Vertical Acquisition Research Articles

Vertical acquisition and carbon capture and storage choices under cap-and-trade regulation with sustainable finance

In this paper, we establish a contingent claim framework for environmental management. The paper focuses on the vertical acquisition of a supply chain in the context of sustainable insurance (i.e., sustainable finance), specifically considering carbon capture and storage (CCS) technology choices and cap-and-trade regulations. The main results are as follows. Firstly, a more stringent cap-and-trade scheme increases equity efficiency in sustainable insurance, particularly when the green upstream manufacturer with advanced CCS technology acquires the brown downstream manufacturer, which also uses advanced CCS technology. Secondly, it harms risk efficiency, especially when the green upstream manufacturer with backward CCS technology acquires the brown downstream manufacturer, which uses advanced CCS technology. Thirdly, it increases the default risk in the insurer's equity, especially when the green upstream manufacturer with backward CCS technology acquires the brown downstream manufacturer, which also uses backward CCS technology. Overall, cap-and-trade's effects on equity and risk efficiency in vertical acquisition and default risk in insurer's equity within sustainable insurance depend on adopting CCS technology. Policymakers should incentivize advanced CCS technologies in vertical acquisitions to enhance equity and reduce default risks, supporting long-term financial stability and environmental sustainability toward Sustainable Development Goals.

Acceptability of hepatitis C screening and treatment during pregnancy in pregnant women in Egypt, Pakistan, and Ukraine: A cross-sectional survey.

Chronic hepatitis C (HCV) in women of childbearing age is a major public health concern with ∼15 million women aged 15-49 years living with HCV globally in 2019. Evidence suggests HCV in pregnancy is associated with adverse pregnancy and infant outcomes. This includes ∼6% risk of infants acquiring HCV vertically, and this is the leading cause of HCV in children globally. However, few countries offer routine universal antenatal HCV screening, and direct-acting antivirals (DAAs) are not approved for pregnant or breastfeeding women although small clinical trials are ongoing. We conducted a survey of pregnant and postpartum women in 3 high HCV burden lower-middle-income countries to assess the acceptability of universal antenatal HCV screening and DAA treatment in the scenario that DAAs are approved for use in pregnancy. Pregnant and postpartum women attending antenatal clinics in Egypt, Pakistan, and Ukraine were invited to complete a survey and provide demographic and clinical data on their HCV status. Among the 630 women included (n=210 per country), 73% were pregnant and 27% postpartum, 27% were ever HCV antibody or PCR positive. Overall, 586 (93%) reported acceptability of universal antenatal HCV screening and 544 (88%) would take DAAs in pregnancy (92%, 98%, and 73% in Egypt, Pakistan, and Ukraine, respectively). Most said they would take DAAs in pregnancy to prevent vertical acquisition and other risks for the baby, and a smaller proportion would take DAAs for maternal cure. Our findings suggest that should DAAs be approved for use in pregnancy, the uptake of both HCV screening and DAA treatment may be high in women living in lower-middle-income countries.

Optimal capital structure with supplier market power

AbstractWe use a real‐option model to study the effect of input supplier's market power on a firm's capital structure, and identify the Nash equilibrium outcome (firm's investment and financing policies and its supplier's pricing policy). When its supplier has market power, the firm will reduce leverage ratio and delay investment. This can help explain why observed leverage ratios are lower than in traditional capital‐structure models (without supplier market power). Firm value can be increased by the vertical acquisition of the supplier, which would also result in a higher leverage ratio. This helps explain the observed increase in leverage ratios after acquisitions.

FCGR3A gene duplication, FcγRIIb-232TT and FcγRIIIb-HNA1a associate with an increased risk of vertical acquisition of HIV-1.

