Chairs
Professor Debashish Bhattacharya, Rutgers University, USA
Professor Debashish Bhattacharya, Rutgers University, USA
Debashish Bhattacharya is an evolutionary biologist who uses the tools of genomics and bioinformatics to study the origin of the photosynthetic organelle, the plastid, in diverse algae to understand how organelles are integrated into host metabolism. Other areas of specialization include single cell genomics and transcriptomics to explore uncultivated biodiversity and algal biofuel research using the green algal lineage Picochlorum spp. The Bhattacharya group and collaborators have also recently embarked on a large-scale study of coral genome evolution, the origin and developmental control of biomineralization in this lineage, and coral interactions with their dinoflagellate symbionts. Teaching interests at Rutgers include courses in fundamental genomics and the evolution of photosynthesis in eukaryotes.
13:00-13:35
Was the chlamydial adaptive strategy to tryptophan starvation an early determinant of plastid endosymbiosis?
Professor Steven Ball, University of Lille, France
Abstract
Chlamydiales were recently proposed to have sheltered the future cyanobacterial ancestor of plastids in a common inclusion. The intracellular pathogens are thought to have donated those critical transporters that triggered the efflux of photosynthetic carbon and the consequent onset of symbiosis. Chlamydiales are also suspected to have encoded glycogen metabolism TTS (Type Three Secretion) effectors responsible for photosynthetic carbon assimilation in the eukaryotic cytosol.
We now review the reasons underlying other chlamydial lateral gene transfers evidenced in the descendants of plastid endosymbiosis. In particular, we show that half of the genes encoding enzymes of tryptophan synthesis in Archaeplastida are of chlamydial origin. Tryptophan is known to define an essential cue triggering two alternative modes of replication in Chlamydiales. In addition, sophisticated tryptophan starvation mechanisms are known to have been implemented as antibacterial defences by their eukaryotic hosts. We propose that Chlamydiales have donated their tryptophan operon to the emerging plastid to ensure increased synthesis of tryptophan by the plastid ancestor. This would have allowed massive expression of the tryptophan rich chlamydial transporters responsible for symbiosis. It would also have allowed possible export of this valuable amino-acid in the inclusion of the tryptophan hungry pathogens. Free-living single cell cyanobacteria are devoid of proteins able to transport this amino-acid. We therefore investigated the phylogeny of the E.coli Tyr/Trp transporters and found yet another LGT from Chlamydiales to Archaeplastida thereby considerably strengthening our proposal.
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Professor Steven Ball, University of Lille, France
Professor Steven Ball, University of Lille, France
Steven Ball got his PhD from the Agronomy Faculty of Gembloux (Belgium) following work on the molecular genetics of the yeast killer dsRNA virus like particles under the supervision of Reed B Wickner at NIH (Bethesda – Maryland). In 1985 he got a permanent position as assistant professor in Gembloux and got a full professorship at the University of Lille in 1987. Since 1986 he focused all of his experimental work on storage polysaccharide metabolism first in yeast and then very rapidly and predominantly in Chlamydomonas reinhardtii. Steven Ball is internationally recognized for his contribution to the understanding of those functions that distinguish starch from glycogen synthesis. He has recently suggested that storage polysaccharide metabolism acted as a biochemical buffer between unrelated networks at the onset of plastid endosymbiosis. This led him to propose that intracellular Chlamydiales pathogens may have had a major role in this process.
13:35-14:10
The Use of Comparative Genomics and the GreenCut Assemblage of Proteins to Identify Novel Photosynthetic Functions
Professor Arthur Grossman, Carnegie Institution for Science, USA
Abstract
Using powerful bioinformatics tools and comparative genomics is allowing us to identify novel components of photosynthesis. This information will help elucidate new photosynthetic functions and provide opportunities for engineering plants and algae for efficient solar energy utilization, increased agricultural outputs and improved resiliency to changing global environments. The GreenCut represents an informatics assemblage of nuclear-encoded proteins that are conserved among photosynthetic organisms of the green lineage (Viridiplantae), but that are either not present, or poorly conserved in heterotrophic (nonphotosynthetic) organisms. Many uncharacterized GreenCut proteins (unknown specific functions) appear to have regulatory functions or roles in the biogenesis of the photosynthetic apparatus based on specific domains in their protein sequences. Other GreenCut proteins have no domains that are currently informative with respect to function. Generating insertional mutants of genes encoding GreenCut proteins in Chlamydomonas reinhardtii has allowed for the characterization of mutant phenotypes, suggesting roles for a number of these proteins with respect to photosynthetic activities. One GreenCut protein was recently shown to be involved in stabilizing the assembly of photosystem I (PSI) under oxic conditions, and is potentially involved in protecting oxygen sensitive PSI cofactors (e.g. Fe-S clusters) during the assembly process; as the Earth became oxygenated mechanisms must have evolved that protect existing oxygen sensitive cofactors from disruption. Other novel proteins of the GreenCut appear to be important for the biogenesis/stability of the cytochrome b6f complex. I will discuss the GreenCut and the ways in which it is being used to examine photosynthetic function and evolution.
