Host Identity Research Articles

Deterministic processes have limited impacts on foliar fungal endophyte communities along a savanna-forest successional gradient

Patterns and drivers of succession provide insight into the mechanisms that govern community assembly, but remain poorly understood for microbial communities. We assess whether successional trends of trees are mirrored by foliar endophyte communities of three tree species across a deterministic woody successional gradient. Additionally, we test the relative contribution of abiotic predictors, biotic factors, and spatial distance between sites in predicting composition and richness of endophyte communities. Unlike the tree community, endophyte communities showed no consistent evidence of deterministic succession. Host identity was the most important factor structuring endophyte community composition; within hosts, spatial distance from the indigenous forest and between samples was important, while environmental predictors had small and inconsistent effects. Much variation in endophyte composition remained unexplained. In contrast, endophyte richness was well-explained by predictor variables. Host identity was most important in predicting endophyte richness, while the effect of other predictors on richness differed between host species. We conclude that deterministic succession in trees did not result in deterministic succession in endophyte communities; instead community assembly was most strongly influenced by host identity; while within hosts, neutral processes may be more important for endophyte assembly than deterministic factors.

Diversity and composition of mixed-ploidy unisexual salamander assemblages reflect the key influence of host species.

Understanding processes that govern and sustain biological diversity is a central goal of community ecology. Unisexual complexes, where reproduction depends on sperm from males of one or more bisexual host species, are rare and the processes driving their diversity and structure remain poorly understood. Unisexual Ambystoma salamanders produce distinct biotypes ('genomotypes') depending on which bisexual species they 'steal' sperm from. This reproductive mode should generate distinct assemblages depending on the locally available bisexual host species. Yet, how availability and relative abundance of multiple bisexual hosts influences composition and diversity of natural unisexual assemblages at local or regional scales remains unknown. We hypothesize that host identity most directly drives local assemblage composition, with host variation associated with increased beta and gamma diversity within unisexuals. We collected genetic samples from Ambystoma salamanders across Pelee Island, Ontario, Canada (2015-2022). Two host species were identified (A. texanum and A. laterale) with nine sites having a single host and one site having both. Unisexual assemblages were grouped into four clusters by similarity, with host identity being a key determinant. Gamma diversity increased as a result of distinct host-specific assemblages forming at different sites on the island (i.e., high beta diversity). Assemblage composition, but not diversity, was correlated with relative host abundance, which may reflect matching niche requirements between host and unisexual forms they produce. Our results demonstrate that diversity and structure of unisexual assemblages are clearly shaped by their host(s) and such systems may serve as models for studying how biotic interactions shape ecological communities.

Microbial Pathogenesis in the Era of Spatial Omics.

The biology of a cell, whether it is a unicellular organism or part of a multicellular network, is influenced by cell type, temporal changes in cell state, and the cell's environment. Spatial cues play a critical role in the regulation of microbial pathogenesis strategies. Information about where the pathogen is-in a tissue or in proximity to a host cell-regulates gene expression and the compartmentalization of gene products in the microbe and the host. Our understanding of host and pathogen identity has bloomed with the accessibility of transcriptomics and proteomics techniques. A missing piece of the puzzle has been our ability to evaluate global transcript and protein expression in the context of the subcellular niche, primary cell, or native tissue environment during infection. This barrier is now lower with the advent of new spatial omics techniques to understand how location regulates cellular functions. This review will discuss how recent advances in spatial proteomics and transcriptomics approaches can address outstanding questions in microbial pathogenesis.

Mosquito Blood Meal Analysis.

The host associations of mosquitoes vary by species, with some species being relative generalists, whereas others specialize, to varying extents, on a particular subset of the available host community. These host associations are driving factors in transmission dynamics of mosquito-vectored pathogens. For this reason, characterizing the host associations of mosquito species is critical for understanding the epidemiology of mosquito-vectored pathogens. Diverse methods have been used to associate mosquito species with their hosts. These typically include collecting mosquitoes that bite a restrained host (bait) or collecting wild blood-engorged mosquitoes and matching their blood meal to reference samples (blood meal analysis). Blood meal analysis refers to a collection of molecular techniques for determining the taxonomic identity of the source of a mosquito blood meal using cytological, serological, or DNA-based characteristics of the blood meal. Blood meal analyses that are based on DNA markers have advantages over cytological and serological methods and are effective for determining species-level identities of hosts from a broad range of potential host taxa. Here, we discuss effective techniques for analyzing blood meals.

