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Host-microbe interactions play crucial roles in marine ecosystems. However, we still have very little understanding of the mechanisms that govern these relationships, the evolutionary processes that shape them, and their ecological consequences. The holobiont concept is a renewed paradigm in biology that can help to describe and understand these complex systems. It posits that a host and its associated microbiota with which it interacts, form a holobiont, and have to be studied together as a coherent biological and functional unit to understand its biology, ecology, and evolution. Here we discuss critical concepts and opportunities in marine holobiont research and identify key challenges in the field. We highlight the potential economic, sociological, and environmental impacts of the holobiont concept in marine biological, evolutionary, and environmental sciences. Given the connectivity and the unexplored biodiversity specific to marine ecosystems, a deeper understanding of such complex systems requires further technological and conceptual advances, e.g., the development of controlled experimental model systems for holobionts from all major lineages and the modeling of (info)chemical-mediated interactions between organisms. Here we propose that one significant challenge is to bridge cross-disciplinary research on tractable model systems in order to address key ecological and evolutionary questions. This first step is crucial to decipher the main drivers of the dynamics and evolution of holobionts and to account for the holobiont concept in applied areas, such as the conservation, management, and exploitation of marine ecosystems and resources, where practical solutions to predict and mitigate the impact of human activities are more important than ever.

Abstract Microbial ecology provides insights into the ecological and evolutionary dynamics of microbial communities underpinning every ecosystem on Earth. Microbial communities can now be investigated in unprecedented detail, although there is still a wealth of open questions to be tackled. Here we identify 50 research questions of fundamental importance to the science or application of microbial ecology, with the intention of summarising the field and bringing focus to new research avenues. Questions are categorised into seven themes: host–microbiome interactions; health and infectious diseases; human health and food security; microbial ecology in a changing world; environmental processes; functional diversity; and evolutionary processes. Many questions recognise that microbes provide an extraordinary array of functional diversity that can be harnessed to solve real-world problems. Our limited knowledge of spatial and temporal variation in microbial diversity and function is also reflected, as is the need to integrate micro- and macro-ecological concepts, and knowledge derived from studies with humans and other diverse organisms. Although not exhaustive, the questions presented are intended to stimulate discussion and provide focus for researchers, funders and policy makers, informing the future research agenda in microbial ecology. We identify research questions in the field of microbial ecology, with emerging themes that recognise vast microbial functions that could benefit humanity, and the need to integrate knowledge across organisms.

Understanding population genetic structure can help us to infer dispersal patterns, predict population resilience and design effective management strategies. For sessile species with limited dispersal, this is especially pertinent because genetic diversity and connectivity are key aspects of their resilience to environmental stressors. Here, we describe the population structure of Ircinia campana, a common Caribbean sponge subject to mass mortalities and disease. Microsatellites were used to genotype 440 individuals from 19 sites throughout the Greater Caribbean. We found strong genetic structure across the region, and significant isolation by distance across the Lesser Antilles, highlighting the influence of limited larval dispersal. We also observed spatial genetic structure patterns congruent with oceanography. This includes evidence of connectivity between sponges in the Florida Keys and the southeast coast of the United States (>700 km away) where the oceanographic environment is dominated by the strong Florida Current. Conversely, the population in southern Belize was strongly differentiated from all other sites, consistent with the presence of dispersal-limiting oceanographic features, including the Gulf of Honduras gyre. At smaller spatial scales (<100 km), sites showed heterogeneous patterns of low-level but significant genetic differentiation (chaotic genetic patchiness), indicative of temporal variability in recruitment or local selective pressures. Genetic diversity was similar across sites, but there was evidence of a genetic bottleneck at one site in Florida where past mass mortalities have occurred. These findings underscore the relationship between regional oceanography and weak larval dispersal in explaining population genetic patterns, and could inform conservation management of the species.