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Professor Arthur Grossman, Carnegie Institution for Science, USA
Professor Arthur Grossman, Carnegie Institution for Science, USA
Dr. Arthur Grossman has spent over thirty years in microalgal research and is widely recognized as an expert in this field, concentrating on algal physiology, genetics and genomics. He received a Ph.D. in Plant Biology from Indiana University, performed postdoctoral research at The Rockefeller University and is currently a Senior Staff Scientist at the Carnegie Institution for Science, a Courtesy Professor at Stanford University and Chief of Genetics for Solazyme Inc. Most of Dr. Grossman's academic research has focused on the ways in which algae perceive and respond to changes in their environment. He has received the prestigious Darbaker Prize from the Botanical Society for algal research in 2002, and in 2009 was awarded the Gilbert Morgan Smith Medal for excellence in published research on marine and/or freshwater algae. The award, which only recognizes one scientist every three years, was established through the Helen P. Smith Fund and is awarded by the National Academy of Sciences USA.
14:10-14:45
Seaweed microbiomes: a new age of discovery
Professor Juliet Brodie, Natural History Museum, UK
Abstract
Marine macroalgae are host to a wide range of prokaryotic and eukaryotic life, creating a dynamic and complex community of specialists or generalists that can be beneficial (mutualistic), neutral (commensal) or harmful (parasitic) organisms. Bacteria are the dominant active group that make up the microbiome, and macroalgal-bacterial studies suggest that there is a core microbiome at the phylum level consisting of the Gammaproteobacteria, Bacteroidetes, Alphaproteobacteria, Firmicutes and Actinobacteria. Until relatively recently, studies of bacteria associated with various macroalgal hosts were undertaken using cultures and electron microscopy. Next generation sequencing (NGS) is now revolutionising the subject and revealing the extent of bacterial diversity in these microbiomes. This talk will review what is known about microbiomes of marine macroalgae with a particular focus on the red algae. It will explore the notion of a core microbiome for different host groups and also the spatial and temporal ecological impact on host photosynthesis of different types of epiphytes. Focussing in particular on the prokaryote component of the microbiome, the nature of the relationships between the bacteria and host and the implications for ecosystem function and environmental change including ocean acidification and increasing sea surface temperatures will be explored. Drawing upon our results of the microbiome of Corallina officinalis – the first for a geniculate coralline alga – differences in microbiome composition will be compared both within and between fleshy and calcified species. Evidence that the epiphytic bacteria provide important services to hosts that are vital to their health, performance and resilience will be discussed. Ways forward to identify prokaryote and eukaryote diversity, to understand their roles in productivity, and the overall nature of these relationships will be explored.
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Professor Juliet Brodie, Natural History Museum, UK
Professor Juliet Brodie, Natural History Museum, UK
Juliet Brodie is a research leader in phycology at the Natural History Museum, London. She graduated from the University of Bristol with a degree in Botany and Zoology and has studied macroalgae for over 30 years. Her doctoral research was undertaken at NUI Galway and focussed on life histories, crossing studies, morphology and photoperiodic responses of red algae. Postdoctoral studies on the systematics and life histories of calcified red algae associated with coral barrier reefs were undertaken at the Smithsonian Institution, USA. She embraced molecular techniques early on in their use in algal taxonomy, is a leading authority on the Bangiales, a cosmopolitan order of red seaweeds including nori, and is a leader in the conservation of macroalgae in the UK. Her current research specialises in using genomic approaches to address questions relating to macroalgae and microbiomes in a time of rapid environmental change.
