Choice Of Host Research Articles

Host preference of a haematophagous avian ectoparasite: a micronutrient supplementation experiment to test an evolutionary trade-off

Immune responses vary greatly depending on physiological and ecological circumstances, but the causes of this variation and its consequences for host–parasite interactions are not clear. One problem is whether resource trade-offs within hosts affect host choice by macroparasites. We aimed experimentally to disentangle the effects of the nutritional and immunological parameters of the host on the choice of host by a blood-feeding ectoparasitic fly, Carnus hemapterus. We used micronutrient supplementation to enhance host immunity and antioxidant capacity and balance the resource allocation of the host from growth to immune function in nestlings of the European roller, Coracias garrulus. Micronutrient-supplemented nestlings showed lower growth rate and body condition than sham-supplemented nestlings. Nestlings receiving micronutrients also had a higher albumin-to-globulin ratio and β- and γ-globulin concentrations, but lower α1- and α2-globulin concentrations, total protein level and cutaneous response to phytohaemagglutinin. Our results revealed that the phytohaemagglutinin response and β- and γ-globulin concentrations reflect body condition, whereas the strength of the acute phase response (α1- and α2-globulin concentrations) reflects the protein status in nestling European rollers. Ectoparasitic C. hemapterus flies generally chose hosts according to their body condition. However, this choice was moderated by host immunity when the host had poor body condition or posed a high risk for parasites in terms of the acute phase immune response.

Adaptive thresholds determination for saving cloud energy using three-way decisions

Determining the two thresholds in three-way decisions is one of hot issues, it needs to be considered in a specific field and targetedly. In the research of cloud computing, on the one hand, it is necessary to pursue service quality and economy, on the other hand, there is a large number of problems such as low utilization of cluster and high energy consumption. In this paper, the adaptive thresholds migration (ATM) algorithm is proposed by introducing three-way decisions into virtual machine migration. First of all, the proposed method evaluate load in cluster according to resource usage, and then dynamically determine two thresholds, thereby the VMs will be divided into three types with the help of ideas of three-way decisions, that is, idle state nodes, the normal nodes and overload nodes. Secondly, for nodes in different regions take different acting. For the normal nodes, we do nothing. For the idle and overloaded nodes in the cluster, ATM determine the virtual machine to be migrated and optimize the choice of target host based on the balance of resource usage and transmission overhead. Experiments based on CloudSim show that the ATM algorithm reduces power consumption by about 20% compared to TCEA and MM.

The Role of Culex pipiens L. (Diptera: Culicidae) in Virus Transmission in Europe.

Over the past three decades, a range of mosquito-borne viruses that threaten public and veterinary health have emerged or re-emerged in Europe. Mosquito surveillance activities have highlighted the Culex pipiens species complex as being critical for the maintenance of a number of these viruses. This species complex contains morphologically similar forms that exhibit variation in phenotypes that can influence the probability of virus transmission. Critical amongst these is the choice of host on which to feed, with different forms showing different feeding preferences. This influences the ability of the mosquito to vector viruses and facilitate transmission of viruses to humans and domestic animals. Biases towards blood-feeding on avian or mammalian hosts have been demonstrated for different Cx. pipiens ecoforms and emerging evidence of hybrid populations across Europe adds another level of complexity to virus transmission. A range of molecular methods based on DNA have been developed to enable discrimination between morphologically indistinguishable forms, although this remains an active area of research. This review provides a comprehensive overview of developments in the understanding of the ecology, behaviour and genetics of Cx. pipiens in Europe, and how this influences arbovirus transmission.

Optimizing the motion of a folding molecular motor in soft matter.

