Our researchers co-authors of a publication on freshwater Nanopelagicales bacteria

16 02 2026

Dr Anna Bednarska and Dr hab. Mirosław Ślusarczyk, professor at the University of Warsaw, from the
Institute of Ecology, Faculty of Biology, University of Warsaw, are co-authors of a publication focused
on improving our understanding of freshwater bacteria from the order Nanopelagicales, which inhabit
lakes and rivers. The paper entitled “Ecological success in freshwater lakes: insights from novel
cultivated lineages of the abundant Nanopelagicales order” was published in the journal Microbiome
and is the result of work carried out by the international Pan-European Lake Sampling – Microbial
Eco-genomics (PELAGICS) consortium, funded by the EXPRO programme of the Czech Science
Foundation.

Nanopelagicales are bacteria with very small cells and highly reduced genomes, adapted to life in
environments poor in nutrients. For many years, however, they posed a challenge for laboratory
cultivation. In this study, the authors successfully cultivated and sequenced 72 new isolates from 20
locations, including five lakes in Poland, which allowed them to describe numerous new species.

Analyses of environmental data showed that only a few Nanopelagicales species are truly widespread
and reach high abundances. Their occurrence is seasonal, with clear peaks in spring and autumn. The
dominance of particular species depends mainly on water pH and the availability of organic
compounds.

The authors also identified traits that support the survival of Nanopelagicales in nutrient-poor
ecosystems. One of these is the presence of rhodopsin, a protein that enables the use of light as an
additional energy source. Another important feature is the simplification of metabolism through the
reduction of part of the pentose phosphate pathway, which in many organisms is involved in the
production of compounds needed for biomass synthesis. Limiting this pathway reduces the cell’s
demand for energy and resources, which is advantageous in environments with very low nutrient
availability and allows metabolism to focus on processes essential for survival.

In addition, these bacteria show microdiversification, meaning high genetic variability even between
very closely related lineages. This variability includes genes encoding surface proteins involved in
interactions with the environment, such as recognition by predatory protists and viruses. Such
diversity may hinder effective detection and infection of the bacteria. An important role is also played
by so-called genomic islands, which are variable regions of the genome containing genes related to the
uptake and use of different organic compounds. This enables specialization of individual lineages and
their coexistence within the same water body.

We congratulate the authors on this interesting study.

The publication is available at: https://link.springer.com/article/10.1186/s40168-025-02272-x