First report of Athelia rolfsii (=Sclerotium rolfsii) associated with foot rot disease of Chrysanthemum morifolium in India.

Chrysanthemum morifolium L. is an important flower crop grown in different parts of Karnataka for its striking cut flowers and international market value. During a field survey (Mysore district, Karnataka, February, 2022), chrysanthemum fields were found infected with foot rot disease. The presence of white mycelial structures with sclerotia were recorded near the stem-soil interface. The disease incidence ranged 10-12% measured in an area of approximately 10 hectares. The infected plants showed quick wilt, yellowing and toppling of the entire plant. Infected plants from Doddamaragowdanahally and Rayanahally (n=15) were collected and associated fungal pathogen isolated after surface sterilization with NaOCl (1%) on potato dextrose agar (PDA) amended with chloramphenicol (50 mg/L). Fungal mycelia developed from the infected tissues were inoculated on to fresh PDA plates to obtained pure cultures for further identification. Fungal colonies with dense, aerial whitish-cottony mycelia with uniformly globoid sclerotia (0.284.2 mm) were observed after 15 days of incubation (28 ± 2°C). Sclerotia were white in the beginning and turned brown at maturity. The average number of sclerotia produced per plate ranged from 240 to >480 (n = 10). To further to confirm the identity of the isolates, two representative isolates (CmSr1 and CmSr2) was subjected to molecular identification based on ITS-rDNA sequences. Briefly, genomic DNA was isolated from 12 day old cultures using the CTAB method and ITS-rDNA was amplified using ITS1-ITS4 primers (White et al., 1990). An expected amplicon of >650 bp (ITS) was obtained and later sequenced from both the directions. The consensus sequences were analysed through nBLAST search which revealed that 100% sequence similarity with reference sequences of Athelia rolfsii (S. rolfsii) from GenBank database (MT127465, MN974137, KC292637; identity 656/656; 0 gaps). A phylogenetic tree obtained by the neighbor-joining method using MEGAX shared a common clade with the reference sequences retrieved and computed, thus confirming the identification based on sequence analysis and molecular phylogeny. The representative sequence of A. rolfsii isolates CmSr1 and CmSr2 isolates deposited in GenBank with Accession nos. ON456153 and ON456154, respectively. Based on etiology, morphological, cultural and molecular data the pathogen was identified as Athelia rolfsii (Curzi) Tu & Kimbrough (Syn: Sclerotium rolfsii Sacc.) (Mordue, 1974; Mahadevakumar et al., 2016, 2018). Plants (n=60) were inoculated with sclerotial bodies (2 sclerotia/plant) near stem soil interface under green house and covered with polythene bags (at 27 ± 2°C and 80% RH). Non-inoculated plants (n=20) served as controls. The development of foot rot disease was observed eight days after inoculation. A total of 48 plants showed the foot rot symptoms and 12 inoculated plants and control plants remained healthy. The identity of the fungus was confirmed by morphological and cultural characters after re-isolation. C. morifolium is an important flower crop in Karnataka. S. rolfsii is known to be associated with blight and collar rot of Chrysanthemum spp. from Kerala (Beena et al., 2002) but no species (host) identity provided. Therefore, to the best of our knowledge, this is the first report of foot rot disease caused by Athelia rolfsii on C. morifolium in India. Early diagnosis of this disease will help the farmers to adopt suitable management practices to avoid loss.

Host age affects the performance of the root hemiparasitic plant Rhinanthus alectorolophus.

Interactions between root hemiparasitic plants and their hosts are strongly affected by host identity, but may also depend on the condition of the host. An important determinant of host quality could be host age, as it may influence host size, allocation patterns, responses to infection, and the strength of competition for light between parasite and host. We investigated the effects of host species identity, host age and above-ground separation of hemiparasite and host on the interactions between the hemiparasite Rhinanthus alectorolophus and five host species in a factorial experiment. The host species were planted at six different times, from 10 weeks before the parasite was planted to 4 weeks after. Host age strongly influenced the performance of the parasite, but these effects also varied among host species. Parasites grew largest with hosts planted at the same time or 2 weeks earlier, but their performance strongly declined both with increasing host age and with the time they grew autotrophically. A large part of the variation due to host age but not of that due to host species identity could be related to the negative influence of host size at the likely time of parasite attachment. The low quality of older hosts was not due to light competition, suggesting that effective exploitation of these hosts was prevented by other factors like harder roots, stronger defense against parasite attack or competition for resources taken up by the host roots. Suppression of host growth by the parasites declined with increasing host age. The results indicate that the choice of host age may influence the results of studies on hemiparasites. They also highlight the importance for annual root hemiparasites of attachment in early spring, that is, at a time when their mostly perennial hosts produce fresh roots but are still poorly developed above ground.