We use molecular dynamics simulations to investigate the displacement of a periodically folding molecular motor in a viscous environment. Our aim is to find significant parameters to optimize the displacement of the motor. We find that the choice of a massy host or of small host molecules significantly increase the motor displacements. While in the same environment, the motor moves with hopping solid-like motions while the host moves with diffusive liquid-like motions, a result that originates from the motor's larger size. Due to hopping motions, there are thresholds on the force necessary for the motor to reach stable positions in the medium. These force thresholds result in a threshold in the size of the motor to induce a significant displacement, that is followed by plateaus in the motor displacement.

Challenges in the microbial production of flavonoids

As flavonoids have beneficial health effects on humans, they are gaining increasing interest from pharmaceutical and health industries. However, current production methods, such as plant extraction and chemical synthesis, are inadequate to meet the demand. Therefore, microbial production might offer a promising alternative. During recent years, microbial strains able to produce flavonoids to a certain extent have been developed. However production titers are limited to the mg l−1 range, hampering the industrial exploitation of these strains. The latter will not be achieved by simply introducing the heterologous pathway in the production host and optimizing the fermentation process, but will depend on the interaction of different aspects of metabolic engineering and process engineering to overcome the current limitations. Next to engineering the production strain to optimize the availability of precursors, the pathway itself also requires intensive engineering. Currently utilized strategies result in a wide variety of different production strains, requiring high-throughput screening methods to identify optimal performing strains. As more and more organisms are being characterized, each with their own specific properties which might be beneficial for the heterologous production of flavonoids, the choice of the production host is another important aspect. Finally, the use of co-cultures might offer an alternative in which different parts of the process are performed by different organisms. This review aims to provide an overview of the research that has been done on these separate aspects. The work presented here could be used as a framework for further research.

Immunisation - Choice of host, adjuvants and boosting schedules with emphasis on polyclonal antibody production.

Polyclonal antibodies are frequently used as immunodiagnostic tools in fundamental research. They are also used for routine diagnostic purposes in human and veterinary medicine and for quality control procedures in the food-processing industry. The antibody is a major component of the detection system. It binds with the molecule to be identified. This conjugate is subsequently revealed by means of binding the antibody with a radio-isotope, a fluorescent substance, an enzyme inducing a color change, or a biosensor based analytical system. Polyclonal antibodies are also used for treatment purposes in various pathologies. They might have immunomodulating or anti-inflammatory properties. Snake venom, rabies and tetanus antisera are examples of a therapeutic application; immunosuppressive antithymocyte serum used in order to avoid rejection in organ transplantation is another example from human medicine. These therapeutic aids need hyperimmunisation of animals. Since these are subject to a certain number of interventions such as injections and blood samplings, animal welfare prescriptions have to be taken into account. The optimisation of the immunisation protocol allows for reducing the numbers of animals used as well as reducing stress and pain while obtaining high quality antibodies. This article describes the critical steps in polyclonal antibody production with a particular focus on the choice of the animal species, the age of the subjects, the injection protocol and the sampling times.

Effective factors on host choice of phytophagous thrips and possibilities of use for control

Thrips are cause directly damage by laying egg and feeding, indirectly by transmitting tospoviruses on plants. Many factors depending host have important role in plant selection for nutrition, shelter and reproductive. It is known that the first stimulant is host colour and as to second is host odors in host selection. Factors such as the nutrient content and morphological characteristic, different plant parts and also infection status by different organisms indicate changes according to the thrips species which can be influence on the choice of host. The stimulants which effective on host choice are important in determining the strategy of monitoring and control of pest thrips populations. Considering of stimulants that depending on host and combining of them are make more efficient combat with thrips. Specific behavioral features of the thrips reveals necessity of alternative methods and supportive strategies in control of the thrips. In this study, factors that effective on host choice of phytophagous thrips were discussed and evaluated use status of this factors in control of thrips.

