Mary, Mary, quite contrary, how does your (bacterial) garden grow?

To celebrate World Oceans Day 2019 – read more about Mahasweta Saha and Florian Weinberger‘s paper on microbial gardening below. 

This classic nursery rhyme is very much applicable to our recently published Journal of Ecology study. How? To answer that I have a question for you: what do we have in common between a seaweed and a pro-biotic yoghurt?

Well, they both have good bacteria. Like we eat pro-biotic bacteria to promote good gut microbiota, our study found that seaweeds can promote the settlement of good bacteria on their surface while reducing settlement by pathogenic bacteria. How do they do that? They employ their surface chemistry to modify, or rather manipulate, the colonization by bacterial allies and enemies to the benefit of resistance against disease.

We found that the surface microbiome of the invasive red alga Gracilaria vermicullophylla (recently renamed as Agarophyton vermicullophylum) harbours both protective and pathogenic bacteria. However, we found that the protective bacteria can provide resistance against pathogenic ones. Interestingly, the alga can selectively encourage recruitment of the “good” ones while discouraging the “bad” ones.

The capacity of an aquatic macrophyte to chemically “garden” protective micro‐organisms to the benefit of strengthened disease resistance is demonstrated for the first time – making this study novel and potentially significant for seaweed farming industries.

Such a role of surface chemistry in “gardening” of microbes as found in the study could also be applicable to other host plant-microbe interactions. We think that our results may open new avenues towards manipulation of the surface microbiome of seaweeds via chemical gardening, enhancing sustainable production of healthy seaweeds.

Mahasweta Saha, Plymouth Marine Lab, UK

Read the full paper: Microbial “gardening” by a seaweed holobiont: Surface metabolites attract protective and deter pathogenic epibacterial settlement. You can also read the GEOMAR Helmholtz Centre for Ocean Research Kiel and Plymouth Marine Laboratory press release for this paper. 

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