BackgroundSome mother-to-child transmission (MTCT) studies suggest that allelic variations of Fc gamma receptors (FcγR) play a role in infant HIV-1 acquisition, but findings are inconsistent. To address the limitations of previous studies, the present study investigates the association between perinatal HIV-1 transmission and FcγR variability in three cohorts of South African infants born to women living with HIV-1.MethodsThis nested case-control study combines FCGR genotypic data from three perinatal cohorts at two hospitals in Johannesburg, South Africa. Children with perinatally-acquired HIV-1 (cases, n = 395) were compared to HIV-1-exposed uninfected children (controls, n = 312). All study participants were black South Africans and received nevirapine for prevention of MTCT. Functional variants were genotyped using a multiplex ligation-dependent probe amplification assay, and their representation compared between groups using logistic regression analyses.ResultsFCGR3A gene duplication associated with HIV-1 acquisition (OR = 10.27; 95% CI 2.00–52.65; P = 0.005) as did the FcγRIIb-232TT genotype even after adjusting for FCGR3A copy number and FCGR3B genotype (AOR = 1.72; 95%CI 1.07–2.76; P = 0.024). The association between FcγRIIb-232TT genotype and HIV-1 acquisition was further strengthened (AOR = 2.28; 95%CI 1.11–4.69; P = 0.024) if adjusted separately for FCGR2C c.134-96C>T. Homozygous FcγRIIIb-HNA1a did not significantly associate with HIV-1 acquisition in a univariate model (OR = 1.42; 95%CI 0.94–2.16; P = 0.098) but attained significance after adjustment for FCGR3A copy number and FCGR2B genotype (AOR = 1.55; 95%CI 1.01–2.38; P = 0.044). Both FcγRIIb-232TT (AOR = 1.83; 95%CI 1.13–2.97; P = 0.014) and homozygous FcγRIIIb-HNA1a (AOR = 1.66; 95%CI 1.07–2.57; P = 0.025) retained significance when birthweight and breastfeeding were added to the model. The common FCGR2A and FCGR3A polymorphisms did not associate with HIV-1 acquisition.ConclusionsCollectively, our findings suggest that the FcγRIIb-232TT genotype exerts a controlling influence on infant susceptibility to HIV-1 infection. We also show a role for less studied variants–FCGR3A duplication and homozygous HNA1a. These findings provide additional insight into a role for FcγRs in HIV-1 infection in children.

The methylation-independent mismatch repair machinery in Pseudomonas aeruginosa.

Over the last 70 years, we’ve all gotten used to an Escherichia coli -centric view of the microbial world. However, genomics, as well as the development of improved tools for genetic manipulation in other species, is showing us that other bugs do things differently, and that we cannot simply extrapolate from E. coli to everything else. A particularly good example of this is encountered when considering the mechanism(s) involved in DNA mismatch repair by the opportunistic human pathogen, Pseudomonas aeruginosa (PA). This is a particularly relevant phenotype to examine in PA, since defects in the mismatch repair (MMR) machinery often give rise to the property of hypermutability. This, in turn, is linked with the vertical acquisition of important pathoadaptive traits in the organism, such as antimicrobial resistance. But it turns out that PA lacks some key genes associated with MMR in E. coli , and a closer inspection of what is known (or can be inferred) about the MMR enzymology reveals profound differences compared with other, well-characterized organisms. Here, we review these differences and comment on their biological implications.

Commensal Escherichia coli Antimicrobial Resistance and Multidrug-Resistance Dynamics during Broiler Growing Period: Commercial vs. Improved Farm Conditions.

Simple SummaryThis experiment was designed to evaluate the differences in antimicrobial and multidrug resistance dynamics in broilers reared under two different farm conditions (commercial vs. improved) during the growing period, using Escherichia coli as sentinel bacterium. Although no antibiotics were applied during rearing for two different management conditions tested, high rates of antimicrobial and multidrug-resistant bacteria were observed throughout rearing, with the percentages of resistant bacteria observed being of particular concern in day-old chicks on arrival day and in chickens at the end of the growing period, just before delivery to the slaughterhouse.New measures applied to reduce antimicrobial resistances (AMR) at field level in broiler production are focused on improving animals’ welfare and resilience. However, it is necessary to have better knowledge of AMR epidemiology. Thus, the aim of this study was to evaluate AMR and multidrug resistance (MDR) dynamics during the rearing of broilers under commercial (33 kg/m2 density and max. 20 ppm ammonia) and improved (17 kg/m2 density and max. 10 ppm ammonia) farm conditions. Day-old chicks were housed in two poultry houses (commercial vs. improved), and no antimicrobial agents were administered at any point. Animals were sampled at arrival day, mid-period and at slaughter day. High AMR rates were observed throughout rearing. No statistical differences were observed between groups. Moreover, both groups presented high MDR at slaughter day. These results could be explained by vertical or horizontal resistance acquisition. In conclusion, AMR and MDR are present throughout rearing. Moreover, although a lower level of MDR was observed at mid-period in animals reared under less intensive conditions, no differences were found at the end. In order to reduce the presence of AMR bacteria in poultry, further studies are needed to better understand AMR acquisition and prevalence in differing broiler growing conditions.

