Hugo Sentenac: Biofilms, an underrated yet important way of life

In this new post, Hugo Sentenac, a PhD student at Labaoratoire Ecologie Fonctionnelle et Environnement (LEFE), Institut National Polytechnique de Toulouse, France, discusses his review paper: The significance of biofilms to human, animal, plant and ecosystem health—recently shortlisted for the 2022 Haldane Prize for Early Career Researchers.

About the paper

Microbes are everywhere: in soil, on rocks, in—and on—us, animals, plants, etc. All this is fairly well known, but what is less well known is that these microorganisms usually live in biofilms, i.e. inside a gelatinous matrix. The matrix acts as a fortress, allowing steady juxtaposition of microbes in space and time. Biofilms can be seen as cities of microbes, composed of hundreds or thousands of species that can interact like an ecosystem and exhibit properties that would not be observable in the same microbes in their planktonic life—cooperation between cells with signs of division of labour. It is these properties and stability that make biofilms and microbial communities in general so productive and important for life on Earth.

Abundant biofilm growing on a piece of wood placed in a Pyrenean mountain lake. Such a small amount of biofilm can contained hundreds of prokaryotic and micro-eukaryotic amplicon sequence variants (taxonomic units ­© Hugo Sentenac)

The primary objective of our paper was to review the role(s) and importance of biofilms for our health and that of animals, plants, and entire ecosystems. To this end, we used a holistic approach to summarise and synthesise existing information in an effective manner. The ubiquity and global relevance of microbes made the prospect of writing this paper both exciting and terrifying! But thanks to the confinement induced by COVID, I was able to really immerse myself in the literature and subsequently focus and produce what would be my first publication—in the end, the confinement had a silver lining. Like microbes in general, biofilm communities are generally beneficial for host and ecosystem health, although they can be detrimental when they are dominated by one single pathogenic or toxigenic species (e.g. Staphylococcus aureus for animal health or cyanobacteria for ecosystem health).

Ibon Acherito, our only study site located in Spain, where amphibian chytridiomycosis due to Bd emerged in 2002 and caused mass mortalities of the common midwife toad (Alytes obstetricans) (© Hugo Sentenac)

Another objective of this review was to highlight the gaps in knowledge about biofilms. We found that there is still a lot to learn about the effects of climate change (warming and drought), pollution, habitat destruction/degradation, our urbanised lifestyle, our use of antibiotics, etc., on the biofilms that live with us or in the environment, and, ultimately, on our health. Also, very little is known about the interactions between environmental biofilms and free-living pathogens that cause non-human diseases, and this was particularly relevant in the context of our research.

The systemic approach used in this paper—based on the common-sense analogy of health—has the advantage of helping to explain and conceptualise complex processes such as ecosystem functioning and the ecological drivers of health. It has also helped to break down the disciplinary silos inherent in the very disparate field of biofilm research and to comprehensively identify the known roles of biofilms and existing knowledge gaps. We have endeavoured to find compelling examples in order to integrate our work with ecological theories, and to propose new avenues of research. In particular, we have suggested that biofilms should be considered as ecosystems—with their own health—which should be closely monitored to ensure a sustainable future. For these reasons, this paper should be of interest to both laymen and specialists.

Pic rouge and Etangs de Bassiès (credit: Hugo Sentenac)

About the research

Our research is part of the GloMEc (Global change in Mountain Ecosystems) project, which focuses on lakes in the French Pyrenees. The GloMEc project aims to link changes in the biota of these lakes to environmental changes (e.g. climatic) or other threats (e.g. chemical pollution). An important part of the project was to study biodiversity in biofilms, which essentially formed the core of my PhD.

We are also studying the infection dynamics of major amphibian pathogens, in particular Batrachochytrium dendrobatidis (Bd). The latter is the causative agent of the panzootic chytridiomycosis, which has caused a significant decline in amphibian populations in the Pyrenees (and elsewhere). Part of our research is to test whether biotic environmental factors—such as zooplankton, biofilms and other microbiomes—are epidemiologically important in these fragile ecosystems. Ultimately, our aim is to provide further evidence that environmental changes can promote the emergence of infections and diseases.

Fieldwork is what I love most about this research! Hiking in the mountains and observing the wildlife are my favourite pastimes—being able to do so in the Pyrenees is a privilege. Even as a child, when I was hiking in the Pyrenees with my family, I would spend hours trying to catch frogs in small ponds. When I told my father that I had been awarded funding for a PhD involving amphibian sampling in the Pyrenees, he laughed and said that he never thought that the fact that I spent so much time catching amphibians as a child would come in handy at some point!

About the author

Hugo finally getting out of the lab to do some fieldwork in the stunning Neouvielle reserve, Pyrenees (FR­© Antoine Firmin)

My path to ecology has been winding. Fascinated by free-ranging animals, I first obtained a degree in veterinary medicine at VetAgro Sup Lyon (FR), where I developed an interest in wild animal diseases. My veterinary thesis focused on ecotoxicology and the possible causes of hatching failure in birds. Although I wanted to pursue an academic career in wildlife health research, I did not find the right opportunity and instead worked as a general veterinarian (mainly companion animals and farm animals, but also wildlife rehabilitation) for some years. I soon realised that the individual approach to medicine was not enough for me and that I had to contribute to the preservation of biodiversity. I undertook an MSc in wild animal health in London (UK), in which I had the chance to work on chytridiomycosis in amphibians with Prof. Andrew Cunningham at the Zoological Society of London and with Prof. Claudio Azat and Dr. Andrés Valenzuela-Sanchez in Chile. This was an exciting project that allowed me to immerse myself in epidemiology, ecology and conservation. I then had the opportunity to do a PhD with Prof. Dirk Schmeller and Dr. Adeline Loyau at the LEFE in Toulouse (FR), which I am about to finish in a few weeks. I hope to continue ecological research by studying the links between health and biodiversity.

What scares me the most about ecology is that it is extremely broad in that it covers literally all living things, and through my various experiences I have learned that living things are anything but simple! That said, you can study what you love the most and improve existing knowledge so that you can help to tackle the great challenges of our time (the loss of biodiversity due to human activities). This is a great feeling. If I had to give advice to young students, I would say to be persistent and always do things 100%, even if it doesn’t seem to be useful for your goals. I would advise them to work on projects that they are passionate about, but most of all with people they get on well with. Apart from hiking and wildlife watching, I am a keen rugby enthusiast and fan of the French national team (I can’t play anymore, I am getting old), and I also enjoy cycling and rock climbing. In my spare time, I also like to grow vegetables in a garden (as biodiverse as possible!). Last but not least, I am a father of two!

Hugo looking for tadpoles in Etang d’Arbu, FR—quite larger than the small ponds I was used to as a kid! (credit: Dirk Schmeller)

The best place to follow my research is on Twitter, and more information (including videos) can be found on the GloMEc project.

Enjoyed the blogpost? Read the research here!

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