Exploring mutualistic interactions between microalgae and bacteria in the omics age.

Microalgae undertake a wide range of mutualistic interactions with bacteria. Here we consider how transcriptomic, metagenomic and metabolomic approaches have been combined with microbiological and biochemical analyses to expand our understanding of algal-bacterial interactions. Identification of the major bacterial species associated with algae indicates that specific bacterial groups, particularly the alpha-Proteobacteria, are found more frequently, suggesting that these may have the means to initiate and maintain symbiotic relationships. Nutrient exchange is frequently the basis of algal-bacterial mutualism, and as the compounds involved are characterised, evidence is accumulating that these are complex and specific molecules, offering opportunities for signalling processes and regulation rather than merely passive diffusion. At the same time, it is clear that the interactions are not static, but can be initiated and broken in response to environmental and developmental cues.We thank the Biotechnology and Biological Sciences Research Council (BBSRC) of the UK, and PML Applications Ltd., Plymouth UK, for the CASE studentship for MBC.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.pbi.2015.07.00

Extrahepatic tissue concentrations of vitamin K are lower in rats fed a high vitamin E diet

BACKGROUND: An adverse hematological interaction between vitamins E and K has been reported, primarily in patients on anticoagulants. However, little is known regarding circulating levels or tissue concentrations of vitamin K in response to vitamin E supplementation. The purpose of this study was to examine the effect of different levels of dietary α-tocopherol on phylloquinone and menaquinone-4 concentrations, while maintaining a constant intake of phylloquinone, in rat tissues. METHODS: Male 4-wk old Fischer 344 rats (n = 33) were fed one of 3 diets for 12 wk: control (n = 13) with 30 mg all-rac-α-tocopherol acetate/kg diet; vitamin E-supplemented (n = 10) with 100 mg all-rac-α-tocopherol acetate/kg diet; and vitamin E-restricted (n = 10) with <10 mg total tocopherols/kg diet. All 3 diets contained 470 ± 80 μg phylloquinone/kg diet. RESULTS: Phylloquinone concentrations were lower (P ≤ 0.05) in the vitamin E-supplemented compared to the vitamin E-restricted group (mean ± SD spleen: 531 ± 58 vs.735 ± 77; kidney: 20 ± 17 vs. 94 ± 31, brain: 53 ± 19 vs.136 ± 97 pmol/g protein respectively); no statistically significant differences between groups were found in plasma, liver or testis. Similar results were noted with menaquinone-4 concentrations in response to vitamin E supplementation. CONCLUSION: There appears to be a tissue-specific interaction between vitamins E and K when vitamin E is supplemented in rat diets. Future research is required to elucidate the mechanism for this nutrient-nutrient interaction

Methacholine and PDGF activate store-operated calcium entry in neuronal precursor cells via distinct calcium entry channels

Neurons are a diverse cell type exhibiting hugely different morphologies and neurotransmitter specifications. Their distinctive phenotypes are established during differentiation from pluripotent precursor cells. The signalling pathways that specify the lineage down which neuronal precursor cells differentiate remain to be fully elucidated. Among the many signals that impinge on the differentiation of neuronal cells, cytosolic calcium (Ca2+) has an important role. However, little is known about the nature of the Ca2+ signals involved in fate choice in neuronal precursor cells, or their sources. In this study, we show that activation of either muscarinic or platelet-derived growth factor (PDGF) receptors induces a biphasic increase in cytosolic Ca2+ that consists of release from intracellular stores followed by sustained entry across the plasma membrane. For both agonists, the prolonged Ca2+ entry occurred via a store-operated pathway that was pharmacologically indistinguishable from Ca2+ entry initiated by thapsigargin. However, muscarinic receptor-activated Ca2+ entry was inhibited by siRNA-mediated knockdown of TRPC6, whereas Ca2+ entry evoked by PDGF was not. These data provide evidence for agonist-specific activation of molecularly distinct store-operated Ca2+ entry pathways, and raise the possibility of privileged communication between these Ca2+ entry pathways and downstream processes

Care home resident and staff perceptions of the acceptability of nutrition intervention trial procedures:A qualitative study embedded within a cluster randomised feasibility trial

