some proteins, including transferrin and apolipophorin III, also demonstrate multifunctional properties, participating in metabolism, homeostasis, and pathogen recognition. This review discusses the molecular intricacies of these HPI, highlighting the interplay between immunity, stress management, and metabolism. Increased knowledge in this area could enhance the efficacy of EPF, ensuring their future in integrated pest management programs.

HCE&lt;SUB align="right"&gt;m model and a comparative workload analysis of Hadoop cluster

This paper describes the HCEm model, designed to estimate the size of a cluster running Hadoop, in a given timeframe on cloud environments. The HCEm consists of a light optimisation layer for MapReduce jobs and a model to estimate the size of a Hadoop cluster. Additionally, this paper presents a comparative study of HCEm using similar applications and workloads in two production Hadoop clusters, the Amazon Elastic MapReduce and a private cloud in a large financial company, in order to evaluate the performance of the model in real and intensive processing environments. The estimates generated by the HCEm model and processing performed are representative and consistent, which can help researchers and engineers understand the workload characteristics of Hadoop clusters in their production environments. The performance differences shown between the real environments, confirmed that the increased sharing of physical computing host resources reduces the accuracy of the model.

A new big data storage architecture with intrinsic search engines

The data storage system is central in determining the performance and cost in data mining or ITS. As the computing power of servers has increased so have the problems caused by the bottlenecks from slower storage protocol interfaces, which restrict data throughput and the accessing raw data from the physical storage systems. This paper presented new big data storage architecture to optimize the efficiency of data mining or mass surveillance by integrating a distributed and embedded searching engine inside each storage drive. By integrating the intrinsic search engine (iSearch) into the core controller chip some of the work of searching for patterns and keywords takes place inside the drive freeing up resources of a higher level host and ultimately the server. Only those drives, in which the expected pattern or keywords were detected, are analyzed by the higher level host. Not only does iSearch free up the server for other high level computing tasks it also helps preserve as the bandwidth of the big data storage interface.

Interactions among bacterial strains and fluke genotypes shape virulence of co-infection.

Most studies of virulence of infection focus on pairwise host-parasite interactions. However, hosts are almost universally co-infected by several parasite strains and/or genotypes of the same or different species. While theory predicts that co-infection favours more virulent parasite genotypes through intensified competition for host resources, knowledge of the effects of genotype by genotype (G × G) interactions between unrelated parasite species on virulence of co-infection is limited. Here, we tested such a relationship by challenging rainbow trout with replicated bacterial strains and fluke genotypes both singly and in all possible pairwise combinations. We found that virulence (host mortality) was higher in co-infections compared with single infections. Importantly, we also found that the overall virulence was dependent on the genetic identity of the co-infecting partners so that the outcome of co-infection could not be predicted from the respective virulence of single infections. Our results imply that G × G interactions among co-infecting parasites may significantly affect host health, add to variance in parasite fitness and thus influence evolutionary dynamics and ecology of disease in unexpected ways.

Beyond Mortality: Sterility As a Neglected Component of Parasite Virulence.

Virulence is generally defined as the reduction in host fitness following infection by a parasite (see Box 1 for glossary) [1]. In general, parasite exploitation of host resources may reduce host survival (mortality virulence), decrease host fecundity (sterility virulence), or even have sub-lethal effects that disturb the way individuals interact within a community (morbidity) [2,3]. In fact, the virulence of many parasites involves a combination of these various effects (Box 2). In practice, however, virulence is most often defined as disease-induced mortality [1, 4–6]. This is especially true in the theoretical literature, where the evolution of sterility virulence, morbidity, and mixed strategies of host exploitation have received relatively little attention. While the focus on mortality effects has allowed for easy comparison between models and, thus, rapid advancement of the field, we ask whether these theoretical simplifications have led us to inadvertently minimize the evolutionary importance of host sterilization and secondary virulence effects. As explicit theoretical work on morbidity is currently lacking (but see [7]), our aim in this Opinion piece is to discuss what is understood about sterility virulence evolution, its adaptive potential, and the implications for parasites that utilize a combination of host survival and reproductive resources.

The herbaceous landlord: integrating the effects of symbiont consortia within a single host.

Plants are typically infected by a consortium of internal fungal associates, including endophytes in their leaves, as well as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) in their roots. It is logical that these organisms will interact with each other and the abiotic environment in addition to their host, but there has been little work to date examining the interactions of multiple symbionts within single plant hosts, or how the relationships among symbionts and their host change across environmental conditions. We examined the grass Agrostis capillaris in the context of a climate manipulation experiment in prairies in the Pacific Northwest, USA. Each plant was tested for presence of foliar endophytes in the genus Epichloë, and we measured percent root length colonized (PRLC) by AMF and DSE. We hypothesized that the symbionts in our system would be in competition for host resources, that the outcome of that competition could be driven by the benefit to the host, and that the host plants would be able to allocate carbon to the symbionts in such a way as to maximize fitness benefit within a particular environmental context. We found a correlation between DSE and AMF PRLC across climatic conditions; we also found a fitness cost to increasing DSE colonization, which was negated by presence of Epichloë endophytes. These results suggest that selective pressure on the host is likely to favor host/symbiont relationships that structure the community of symbionts in the most beneficial way possible for the host, not necessarily favoring the individual symbiont that is most beneficial to the host in isolation. These results highlight the need for a more integrative, systems approach to the study of host/symbiont consortia.