Adoption of alternative life cycles in a parasitic trematode is linked to microbiome differences.

For parasites with complex multi-host life cycles, the facultative truncation of the cycle represents an adaptation to challenging conditions for transmission. However, why certain individuals are capable of abbreviating their life cycle while other conspecifics are not remains poorly understood. Here, we test whether conspecific trematodes that either follow the normal three-host life cycle or skip their final host by reproducing precociously (via progenesis) in an intermediate host differ in the composition of their microbiomes. Characterization of bacterial communities based on sequencing of the V4 hypervariable region of the 16S SSU rRNA gene revealed that the same bacterial taxa occur in both normal and progenetic individuals, independent of host identity and temporal variation. However, all bacterial phyla recorded in our study, and two-thirds of bacterial families, differed in abundance between the two morphs, with some achieving higher abundance in the normal morph and others in the progenetic morph. Although the evidence is purely correlative, our results reveal a weak association between microbiome differences and intraspecific plasticity in life cycle pathways. Advances in functional genomics and experimental microbiome manipulation will allow future tests of the significance of these findings.

Parvicapsula pseudobranchicola in the northeast Pacific Ocean is rare in farmed Atlantic salmon Salmo salar despite widespread occurrence and pathology in wild Pacific salmon Oncorhynchus spp.

BackgroundInfection with the myxozoan parasite Parvicapsula pseudobranchicola causes disease in wild and farmed salmonids in Norway. In the northeast Pacific Ocean, the parasite has been reported in Pacific salmon Oncorhynchus spp. without evidence of disease. The objectives of the present study were to confirm the identity of P. pseudobranchicola in the Pacific, document its host and geographic ranges, and describe associated pathological changes.MethodsOcean-entry year wild pink salmon Oncorhynchus gorbuscha, chum salmon O. keta, Chinook salmon O. tshawytscha, coho salmon O. kisutch and sockeye salmon O. nerka were collected in summer and autumn surveys near Vancouver Island (VI) and from a winter survey in the Gulf of Alaska. Samples were also obtained from farmed Atlantic salmon Salmo salar and Chinook salmon near VI. Samples were analysed by qPCR and histology using conventional staining or in situ hybridisation. Parasite sequence was obtained from small subunit ribosomal RNA gene (SSU rDNA).ResultsIdentical 1525 base-pair SSU rDNA sequences from infected pink salmon, chum salmon and Chinook salmon shared 99.93% identity with a P. pseudobranchicola sequence from Norwegian Atlantic salmon. In autumn surveys, the prevalence was greatest in chum salmon (91.8%) and pink salmon (85.9%) and less so in Chinook salmon (68.8%) and sockeye salmon (8.3%). In farmed salmon, the prevalence was zero in Atlantic salmon (n = 967) and 41% in Chinook salmon (n = 118). Infections were preferentially sited in pseudobranch and visualised by in situ hybridisation. Heavy parasite burdens in all species of Pacific salmon were inconsistently associated with focal granulomatous pseudobranchitis.ConclusionsIn the northeast Pacific, widespread occurrence of P. pseudobranchicola in Pacific salmon together with its absence or sporadic occurrence in farmed Atlantic salmon differs from its epidemiology in Norway, despite similar pathological development in the pseudobranch. Consequences of the infections to the health of wild Pacific salmon, identity of the invertebrate host and the distribution and abundance of infective actinospores are unknown and remain high priorities for research.Graphical

Bloodmeal host identities among sympatric Glossina austeni and Glossina pallidipes tsetse flies in Shimba Hills National Reserve, Kwale, Kenya.

