BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Why Algal Blooms Suppress Duckweed Growth: Mechanisms Behind Growt h Inhibition DTSTART;VALUE=DATE-TIME:20260930T080000Z DTEND;VALUE=DATE-TIME:20260930T081500Z DTSTAMP;VALUE=DATE-TIME:20260916T013402Z UID:indico-contribution-435-2914@cern.ch DESCRIPTION:Speakers: Sandor Szabo (University of Nyiregyhaza)\nIn duckwee d pond systems established either for biofiltration or biomass production\ , excessive proliferation of planktonic algae reduces ecosystem services. In this study we revealed those algal related mechanisms resulting duckwee d growth inhibition. We isolated 26 algal species from duckweed covered me socosms and measured their impact on axenic culture of Lemna gibba. At low duckweed coverage (<50%)\, 18 algal and cyanobacterial species significan tly reduced the growth rate of duckweed. The strongest inhibitory effects were exerted by unicellular green algae. When the combined effects of domi nant algal species were examined\, all tested algae drastically inhibited duckweed growth. The elemental flux between the water\, algal biomass and Lemna fronds was followed in time. Algal biomass increase was closely ass ociated with the depletion of nutrients from the water column. In aquarium experiment\, under low and moderate nitrogen concentrations together with the absence of algal shading\, algae significantly inhibited the growth a nd chlorophyll content of Lemna by 60-80%. The algal inhibitory effect wea kened with increasing nitrogen concentration and under conditions of stron ger shading affecting the algae. Laboratory experiments demonstrated that duckweed growth was most strongly inhibited by algal-induced nitrogen defi ciency\, followed by elevated pH (10.2)\, phosphorus deficiency\, and iron deficiency\, resulting in growth inhibition of 72%\, 52%\, 51%\, and 47%\ , respectively. By the final day of the experiment\, both algal-induced ni trogen depletion and high pH completely reduced duckweed growth.\n\nhttps ://indico.unina.it/event/117/contributions/2914/ LOCATION:Department of Agricultural Sciences of the University of Napoli F ederico II\, Portici\, Italy Sala Cinese URL:https://indico.unina.it/event/117/contributions/2914/ END:VEVENT BEGIN:VEVENT SUMMARY:Microbiome Assembly and Transmission Across the Turion–Vegetativ e Growth Cycle in Spirodela polyrhiza DTSTART;VALUE=DATE-TIME:20260930T074500Z DTEND;VALUE=DATE-TIME:20260930T080000Z DTSTAMP;VALUE=DATE-TIME:20260916T013402Z UID:indico-contribution-435-2913@cern.ch DESCRIPTION:Speakers: François Prudot D'Avigny (INRAe BGU)\nDuckweeds are small\, fast-growing aquatic plants that provide a useful model for study ing plant–microbiome interactions in aquatic environments. Among them\, Spirodela polyrhiza is particularly interesting because it can switch from active vegetative growth to dormant turion formation (starch-rich vegetat ive propagules)\, in a turion–plant–turion cycle that allows to examin e plant-associated microbiome transmission across contrasting developmenta l stages within a clonal lineage. We investigated the transmission of epip hytic and endophytic microbiomes across the life cycle of S. polyrhiza. Sp ecifically\, we examined whether microbial communities associated with tur ions persist during germination and vegetative growth\, and whether newly formed turions retain microbial signatures from the preceding plant stage. We also compared epiphytic and endophytic fractions to determine whether they display distinct patterns of continuity\, turnover\, and reassembly. Our results indicate that microbiome transmission across the growth cycle involves both persistence and community reassembly. Turion-associated comm unities partially overlapped with those of fronds and roots\, showing that a subset of microorganisms was retained across developmental transitions\ , yet with substantial community turnover\, and variation associated with plant genotype and the surrounding medium. Epiphytic and endophytic commun ities were not completely differentiated based on their overall compositio n. We hypothesize that endophytic communities show stronger persistence ac ross developmental transitions\, whereas epiphytic communities are more st rongly reshaped by interactions with the surrounding aquatic environment. By resolving microbiome dynamics across the turion–plant–turion cycle\ , this study clarifies the role of dormant vegetative propagules in mainta ining host-associated microbial communities and improves our understanding of microbiome transmission in clonal aquatic plants.