Unveiling Bacterial Diversity in Es Trenc Salt Flats: A Deep Dive into Microdiversity


The definition and quantity of different types of bacteria in a natural population remain debated topics, yet they are crucial for understanding how these microbial communities impact health and the environment.

Photo: Microscopy image of Salinibacter ruber. Author: Tomeu Viver.


An international team of scientists, led by Ramon Rosselló-Móra from IMEDEA in Mallorca, Spain, Kostas Konstantinidis from the Georgia Institute of Technology in Atlanta, USA, and Rudolf Amann from the Max Planck Institute for Marine Microbiology in Bremen, Germany, have provided new insights into the structure of natural bacterial populations at an intra-species level.

The IMEDEA Marine Microbiology Group has been studying microbial diversity in hypersaline environments, such as the salt flats of s'Avall and Es Trenc in Mallorca, for nearly 25 years, as well as the theoretical and practical aspects of the species concept in bacteria. In this context, the model species Sal. ruber has been used to study the diversity of individuals within the same species coexisting in the same location and among different geographic locations.


This study represents the first step in demonstrating that bacterial species exist as discrete groups that separate from others by evolutionary leaps observable through genomic analysis.


In this study, the genomes of 138 strains of the species Salinibacter ruber, isolated from the solar salterns of Es Trenc in Mallorca and Fuerteventura in the Canary Islands, were sequenced. These genomes were then compared with metagenomes obtained from the same samples. The analysis revealed a discrete distribution of populations within the species, with a low average nucleotide identity (ANI) between 99.6% and 99.8%, indicating significant genetic diversity.

Using this ANI threshold, the researchers defined the term "genomovar" and established an ANI value >99.99% and a shared gene content >99.0% for the definition of strains.

When comparing the sequenced genomes with the metagenomes representing the natural population, the researchers estimated that, although the 138 studied strains constituted approximately 80% of the Sal. ruber population, the total population in a saltern consists of between 5,500 and 11,000 genomovars, most of which appear to be rare in their natural environment.

Furthermore, it was observed that the most cultivated strains in the laboratory did not necessarily represent the most abundant strains in the natural environment, indicating significant biases in cultivation methods.

These findings enhance our understanding of microbial diversity and the structure of natural bacterial populations, with important implications for microbial ecology and public health. Moreover, they underscore the importance of addressing intra-species diversity for a comprehensive understanding of microbial ecosystems. This study represents a significant advancement in our understanding of natural bacterial populations and provides a methodological framework and ANI thresholds that could benefit future research on microbial diversity.


Link to the original publication here.



This study has been the result of research led by Ramon Rossello-Mora and funded by projects from the Ministry of Science, Innovation and Universities of Spain (PGC2018-096956-B-C41, RTC-2017-6405-1, and PID2021-126114NB-C42), also co-financed by the European Regional Development Fund (FEDER), and carried out within the research activities of the "Maria de Maeztu" center accreditation CEX2021-001198. The international research team includes Konstantinos Konstantinidis (Georgia Institute of Technology, Atlanta, US), Rudolf Amann (Max Planck Institute, Bremen, Germany), and Luis Miguel Rodríguez (University of Innsbruck, Austria). Special thanks to the entire team at Es Trenc Salt Flats and Gusto Mundial Balearides, S.L. (Flor de Sal d'Es Trenc), and at the Salinas de Fuerteventura (Salinas del Carmen) for allowing access to their facilities and providing samples.