Developing a protocol for the effective aplication of Phaeobacter in Ulva cultures for pathogen control in IMTA-RAS

Poster.-- COST ACTION CA 20106: SeaWheat Ulva: Tomorrows "Wheat of the Sea", a Model for an Innovative Mariculture, 1st Conference: From fundamental biology to aquaculture: state-of-the-art, bottlenecks and gaps - Cádiz, Spain, 12-15 September 2022N

Shedding light on the Ulva holobiont: Alga-bacteria interactions with implications for integrated multitrofic aquaculture

Poster.-- Close Encounters IIM (3rd Kind), Vigo, 23 June 2022Macroalgae, like Ulva genus, provides an important niche for epiphytic biofilm-forming bacteria, including those of the genus Phaeobacter with the ability to antagonize fish pathogens such as Vibrio anguillarum, through the production of tropodithietic acid (TDA) [1–3]. P. gallaeciensis has previously demonstrated its effectiveness as a probiotic in aquaculture by reducing mortality in fish larvae experimentally infected with this pathogen as well as its colonization of U. ohnoi surface [1]. This colonization can be used as apathogen control strategy in multitrophic fish-algae cultures in recirculatingwater systems (IMTA-RAS), improving the health of the fish (Fig. 1).However, the optimal conditions for the culture of U. ohnoi could have a determining influence both on the maintenance of these biofilms and on the production of TDA, especially the intensity of lightN

How does light affect antibacterial activity of Phaeobacter in the Ulva ohnoi holobiont?

Poster.-- Close Encounters IIM (3rd Kind), Vigo, 23 June 2022Ulva spp is an economical relevant algal genus with several applications in the industry, including aquaculture It provides an important niche for biofilm forming bacteria, including species belonging to the genus Phaeobacter producing antibiotic compounds such as TDA Tropodithietic acid) with antagonistic activity towards fish pathogens such as Vibrio anguillarum It is thus, interesting from an economic point of view to understand the environmental conditions that promote the growth of Phaeobacter on Ulva spp surface, and its concomitant production of TDAN

How does light affect the presence and antibacterial activity of Phaeobacter in the Ulva ohnoi holobiont?

8th European Phycological Congress: "Scientific Opportunities for a Global Algal Revolution", 20-26 August, Brest (France)Ulva provides an important niche for biofilm-forming bacteria, such as the Phaeobacter genus, producing antibiotic compounds like TDA (tropodithietic acid) with antagonistic activity towards fish pathogens, including Vibrio anguillarum. It is, thus, interesting from an economic point of view to understand the environmental conditions that promote the presence of Phaeobacter on the surface of Ulva used in Integrated Multi-Trophic Aquaculture (IMTA), including the application as a biofilter of fish effluents. Upon inoculation of U. ohnoi with Phaeobacter sp. 4UAC3, it is maintained when U. ohnoi is kept in the dark, however, Phaeobacter sp. eventually disappears when the algae are growing under light in a regular photoperiod. Our study focused on the effect of light on (i) the metabolome of the Ulva holobiont in the two light regimes, (ii) the production of TDA by Phaeobacter forming a biofilm in U. ohnoi, (iii) the inhibition of V. anguillarum by Phaeobacter biofilms in U. ohnoi. Our results show (i) significant differences in the metabolome produced by the Ulva holobiont in the two light regimes, which may be responsible for the disappearance of Phaeobacter in the Ulva biofilm, (ii) an up-regulation of TDA on U. ohnoi cultivated in the dark, (iii) inhibition of V. anguillarum by Phaeobacter when forming a biofilm on U. ohnoi. Our results highlight the challenge of mastering seaweed physiology from the holobiont perspective for applications in aquacultureN

Shedding light on the Ulva holobiont: the role of light in interactions with Phaeobacter bacteria

8th European Phycological Congress, 20-26 August 2013, Brest (France)Natural populations of Ulva seem well adapted to conditions of light heterogeneity, and this adaptation could suggest the involvement of microbial interactions. Since the bacterial communities associated with Ulva spp. play an important role in morphogenesis and reproduction, as in the adaptation to stress, it is possible that bacteria are also important for Ulva spp. adaptation to light conditions. Moreover, Ulva spp. laminar thallus provides an important niche for biofilm-forming bacteria, including bacteria with antagonistic activity against other marine bacteria, such as those from the Phaeobacter genus that produce tropodithietic acid (TDA). The probiotic effect of U. ohnoi experimentally colonized with a Phaeobacter strain, previously isolated from Ulva spp., was demonstrated in experimental infections with V. anguillarum. Those results paved the way to the engineering of Ulvaassociated bacterial communities as strategy for disease control in fish-Ulva IMTA-RAS cultures. However, a negative influence of high light and U. ohnoi growth on the maintenance of Phaeobacter biofilms was observed. This did not happen when U. ohnoi was maintained in the dark, with no growth. Microbial communities and the exo-metabolome of Ulva surfaces were analysed to elucidate the underpinning mechanisms in the response to light variables. Light showed a significant effect in the metabolome produced by the U. ohnoi holobiont but did not affect significantly bacterial communities. Therefore Phaeobacter maintenance and TDA production would be affected by U. ohnoi physiology. Adapting Ulva cultivation within the IMTA-RAS systems to include light and dark phases, ensured Phaeobacter was retained and the probiotic effect promotedN