15:15-15:50
The "virocell" metabolism-metabolic innovations during algal-virus interactions in the ocean
Professor Assaf Vardi, Weizmann Institute of Science, Israel
Abstract
Marine viruses that infect marine microorganisms are recognized as major ecological and evolutionary driving forces, shaping community structure and controlling cycling of nutrient energy in the marine environment. A major challenge in our current understanding of host-virus interactions in the marine environment is to decode the wealth of genomic and metagenomic data and translate it into cellular mechanisms that mediate host susceptibility and resistance to viral infection. Nevertheless, the cellular mechanisms that govern these host-virus dynamics are largely underexplored. Recent reports highlighted a novel genomic inventory found in marine viruses which can encode for auxiliary metabolic genes previously thought to be restricted to their host genomes. Thus, these genes can expand the metabolic capabilities of the infected host cell (Virocell) and the flux of the nutrients and metabolites between the cell and its micro-environment.
Emiliania huxleyi is a globally important coccolithophore forming massive algal blooms in the North Atlantic Ocean that are routinely infected and terminated by large DNA viruses (EhVs) belong to the coccolithoviruses. We explore the molecular and metabolic basis for these host-virus dynamics and the signal transduction pathways that mediate host-virus interactions. By combining genome-enabled technologies, analytical chemistry and advance cell imaging approaches, we were able to identify several fundamental metabolic pathways that mediate these host-virus interactions. We revealed the role of viral-encoded sphingolipid biosynthesis, redox and DMS metabolism and their function in determining host cell fate (e.g. PCD and autophagy) and viral replication strategies.
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Professor Assaf Vardi, Weizmann Institute of Science, Israel
Professor Assaf Vardi, Weizmann Institute of Science, Israel
Assaf Vardi earned a BSc in biology from the Hebrew University of Jerusalem (1994), from which he also received his MSc in environmental sciences (1999) and PhD in molecular ecology (2004). After conducting postdoctoral research at the École Normale Supérieure in Paris and at Rutgers University, he joined the Weizmann Institute faculty as a senior scientist in 2010. He was also appointed as an Adjunct Scientist at the Woods Hole Oceanographic Institution (USA) during 2011-2014.
His research interests focus on elucidating the molecular mechanism that drives microbial interactions in the marine environment. Specifically he studies marine photosynthetic microorganisms (phytoplankton) which are the basis of marine foodwebs and are responsible for nearly 50% of the global annual carbon-based primary production.
He explores the signal transduction pathways related to the origin of programmed cell death, cell-cell communication, host-virus interactions and chemical-based defense (DMS, sphingolipids, ROS). Our work aims at elucidating the cell signalling pathways that regulate cell fate decisions and uncover the chemical signals (infochemicals) involved in microbial trophic-level interactions in the oceans.
15:50-16:25
Pythium porphyrae: a plant pathogen seeing red?
Dr Claire Gachon, Scottish Marine Institute, UK
Abstract
Pythium porphyrae is responsible for devastating outbreaks in seaweed farms of Pyropia, the most valuable seaweed worldwide. While the genus Pythium contains many well studied plant and animal pathogens, the infection strategies and genome content of P. porphyrae remains to be elucidated. Recent reports also indicated the ability of P.porphyrae to infect, colonize and reproduce on a great variety of land plants, begging the question of its potential land origin, as well as the molecular mechanisms underpinning its host specificity. Here, we used RNA sequencing to provide the first description of P. porphyrae gene repertoire and assess its similarity to fully sequenced Pythiums. Using ab-initio detection strategies, similarity based and manual annotation, we found that the P.porphyrae gene repertoire is strikingly similar to the ones described for classical phytopathogenic Pythium species, including Crinklers, elicitins, cellulases, CBEL-like proteins and a total absence of RxLR effectors. Comparative genomics revealed that 1507 genes, including CBEL-like proteins and elicitins, have orthologs in some plant infecting Pythiums but not in the animal pathogen P.insidiosum. Despite 34% of the P.porphyrae proteome having no orthologs in other sequenced Pythiums, we could not identify any enzyme involved in the degradation of red algal-specific cell wall components. Complementary infection experiments indicated that P.porphyrae is specific of Bangiales, contrasting with the general broad host range observed on land plants, perhaps suggesting a recent adaptation linked with the development of Pyropia cultivation.
