Global perspectives on the molecular ecology of photosynthetic picoeukaryotes

Photosynthetic picoeukaryotes (PPEs) are single celled algae of <3μm diameter, present in both marine and freshwater environments. Marine PPEs have begun to gain increasing recognition as important, ubiquitous primary producers, after largely being overlooked in favour of the more numerous picocyanobacteria for many years. Molecular studies have shown the group to be extremely diverse. However, most molecular studies have used PCR with general primers targeting the nuclear 18S rRNA gene to construct clone libraries and have been dominated by heterotrophic picoeukaryotes. To overcome this problem, more recent molecular studies have targeted the 16S rRNA gene of marine algal plastids, an approach which essentially excludes heterotrophic organisms. In this PhD thesis, the molecular diversity of the PPE community was analysed over broad spatial scales using both 16S and 18S rRNA gene markers to begin to draw global conclusions on the phylogenetic composition of this group and identify the major players in marine CO2 fixation. Moreover, distributions of various PPE classes were also analysed along a range of cruise transects with dot blot hybridisation of PCR amplified DNA using class-specific plastid 16S rRNA gene targeted oligonucleotide probes. All major ocean basins were analysed, encompassing a range of nutrient regimes and latitudes. The dot blot hybridisation approach revealed that the classes Prymnesiophyceae and Chrysophyceae appeared to be ubiquitous and dominated the PPE community throughout large expanses of the global ocean. Furthermore, these classes showed strongly complementary distributions along some of the transects analysed. Clone library construction demonstrated that both classes are comprised of an array of genetic lineages, many with no close cultured counterpart. For one cruise transect, the extended Ellett Line in the North Atlantic Ocean, a fluorescent in situ hybridisation approach was used as a PCR-independent assessment of the PPE community. This approach largely supported the dot blot hybridisation data. Other classes, Cryptophyceae, Pinguiophyceae, Pelagophyceae, Eustigmatophyceae, Pavlovophyceae, Trebouxiouphyceae, Chlorarachniophyceae and Prasinophyceae clade VI, were detected at lower abundances by dot blot hybridisation, with some classes restricted to specific sites. Multivariate statistics indicated that the distribution patterns of PPE classes were influenced by both temperature and nutrient concentrations. However, at the global scale, a large proportion of the variation in dot blot hybridisation data could not be explained by the environmental parameters measured. It is likely that the classes harbour different ecotypes which are individually influenced by environmental factors. Furthermore, biotic parameters not measured in this work e.g. viral lysis, predation or parasitic infection may have been important in controlling the PPE community.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Iron mobilization during lactation reduces oxygen stores in a diving mammal

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Shero, M. R., Kirkham, A. L., Costa, D. P., & Burns, J. M. Iron mobilization during lactation reduces oxygen stores in a diving mammal. Nature Communications, 13(1), (2022): 4322, https://doi.org/10.1038/s41467-022-31863-7.The profound impacts that maternal provisioning of finite energy resources has on offspring survival have been extensively studied across mammals. This study shows that in addition to calories, high hemoprotein concentrations in diving mammals necessitates exceptional female-to-pup iron transfer. Numerous indices of iron mobilization (ferritin, serum iron, total-iron-binding-capacity, transferrin saturation) were significantly elevated during lactation in adult female Weddell seals (Leptonychotes weddellii), but not in skip-breeders. Iron was mobilized from endogenous stores for incorporation into the Weddell seal’s milk at concentrations up to 100× higher than terrestrial mammals. Such high rates of iron offload to offspring drew from the female’s own heme stores and led to compromised physiologic dive capacities (hemoglobin, myoglobin, and total body oxygen stores) after weaning their pups, which was further reflected in shorter dive durations. We demonstrate that lactational iron transfer shapes physiologic dive thresholds, identifying a cost of reproduction to a marine mammal.This research was conducted with support from NSF ANT-0838892 to DPC; ANT-0838937 and ANT-1246463 to JMB (which also supported ALK and MRS); and The Investment in Science Fund at WHOI to MRS