Objectives To examine care home resident and staff perceptions of the acceptability of participating in a feasibility trial evaluating nutritional interventions in the treatment of malnutrition. Design Exploratory qualitative methodology was used to gather descriptions of resident and staff perceptions of trial procedures, using semi-structured interviews with residents and focus groups with staff. The interviews were used to explore individual perceptions of the acceptability of the assigned intervention and the outcomes measured. Focus groups were used to explore staff experiences of trial participation and perspectives of nutritional support interventions. Setting The study was embedded within a cluster randomised feasibility trial, which randomised six care homes to provide standard care (SC), food-based (FB) intervention or oral nutritional supplement (ONS) intervention to residents with, or at risk of, malnutrition. Participants Residents in the trial with capacity to consent (n=7) formed the sampling frame for inclusion. Four agreed to be approached by the researcher and to take part in the individual interviews. All were women, representing two arms of the trial (ONS and SC). Twelve staff participated in six focus groups, one at each care home. All participants were women, representing all three arms of the trial. Results Major themes that emerged from both interviews and focus groups included the perceived acceptability of trial involvement, the value of residents completing participant-reported outcome measures and the challenges associated with outcomes measurement in this setting. Themes that emerged from the focus groups alone, included the importance of individualising an intervention, and the perceived value of FB and ONS interventions and dietetic input. Conclusions Residents and staff perceived involvement in a trial evaluating nutritional interventions to be acceptable, although the challenges associated with research in this setting were acknowledged. Resident preferences were highlighted by staff as an important consideration when implementing a nutrition support plan. Trial registration number ISRCTN3804792

Asynchrony of Gambierdiscus spp. abundance and toxicity in the U.S. Virgin Islands: implications for monitoring and management of Ciguatera

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Liefer, J. D., Richlen, M. L., Smith, T. B., DeBose, J. L., Xu, Y., Anderson, D. M., & Robertson, A. Asynchrony of Gambierdiscus spp. abundance and toxicity in the U.S. Virgin Islands: implications for monitoring and management of Ciguatera. Toxins, 13(6), (2021): 413, https://doi.org/10.3390/toxins13060413.Ciguatera poisoning (CP) poses a significant threat to ecosystem services and fishery resources in coastal communities. The CP-causative ciguatoxins (CTXs) are produced by benthic dinoflagellates including Gambierdiscus and Fukuyoa spp., and enter reef food webs via grazing on macroalgal substrates. In this study, we report on a 3-year monthly time series in St. Thomas, US Virgin Islands where Gambierdiscus spp. abundance and Caribbean-CTX toxicity in benthic samples were compared to key environmental factors, including temperature, salinity, nutrients, benthic cover, and physical data. We found that peak Gambierdiscus abundance occurred in summer while CTX-specific toxicity peaked in cooler months (February–May) when the mean water temperatures were approximately 26–28 °C. These trends were most evident at deeper offshore sites where macroalgal cover was highest year-round. Other environmental parameters were not correlated with the CTX variability observed over time. The asynchrony between Gambierdiscus spp. abundance and toxicity reflects potential differences in toxin cell quotas among Gambierdiscus species with concomitant variability in their abundances throughout the year. These results have significant implications for monitoring and management of benthic harmful algal blooms and highlights potential seasonal and highly-localized pulses in reef toxin loads that may be transferred to higher trophic levels.This work was funded in part by the National Oceanic and Atmospheric Administration, Ecology and Oceanography of Harmful Algal Blooms Program (ECOHAB publication number 984) through the CiguaHAB project (NA11NOS4780028), and also contributes to CIGUATOX (NA17NOS4780181) granted to coauthors AR, TBS, DMA, and MLR. Additional support was provided by NSF Partnerships in International Research and Education (1743802), and the Greater Caribbean Center for Ciguatera Research (NIH 1P01ES028949-01 and NSF 1841811). Financial support of YX was from the National Natural Science Foundation of China (41976155), the Natural Science Foundation of Guangxi Province (2020GXNSFDA297001)

Cross-exchange of B-vitamins underpins a mutualistic interaction between Ostreococcus tauri and Dinoroseobacter shibae.