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Dr Claire Gachon, Scottish Marine Institute, UK
Dr Claire Gachon, Scottish Marine Institute, UK
A graduate of the Ecole Normale Supérieure (Paris), Claire Gachon originally trained as a molecular plant pathologist and now develops research on the ecology and physiology of diseases of marine algae. Notably, she set up a model laboratory interaction between the intracellular oomycete pathogen Eurychasma dicksonii and the brown algal genome model Ectocarpus siliculosus, using a using an interdisciplinary array of approaches (mostly biochemistry, molecular biology, genomics and bioinformatics). Claire has participated to several seaweed genome projects, including Ectocarpus siliuclosus, Chondrus crispus, Pythium ultimum and Porphyra umbilicalis. Her research now also encompasses freshwater algae and a broader range of pathogens, with an increasingly pronounced focus on applied topics. Claire is also in interested in infrastructure, training and networking initiatives. In particular, she currently coordinates the Marie Curie ITN ALFF (Agal Microbiome: Friends and Foes) and the NERC-funded GlobalSeaweed network on macroalgal breeding and cultivation.
16:25-17:00
Chemical interaction between seaweeds and their epibacterial ‘friends’ and ‘foes’
Dr Mahasweta Saha, Helmholtz Center for Ocean Research, GEOMAR, Germany
Abstract
Fouling is a paramount phenomenon in the marine environment. However, surfaces of certain seaweeds like the brown alga Fucus vesciculosus, remain relatively free from heavy fouling and are covered by a thin film of epibiotic microorganisms. We found that Fucus in a given habitat harbors a distinct epibacterial community. Fucus also produces defence compounds like fucoxanthin, DMSP reducing bacterial settlement. These compounds have also been found to be strain specific in their action, thus probably assisting Fucus in ‘gardening’ a distinct bacterial community on its surface. This idea was further supported by a study that correlated the surface concentration of the defence compounds with the presence or absence of different bacterial clades. Several bacterial groups were found to be positively or negatively affected by the compounds present on surfaces of Fucus individuals. Seaweeds also account for a substantial proportion of all introduced species. The East Asian red macroalga Gracilaria vermiculophylla has successfully invaded several temperate areas of the Northern hemisphere. Although foulers have the potential to determine invasion success or failure of invasive seaweeds, this perspective has been ignored so far. We tested whether the impressive invasion success of Gracilaria may be enhanced by a rapid adaptation of defence against potentially facultative new target microfoulers in the invaded range. Native and invasive Gracilaria populations were equally well defended against presently co-occurring bacterial foulers. However, native populations were weakly defended against bacteria from the invaded range, while invasive populations were weakly defended against bacteria from the native range. Thus, the invasive populations exhibited an adaptation of their defence capacity to cope with the new foes, but have lost capacity to fend off old foes. These results provide the first evidence that confrontation by new foulers can trigger a rapid defence adaptation of aquatic weeds, which could be necessary for algal invasiveness.
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Dr Mahasweta Saha, Helmholtz Center for Ocean Research, GEOMAR, Germany
Dr Mahasweta Saha, Helmholtz Center for Ocean Research, GEOMAR, Germany
Dr Mahasweta Saha studied a Masters in Marine Science at University of Calcutta, India before being employed as a Research Scholar at Marine Natural Product Chemistry Division at National Institute of Oceanography (NIO), India. During her research stay at NIO, she was awarded the international research scholarship in 2008 from DAAD to pursue her PhD in Algal Chemical Ecology at Helmholtz Centre of Ocean Research (GEOMAR) under the supervision of Prof. Dr. Martin Wahl and Dr. Florian Weinberger. Following the completion of her PhD in 2011 and a family care break of 1 year, in 2013, Mahasweta was awarded an international Post Doctorate research grant from the DFG excellence cluster ‘Future Ocean’ and since then working on chemical ecology of invasive seaweeds at GEOMAR. She has been recently awarded a DFG Post-Doctoral fellowship from DFG to pursue her next research project on volatile infochemistry of seaweeds at University of Essex, United Kingdom. Her research interests include seaweed ecology; bacterial biofilm biology and ecology; biofouling and antifouling; environmental change; invasion ecology and volabolomics. She has supervised >10 Bachelor, Master and Internship students towards successful completion of their project and acts as a reviewer of leading scientific journals.
17:00-18:00
Poster Session