Microorganisms in aquaponics: Insights on the composition of the root microbiome of lettuces of varying age

Aquaponics is a developing, soilless production technique combining hydroponics and recirculating aquaculture and is now spreading worldwide. Nevertheless, several aspects of aquaponics still need research. Indeed, despite being key-players in the dynamic equilibrium of aquaponic systems, microorganisms and their roles in aquaponics are still scarcely known. The aim of this study is thus to explore the microorganisms communities thriving in the root compartments of lettuce in the closed-loop aquaponic system of Gembloux Agro-Bio Tech and to focus on the differences between the microbial communities of lettuce of varying age. Therefore, root samples were collected from lettuces of five different age groups and microorganisms from the rhizoplane and from the endosphere were harvested. DNA was then extracted and sequenced on an Illumina MiSeq platform, targeting the V1-V3 region of the 16S rRNA gene. Results show that no significant difference could be noted between the different age groups despite a visible trend on the Bray-Curtis PCoA. However, significant differences in alpha- and beta-diversity could be observed between the rhizoplane and endosphere compartments. In terms of taxonomy, the composition of the root community is similar to what can be found in the literature and coherent with the previous experiments conducted in the same aquaponic system.