Commensal microbiota modulates larval foraging behaviour, development rate and pupal production in Bactrocera tryoni

BackroundCommensal microbes can promote survival and growth of developing insects, and have important fitness implications in adulthood. Insect larvae can acquire commensal microbes through two main routes: by vertical acquisition from maternal deposition of microbes on the eggshells and by horizontal acquisition from the environment where the larvae develop. To date, however, little is known about how microbes acquired through these different routes interact to shape insect development. In the present study, we investigated how vertically and horizontally acquired microbiota influence larval foraging behaviour, development time to pupation and pupal production in the Queensland fruit fly (‘Qfly’), Bactrocera tryoni.ResultsBoth vertically and horizontally acquired microbiota were required to maximise pupal production in Qfly. Moreover, larvae exposed to both vertically and horizontally acquired microbiota pupated sooner than those exposed to no microbiota, or only to horizontally acquired microbiota. Larval foraging behaviour was also influenced by both vertically and horizontally acquired microbiota. Larvae from treatments exposed to neither vertically nor horizontally acquired microbiota spent more time overall on foraging patches than did larvae of other treatments, and most notably had greater preference for diets with extreme protein or sugar compositions.ConclusionThe integrity of the microbiota early in life is important for larval foraging behaviour, development time to pupation, and pupal production in Qflies. These findings highlight the complexity of microbial relations in this species, and provide insights to the importance of exposure to microbial communities during laboratory- or mass-rearing of tephritid fruit flies.

The value of VSP data through early phases of field appraisal and development: A modeling and acquisition case study in the Gulf of Mexico

The Gulf of Mexico is a rich hydrocarbon province that contains a diversity of petroleum systems play types. Often, identifying drilling targets can be challenging when solely using surface seismic data, particularly in areas with complex salt structures in the overburden. In this paper, we present a vertical seismic profile (VSP) modeling and acquisition case study for an oil field located in a subsalt, deepwater, ultrahigh-pressure high-temperature environment. Our objective was to model the subsurface to guide the acquisition of VSP data during the early phases of exploration and appraisal drilling. In the first exploration well, a salt-proximity VSP designed in a walkaway configuration was carried out to help better define the geometry of a salt overhang and verify anisotropy parameters, helping to reduce a critical uncertainty for imaging the subsalt structure across a large segment within our field area. In the first appraisal well, a zero-offset VSP was collected to establish a direct well tie and further calibrate our velocity model. In the second appraisal well, we utilized walkaway VSP data to form a high-frequency stratigraphic image between the two appraisal wellbores. These data were used to generate an enhanced image of the reservoir section that revealed subtle stratigraphic boundaries, another key subsurface uncertainty. Finally, we modeled both ambitious and conservative 3D VSP acquisition designs to understand the imaging area achieved through a 3D acquisition and undertook an assessment to understand the impact of PP and PS imaging for reservoir characterization. We conclude that VSP data are valuable tools in the early phases of field appraisal and development, and we demonstrate the business value of VSPs to optimize development drilling locations in our study area.

Public Services Supply in China and the Subject Assessment of Citizens: A Theoretical Framework

Sense of gain is social science concept with China characteristic, and it is an important criterion to judge the efficiency of governments. Sense of gain combined with actual income and subjective feelings, which can be divided into horizontal acquisition and vertical acquisition. From the perspective of public service, in order to lift citizens’ sense of gain, governments should meet the diversified public service needs of different social groups, and responds to the general public in time. At present, our public services have obvious insufficient investment, mismatch between supply and demand, and unbalanced development between urban and rural areas. It is necessary to reform the supply side of public services, increase investment, promote equalization, and improve the horizontal acquisition of the masses, establish a precise supply mechanism and response mechanism for public services.