\n\nhttps://indico.un ina.it/event/117/contributions/2913/ LOCATION:Department of Agricultural Sciences of the University of Napoli F ederico II\, Portici\, Italy Sala Cinese URL:https://indico.unina.it/event/117/contributions/2913/ END:VEVENT BEGIN:VEVENT SUMMARY:Potential cobalamin-producing Wolffia globosa-associated microbiom e DTSTART;VALUE=DATE-TIME:20260930T073000Z DTEND;VALUE=DATE-TIME:20260930T074500Z DTSTAMP;VALUE=DATE-TIME:20260916T013402Z UID:indico-contribution-435-2912@cern.ch DESCRIPTION:Speakers: Arinthip Thamchaipenet (Kasetsrat University)\nPoten tial cobalamin (vitamin B12)-producing *Wolffia globosa*-associated bacter ia were investigated through shotgun metagenomic sequencing analysis. Taxo nomic classification assigned microbiomes consisting of 5 phyla\, 8 classe s\, 36 families\, and 68 genera. High-quality metagenome-assembled genomes (MAGs) were assigned to *Allorhizobium* sp.\, *Alsobacter* sp.\, *Bosea* sp.\, *Bradyrhizobium* *huaxiensis*\, *Brevundimonas* sp.\, *Methylophilus * sp.\, *Microbacterium* sp.\, *Mycobacterium* sp.\, *Neoroseomonas* *mari na*\, *Nevskia* sp.\, *Novosphingobium* sp.\, *Phenylobacterium* sp.\, *Ps eudonocardia* *carboxydivorans*\, *Rhizobium* sp.\, *Rhizorhabdus* sp.\, * Roseomonas* sp.\, *Sphingomonas* sp.\, and *Xanthomonas* *sontii*. Functio nal annotation across all MAGs revealed potential pathways related to arom atic compound degradation\, cofactor and vitamin metabolism\, serine and t hreonine metabolism\, nitrogen metabolism\, and other carbohydrate metabol ic processes. Several MAGs contained complete modules of cobalamin biosynt hesis including *hem*\, *cob*\, *cbi* genes responsible for corrin ring sy nthesis\, cobalt transport\, lower-ligand formation\, and final cobalamin assembly. Interestingly\, the definitive molecular marker for active B12 p roduction\, *bluB*\, was identified in several MAGs. Subsequently\, eight bacterial genera were isolated using culture dependent methods and three n ovel species have been proposed. Co-cultivation experiments are underway t o understand the associated B12 production of *W. globosa* holobionts.\n\n https://indico.unina.it/event/117/contributions/2912/ LOCATION:Department of Agricultural Sciences of the University of Napoli F ederico II\, Portici\, Italy Sala Cinese URL:https://indico.unina.it/event/117/contributions/2912/ END:VEVENT BEGIN:VEVENT SUMMARY:Vitamin B₁₂ Accumulation in Duckweed Emerges from a Cooperativ e\, Environmentally Responsive Microbiome DTSTART;VALUE=DATE-TIME:20260930T071500Z DTEND;VALUE=DATE-TIME:20260930T073000Z DTSTAMP;VALUE=DATE-TIME:20260916T013402Z UID:indico-contribution-435-2911@cern.ch DESCRIPTION:Speakers: Osnat Gillor (Ben Gurion University of the Negev)\nV itamin B₁₂ is synthesized exclusively by bacteria and archaea\, yet du ckweeds accumulate bioavailable B₁₂ despite lacking the capacity to pr oduce or use it. We asked how this function is organized within the duckwe ed microbiome\, and whether cultivation conditions could enhance it.\nBioa vailable B₁₂ was detected across rooted and rootless duckweed genera\, and in additional aquatic plants. Among 16 B₁₂-containing duckweed ha plotypes spanning seven species\, endophyte composition varied markedly\, but neither community structure nor predicted B₁₂-biosynthesis potenti al tracked host taxonomy\; distinct microbiomes converged on the same func tion. In the rootless species Wolffia globosa\, the endosphere formed a ho st-filtered community in which a subset of bacteria encoded complete or ne ar-complete cobalamin pathways\; most co-occurring taxa instead carried pa rtial pathways\, precursor-salvage genes\, or cobamide-remodeling capacity . Network analysis linked putative producers to salvagers\, and endophytic genomes carried fewer biosynthetic genes than related planktonic strains\ , suggesting adaptation to metabolic interdependence over autonomous produ ction. Experimental manipulation confirmed that B₁₂ production is a co mmunity-level trait. Epiphytic Rhizobium and Caulobacter isolates produced B₁₂ in culture\, but co-cultivation with duckweed did not increase pl ant B₁₂ and instead disrupted plant–microbiome performance. Cobalt s upplementation\, by contrast\, increased bioavailable B₁₂ up to fivefo ld without cost to growth\, and reshaped endophyte composition\, diversity \, and core-community membership in species-specific ways.\nOur results sh ow that B₁₂ accumulation in duckweed is an emergent property of a coop erative\, environmentally responsive microbiome\, not the output of a sing le producer. This positions duckweed as a tractable model for cobamide-med iated microbial interactions and a promising platform for microbiome-guide d B₁₂ biofortification.\n\nhttps://indico.unina.it/event/117/contribut ions/2911/ LOCATION:Department of Agricultural Sciences of the University of Napoli F ederico II\, Portici\, Italy Sala Cinese URL:https://indico.unina.it/event/117/contributions/2911/ END:VEVENT END:VCALENDAR