Tree pathogens are a major threat to forest ecosystems. Conservation management strategies can exploit natural mechanisms of resistance, such as tree genotype and host‐associated microbial communities. However, fungal and bacterial communities are rarely looked at in the same framework, particularly in conjunction with host genotype. Here, we explore these relationships and their influence on ash dieback disease, caused by the pathogen Hymenoscyphus fraxineus, in European common ash trees. We collected leaves from UK ash trees and used microsatellite markers to genotype trees, quantitative PCR to quantify H. fraxineus infection load and ITS and 16S rRNA amplicon sequencing to identify fungal and bacterial communities, respectively. There was a significant association between H. fraxineus infection intensity and ash leaf fungal and bacterial community composition. Higher infection levels were positively correlated with fungal community alpha‐diversity, and a number of fungal and bacterial genera were significantly associated with infection presence and intensity. Under higher infection loads, leaf microbial networks were characterized by stronger associations between fewer members than those associated with lower infection levels. Together these results suggest that H. fraxineus disrupts stable endophyte communities after a particular infection threshold is reached, and may enable proliferation of opportunistic microbes. We identified three microbial genera associated with an absence of infection, potentially indicating an antagonistic relationship with H. fraxineus that could be utilized in the development of anti‐pathogen treatments. Host genotype did not directly affect infection, but did significantly affect leaf fungal community composition. Thus, host genotype could have the potential to indirectly affect disease susceptibility through genotype × microbiome interactions, and should be considered when selectively breeding trees. Synthesis. We show that the diversity, composition and network structure of ash leaf microbial communities are associated with the severity of infection from ash dieback disease, with evidence of disease‐induced dysbiosis. We also show that host genotype influences leaf fungal community composition, but does not directly influence tree infection. These findings help to elucidate relationships between host genetics, the microbiome and a tree pathogen, highlighting potential resistance mechanisms and possible co‐infection concerns that could inform ash tree management. We show that the diversity, composition and network structure of ash leaf microbial communities are associated with the severity of infection from ash dieback disease, with evidence of disease‐induced dysbiosis. We also show that host genotype influences leaf fungal community composition, but does not directly influence tree infection. These findings help to elucidate relationships between host genetics, the microbiome and a tree pathogen, highlighting potential resistance mechanisms and possible co‐infection concerns that could inform ash tree management.

Marine sponges are hosts to large, diverse communities of microorganisms. These microbiomes are distinct among sponge species and from seawater bacterial communities, indicating a key role of host identity in shaping its resident microbial community. However, the factors governing intraspecific microbiome variability are underexplored and may shed light on the evolutionary and ecological relationships between host and microbiome. Here, we examined the influence of genetic variation and geographic location on the composition of the Ircinia campana microbiome. We developed new microsatellite markers to genotype I. campana from two locations in the Florida Keys, USA, and characterized their microbiomes using V4 16S rRNA amplicon sequencing. We show that microbial community composition and diversity is influenced by host genotype, with more genetically similar sponges hosting more similar microbial communities. We also found that although I. campana was not genetically differentiated between sites, microbiome composition differed by location. Our results demonstrate that both host genetics and geography influence the composition of the sponge microbiome. Host genotypic influence on microbiome composition may be due to stable vertical transmission of the microbial community from parent to offspring, making microbiomes more similar by descent. Alternatively, sponge genotypic variation may reflect variation in functional traits that influence the acquisition of environmental microbes. This study reveals drivers of microbiome variation within and among locations, and shows the importance of intraspecific variability in mediating eco‐evolutionary dynamics of host‐associated microbiomes. For the first time, the authors show that intraspecific genetic variation affects microbiome composition in a marine sponge (Ircinia campana), with positive correlations observed between genetic and microbiome similarity. This has significant implications for our understanding of the ecological and evolutionary relationships between host and microbiome in this important model system.