Synthesis and device performance of an oxygen‐interrupted bipolar polymer host with carbazole and triphenylphosphine oxide in the main chain

ABSTRACTA novel bipolar polymer host PC10CzPO, carrying hole‐transporting carbazole and electron‐transporting triphenylphosphine oxide units in the oxygen‐interrupted main chain, was synthesized and characterized. In addition to its excellent thermal stability and miscibility with phosphors, PC10CzPO is also reported to have a triplet energy (ET) as high as 2.83 eV due to oxygen‐interrupted π‐conjugation, ensuring that PC10CzPO can be used as a suitable host material. The PC10CzPO‐based phosphorescent devices were investigated and compared, while doping with typical blue phosphor {iridium(III)[bis(4,6‐difluorophenyl)pyridinato‐N, C2]picolinate, FIrpic)}, green phosphor {tris[2‐(p‐tolyl)pyridine]iridium(III), Ir(mppy)3}, and red phosphor [bis(1‐phenyl‐isoquinoline‐C2,N)(acetylacetonato)iridium(III), Ir(piq)2acac]. As a result, the FIrpic‐based blue devices showed better device performances than those of red and green devices, which was ascribed to more effective energy transfer. This indicates that the choice of proper host and dopant emitters to fabricate phosphorescent polymer light emitting diodes (PhPLED) is a simple and effective approach to optimize device performances. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44461.

Mycobacterium tuberculosis H37Ra: a surrogate for the expression of conserved, multimeric proteins of M.tb H37Rv.

BackgroundObtaining sufficient quantities of recombinant M.tb proteins using traditional approaches is often unsuccessful. Several enzymes of the glycolytic cycle are known to be multifunctional, however relatively few enzymes from M.tb H37Rv have been characterized in the context of their enzymatic and pleiotropic roles. One of the primary reasons is the difficulty in obtaining sufficient amounts of functionally active protein.ResultsIn the current study, using M.tb glyceraldehyde-3-phosphate dehydrogenase (GAPDH) we demonstrate that expression in E. coli or M. smegmatis results in insolubility and improper subcellular localization. In addition, expression of such conserved multisubunit proteins poses the problem of heteromerization with host homologues. Importantly the expression host dramatically affected the yield and functionality of GAPDH in terms of both enzymatic activity and moonlighting function (transferrin binding). The applicability of this system was further confirmed using two additional enzymes i.e. M.tb Pyruvate kinase and Enolase.ConclusionsOur studies establish that the attenuated strain M.tb H37Ra is a suitable host for the expression of highly hydrophobic, conserved, multimeric proteins of M.tb H37Rv. Significantly, this expression host overcomes the limitations of E. coli and M. smegmatis expression and yields recombinant protein that is qualitatively superior to that obtained by traditional methods. The current study highlights the fact that protein functionality (which is an an essential requirement for all in vitro assays and drug development) may be altered by the choice of expression host.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0537-0) contains supplementary material, which is available to authorized users.

Variation of parasitism patterns in bats during hibernation: the effect of host species, resources, health status, and hibernation period.

During critical periods of food shortage or variable climatic conditions, the choice of an appropriate host can increase the survival and reproductive performance of parasites. In turn, one of the unique adaptations to periodical food shortages is hibernation, which is often found among insectivorous bat species in the temperate zone. While hibernating, bats are completely defenseless against both predators and ectoparasites, their immune and endocrine systems are diminished, and survival is dependent on the accumulated fat reserves. Differences in the health status or in the rate of consumption of the resources might also explain species-specific differences in ectoparasite abundance, especially between closely related host species, such as the greater mouse-eared bat (Myotis myotis) and the lesser mouse-eared bat (M. blythii) during hibernation. In the present study, the abundance of two ecologically distinct (summer and winter) types of ectoparasites was examined in terms of its influence on the body condition and hemoglobin content of the two host species. The effects of demographic factors, such as host sex and age, were also investigated. Despite a similar pattern of deteriorating body condition and hemoglobin concentration, M. myotis was more parasitized than was M. blythii. The marked decrease in hemoglobin content in first-year females of both host species correlated with the highest parasite load and indicated a risk of anemia. At the intraspecific level, ectoparasite abundance was not correlated with body condition (resources), but it negatively affected hemoglobin content; however, this mostly concerned M. blythii, which had a lower parasite load. Therefore, it can be concluded that interspecific differences in ectoparasite abundance may result from parasites selecting the host species that is less sensitive to their activity. In turn, in summer ectoparasites, the preference for female hosts is probably attributable to the likelihood of reinfection rather than to an effect of host resources or health status. The absence of sex-based preferences in winter ectoparasites could be explained by equal host availability.

