Effect of essential oil- and iodine treatments on the bacterial microbiota of the brown alga Ectocarpus siliculosus
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Effect of essential oil- and iodine treatments on the bacterial microbiota of the brown alga Ectocarpus siliculosus Bertille Burgunter-Delamare 1
&
Catherine Boyen 1 & Simon M. Dittami 1
Received: 26 May 2020 / Revised and accepted: 28 September 2020 # Springer Nature B.V. 2020
Abstract Macroalgae live in tight association with bacterial communities, which impact most aspects of their biology. Clean, ideally axenic, algal starting material is required to control and study these interactions. Antibiotics are routinely used to generate clean tissue; however, bacterial resistance to antibiotics is increasingly widespread and sometimes related to the emergence of potentially pathogenic, multi-resistant strains. In this study, we explore the suitability of two alternative treatments for use with algal cultures: essential oils (EOs; thyme, oregano and eucalyptus) and povidone-iodine. The impact of these treatments on bacterial communities was assessed by bacterial cell counts, inhibition diameter experiments and 16S-metabarcoding. Our data show that thyme and oregano essential oils (50% solution in DMSO, 15 h incubation) efficiently reduced the bacterial load of algae without introducing compositional biases, but they did not eliminate all bacteria. Povidone-iodine (2% and 5% solution in artificial seawater, 10 min incubation) both reduced and changed the alga-associated bacterial community, similar to the antibiotic treatment. The proposed EO- and povidone-iodine protocols are thus promising alternatives when only a reduction of bacterial abundance is necessary and where the phenomena of antibiotic resistance are likely to arise. Keywords Antibiotics . Essential oils . Povidone-iodine . Brown algae . Microbiome . Metabarcoding
Introduction The biology of macroalgae can only be fully understood by taking into account the interactions with their microbiomes which impact their health, performance and resistance to stress (Goecke et al. 2010). Together both components form a singular functional entity, the holobiont (Margulis 1991). Studying holobiont systems implies studying the individual components of the holobiont, their diversity, their activities and the (chemical) interactions between them (Goecke et al. 2010; Wahl et al. 2012; Hollants et al. 2013; Dittami et al. 2020). Elucidating these interactions requires controlled algal-bacterial co-cultivation experiments to test hypotheses about the functions of specific microbes. Supplementary Information The online version of this article (https:// doi.org/10.1007/s10811-020-02286-y) contains supplementary material, which is available to authorized users. * Bertille Burgunter-Delamare [email protected] * Simon M. Dittami [email protected] 1
Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M) Station Biologique de Roscoff, 29680 Roscoff, France
This, in turn, equally depends on the isolation of bacterial strains and the availability of aposymbiotic algal starting material, i.e. algae without the presence of any sy
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