Odor from preferred/non-preferred tsetse fly vertebrate hosts have been exploited in R&D of attractants/repellents of the fly for human and livestock protection. Odors from vertebrate hosts of Glossina austeni and Glossina pallidipes tsetse flies can facilitate formulation of novel attractants effective against G. austeni or improvement of existing attractant blends for G. pallidipes. We compared vertebrate blood meal sources of both fly species at Shimba Hills National Reserve, Kenya, to establish putative preferred host of either species, hence potential source of G. austeni or G. pallidipes specific odors. We trapped sympatric adult flies in 2021 and 2022 using NGU traps/sticky panels baited with POCA, collected their blood meals and characterize the meals using HRM vertebrate 16S rRNA- PCR (for host identification), and compared host profiles using GLM and Fisher's exact tests. We collected 168 and 62 sympatric G. pallidipes and G. austeni with bloodmeal, respectively in 2021 and, 230 and 142 respectively in 2022. In 2021, we identified putative hosts of 65.48 and 69.35 % of the G. pallidipes and G. austeni respectively and 82.61 and 80.28%, respectively in 2022. In 2021, we detected harnessed bushbuck, buffalo, common warthog and cattle putative host bloodmeals, and additionally bushpig and suni antelope bloodmeals in 2022. Putative vertebrate bloodmeal sources were significantly different by tsetse fly species (χ2(1, N=457) = 43.215, p < 0.001) and sampling year (χ2(1, N=457) = 8.044, p = 0.005). Frequency of common warthog bloodmeals was higher in G. pallidipes (65.79 %) than G. austeni (38.60%), and that of suni antelope and harnessed bushbuck putative bloodmeals higher in G. austeni (21.05-28.07%) than in G. pallidipes (6.84 - 17.37%) in 2022. There was an apparent change in putative feeding preference/host choices in both fly species between 2021 and 2022. Host bloodmeals in G. pallidipes or G. austeni predominantly from putative harnessed bushbuck, suni antelope or common warthog reveal these vertebrates with potential odors that can be harnessed and formulated into appropriate attractants for respective species and integrated into routine control regiment for G. pallidipes and/or G. austeni.

Host identity affects the response of mycorrhizal fungal communities to high severity fires in Alaskan boreal forests

Host identity affects the response of mycorrhizal fungal communities to high severity fires in Alaskan boreal forests

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

Multiple facets of cutting-edge mycorrhizal research: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, August 2022: 11th International Conference on Mycorrhiza (ICOM 11), Beijing, China, 1-5 August 2022.

External and Internal Microbiomes of Antarctic Nematodes are Distinct, but More Similar to each other than the Surrounding Environment.

Host-associated microbiomes have primarily been examined in the context of their internal microbial communities, but many animal species also contain microorganisms on external host surfaces that are important to host physiology. For nematodes, single strains of bacteria are known to adhere to the cuticle (e.g., Pasteuria penetrans), but the structure of a full external microbial community is uncertain. In prior research, we showed that internal gut microbiomes of nematodes (Plectus murrayi, Eudorylaimus antarcticus) and tardigrades from Antarctica's McMurdo Dry Valleys were distinct from the surrounding environment and primarily driven by host identity. Building on this work, we extracted an additional set of individuals containing intact external microbiomes and amplified them for 16S and 18S rRNA metabarcoding. Our results showed that external bacterial microbiomes were more diverse than internal microbiomes, but less diverse than the surrounding environment. Host-specific bacterial compositional patterns were observed, and external microbiomes were most similar to their respective internal microbiomes. However, external microbiomes were more influenced by the environment than the internal microbiomes were. Non-host eukaryotic communities were similar in diversity to internal eukaryotic communities, but exhibited more stochastic patterns of assembly compared to bacterial communities, suggesting the lack of a structured external eukaryotic microbiome. Altogether, we provide evidence that nematode and tardigrade cuticles are inhabited by robust bacterial communities that are substantially influenced by the host, albeit less so than internal microbiomes are.

First report of Phyllactinia chubutiana causing powdery mildew on Goji berry plants (Lycium barbarum and L. chinense) in the United States.

