#FEMSmicroBlog: Mangrove trees in the Caribbean as cyanobacterial reservoirs


Cyanobacteria are important for aquatic ecosystems as they produce numerous bioactive molecules. Many cyanobacteria form large biofilms on different surfaces which can even become visible to the naked eye. The study “Genomes of nine biofilm-forming filamentous strains of Cyanobacteria (genera Jaaginema, Scytonema, and Karukerafilum gen. nov.) isolated from mangrove habitats of Guadeloupe (Lesser Antilles)” identified metabolically diverse cyanobacteria species in mangrove biofilms. In this interview, Sebastien Duperron explains why biodiversity is not only about large plants or animals but also involves the sometimes overlooked microbial world. #TheCulturePlate


Can you summarize the significance of your paper for microbiologists outside of your field?

In tropical ecosystems, cyanobacterial biofilms are particularly abundant due to favorable conditions. The high light intensity, long days and warm temperature provide cyanobacteria with optimal growth conditions. Yet, they have received little attention and scientists know very little about the residing species and their metabolic products.

Notably, in the extensive mangroves of Guadeloupe in the Lesser Antilles in the Caribbean Sea, several interesting bacteria and archaea have recently been discovered. That’s why in our study, we set out to characterize biofilm samples from mangrove habitats from this area.

Mangrove trees in Guardelope. Courtesy of Sebastien Duperron.

We isolated nine strains, of which five correspond to new strains within the already-known genera Scytonema and Jaaginema. The four other strains represent a novel genus, which we coined Karukerafilum. Native Caribbean inhabitants called Guadeloupe ‘Karukera’ before colonization and it means ’island of beautiful waters’.

Within each of these genera, strains have variable metabolic abilities. For example, only two of the four Karukerafilum strains contain genes for nitrogen fixation, an ecologically important function in mangrove ecosystems.


What can policymakers learn from your research results?

Cyanobacteria-dominated biofilms can be found on a variety of surfaces in mangrove ecosystems, including sediment, tree bark, and even waste. Here, they may provide habitats for undiscovered species playing major roles in the ecosystem. They fix not only carbon through photosynthesis but also nitrogen to make it available to other organisms.

Besides important ecological services, cyanobacterial biofilms represent an untapped reservoir of bioactive compounds that may be of pharmacological interest based on nature-inspired solutions. Policymakers need to understand that bacteria are key actors of ecosystems and their services, and protect habitats or ecosystems as a whole.

This is particularly true for mangroves as they play major roles in coastline protection and fish reproduction, amongst others. Yet, coastal forests are vulnerable and under high anthropic pressure due to pollution, waste disposal, and the exploitation of wood.


What is a surprising finding you stumbled upon while doing your research?

When characterizing bacterial communities in mangrove biofilms, we were surprised to see how species-rich they were, and how different one biofilm was from another. This diversity is certainly something worth exploring further!

Light microscopy images of cyanobacterial strains.
Light microscopy images of cyanobacterial strains identified in Halary et al. (2023).


Why did you choose to dive into the topic of this paper?

Even though lots of work has been done on mangrove ecosystems, including in water and sediment microbiology, very little data was available regarding their biofilms. Yet, they are everywhere!

We were curious to learn about this underexplored bacterial lifestyle and chose to focus on cyanobacteria. They are important primary producers and are able to synthesise a broad range of bioactive compounds with potential applications.

Once in the field, the only possible first step was simply to look for and sample any greenish to brownish crust and hope to find something interesting!


You decided to opt for the Transparent Peer Review route offered by FEMS Microbes. What motivated you to do so, and what are the benefits in your opinion?

Science publishing is a complex process and the critical assessment by reviewers is a very important step to improve a paper’s quality. In our paper, we received very insightful comments that challenged and motivated us to improve our description of cyanobacteria and their genomes.

We are grateful for the input from the reviewers and think the resulting paper was greatly improved. We think that the reviewer’s work is not acknowledged enough.


About the author of this blog

As a professor at the French Museum of Natural History, Sebastien Duperron‘s research aims at deciphering the role of interactions involving microorganisms in aquatic ecosystems. He is particularly interested in how these interactions, with other microorganisms or with larger hosts, contribute to the functioning of ecosystems and may mitigate the effect of human-induced (contaminated peri-urban lakes, mangroves) or natural stress (hypersaline lakes, deep-sea hydrothermal vents).

About this blog section

#BehindThePaper posts on the #FEMSmicroBlog aim to bring science closer to different audiences and to tell more about the scientific or personal journey to come to the results.

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