Power Efficient Hybrid VM Allocation Algorithm

Virtualization technology in Cloud computing has become important technology to reduce power consumption in data centers. Virtual Machine allocation to hosts is the main concept which carried out during Virtual Machine migrations in data centers. Virtual Machine allocation helps to utilize hardware resources of hosts and leads to power efficiency in Data centers. In the past few years, various mechanisms were proposed to apply algorithms to achieve power efficiency. In this paper, we have proposed a genetic algorithm to optimize various parameters i.e. power consumption, response time, SLA violation and VM migrations. Our proposed hybrid algorithm provisions various VMs to hosts in a way that to minimize power consumption, while delivering approved Quality of Service. Results demonstrate that proposed HVMA algorithm helps to minimize power consumption and to optimize various performance parameters during live migrations in various environment conditions.

The placid slavemaker: avoiding detection and conflict as an alternative, peaceful raiding strategy

Host entry is a crucial step in a parasite’s life cycle. When parasites manage to circumvent host detection, exploitation of host resources is facilitated, as host defenses have not to be counteracted. Social parasites exploit animal societies and, likewise, detection avoidance can be beneficial. Yet, due to strong selection pressures, hosts of socially parasitic slavemaking ants often recognize them as enemies, so that slavemakers use open force to raid host colonies. These fights, however, prohibit the enslavement of adult host workers (eudulosis), which cannot be manipulated to work for them. Instead, they steal brood during raids, and enslave those upon emergence. In contrast to the violent raids of most slavemakers, no aggression occurs during most of the raids of the newly described slavemaker Temnothorax pilagens. Thereby, T. pilagens regularly induces adult host workers to be part of their slave workforce. We demonstrate that non-enslaved colonies of its host species respond to this slavemaker with little aggression. We further investigate how the slavemaker circumvents recognition and show that chemical resemblance of host profiles might explain the low aggressive responses. But, which parameters determine whether slave raids escalate, resulting in carnage among defenders? Our experiments reveal that host aggression is counterproductive as aggressive host colonies suffer from more fatalities during raids, but cannot save more brood. The slavemaker, however, benefits from not eliciting fights, as it doubles its enslaved workforce by capturing brood plus adult host workers. Hence, undercutting recognition allows the slavemaker to avoid raid escalation with its associated fitness benefits.

The importance of spatial heterogeneity and self-restraint on mutualism stability - a quantitative review.

Understanding the factors that enable mutualisms to evolve and to subsequently remain stable over time, is essential to fully understand patterns of global biodiversity and for evidence based conservation policy. Theoretically, spatial heterogeneity of mutualists, through increased likelihood of fidelity between cooperative partners in structured populations, and ‘self-restraint’ of symbionts, due to selection against high levels of virulence leading to short-term host overexploitation, will result in either a positive correlation between the reproductive success of both mutualists prior to the total exploitation of any host resource or no correlation after any host resource has been fully exploited. A quantitative review by meta-analysis on the results of 96 studies from 35 papers, showed no evidence of a significant fitness correlation between mutualists across a range of systems that captured much taxonomic diversity. However, when the data were split according to four categories of host: 1) cnidarian corals, 2) woody plants, 3) herbaceous plants, and 4) insects, a significantly positive effect in corals was revealed. The trends for the remaining three categories did not significantly differ to zero. Our results suggest that stability in mutualisms requires alternative processes, or mechanisms in addition to, spatial heterogeneity of hosts and/or ‘self-restraint’ of symbionts.

Understanding Host-Switching by Ecological Fitting.

Despite the fact that parasites are highly specialized with respect to their hosts, empirical evidence demonstrates that host switching rather than co-speciation is the dominant factor influencing the diversification of host-parasite associations. Ecological fitting in sloppy fitness space has been proposed as a mechanism allowing ecological specialists to host-switch readily. That proposal is tested herein using an individual-based model of host switching. The model considers a parasite species exposed to multiple host resources. Through time host range expansion can occur readily without the prior evolution of novel genetic capacities. It also produces non-linear variation in the size of the fitness space. The capacity for host colonization is strongly influenced by propagule pressure early in the process and by the size of the fitness space later. The simulations suggest that co-adaptation may be initiated by the temporary loss of less fit phenotypes. Further, parasites can persist for extended periods in sub-optimal hosts, and thus may colonize distantly related hosts by a "stepping-stone" process.