Goji berries, both Lycium barbarum, and L. chinense, are native to Asia and have been highly valued for food and medicinal purposes for more than 2,000 years (Wetters et al. 2018). These species are difficult to distinguish due to the extensive cultivar development of the former and the plasticity of the latter's phenotypes. During the summers (from July to September) of 2021 and 2022, powdery mildew was observed in Goji berry plants (L. barbarum and L. chinense) in both community and residential gardens, in Yolo Co., California. Disease severity varied between 30 and 100% of infected leaves per plant. Host identity was confirmed by phylogenetic analysis using sequences of the psbA-trnH intergenic region (Wetters et al. 2018). Powdery mildew was characterized by the presence of white fungal colonies on both sides of the leaves and the fruit sepals. Colorless adhesive tape mounts of the fungal structures were examined in drops of 3% KOH. Epidermal strips of infected leaves were peeled off for analysis of the mycelia. Hyphae were both external and internal, hyaline, septate, branched, smooth, and 2.5 to 5.8 (4.3) µm wide (n = 50). Appressoria were nipple-shaped to irregularly branched and solitary or opposite in pairs. Conidiophores were hyaline, erect, and simple. Foot cells were cylindrical, straight, 13.1 to 48.9 (29.8) × 5.0 to 8.2 (6.8) µm (n = 20), followed by 0 to 2 cells. Conidia lacked fibrosin bodies, were borne singly, unicellular, hyaline, and ellipsoid when young. Mature conidia were either cylindrical or slightly centrally constricted to dumb-bell-like, and 36.2 to 51.8 (44.9) × 15.1 to 22.0 (18.9) µm (n = 50), with conspicuous subterminal protuberances. Germ tubes were subterminal, either short with multilobate apex or moderately long with a simple end. Chasmothecia were not observed. Morphologically the fungus matched the description of Phyllactinia chubutiana Havryl., S. Takam. & U. Braun (Braun and Cook, 2012). The pathogen identity was further confirmed by amplifying and sequencing the rDNA internal transcribed spacer (ITS) and the 28S rDNA gene using the primer pairs ITS1/ITS4 (White et al. 1990) and PM3/TW14 (Takamatsu and Kano 2001, Mori et al. 2000). The resulting sequences (GenBank OP434568 to OP434569; and OP410969 to OP410970) were compared with the NCBI database using BLAST, showing 99% similarity to the ex-type isolate of P. chubutiana (BCRU 4634, GenBank AB243690). Maximum parsimony phylogenetic analysis clustered our isolates with reference sequences of P. chubutiana from various hosts deposited in GenBank. Pathogenicity was confirmed by inoculating two two-year-old L. barbarum potted plants. Four leaves per plant were surface disinfected (75% ethanol, 30 s) before gently rubbing powdery mildew infected leaves onto healthy leaves. Healthy leaves were used for mock inoculations. All plants were maintained in a growth chamber at 22°C and 80% relative humidity (RH) for five days and then 60% RH thereafter. Inoculated leaves developed powdery mildew symptoms after 28 days, and P. chubutiana colonies were confirmed by morphology, hence fulfilling Koch's postulates. Control leaves remained symptomless. Phyllactinia chubutiana (= Oidium insolitum, Ovulariopsis insolita) was first described on L. chilense in Argentina (Braun et al. 2000, Havrylenko et al. 2006), and later reported on L. chinense in China (Wang Yan et al. 2016). To our knowledge, this is the first report of P. chubutiana causing powdery mildew on L. barbarum and L. chinense in the United States, which provides crucial information for developing effective strategies to monitor and control this newly described disease.

Forest Matters Most for Hirsutiella zachvatkini (Schluger, 1948): A Survey of Rodent Infestation in Four Localities within the Mazury Lake District, NE Poland

The family Trombiculidae encompasses numerous and widespread mites, the larvae of which are obligatory parasites of vertebrates. Our research objective was to assess how trombiculid burdens on rodents inhabiting three forested and one open area in NE Poland vary in relation to host identity, sex and body size, and how they are influenced by qualities of the habitat. Trapped rodents (n = 240) were measured, weighted and screened for ectoparasites. Apodemus flavicollis (n = 42) and Myodes glareolus (n = 173) harbored a total of 4652 Hirsutiella zachchvatkini larvae. Statistical tests revealed that both prevalence and abundance were significantly higher in voles (93%, 27 larvae/ind.) than in mice (14%, 0.24 larvae/ind.) but there was no effect of host sex. Among the localities, H. zachvatkini was most prevalent (98%) and abundant (41 larvae/ind.) in rodents from the deciduous mixed forest in Tałty compared to fallow land (2.6%, 0.13 larvae/ind.). The highest prevalence and abundance were found in bank voles; in this host species in Tałty, prevalence reached 100% and the mean abundance was &gt;42 larvae/ind. Significant positive correlations were found between the body mass and body length of voles and the number of attached larvae. Our results confirm the sylvan nature of H. zachvatkini and its preference for bank voles inhabiting deciduous forests with rich and humid undergrowth. The lack of a sex bias and the moderate correlation between mite burden and host size are in line with observations already made on other rodent-associated Trombiculidae.