Biosynthesis of fluorescent CdS nanocrystals with semiconductor properties: Comparison of microbial and plant production systems

This study investigated fission yeast (Schizosaccharomyces pombe) and hairy roots of tomato (Solanum lycopersicum) as in vitro production vehicles for biological synthesis of CdS quantum dots. Cd added during the mid-growth phase of the cultures was detoxified within the biomass into inorganic sulphide-containing complexes with the quantum confinement properties of semiconductor nanocrystals. Significant differences were found between the two host systems in terms of nanoparticle production kinetics, yield and quality. The much slower growth rate of hairy roots compared with yeast is a disadvantage for commercial scaled-up production. Nanoparticle extraction from the biomass was less effective for the roots: 19% of the Cd present in the hairy roots was recovered after extraction compared with 34% for the yeast. The overall yield of CdS quantum dots was also lower for the roots: relative to the amount of Cd taken up into the biomass, 8.5% was recovered in yeast gel filtration fractions exhibiting quantum dot properties whereas the result for hairy roots was only 0.99%. Yeast-produced CdS crystallites were somewhat smaller with diameters of approximately 2–6nm compared with those of 4–10nm obtained from the roots. The average ratio of inorganic sulphide to Cd for the purified and size-fractionated particles was 0.44 for the yeast and 1.6 for the hairy roots. Despite the limitations associated with hairy roots in terms of culture kinetics and product yield, this system produced CdS nanoparticles with enhanced photostability and 3.7–13-fold higher fluorescence quantum efficiency compared with those generated by yeast. This work demonstrates that the choice of cellular host can have a significant effect on nanoparticle functional properties as well as on the bioprocessing aspects of biological quantum dot synthesis.

Demonstration Using Field Collections that Argentina Fall Armyworm Populations Exhibit Strain-specific Host Plant Preferences.

Spodoptera frugiperda, the fall armyworm, is a major economic pest throughout the Western Hemisphere of corn (maize), cotton, sorghum, and a variety of agricultural grasses and vegetable crops. Studies in the United States, the Caribbean, and Brazil demonstrated the existence of two subpopulations (previously designated "host strains") that differ in their choice of plant host. Specifically, the corn strain is preferentially found in corn and sorghum, while the rice strain is dominant in rice, turf grass, and alfalfa. However, inconsistent results were reported in surveys of fall armyworm in Argentina, with some indicating that the host plant preferences of the two strains might be compromised or even nonexistent. If correct, this would complicate efforts to control this pest by considerably expanding the range of habitats that would have to be considered as potential sources for fall armyworm infestations in specific crops. A reexamination of Argentine fall armyworm, this time with field collections rather than the laboratory colonies used in previous studies, confirmed the existence of the two strains and their host preferences. Specifically, the corn strain was consistently the majority population infesting corn and was usually so in sorghum, while the rice strain was predominant in pasture/turf grasses and alfalfa. The one outlier was a collection from rice, which had a corn strain majority. Overall, the data were generally consistent with strain behaviors observed in other areas of the Western Hemisphere.