Ostreococcus tauri, a picoeukaryotic alga that contributes significantly to primary production in oligotrophic waters, has a highly streamlined genome, lacking the genetic capacity to grow without the vitamins thiamine (B1) and cobalamin (B12). Here we demonstrate that the B12 and B1 auxotrophy of O. tauri can be alleviated by co-culturing with a heterotrophic bacterial partner Dinoroseobacter shibae, a member of the Rhodobacteraceae family of alpha-proteobacteria, genera of which are frequently found associated with marine algae. D. shibae lacks the complete pathway to synthesise three other B-vitamins: niacin (B3), biotin (B7), and p-aminobenzoic acid (a precursor for folate, B9), and the alga is in turn able to satisfy the reciprocal vitamin requirements of its bacterial partner in a stable long-term co-culture. Bioinformatics searches of 197 representative marine bacteria with sequenced genomes identified just nine species that had a similar combination of traits (ability to make vitamin B12, but missing one or more genes for niacin and biotin biosynthesis enzymes), all of which were from the Rhodobacteraceae. Further analysis of 70 species from this family revealed the majority encoded the B12 pathway, but only half were able to make niacin, and fewer than 13% biotin. These characteristics may have either contributed to or resulted from the tendency of members of this lineage to adopt lifestyles in close association with algae. This study provides a nuanced view of bacterial-phytoplankton interactions, emphasising the complexity of the sources, sinks and dynamic cycling between marine microbes of these important organic micronutrients.EU FP

Mixed A-Cation Perovskites for Solar Cells:Atomic-Scale Insights into Structural Distortion, Hydrogen Bonding, and Electronic Properties

Hybrid lead halide perovskites containing a mixture of A-site cations such as the formamidinium (CH­(NH₂)₂⁺, FA) and the smaller cesium (Cs⁺) cations have attracted considerable interest due to their improved stability and solar cell performance. However, the structural changes at the atomic scale and modifications to the optoelectronic properties of these mixed cation perovskites are not fully understood. Here, we investigate the FA_1–<i>x</i>Cs_<i>x</i>PbI₃ (<i>x</i> ≤ 0.25) system using a combination of static and dynamic <i>ab initio</i> computational methods. We find that the incorporation of Cs⁺ cations into the parent FAPbI₃ structure induces a chemical pressure or lattice strain effect through Cs/FA ion size mismatch resulting in structural distortion and stronger FA-iodide (N–H···I) hydrogen bonding interactions. The dynamic tilting of PbI₆ octahedra and the rotational motion of FA cations are also suppressed, which leads to symmetry-breaking of the lattice. Such symmetry-breaking distortions of the Pb/I lattice give rise to a Rashba-type effect, which spin-splits the frontier electronic bands making the band gap indirect. Our results suggest that the direct–indirect band gap transition may be a factor in the reduced charge-carrier recombination rate in these mixed cation perovskites

Hair cortisol as a biomarker of stress in mindfulness training for smokers.

OBJECTIVES: Stress is a well-known predictor of smoking relapse, and cortisol is a primary biomarker of stress. The current pilot study examined changes in levels of cortisol in hair within the context of two time-intensity matched behavioral smoking cessation treatments: mindfulness training for smokers and a cognitive-behavioral comparison group. PARTICIPANTS: Eighteen participants were recruited from a larger randomized controlled trial of smoking cessation. OUTCOME MEASURES: Hair samples (3 cm) were obtained 1 month after quit attempt, allowing for a retrospective analysis of hair cortisol at preintervention and post-quit attempt time periods. Self-reported negative affect was also assessed before and after treatment. INTERVENTION: Both groups received a 7-week intensive intervention using mindfulness or cognitive-behavioral strategies. RESULTS: Cortisol significantly decreased from baseline to 1 month after quit attempt in the entire sample (d=-0.35; p=.005). In subsequent repeated-measures analysis of variance models, time by group and time by quit status interaction effects were not significant. However, post hoc paired t tests yielded significant pre-post effects among those randomly assigned to the mindfulness condition (d=-0.48; p=.018) and in those abstinent at post-test (d=-0.41; p=.004). Decreased hair cortisol correlated with reduced negative affect (r=.60; p=.011). CONCLUSIONS: These preliminary findings suggest that smoking cessation intervention is associated with decreased hair cortisol levels and that reduced hair cortisol may be specifically associated with mindfulness training and smoking abstinence. RESULTS support the use of hair cortisol as a novel objective biomarker in future research