A global perspective on marine photosynthetic picoeukaryote community structure

A central goal in ecology is to understand the factors affecting the temporal dynamics and spatial distribution of microorganisms and the underlying processes causing differences in community structure and composition. However, little is known in this respect for photosynthetic picoeukaryotes (PPEs), algae that are now recognised as major players in marine CO2 fixation. Here, we analysed dot blot hybridisation and cloning–sequencing data, using the plastid-encoded 16S rRNA gene, from seven research cruises that encompassed all four ocean biomes. We provide insights into global abundance, α- and β-diversity distribution and the environmental factors shaping PPE community structure and composition. At the class level, the most commonly encountered PPEs were Prymnesiophyceae and Chrysophyceae. These taxa displayed complementary distribution patterns, with peak abundances of Prymnesiophyceae and Chrysophyceae in waters of high (25:1) or low (12:1) nitrogen:phosphorus (N:P) ratio, respectively. Significant differences in phylogenetic composition of PPEs were demonstrated for higher taxonomic levels between ocean basins, using Unifrac analyses of clone library sequence data. Differences in composition were generally greater between basins (interbasins) than within a basin (intrabasin). These differences were primarily linked to taxonomic variation in the composition of Prymnesiophyceae and Prasinophyceae whereas Chrysophyceae were phylogenetically similar in all libraries. These data provide better knowledge of PPE community structure across the world ocean and are crucial in assessing their evolution and contribution to CO2 fixation, especially in the context of global climate change

A role for the cell-wall protein silacidin in cell size of the diatom Thalassiosira pseudonana

Diatoms contribute 20% of global primary production and form the basis of many marine food webs. Although their species diversity correlates with broad diversity in cell size, there is also an intraspecific cell-size plasticity due to sexual reproduction and varying environmental conditions. However, despite the ecological significance of the diatom cell size for food-web structure and global biogeochemical cycles, our knowledge about genes underpinning the size of diatom cells remains elusive. Here, a combination of reverse genetics, experimental evolution and comparative RNA8 sequencing analyses enabled us to identify a previously unknown genetic control of cell size in the diatom Thalassiosira pseudonana. In particular, the targeted deregulation of the expression of the cell-wall protein silacidin caused a significant increase in valve diameter. Remarkably, the natural downregulation of the silacidin gene transcript due to experimental evolution under low temperature also correlated with cell-size increase. Our data give first evidence for a genetically controlled regulation of cell size in Thalassiosira pseudonana and possibly other centric diatoms as they also encode the silacidin gene in their genomes

Antipsychotic medication versus psychological intervention versus a combination of both in adolescents with first-episode psychosis (MAPS): a multicentre, three-arm, randomised controlled pilot and feasibility study