Heterologous expression of a fungal sterol esterase/lipase in different hosts: Effect on solubility, glycosylation and production

Ophiostoma piceae secretes a versatile sterol-esterase (OPE) that shows high efficiency in both hydrolysis and synthesis of triglycerides and sterol esters. This enzyme produces aggregates in aqueous solutions, but the recombinant protein, expressed in Komagataella (synonym Pichia) pastoris, showed higher catalytic efficiency because of its higher solubility. This fact owes to a modification in the N-terminal sequence of the protein expressed in Pichia pastoris, which incorporated 4-8 additional amino acids, affecting its aggregation behavior. In this study we present a newly engineered P.pastoris strain with improved protein production. We also produced the recombinant protein in the yeast Saccharomyces cerevisiae and in the prokaryotic host Escherichia coli, corroborating that the presence of these N-terminal extra amino acids affected the protein's solubility. The OPE produced in the new P.pastoris strain presented the same physicochemical properties than the old one. An inactive form of the enzyme was produced by the bacterium, but the recombinant esterase from both yeasts was active even after its enzymatic deglycosylation, suggesting that the presence of N-linked carbohydrates in the mature protein is not essential for enzyme activity. Although the yield in S.cerevisiae was lower than that obtained in P.pastoris, this work demonstrates the importance of the choice of the heterologous host for successful production of soluble and active recombinant protein. In addition, S.cerevisiae constitutes a good engineering platform for improving the properties of this biocatalyst.

Towards Improved Energy Efficiency of Aprotic Li-O2 Batteries

Aprotic Li-O2 batteries have attracted intensive focus worldwide owing to its high energy density (up to 2-3 kWh kg-1), which is theoretically beyond that provided by any other rechargeable devices. Non-aqueous Li-O2 chemistry is based on reversible formation-decomposition of electrically insulating and corrosive Li2O2 at the cathode interface. Presumably, a chemically stable and conductive cathode interface is prerequisite for sustainable cell operation. Until very recently, carbon was the ubiquitous choice of cathode host in a Li-O2 cell. However, it is now accepted that the corrosion processes triggered by Li2O2 and the in-situ generated reactive oxygen intermediates render the Li-O2 cell employing carbon based cathodes highly energy-inefficient (~70%). And a major part of this inefficiency arises out of very high charge overpotential (1-1.5 V) and incomplete charge. In this context, non-carbonaceous cathode hosts possessing stable conductive interface for reduced polarization in O2 evolution, and soluble oxidation catalysts capable of Li2O2 oxidation without a direct electrical contact with the cathode are gaining immense interest. Here, we introduce novel high surface area and conductive inorganic nanostructures as cathode host in Li-O2 cells that improves charge overpotential to a great extent as a direct consequence of suppressed cathode corrosion. We also propose a novel redox mediator with highly favorable features for soluble oxidation catalysis. Characterization techniques ranging from electron microscopy, surface spectroscopy to operando electrochemical mass spectrometry have been applied to investigate the viability of the proposed systems. Through this presentation we not only discuss novel materials and catalysts capable of electrocatalytic oxygen reduction and evolution with improved voltage characteristics, but also present a new understanding of the critical parameters for the positive electrodes in aprotic Li-O2 batteries.

Improved cultivation and metagenomics as new tools for bioprospecting in cold environments.

Only a small minority of microorganisms from an environmental sample can be cultured in the laboratory leaving the enormous bioprospecting potential of the uncultured diversity unexplored. This resource can be accessed by improved cultivation methods in which the natural environment is brought into the laboratory or through metagenomic approaches where culture-independent DNA sequence information can be combined with functional screening. The coupling of these two approaches circumvents the need for pure, cultured isolates and can be used to generate targeted information on communities enriched for specific activities or properties. Bioprospecting in extreme environments is often associated with additional challenges such as low biomass, slow cell growth, complex sample matrices, restricted access, and problematic in situ analyses. In addition, the choice of vector system and expression host may be limited as few hosts are available for expression of genes with extremophilic properties. This review summarizes the methods developed for improved cultivation as well as the metagenomic approaches for bioprospecting with focus on the challenges faced by bioprospecting in cold environments.

