Interaction between fish probiotic roseobacters and the natural microbiota in aquaculture settings

• Main Author: Dittmann, Karen Kiesbye
• Format: Book
• Language: English
• Published: Technical University of Denmark 2019
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/good_health_and_well_being; SDG 3 - Good Health and Well-being; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; SDG 14 - Life Below Water; Scophthalmus maximus; Turbot
• Online Access: https://orbit.dtu.dk/en/publications/d84f19eb-9738-4fd4-b4da-d737d543e99d; https://backend.orbit.dtu.dk/ws/files/196724214/Final_KKD_Thesis_30_05_2019_2_compile_rev5.pdf

Aquaculture is the fastest growing protein producing sector in the world and this growth is required to feed the growing world population. Microbial diseases are a major bottle-neck in aquaculture, which must be controlled to avoid great, economic losses. Adult fish can be vaccinated against the most common bacterial diseases. However, the vaccines cannot be used on fish larvae because they have underdeveloped immune systems. Antibiotics are commonly used for acute treatment of infection, however, this increases the risk of antibiotic resistance dissemination. Therefore, more sustainable, preventive measures are sought and probiotics has been proposed as one of the solutions. Probiotics are “live organisms which when administered in adequate amounts confer a health benefit on the host” (FAO and WHO, 2001). Tropodithietic acid (TDA) producing members of the Roseobacter group, such as Ruegeria spp. and Phaeobacter spp., have potential as probiotics in aquaculture. They have repeatedly been isolated from aquaculture environments and they can reduce mortality of fish larvae challenged with pathogens. However, it is uncertain how the probiotic treatment affects the commensal microbiome of the larvae. The purpose of the present PhD project was to determine how probiotic Phaeobacter inhibens affect the natural microbiota in marine eukaryote systems related to aquaculture. Given that roseobacters are commonly found in complex communities of marine eukaryotes in nature and that they are indigenous to the aquaculture environment, the main hypothesis of this work is that P. inhibens can establish itself in microbiomes associated with aquaculturerelated eukaryotes and protect the host with minor impact on the commensal bacteria. In this study, 16S rRNA amplicon taxonomics was used to characterize the microbiota of different trophic levels – Tetraselmis suecica (microalga), Acartia tonsa (copepod), and Scophthalmus maximus (turbot) larvae – and determine the changes in diversity induced by treatment with probiotic P. ...