Background Evidence for the effectiveness of treatments in early-onset psychosis is sparse. Current guidance for the treatment of early-onset psychosis is mostly extrapolated from trials in adult populations. The UK National Institute for Health and Care Excellence has recommended evaluation of the clinical effectiveness and cost-effectiveness of antipsychotic drugs versus psychological intervention (cognitive behavioural therapy [CBT] and family intervention) versus the combination of these treatments for early-onset psychosis. The aim of this study was to establish the feasibility of a randomised controlled trial of antipsychotic monotherapy, psychological intervention monotherapy, and antipsychotics plus psychological intervention in adolescents with first-episode psychosis. Methods We did a multicentre pilot and feasibility trial according to a randomised, single-blind, three-arm, controlled design. We recruited participants from seven UK National Health Service Trust sites. Participants were aged 14–18 years; help-seeking; had presented with first-episode psychosis in the past year; were under the care of a psychiatrist; were showing current psychotic symptoms; and met ICD-10 criteria for schizophrenia, schizoaffective disorder, or delusional disorder, or met the entry criteria for an early intervention for psychosis service. Participants were assigned (1:1:1) to antipsychotics, psychological intervention (CBT with optional family intervention), or antipsychotics plus psychological intervention. Randomisation was via a web-based randomisation system, with permuted blocks of random size, stratified by centre and family contact. CBT incorporated up to 26 sessions over 6 months plus up to four booster sessions, and family intervention incorporated up to six sessions over 6 months. Choice and dose of antipsychotic were at the discretion of the treating consultant psychiatrist. Participants were followed up for a maximum of 12 months. The primary outcome was feasibility (ie, data on trial referral and recruitment, session attendance or medication adherence, retention, and treatment acceptability) and the proposed primary efficacy outcome was total score on the Positive and Negative Syndrome Scale (PANSS) at 6 months. Primary outcomes were analysed by intention to treat. Safety outcomes were reported according to as-treated status, for all patients who had received at least one session of CBT or family intervention, or at least one dose of antipsychotics. The study was prospectively registered with ISRCTN, ISRCTN80567433. Findings Of 101 patients referred to the study, 61 patients (mean age 16·3 years [SD 1·3]) were recruited from April 10, 2017, to Oct 31, 2018, 18 of whom were randomly assigned to psychological intervention, 22 to antipsychotics, and 21 to antipsychotics plus psychological intervention. The trial recruitment rate was 68% of our target sample size of 90 participants. The study had a low referral to recruitment ratio (around 2:1), a high rate of retention (51 [84%] participants retained at the 6-month primary endpoint), a high rate of adherence to psychological intervention (defined as six or more sessions of CBT; in 32 [82%] of 39 participants in the monotherapy and combined groups), and a moderate rate of adherence to antipsychotic medication (defined as at least 6 consecutive weeks of exposure to antipsychotics; in 28 [65%] of 43 participants in the monotherapy and combined groups). Mean scores for PANSS total at the 6-month primary endpoint were 68·6 (SD 17·3) for antipsychotic monotherapy (6·2 points lower than at randomisation), 59·8 (13·7) for psychological intervention (13·1 points lower than at randomisation), and 62·0 (15·9) for antipsychotics plus psychological intervention (13·9 points lower than at randomisation). A good clinical response at 6 months (defined as ≥50% improvement in PANSS total score) was achieved in four (22%) of 18 patients receiving antipsychotic monotherapy, five (31%) of 16 receiving psychological intervention, and five (29%) of 17 receiving antipsychotics plus psychological intervention. In as-treated groups, serious adverse events occurred in eight [35%] of 23 patients in the combined group, two [13%] of 15 in the antipsychotics group, four [24%] of 17 in the psychological intervention group, and four [80%] of five who did not receive any treatment. No serious adverse events were considered to be related to participation in the trial. Interpretation This trial is the first to show that a head-to-head clinical trial comparing psychological intervention, antipsychotics, and their combination is safe in young people with first-episode psychosis. However, the feasibility of a larger trial is unclear because of site-specific recruitment challenges, and amendments to trial design would be needed for an adequately powered clinical and cost-effectiveness trial that provides robust evidence

Incidental retrieval of prior emotion mimicry.

When observing emotional expressions, similar sensorimotor states are activated in the observer, often resulting in physical mimicry. For example, when observing a smile, the zygomaticus muscles associated with smiling are activated in the observer, and when observing a frown, the corrugator brow muscles. We show that the consistency of an individual's facial emotion, whether they always frown or smile, can be encoded into memory. When the individuals are viewed at a later time expressing no emotion, muscle mimicry of the prior state can be detected, even when the emotion itself is task irrelevant. The results support simulation accounts of memory, where prior embodiments of other's states during encoding are reactivated when re-encountering a person

A three-arm feasibility randomised controlled trial comparing antipsychotic medication to psychological intervention to a combined treatment in adolescents with first episode psychosis: The Managing Adolescent first episode Psychosis Study (MAPS)