Background Researchers are required to determine whether a person has capacity to consent to a research study before they are able to participate. The Mental Capacity Act and accompanying Code of Practice for England and Wales provide some guidance on this process, but researchers have identified that it can be difficult to determine capacity to consent when a person has complex cognitive or communication needs. This study aimed to understand the experiences and opinions of researchers who recruit people with dementia to research projects, to inform the future development of training resources. Methods A mixed method, cross-sectional, electronic survey was circulated via social media and research networks in England and Wales. The survey remained open for ten weeks and included open and closed questions exploring respondents’ confidence in determining capacity in the context of recruiting people with dementia to consent, their views on training and support they have experienced and their suggestions for future training and support needs. Results 60 respondents completed the survey from across England and Wales. Although 75% of respondents had experience of determining capacity to consent with people with dementia to research, only 13% rated themselves as feeling ‘very confident’ in this. Qualitative content analysis of open responses led to the generation of six themes, explaining researchers’ confidence, competence and future training needs in this area: (1) Researcher uncertainties, (2) Lack of time, (3) Balancing information complexity with accessibility, (4) Gatekeepers, (5) Existing enablers and (6) Envisioning future training. Conclusions Researchers would benefit from specific training in undertaking conversations around consent with people with dementia. People with dementia may have fluctuating capacity, and despite support from caregivers, researchers have little practical guidance on methods of determining a person’s ability to understand or appreciate the information they have provided during the consent process. Given the development of large complex trials within dementia research, there is an urgency to develop specific and practical guidance and training for researchers working with people with dementia and their families.

The need to improve support following a diagnosis of dementia is widely recognised, but it is unclear how this can best be achieved within UK health and social care systems. A task-shared and task-shifted approach has been recommended, but there is limited guidance on how to achieve this in practice. As part of a programme of research, we developed an intervention to enhance the role of primary care in post-diagnostic care and support for people living with dementia and carers. We used the Theory of Change to develop a complex intervention informed by initial literature reviews and qualitative work. The intervention was developed through an iterative series of workshops, meetings and task groups with a range of stakeholders, including the multidisciplinary project team, people living with dementia and carers, service managers, frontline practitioners, and commissioners. 142 participants contributed to intervention development through face-to-face or virtual meetings. The intervention comprises three complementary strands of work focusing on: developing systems, delivering tailored care and support, and building capacity and capability. Clinical dementia leads, based in primary care networks, will facilitate the intervention providing tailored expertise and support. The Theory of Change proved useful in providing structure and engaging stakeholders. The process was challenging, took longer and was less participative than intended due to restrictions caused by the COVID-19 pandemic. We will next conduct a feasibility and implementation study to explore whether the intervention can be successfully delivered within primary care. If successful, the intervention offers practical strategies for delivering a task-shared and task-shifted approach to post-diagnostic support that could be adapted for similar health and social care contexts internationally.

Background An emerging literature suggests that autistic adults are at increased risk of experiencing suicidal thoughts, making suicidal plans and attempts, and dying by suicide. However, few studies have investigated whether autistic traits are related to suicidal behaviour. The current study examined autistic traits in a sample of adults who reported at least one suicide attempt. Methods An online questionnaire was advertised between June and September 2017 on suicide prevention websites, research databases, and social media. Participants reported whether they had ever attempted suicide (yes/no), and if so, how many times they had attempted (once/more than once). They also reported diagnosed and suspected mental health or neurodevelopmental conditions, and completed the Autism Spectrum Quotient (AQ). Two hundred forty-five adults accessed the survey; 132 reported having attempted suicide and also completed the AQ. It was hypothesised that AQ total scores and subscale scores would be higher in adults who had attempted suicide more than once compared to adults who had attempted once. These hypotheses were tested using an independent samples t test, Mann-Whitney U tests, and binary logistic regression. Results Most participants were female (83.3%, male = 12.9%, other = 3.8%), and ages ranged from 18 to 65 (median = 36.00; IQR = 19.00). Total AQ scores, as well as communication and imagination subscale scores were significantly higher in adults who had attempted suicide more than once compared to adults who had attempted suicide once. Even after removing participants with diagnosed or suspected autism ( n  = 34), 40.6% had an AQ score indicative of clinical concern (≥ 26). Conclusions The findings suggest that high levels of autistic traits may frequently be present in adults who have attempted suicide, and that AQ scores are higher in those with a history of more than one suicide attempt. It may be possible to better identify suicide risk by screening autistic adults with mental health conditions for suicidal thoughts and behaviours, and by screening people with suicidal thoughts and/or behaviours for autism.