Influence of host matrix on thermally-activated delayed fluorescence: Effects on emission lifetime, photoluminescence quantum yield, and device performance

The influence of the host molecules on the photoluminescent (PL) and electroluminescent (EL) properties of organic light-emitting diode (OLED) emitters showing efficient thermally-activated delayed fluorescence (TADF) has yet to be investigated in detail. Here we demonstrate that the choice of host can cause large variations in the PL quantum yield (ΦPL∼15–70%) and delayed PL transient decay (τdel∼2–70ms) of a spiro-acridine-based TADF guest. We show that the effect of exciplex formation on ΦPL must be considered even at low concentrations of the TADF guest. Using the same TADF guest but changing the host layer, we are able to greatly vary the PL transient decay time from ∼4 to ∼70ms while maintaining a high ΦPL ∼70%, which can lead to new applications. Detailed spectral characterization during PL decay reveals a gradually increasing singlet–triplet energy gap (ΔEST) as the origin of these observations. The time-varying ΔEST is explained based on dipole interactions between the host and guest molecules. Finally, PL and electrical considerations for host selection are discussed based on the performance of OLED devices.

Golgi engineering of CHO cells by targeted integration of glycosyltransferases leads to the expression of novel Asn-linked oligosaccharide structures at secretory glycoproteins

Background and novelty N-glycans constitute an important information carrier in protein-driven signaling networks. Amongst others, N-glycans contribute to protein folding quality, adjust protein turnover and operate as address label for targeting proteins to specific cells and tissues [1]. Hence, the composition of N-glycans attached to recombinant glycoprotein therapeutics is vital for in-vivo therapeutic efficacy and strongly depends on the choice of the expression host [2,3]. Due to absence or silencing of glycosyltransferase genes homologue to human enzymes, biotechnologically used cell lines are limited by their intrinsic glycosylation machinery and produce host specific glycoforms. Cetuximab, a therapeutic chimeric mouse/human monoclonal antibody (IgG1), is N-glycosylated both at the CH2-domain (Asn299) and at the VH-domain (Asn88) (Figure 1A). Sold under the trade name Erbitux, Cetuximab is expressed from a murine myeloma cell line and targets the human EGF receptor [4], which is overexpressed in about 1/3 of all human cancers. The antibody is highly decorated with the aGal-epitope (Gala1-3Galb14GlcNAc) which has been shown to result in fatal allergic/ hypersensitivity response in several patients [5]. The design of new quality-optimized and functionally improved biopharmaceuticals with properties conferred by host cell unrelated N-glycans requires a rational Golgi engineering strategy. Here, we apply GET, a system that enables the positioning of a desired catalytic glycosyltransferase activity into a favorable localization within the intracellular glycosylation machinery, to suspension CHO cells developed to secrete suitable amounts (200 μg/ml) of Cetuximab as a model glycoprotein. The presented Golgi engineering project aims in the extension of the intrinsic glycosylation repertoire enabling CHO cells to produce new human-type glycosylation motifs as indicated in Figure 1A: (i) GalNAcb1,4GlcNAc-R (LacdiNAc, LDN),(ii) GlcNAc in b1,4 linkage to central mannose residue (bisecting GlcNAc, bGN), (iii) Galb1,4(Fuca1,3)GlcNAc-R (Lewis, Le) and (iv) NeuAca2,3Galb1,4 (Fuca1,3)GlcNAc-R (Sialyl-LewisX, sLe). To assemble (ii) and (iv), we coexpress GnT3 and FT7. As shown earlier, the latter enzyme catalyzes fucosylation exclusively of (iv). Therefore, we included in our study a variant of FT6 that is targeted to the early Golgi compartment with the aim to additionally generate structure (iii) [6,7]. The uncommon LDN motif (i) which is e.g. detected on lutropin is assembled by human B4GalNT3 [8,9]. We analyze oligosaccharides released from the products of genetically engineered CHO cells based on the resolution of single glycosylation sites of VHand CH2glycopeptides by quantitative NP-HPLC-FLD and use our comprehensive oligosaccharide standard library to identify novel oligosaccharide motifs.