Comparison between vertical acceleration data from acquired signals and multibody model for an off-road vehicle

SAE Mini Baja competitions require efforts in developing a reliable vehicle project that enables their teams to manage time and resources wisely. Vehicle simulations are one the best ways to deal with these conditions and prevent failure during a test. This work outlines the methodology that was carried out for validating the multibody dynamics model of a Mini Baja vehicle through vertical acceleration data acquisition. The data was acquired with the vehicle in different sets of obstacles, based on those seen in previously held competitions. Simulation was done through ADAMS/Car, with the vehicle’s multibody model being simulated in different three-dimensional roads, counterpart to those where data acquisition took place. Simulation data, when compared to acquired acceleration signals for most of the obstacles, exhibited equivalence. Additional data computation revealed that the spectra in the frequency domain presented most severe loads concentrated between 0 and 20 Hz, incoming mostly from road unevenness. Gathering such data, by the presented approach can assist future analyses and guide the Baja Team in defining an improved project by predicting its dynamic behavior. http://dx.doi.org/10.18226/23185279.v6iss1p29

Finite Element Analysis in different Subtype of Sagittal Alignment

In humans, vertical posture acquisition caused several changes in bones and muscles which can be assumed as verticalization. It’s widely known that six different morphological categories exist; each category differs from the others by pelvic parameters and vertebral column curvatures. Both values depend on the Pelvic Incidence, calculated as the angle between the axis passing through the rotation centre of the two femur heads and the vertical axis passing through the superior plate of the sacrum. The aim of this study is to evaluate the distribution of stress and the resulting strain along the axial skeleton using finite element analysis. The use of this computational method allows performing different analyses investigating how different bony geometries and skeletal structures can behavior under specific loading conditions. A CT of artificial bones, was used to obtain geometrical data of the model developed. Lines were imported into a commercial code in order to interpolate main surfaces and create the solid version of the model. Six different models were created according Roussouly’s classification, by arranging geometrical position of the skeletal components. Loading conditions were obtained by applying muscular forces components to T1 to L5, and a fixed constrain was at the distal epiphisis of femurs. Materials were assumed as elastic; Elastic modulus of 15 GPa, a Shear Modulus of 7 GPa for bony parts; Elastic modulus of 6 MPa, a Shear Modulus of 3 MPa for cartilaginous parts [1]. Six different simulations have been carried out. Results confirm higher solicitations obtained varying configurations from case I to case VI. In particular way, first three cases seem to supply the different loading configurations spreading stresses in almost all the bony parts of the column, while the remaining others three cases produce a higher concentration of stress around the lower part of spine (L3, L4, L5). Results confirm a good agreement with those present in literature, an equivalent Von Mises average stress of 0,55 MPa was found on the intervertebral disks with the higher values reached on the lower part of the model. A comparison of results obtained for Case I with literature, shows a good agreement in terms of normal compressive force, while more evident differences can be found for shear force and sagittal moment. The results underline a relationship between PI increase, and accordingly of PT and LL, and the distribution of load forces. Load forces is exerted mainly on distal vertebrae, especially on L4 and L5.

Acquisition of Predictable Vertical Visual Targets: Eye-Head Coordination and the Triggering Effect

ABSTRACTThe study was designed to investigate target acquisition in the vertical plane with emphasis on establishing strategy differences associated with acquisition triggering methods. Eight subjects were tested. Measurements consisted of target acquisition time, eye-head latency differences, velocity of gaze, eyes and head, and head amplitude. Using 3-way repeated measures analyses of variance the results show that the strategy for acquisition of predictable visual targets in vertical plane with the head unrestrained significantly depended on (a) the direction of the gaze motion with respect to the gravity vector (i.e., there is significant up-down asymmetry), (b) the angular distance of the target, and (c) the method of triggering the command to acquire the target—external versus internal. The data also show that when vertical acquisition is compared with triggering methods in the horizontal plane there is a difference in overall strategy for the acquisition of targets with the same spatial distances from straight ahead gaze when both the eyes and head are used. Among the factors contributing to the difference in strategy for vertical target acquisition are the gravitational vector, the relationship of target displacement and vestibular activitation, biomechanical and neural control asymmetries, and the difference in the vertical field of view.