Factors influencing carrion communities are only partially consistent with those of deadwood necromass

Research on decomposer communities has traditionally focused on plant litter or deadwood. Even though carrion forms highly nutrient-rich necromass that enhance ecosystem heterogeneity, the factors influencing saprophytic communities remain largely unknown. For deadwood, experiments have shown that different drivers determine beetles (i.e., decay stage, microclimate, and space), fungi (i.e., decay stage and tree species) and bacteria (decay stage only) assemblages. To test the hypothesis that similar factors also structure carrion communities, we sampled 29 carcasses exposed for 30 days that included Cervus elaphus (N = 6), Capreolus capreolus (N = 18), and Vulpes vulpes (N = 5) in a mountain forest throughout decomposition. Beetles were collected with pitfall traps, while microbial communities were characterized using amplicon sequencing. Assemblages were determined with a focus from rare to dominant species using Hill numbers. With increasing focus on dominant species, the relative importance of carcass identity on beetles and space on bacteria increased, while only succession and microclimate remained relevant for fungi. For beetle and bacteria with focus on dominant species, host identity was more important than microclimate, which is in marked contrast to deadwood. We conclude that factors influencing carrion saprophytic assemblages show some consistency, but also differences from those of deadwood assemblages, suggesting that short-lived carrion and long-lasting deadwood both provide a resource pulse with different adaptions in insects and microbes. As with deadwood, a high diversity of carcass species under multiple decay stages and different microclimates support a diverse decomposer community.

The effect of warming on seagrass wasting disease depends on host genotypic identity and diversity.

Temperature increases due to climate change have affected the distribution and severity of diseases in natural systems, causing outbreaks that can destroy host populations. Host identity, diversity, and the associated microbiome can affect host responses to both infection and temperature, but little is known about how they could function as important mediators of disease in altered thermal environments. We conducted an 8-week warming experiment to test the independent and interactive effects of warming, host genotypic identity, and host genotypic diversity on the prevalence and intensity of infections of seagrass (Zostera marina) by the wasting disease parasite (Labyrinthula zosterae). At elevated temperatures, we found that genotypically diverse host assemblages had reduced infection intensity, but not reduced prevalence, relative to less diverse assemblages. This dilution effect on parasite intensity was the result of both host composition effects as well as emergent properties of biodiversity. In contrast with the benefits of genotypic diversity under warming, diversity actually increased parasite intensity slightly in ambient temperatures. We found mixed support for the hypothesis that a growth-defense trade-off contributed to elevated disease intensity under warming. Changes in the abundance (but not composition) of a few taxa in the host microbiome were correlated with genotype-specific responses to wasting disease infections under warming, consistent with the emerging evidence linking changes in the host microbiome to the outcome of host-parasite interactions. This work emphasizes the context dependence of biodiversity-disease relationships and highlights the potential importance of interactions among biodiversity loss, climate change, and disease outbreaks in a key foundation species.

Biculturalism as a double-edged sword: The perspectives of Mexican American emerging adults

Cultural and ethnic identity research largely highlights the adaptiveness of biculturalism among Latino youth in the United States. Less is known about how Latino youth themselves define and experience biculturalism, the cultural identity content that they deem relevant, and how heritage and host identities intersect. Using an inductive approach, this study examines the salience, valence, and meaning of biculturalism among Latino youth living in a multicultural U.S. city. Twenty-six Mexican American emerging adults (Mage = 22.35 years) participated in semi-structured interviews and constructed cultural identity maps focusing on their experiences of biculturalism. Qualitative analysis reveals that participants overwhelmingly deem biculturalism to be positive and explores the duality (i.e.: opposition or contrast) that lies beneath that positivity. Participants emphasized individual-level advantages of biculturalism, namely, that their Mexican heritage provides identity rootedness and enables expanded career and educational opportunities. The bicultural challenges that participants discussed were overwhelmingly relational: familial cultural gaps due to dissonant values and critical gazes from others due to inadequate cultural performances. By revealing that and why biculturalism is mostly positive in the eyes of participants, and exploring the duality that lies beneath that positivity, this study draws attention to the complexity of biculturalism that can be obscured by exclusive reliance on quantitative self-report measures.

