Browsing by Author "Wichard, Thomas"
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- Cultivating the macroalgal holobiont: effects of integrated multi-trophic aquaculture on the microbiome of Ulva rigida (chlorophyta)Publication . Califano, Gianmaria; Kwantes, Michiel; Abreu, Maria Helena; Da Silva Costa, Rodrigo; Wichard, ThomasUlva is a ubiquitous macroalgal genus of commercial interest. Integrated Multi-Trophic Aquaculture (IMTA) systems promise large-scale production of macroalgae due to their high productivity and environmental sustainability. Complex host-microbiome interactions play a decisive role in macroalgal development, especially in Ulva spp. due to algal growth- and morphogenesis-promoting factors released by associated bacteria. However, our current understanding of the microbial community assembly and structure in cultivated macroalgae is scant. We aimed to determine (i) to what extent IMTA settings influence the microbiome associated with U. rigida and its rearing water, (ii) to explore the dynamics of beneficial microbes to algal growth and development under IMTA settings, and (iii) to improve current knowledge of host-microbiome interactions. We examined the diversity and taxonomic composition of the prokaryotic communities associated with wild versus IMTA-grown Ulva rigida and surrounding seawater by using 16S rRNA gene amplicon sequencing. With 3141 Amplicon Sequence Variants (ASVs), the prokaryotic richness was, overall, higher in water than in association with U. rigida. Bacterial ASVs were more abundant in aquaculture water samples than water collected from the lagoon. The beta diversity analysis revealed distinct prokaryotic communities associated with Ulva collected in both aquacultures and coastal waters. Aquaculture samples (water and algae) shared 22% of ASVs, whereas natural, coastal lagoon samples only 9%. While cultivated Ulva selected 239 (8%) host-specific ASVs, wild specimens possessed more than twice host-specific ASVs (17%). Cultivated U. rigida specimens enriched the phyla Cyanobacteria, Planctomycetes, Verrucomicrobia, and Proteobacteria. Within the Gammaproteobacteria, while Glaciecola mostly dominated the microbiome in cultivated algae, the genus Granulosicoccus characterized both Ulva microbiomes. In both wild and IMTA settings, the phylum Bacteroidetes was more abundant in the bacterioplankton than in direct association with U. rigida. However, we observed that the Saprospiraceae family within this phylum was barely present in lagoon water but very abundant in aquaculture water. Aquaculture promoted the presence of known morphogenesis-inducing bacteria in water samples. Our study suggests that IMTA significantly shaped the structure and composition of the microbial community of the rearing water and cultivated U. rigida. Detailed analysis revealed the presence of previously undetected taxa associated with Ulva, possessing potentially unknown functional traits.
- A European biobanking strategy for safeguarding macroalgal genetic material to ensure food security, biosecurity and conservation of biodiversityPublication . Hofmann, Laurie C.; Brakel, Janina; Bartsch, Inka; Arismendi, Gabriel Montecinos; Bermejo, Ricardo; Parente, Manuela I.; Creis, Emeline; Clerck, Olivier De; Jacquemin, Bertrand; Knoop, Jessica; Lorenz, Maike; Machado, Levi Pompermayer; Orfanidis, Sotiris; Probert, Ian; Menendez, , Cecilia Rad; Ross, Michael; Rautenberger, Ralf; Schiller, Jessica; Serrao, Ester A.; Steinhagen, Sophie; Sulpice, Ronan; Valero, Myriam; Wichard, Thomas; Serrao, Ester A.; Martins, neuzaBiobanking (also known as germplasm banking) of genetic material is a well-established concept for preserving plant genetic diversity and also contributes to food security, conservation and restoration. Macroalgae currently represent a very small percentage of the strains in publicly accessible European germplasm banks, despite the increasing recognition of their contribution to achieving several of the United Nations Sustainable Development Goals. There is no strategic coordination of existing macroalgal strains, which could have severe ecological and economic implications as species and their genetic diversity disappear rapidly due to local and global environmental stressors. In this opinion paper, we stress the importance of a coordinated European effort for preserving macroalgal genetic diversity and suggest the development of a three-pillared system to safeguard European macroalgal genetic material consisting of (1) a European Board of Macroalgal Genetic Resources (EBMGR) to provide supervision, support and coordination, (2) a network of germplasm banks consisting of currently existing and newly established infrastructures and (3) an interoperable databank integrating existing databanks. While it will be the task of the EBMGR to identify and coordinate priorities, we offer initial recommendations for preserving macroalgal genetic material, discuss the risks of inaction, and highlight the challenges that must be overcome.