Perinatal HIV transmission and prevention

Perinatal HIV transmission occurs during pregnancy, labor, delivery or breastfeeding. Maternal factors associated with increased perinatal transmission include timing of infection, immune status, mode of delivery, co-existing sexually transmitted diseases, illicit drug use, increased duration of ruptured membranes, chorioamnionitis, viral load & invasive procedures. Infant risk factors include premature birth, low birth weight, skin & mucous membrane lesions. Preventive measures include anti retroviral therapy, treatment of chorioamnionitis with antibiotics, opting for caesarean section & avoiding breastfeeding. Early appropriate treatment of subclinical chorioamnionitis & virocidal cleaning of birth canal reduces perinatal HIV transmission. Caesarean section before onset of labour & membrane rupture reduces risk of mother–infant transmission by almost 50%. Vertical HIV transmission can occur through breast-feeding mostly during first 6 weeks of life & hence avoiding breastfeeding reduces transmission. Interrupting intrapartum transmission like giving ART in late gestation/ peri-partum & elective caesarean section reduce vertical HIV acquisition. As monotherapy & dual therapy are less effective, current guidelines recommend 2 nucleoside reverse transcriptase inhibitors & either a nonnucleoside reverse transcriptase inhibitor or a protease inhibitor. Perinatal HIV transmission can be reduced through a comprehensive approach including Universal access to prenatal care & routine HIV counselling & testing, access to antiretroviral therapy during pregnancy, at delivery & postpartum, education about treatment options & regimen adherence.

Uncovering different forms of customer network changes in M & A

Purpose– The purpose of this paper is to illustrate the forms of change that horizontal and vertical mergers and acquisitions (M & As) may evoke in acquired firms’ customer networks. M & As have increasingly become a dominant mechanistic growth path,pursued relentlessly by companies with varying attributes. However,acquiring a firm does not automatically imply that the market position of the acquired firm and its networks can be taken over,as conventionally held.Design/methodology/approach– The approach takes the form of two qualitative interview-based case illustrations.Findings– The illustrative empirical cases within the context of this study suggest that customer network changes may be rapid and/or radical,and gradual,depending on the specific acquisition type,context and managerial actions following the acquisition. Moreover,the visual simplicity of the network drawing in the post-acquisition network environment of a vertical acquisition type is not equivalent to lesser complexity of managing within the network. Rather,it shows a greater complexity as the M & A induces more direct customer relationships to manage and be managed. The study also shows that connected network changes may cause a revision of a specific industry’s business rules,and the management of these changes is critical for acquisition success.Research limitations/implications– While the two illustrative M & A cases are deemed practically significant in strategic and social terms within their industry and country settings,further research is required to establish the generalizability of the findings to wider industry and geographical contexts.Originality/value– This paper contributes to the discussion on the important role of the business network approach in elaborating the understanding of a strategic management event,particularly M & A.

Environmental factors shape the community of symbionts in the hoopoe uropygial gland more than genetic factors.

Exploring processes of coevolution of microorganisms and their hosts is a new imperative for life sciences. If bacteria protect hosts against pathogens, mechanisms facilitating the intergenerational transmission of such bacteria will be strongly selected by evolution. By disentangling the diversity of bacterial strains from the uropygium of hoopoes (Upupa epops) due to genetic relatedness or to a common environment, we explored the importance of horizontal (from the environment) and vertical (from parents) acquisition of antimicrobial-producing symbionts in this species. For this purpose, we compared bacterial communities among individuals in nonmanipulated nests; we also performed a cross-fostering experiment using recently hatched nestlings before uropygial gland development and some nestlings that were reared outside hoopoe nests. The capacity of individuals to acquire microbial symbionts horizontally during their development was supported by our results, since cross-fostered nestlings share bacterial strains with foster siblings and nestlings that were not in contact with hoopoe adults or nests also developed the symbiosis. Moreover, nestlings could change some bacterial strains over the course of their stay in the nest, and adult females changed their bacterial community in different years. However, a low rate of vertical transmission was inferred, since genetic siblings reared in different nests shared more bacterial strains than they shared with unrelated nestlings raised in different nests. In conclusion, hoopoes are able to incorporate new symbionts from the environment during the development of the uropygium, which could be a selective advantage if strains with higher antimicrobial capacity are incorporated into the gland and could aid hosts in fighting against pathogenic and disease-causing microbes.