Background: The evidence base for treatments for early-onset psychosis (EOP) is limited and of low quality. Current guidance for the treatment of EOP is mostly extrapolated from trials in adult populations. NICE, in the United Kingdom (UK), make a specific research recommendation for the evaluation of clinical and cost-effectiveness of antipsychotics (AP), versus psychological intervention (cognitive behaviour therapy [CBT] and family intervention), versus combination treatment for EOP. The National Institute for Health Research (NIHR) in the UK commissioned this research to establish feasibility and acceptability of a definitive trial examining these three treatment options. Methods: We conducted a multi-site, Prospective Randomised Open Blinded Evaluation (PROBE) design, feasibility randomised controlled trial (RCT) comparing AP monotherapy with psychological intervention monotherapy (PI) plus a combination of these treatments in 14-18-year olds with a first episode of psychosis. We recruited participants from seven United Kingdom sites. Participants were followed-up at six and 12 months. Cognitive behavioural therapy incorporated up to 26 sessions over 6 months plus up to four booster sessions. Family intervention included up to six sessions over 6 months. Choice and dose of antipsychotic were at the discretion of the treating consultant psychiatrist. The primary outcome was feasibility data (recruitment, retention, acceptability) and the main effectiveness outcome was the Positive and Negative Syndrome Scale (PANSS) total score at 6 months. We conducted a repeated-measures analysis of the proposed primary outcome (PANSS) and the secondary outcome, the Questionnaire about the Process of Recovery (QPR) using a mixed effects model to account for the discrete timing of the follow-up assessments and adjusted for site. Safety outcomes were reported on the basis of as treated status defined as any one session of CBT or any one dose of APs; descriptive statistics are reported for safety outcomes. The study was prospectively registered on 27th February 2017, http://www.isrctn.com/ISRCTN80567433. Findings: 61 patients (aged 14-18 years; mean 16.3, SD 1.3) were recruited from 1st April 2017 to 31st October 2018, 18 were assigned to psychological intervention, 22 to antipsychotics and 21 to the combination. The feasibility of recruitment was unclear, since the trial only recruited 61 of a target of 90 participants. The study had a low referral: randomisation ratio (101:61), high rates of retention (>80%), high rates of adherence for psychological intervention (82.1%) defined as 6 or more sessions of CBT, and moderate rates of adherence for antipsychotic medication (65.1%), defined as 6 or more consecutive weeks of APs. The median number of sessions for CBT for those in the PI arm was 14 (IQR 9, 23) and 15 in the combined arm (IQR 9, 17). Of those in receipt of APs the mean duration that the participant remained on the medication was 31.5 weeks (SD 14.6, minimum 8.7 and maximum 52). There were no serious adverse events considered to be related to the trial. Interpretation: This is the first trial to show that it is safe to conduct a head-to-head clinical trial comparing psychological intervention with antipsychotics and the combination in people in young people with a first-episode psychosis. However, feasibility is unclear due to not meeting the recruitment progression criteria, so amendments to trial design are required in order to conduct an adequately powered clinical and cost effectiveness trial to provide robust evidence

Building a transdisciplinary expert consensus on the cognitive drivers of performance under pressure: An international multi-panel Delphi study

IntroductionThe ability to perform optimally under pressure is critical across many occupations, including the military, first responders, and competitive sport. Despite recognition that such performance depends on a range of cognitive factors, how common these factors are across performance domains remains unclear. The current study sought to integrate existing knowledge in the performance field in the form of a transdisciplinary expert consensus on the cognitive mechanisms that underlie performance under pressure.MethodsInternational experts were recruited from four performance domains [(i) Defense; (ii) Competitive Sport; (iii) Civilian High-stakes; and (iv) Performance Neuroscience]. Experts rated constructs from the Research Domain Criteria (RDoC) framework (and several expert-suggested constructs) across successive rounds, until all constructs reached consensus for inclusion or were eliminated. Finally, included constructs were ranked for their relative importance.ResultsSixty-eight experts completed the first Delphi round, with 94% of experts retained by the end of the Delphi process. The following 10 constructs reached consensus across all four panels (in order of overall ranking): (1) Attention; (2) Cognitive Control—Performance Monitoring; (3) Arousal and Regulatory Systems—Arousal; (4) Cognitive Control—Goal Selection, Updating, Representation, and Maintenance; (5) Cognitive Control—Response Selection and Inhibition/Suppression; (6) Working memory—Flexible Updating; (7) Working memory—Active Maintenance; (8) Perception and Understanding of Self—Self-knowledge; (9) Working memory—Interference Control, and (10) Expert-suggested—Shifting.DiscussionOur results identify a set of transdisciplinary neuroscience-informed constructs, validated through expert consensus. This expert consensus is critical to standardizing cognitive assessment and informing mechanism-targeted interventions in the broader field of human performance optimization