Does natal habitat preference modulate cereal kernel preferences in the rice weevil?

The influence of larval diet source in Sitophilus oryzae (L.), a primary grain feeder, on the choice of a new cereal host by young adult was investigated through a multiple choice comparative bioassay. For this purpose, virgin male and female adults, which had been reared as immatures in different grain commodities, were monitored according to their food preference in cylindrical arenas containing whole kernels of maize, rice, barley and wheat. The adults showed a clear individual preference for maize kernels, regardless of the previous food experience, sex and also the interval on which the adults are exposed to food. Males were much more mobile than females and visited more vigorously different commodities before the final choice. Female response was found to be related with male response to specific food sources. Hence, our results indicate that there was no natal habitat preference induction, since maize was, in most cases, the final commodity choice.

Investigating host dependence of xylose utilization in recombinant Saccharomyces cerevisiae strains using RNA-seq analysis.

BackgroundXylose-based ethanol production by recombinant S. cerevisiae is of great interest to basic and applied bioenergy research. By expressing three different fungal pathways in two S. cerevisiae hosts respectively, we found that the xylose utilization efficiency by recombinant S. cerevisiae depends not only on the choice of xylose pathway but also on the choice of host, exhibiting an obvious host or context dependence. To investigate molecular mechanisms of this context dependence, we applied RNA-seq analysis in this study for a systematic characterization of the xylose utilization via different pathways in different S. cerevisiae hosts.ResultsBased on the RNA-seq analysis, the transcripts that were regulated during xylose utilization have been identified. Three transcription factors involved in regulation of amino acid metabolism, responses to oxidative stresses, and degradation of aggregated proteins, respectively, were found to participate in xylose metabolism regulation regardless of which pathway was expressed and which host the xylose pathway was expressed in. Nine transcription factors, involved in homeostasis, regulation of amino acid metabolism, and stress responses, were identified as the key modules responsible for the host-specific responses to the same xylose pathway. In addition, the transcriptional regulations of xylose utilization in different yeast hosts were compared to two reference regulation patterns, which indicated that diverse regulation strategies were adopted by different hosts for improved xylose utilization.ConclusionsThis study provides the first transcriptomic study of the host dependence of xylose utilization in S. cerevisiae. Both the conserved regulatory modules for xylose metabolism and the key modules responsible for host dependence were identified. As indicated by the functions of the conserved transcription factors involved in xylose metabolism regulation, the xylose utilization in recombinant S. cerevisiae may be affected by both carbohydrate metabolism regulation and stress responses. Based on the comparison of transcriptional regulation patterns, the metabolic optimizations of xylose utilization in different hosts went toward different directions, which may explain the host dependence observed in this study. The knowledge revealed by this study could provide valuable insights towards the improvement of metabolic engineering strategies for cellulosic ethanol production.

Host specificity of parasitic gastropods of the genusAnnulobalcisHabe, 1965 (Mollusca, Gastropoda, Eulimidae) from crinoids in Vietnam, with descriptions of four new species

ABSTRACT Parasitic gastropods of the genus Annulobalcis Habe, 1965 (family Eulimidae), associated with the crinoids (comatulids) are common in Nhatrang Bay (Southern Vietnam). Morphological examination of Annulobalcis specimens, collected in this area revealed four distinct forms, significantly different also in host specificity. Mitochondrial cox1 sequence data have shown these forms to comprise four distinct species, their relationships are discussed. As a result of morphological and molecular studies, four new species of the genus Annulobalcis are described: A. albus n. sp., A. wareni n. sp., A. maculatus n. sp., and A. vinarius n. sp. The three former species appeared to be strictly species specific in their choice of host (parasitizing a single host species each), while the latter was found on a number of hosts, although mostly on a single species. Speciation in relation to host specificity of Annulobalcis is discussed.