Comparison of vertical mobile hydroacoustic survey strategies for monitoring fish distributions in the Gironde estuary (France)

Today, hydroacoustic technologies are able to monitor fish populations and assess fish biomass by providing data of a high spatio-temporal resolution, and without damaging the environment. Such techniques are widely used in lakes and marine environments, but they remain much less tested in shallow waters – especially in estuarine habitats. Our study was carried out using a strictly methodological approach. This was necessary in order to take into account the highly changeable nature of the ecosystem in question. Hydroacoustic surveys were conducted in the mesohaline part of the Gironde estuary using SIMRAD EK60 split-beam echosounders, operating simultaneously at two frequencies (70 kHz and 120 kHz). Different mobile hydroacoustic surveys were tested in different seasons, with vertical acquisition, in order to compare variability of results due to the sampling strategy, and to validate the relevance of our design by repeating the surveys. The results obtained on survey design choices gave similar outcomes when sampling was carried out with or against the current and between two mobile designs. The comparison between flood and ebb tides gave different results from one day to another but we observed the same evolution for each flood tide or for each ebb tide on several successive days. This acoustic study in the Gironde estuary was used to validate a reliable sampling mobile design. It is the first step in the process of gaining a better understanding of estuarine ecosystems, an understanding that will be enhanced by combining our data with data from a variety of other sources.

Multicomponent ocean bottom and vertical cable seismic acquisition for wavefield reconstruction

In ocean-bottom seismic and vertical-cable surveying, receiver stations are stationary on the sea floor while a source vessel shoots on a predetermined [Formula: see text] grid on the sea surface. To reduce exploration cost, the shot point interval often is so coarse that the data recorded at a given receiver station are undersampled and thus irrecoverably aliased. However, when the pressure field and its [Formula: see text]- and [Formula: see text]-derivatives are measured in the water column, the nonaliased pressure field can be reconstructed by interpolation. Likewise, if the vertical component of the particle velocity (or acceleration) and its [Formula: see text]- and [Formula: see text]-derivatives are measured, then this component can also be reconstructed by interpolation. The interpolation scheme can be any scheme that reconstructs the field from its sampled values and sampled derivatives. In the case that the two fields’ first-order derivatives are recorded, the total number of components is six. When also their second-order derivatives are measured, the number of components is 10. The properly interpolated measurements of pressure and vertical component of particle velocity from the multicomponent measurements allow true 3D up/down wavefield decomposition (deghosting) and wave-equation demultiple before wave-equation migration.

Chlorhexidine maternal-vaginal and neonate body wipes in sepsis and vertical transmission of pathogenic bacteria in South Africa: a randomised, controlled trial

