The largest study ever conducted on nudibranchs reveals previously unknown bacteria of pharmaceutical interest from museum samples of Spanish specimens
The Microbial Single-Cell Genomics research group at the Institute of Integrative Systems Biology (I2SysBio, UV-CSIC) has led the largest microbial study of nudibranchs carried out to date, proposing a new technique based on the analysis of museum specimens for the detection of beneficial bacteria associated with marine molluscs. The study, published in Microbiome, has led to the discovery of new symbiotic bacteria with the potential to produce bioactive compounds of pharmaceutical interest, demonstrating the value of museum collections for the study of microbial diversity.
28 de july de 2026
The research, entitled “Museomics reveals uncultured symbionts with biosynthetic potential in nudibranchs”, was coordinated by the Microbial Single-Cell Genomics group, led by Maria Dzunkova, and involved the Autonomous University of Madrid and the CIBC-UAM (CSIC, Madrid), the Centre for Microbiome Research at Queensland University of Technology (Australia), the Earlham Institute (United Kingdom), the University of the Basque Country, the Real Club Náutico de San Sebastián, as well as research staff from I2SysBio belonging to various groups.
Nudibranchs, commonly known as sea slugs, are gastropod molluscs characterised by their striking colours. Due to the evolutionary loss of their shell, they have had to develop alternative strategies to defend themselves against predators, such as chemical substances. “Although some of these compounds have attracted interest due to their potential biomedical applications, until now very little was known about the role played by the bacteria associated with these animals,” explains Dafne Porcel, one of the study’s authors.
22 species collected between 1992 and 2022
To address this question, the researchers analysed small tissue samples from 54 specimens belonging to 22 species of nudibranchs, collected between 1992 and 2022. Using metagenomic techniques, they were able to reconstruct microbial communities and bacterial genomes without the need for further sampling campaigns or impacting natural populations.
The study doubled the number of microbial datasets available for nudibranchs and revealed that most of these species do not harbour permanent dominant symbiotic bacteria. However, the researchers identified two previously unknown bacterial groups, specifically associated with nudibranchs of the genera Polycera and Felimare, native to the Spanish coast.
Discovery of new bacteria
“These new bacteria, named Candidatus Polyceribacter and Candidatus Felimaribacter, belong to microbial groups that are extremely rare on a global scale and contain gene sets related to the production of specialised metabolites that could be used by nudibranchs as chemical defence mechanisms,” says Porcel.
The study’s findings suggest that certain species of nudibranchs have developed evolutionary associations with specific bacteria, which are capable of providing unique metabolic functions, such as chemical defence. This may represent a new, as yet unexplored avenue for discovering natural compounds of medical interest.
The study therefore demonstrates, on the one hand, the potential of museomics for analysing microbial communities in species that are difficult to collect or endangered, and, on the other, the value that nudibranchs and their associated bacteria may hold as a source of compounds of pharmaceutical interest.
Article reference: Porcel Sanchis, D., Pola, M., Engelberts, J.P., Guerra-Font O., Messer, L., Alberola-Mora, I., Escobar Sáez, L., Pérez Gómez, N., Portolés Campo, Á., Valero-Tebar, J., Naya Garmendia, L.M., Preciado Barahona, J.C., Gil García, R., Arnau, V., McIlroy, S.J., Džunková, M. (2026). “Museomics reveals uncultured symbionts with biosynthetic potential in nudibranchs”. National Library of Medicine. DOI: 10.1186/s40168-026-02456-z