Background Many older people from minority ethnic groups experience inequalities towards the end of life, including barriers to accessing palliative care. With levels of international migration increasing, there is a need to understand these differences and consider the needs of minority ethnic groups in healthcare policies. This review aimed to map evidence on how older people from minority ethnic groups access and utilise palliative and end of life care, preferences for palliative and end of life care, experiences of palliative and end of life care, and how this varies between minority ethnic groups in different countries, and with different health conditions. Methods Scoping review, following Joanna Briggs Institute (JBI) guidance. Searches of eight online databases (MEDLINE, Embase, Web of Science, CINAHL, PsycInfo, Assia, Scopus, and the Cochrane Library) and grey literature were undertaken in 2024. Qualitative sources that focused on older people from minority ethnic groups’ and carers’ access to and use of palliative and end of life care were included, as well as those focusing on healthcare professionals’ experiences. Results Twenty-three sources were included in the review, the majority of which were interview studies from the USA. Findings reflect a range of preferences, inequalities, facilitators and barriers to accessing palliative and end of life care, with themes relating to: (1) Knowledge of hospice and palliative care, (2) societal and structural issues, (3) language and health literacy, (4) migratory experiences, (5) trust in healthcare services and professionals, (6) religion and hope, and (7) cultural values. Conclusions This review identified areas for healthcare providers to consider developing more culturally appropriate palliative and end of life care practice, including building trust and improving communication, sharing information, reducing language barriers, addressing stigma, and, if relevant, acknowledging the importance of culture and religion. Further qualitative research from an intersectional perspective, such as geographical location or socio-economic status, rather than race, ethnicity, and culture alone, is needed in more diverse geographical settings and on specific health conditions.

There are 900,000 people with dementia in England and Wales. Existing models of post-diagnostic support are unsustainable and unaffordable. The PriDem programme developed a new model of primary care-based dementia care, whereby a Clinical Dementia Lead (CDL) would facilitate systems-level change. To assess barriers and facilitators to implementation of the PriDem intervention. 7 general practices participated in a qualitative process evaluation, as part of the mixed-methods feasibility and implementation study. Practices were located within 4 Primary Care Networks in the North East and South East of England. 26 healthcare professionals, 14 people with dementia and 16 carers linked to participating general practices participated in semi-structured individual and small group interviews. Additional qualitative data were generated through nonparticipant observations and researcher fieldnotes from CDL intervention supervision sessions. Data were analysed using abductive codebook thematic analysis informed by Normalisation Process Theory (NPT). Six themes were generated: 1) The rocky ground of primary care; 2) The power of people; 3) Tension between adaptability and fidelity; 4) Challenging the status quo: reimagining care planning; 5) One size doesn't fit all; 6) Positive effects on people and systems: towards sustainability. Through the lens of NPT we can understand the contextual challenges facing primary care, the mechanisms (e.g., work undertaken by individuals) to overcome those challenges, as well as the potential outcomes of such an approach, in terms of longer-term sustainability of changes made. Despite the pressures facing primary care within England and Wales, meaningful change can be made to practice in the care of people with dementia. The presence of motivated and engaged staff are critical to implementation, as is ensuring understanding of complex interventions, so that fidelity can be maintained. People with dementia and carers benefitted from improved care systems. Commissioners should consider the benefits of a CDL-led approach.