About 500,000 sepsis-related deaths per year arise in the first 3 days of life. On the basis of results from non-randomised studies, use of vaginal chlorhexidine wipes during labour has been proposed as an intervention for the prevention of early-onset neonatal sepsis in developing countries. We therefore assessed the efficacy of chlorhexidine in early-onset neonatal sepsis and vertical transmission of group B streptococcus. In a trial in Soweto, South Africa, 8011 women (aged 12-51 years) were randomly assigned in a 1:1 ratio to chlorhexidine vaginal wipes or external genitalia water wipes during active labour, and their 8129 newborn babies were assigned to full-body (intervention group) or foot (control group) washes with chlorhexidine at birth, respectively. In a subset of mothers (n=5144), we gathered maternal lower vaginal swabs and neonatal skin swabs after delivery to assess colonisation with potentially pathogenic bacteria. Primary outcomes were neonatal sepsis in the first 3 days of life and vertical transmission of group B streptococcus. Analysis was by intention to treat. The trial is registered with ClinicalTrials.gov, number NCT00136370. Rates of neonatal sepsis did not differ between the groups (chlorhexidine 141 [3%] of 4072 vs control 148 [4%] of 4057; p=0.6518). Rates of colonisation with group B streptococcus in newborn babies born to mothers in the chlorhexidine (217 [54%] of 401) and control groups (234 [55%] of 429] did not differ (efficacy -0.05%, 95% CI -9.5 to 7.9). Because chlorhexidine intravaginal and neonatal wipes did not prevent neonatal sepsis or the vertical acquisition of potentially pathogenic bacteria among neonates, we need other interventions to reduce childhood mortality. US Agency for International Development, National Vaccine Program Office and Centers for Disease Control's Antimicrobial Resistance Working Group, and Bill & Melinda Gates Foundation.

Phylogenetic evidence for extensive horizontal gene transfer of type III secretion system genes among enterobacterial plant pathogens

This study uses sequences from four genes, which are involved in the formation of the type III secretion apparatus, to determine the role of horizontal gene transfer in the evolution of virulence genes for the enterobacterial plant pathogens. Sequences of Erwinia, Brenneria, Pectobacterium, Dickeya and Pantoea were compared (a) with one another, (b) with sequences of enterobacterial animal pathogens, and (c) with sequences of plant pathogenic gamma and beta proteobacteria, to evaluate probable paths of lateral exchange leading to the current distribution of virulence determinants among these micro-organisms. Phylogenies were reconstructed based on hrcC, hrcR, hrcJ and hrcV gene sequences using parsimony and maximum-likelihood algorithms. Virulence gene phylogenies were also compared with several housekeeping gene loci in order to evaluate patterns of lateral versus vertical acquisition. The resulting phylogenies suggest that multiple horizontal gene transfer events have occurred both within and among the enterobacterial plant pathogens and plant pathogenic gamma and beta proteobacteria. hrcJ sequences are the most similar, exhibiting anywhere from 2 to 50 % variation at the nucleotide level, with the highest degree of variation present between plant and animal pathogen sequences. hrcV sequences are conserved among plant and animal pathogens at the N terminus. The C-terminal domain is conserved only among the enterobacterial plant pathogens, as are the hrcC and hrcR sequences. Additionally, hrcJ and hrcV sequence phylogenies suggest that at least some type III secretion system virulence genes from enterobacterial plant pathogens are related more closely to those of the genus Pseudomonas, a conclusion neither supported nor refuted by hrcC or hrcR.

Symbiont acquisition strategy drives host–symbiont associations in the southern Great Barrier Reef

Coral larvae acquire populations of the symbiotic dinoflagellate Symbiodinium from the external environment (horizontal acquisition) or inherit their symbionts from the parent colony (maternal or vertical acquisition). The effect of the symbiont acquisition strategy on Symbiodinium-host associations has not been fully resolved. Previous studies have provided mixed results, probably due to factors such as low sample replication of Symbiodinium from a single coral host, biogeographic differences in Symbiodinium diversity, and the presence of some apparently host-specific symbiont lineages in coral with either symbiont acquisition strategies. This study set out to assess the effect of the symbiont acquisition strategy by sampling Symbiodinium from 10 coral species (five with a horizontal and five with a vertical symbiont acquisition strategy) across two adjacent reefs in the southern Great Barrier Reef. Symbiodinium diversity was assessed using single-stranded conformational polymorphism of partial nuclear large subunit rDNA and denaturing gradient gel electrophoresis of the internal transcribed spacer 2 region. The Symbiodinium population in hosts with a vertical symbiont acquisition strategy partitioned according to coral species, while hosts with a horizontal symbiont acquisition strategy shared a common symbiont type across the two reef environments. Comparative analysis of existing data from the southern Great Barrier Reef found that the majority of corals with a vertical symbiont acquisition strategy associated with distinct species- or genus-specific Symbiodinium lineages, but some could also associate with symbiont types that were more commonly found in hosts with a horizontal symbiont acquisition strategy.