- Macroalgal morphogenesis induced by waterborne compounds and bacteria in coastal seawaterPublication . Grueneberg, Jan; Engelen, Aschwin H.; Costa, Rodrigo; Wichard, ThomasAxenic gametes of the marine green macroalga Ulva mutabilis Foyn (Ria Formosa, locus typicus) exhibit abnormal development into slow-growing callus-like colonies with aberrant cell walls. Under laboratory conditions, it was previously demonstrated that all defects in growth and thallus development can be completely abolished when axenic gametes are inoculated with a combination of two specific bacterial strains originally identified as Roseo-bacter sp. strain MS2 and Cytophaga sp. strain MS6. These bacteria release diffusible morphogenetic compounds (= morphogens), which act similar to cytokinin and auxin. To investigate the ecological relevance of the waterborne bacterial morphogens, seawater samples were collected in the Ria Formosa lagoon (Algarve, Southern Portugal) at 20 sampling sites and tidal pools to assess their morphogenetic effects on the axenic gametes of U. mutabilis. Specifically the survey revealed that sterile-filtered seawater samples can completely recover growth and morphogenesis of U. mutabilis under axenic conditions. Morphogenetic activities of free-living and epiphytic bacteria isolated from the locally very abundant Ulva species (i.e., U. rigida) were screened using a multiwell-based testing system. The most represented genera isolated from U. rigida were Alteromonas, Pseudoalteromonas and Sulfitobacter followed by Psychrobacter and Polaribacter. Several naturally occurring bacterial species could emulate MS2 activity (= induction of cell divisions) regardless of taxonomic affiliation, whereas the MS6 activity (= induction of cell differentiation and cell wall formation) was species-specific and is probably a feature of difficult-to-culture bacteria. Interestingly, isolated bacteroidetes such as Algoriphagus sp. and Polaribacter sp. could individually trigger complete Ulva morphogenesis and thus provide a novel mode of action for bacterial-induced algal development. This study also highlights that the accumulation of algal growth factors in a shallow water body separated from the open ocean by barrier islands might have strong implications to, for example, the wide usage of natural coastal seawater in algal (land based) aquacultures of Ulva.
- Macroalgal–bacterial interactions: identification and role of thallusin in morphogenesis of the seaweed Ulva (Chlorophyta)Publication . Wichard, Thomas; Ulrich, Johann F; Mohr, Jan Frieder; Kwantes, Michiel; Engelen, Aschwin; Weiss, Anne; Grueneberg, Jan; Deicke, Michael; Califano, Gianmaria; Alsufyani, TaghreedMacroalgal microbiomes have core functions related to biofilm formation, growth, and morphogenesis of seaweeds. In particular, the growth and development of the sea lettuce Ulva spp. (Chlorophyta) depend on bacteria releasing morphogenetic compounds. Under axenic conditions, the macroalga Ulva mutabilis develops a callus-like phenotype with cell wall protrusions. However, co-culturing with Roseovarius sp. (MS2) and Maribacter sp. (MS6), which produce various stimulatory chemical mediators, completely recovers morphogenesis. This ecological reconstruction forms a tripartite community which can be further studied for its role in cross-kingdom interactions. Hence, our study sought to identify algal growth- and morphogenesis-promoting factors (AGMPFs) capable of phenocopying the activity of Maribacter spp. We performed bioassay-guided solid-phase extraction in water samples collected from U. mutabilis aquaculture systems. We uncovered novel ecophysiological functions of thallusin, a sesquiterpenoid morphogen, identified for the first time in algal aquaculture. Thallusin, released by Maribacter sp., induced rhizoid and cell wall formation at a concentration of 11 pmol l-1. We demonstrated that gametes acquired the iron complex of thallusin, thereby linking morphogenetic processes with intracellular iron homeostasis. Understanding macroalgae-bacteria interactions permits further elucidation of the evolution of multicellularity and cellular differentiation, and development of new applications in microbiome-mediated aquaculture systems.
- Progress and future directions for seaweed holobiont researchPublication . Saha, Mahasweta; Dittami, Simon M.; Chan, Cheong Xin; Raina, Jean‐Baptiste; Stock, Willem; Ghaderiardakani, Fatemeh; John, Ann Mary Valathuparambil Baby; Corr, Shauna; Schleyer, Guy; Todd, Jonathan; Cardini, Ulisse; Bengtsson, Mia M.; Prado, Soizic; Skillings, Derek; Sonnenschein, Eva C.; Engelen, Aschwin; Wang, Gaoge; Wichard, Thomas; Brodie, Juliet; Leblanc, Catherine; Egan, SuhelenIn the marine environment, seaweeds (i.e. marine macroalgae) provide a wide range of ecological services and economic benefits. Like land plants, seaweeds do not provide these services in isolation, rather they rely on their associated microbial communities, which together with the host form the seaweed holobiont. However, there is a poor understanding of the mechanisms shaping these complex seaweed–microbe interactions, and of the evolutionary processes underlying these interactions. Here, we identify the current research challenges and opportunities in the field of seaweed holobiont biology. We argue that identifying the key microbial partners, knowing how they are recruited, and understanding their specific function and their relevance across all seaweed life history stages are among the knowledge gaps that are particularly important to address, especially in the context of the environmental challenges threatening seaweeds. We further discuss future approaches to study seaweed holobionts, and how we can apply the holobiont concept to natural or engineered seaweed ecosystems.