Performance Study on 5G - NSA Backhaul Network Secured with HIP

Fifth generation Non-Stand Alone (5G-NSA) mode offers users an earlier 5G experience before worldwide Stand Alone 5G implementation (5G-SA). In 5G-NSA, operators utilize the existing fourth-generation (4G) networks to provide pre-5G services. In some 5G-NSA deployments, the 4G backhaul network connects the 5G core (5GC) or 4G evolved packet core (EPC) to the 5G new radio (5G NR) network. Nevertheless, implementing security in all network segments is essential to assure end-to-end security in 5G-NSA implementations. Operators must use Internet Protocol security (IPsec) to secure user plane transmissions through 4G backhaul. Host Identity Protocol (HIP) is an alternative method to implement IPsec without disturbing radio or core network protocols to provide node authentication, data encryption with integrity protection, and replay protection to the user plane. This study evaluates the effectiveness of the secure HIP-4G backhaul network to assure end-to-end security in 5G-NSA. According to the results, HIP implementation does not delay message transmissions. Only a slight delay occurs at the security session establishment phase in the HIP Base Exchange process. Hence the HIP implemented 4G backhaul is appropriate to assure end-to-end security in 5G-NSA until the 5G-SA internetworking solutions are implemented.

KDC Placement Problem in Secure VPLS Networks

Virtual Private LAN Service (VPLS) is a VPN technology that connects remote client sites with provider networks in a transparent manner. Session key-based HIPLS (S-HIPLS) is a VPLS architecture based on the Host Identity Protocol (HIP) that provides a secure VPLS architecture using a Key Distribution Center (KDC) to implement security mechanisms such as authentication, encryption etc. It exhibits limited scalability though. Using multiple distributed KDCs would offer numerous advantages including reduced workload per KDC, distributed key storage, and improved scalability, while simultaneously eliminating the single point of failure of S-HIPLS. It would also come with the need for optimally placing KDCs in the provider network. In this work, we formulate the KDC placement (KDCP) problem for a secure VPLS network as an Integer Linear Programming (ILP) problem. The latter is NP-hard, thereby suggesting a high computational cost for obtaining exact solutions especially for large deployments. Therefore, we motivate the use of a primal-dual algorithm to efficiently produce near-optimal solutions. Extensive evaluations on large-scale network topologies, such as the random Internet graph, demonstrate our method’s time-efficiency as well as its improved scalability and usefulness compared to both HIPLS and S-HIPLS.

Proteome analysis of Ehrlichia chaffeensis containing phagosome membranes revealed the presence of numerous bacterial and host proteins.

Tick-transmitted Ehrlichia chaffeensis, the causative agent for human monocytic ehrlichiosis, resides and multiplies within a host cell phagosome. Infection progression of E. chaffeensis includes internalization into a host cell by host cell membrane fusion events following engulfment leading to the formation of E. chaffeensis containing vacuole (ECV). Revealing the molecular composition of ECV is important in understanding the host cellular processes, evasion of host defense pathways and in defining host-pathogen interactions. ECVs purified from infected host cells were analyzed to define both host and bacterial proteomes associated with the phagosome membranes. About 160 bacterial proteins and 2,683 host proteins were identified in the ECV membranes. The host proteins included predominantly known phagosome proteins involved in phagocytic trafficking, fusion of vesicles, protein transport, Ras signaling pathway and pathogenic infection. Many highly expressed proteins were similar to the previously documented proteins of phagosome vacuole membranes containing other obligate pathogenic bacteria. The finding of many bacterial membrane proteins is novel; they included multiple outer membrane proteins, such as the p28-Omps, the 120 kDa protein, preprotein translocases, lipoproteins, metal binding proteins, and chaperonins, although the presence of ankyrin repeat proteins, several Type I and IV secretion system proteins is anticipated. This study demonstrates that ECV membrane is extensively modified by the pathogen. This study represents the first and the most comprehensive description of ECV membrane proteome. The identity of many host and Ehrlichia proteins in the ECV membrane will be a valuable to define pathogenic mechanisms critical for the replication of the pathogen within macrophages.