A recent study has uncovered that certain bacteria in Croatia’s freshwater lakes engage in „selfish polysaccharide uptake,“ a behavior where they internalize entire sugar molecules before digesting them, rather than digesting them externally. This mechanism allows these bacteria to hoard nutrients, potentially disrupting the natural nutrient cycling and food web dynamics in the lakes. The research, published in Cell Reports, highlights the ecological implications of this behavior, especially in the context of climate change.
Comparative study of two croatian lakes
The researchers conducted a comparative study on two Croatian lakes: Kozjak Lake, located in the northern part of Plitvice Lakes National Park, and Crniševo Lake, situated in a Mediterranean climate. Kozjak Lake is oligotrophic, characterized by low nutrient and algae levels, and experiences freezing temperatures in winter. In contrast, Crniševo Lake is mesotrophic, with higher nutrient and algae levels, and does not freeze during winter. This comparison provided insights into how different environmental conditions influence bacterial behavior.
Seasonal variations in bacterial activity
The study found that selfish bacterial activity varied seasonally in both lakes. In Crniševo Lake, selfish activity peaked during summer following a phytoplankton bloom when nutrients were abundant. Conversely, in Kozjak Lake, selfish activity was highest during winter, a period when nutrients were scarce. This finding suggests that bacterial behavior is influenced by seasonal changes in nutrient availability.
The researchers suggest that the behavior of these „selfish“ bacteria could have significant implications for the food web and overall ecosystem health in freshwater lakes. With climate change potentially altering nutrient availability and temperature regimes, understanding these microbial behaviors becomes crucial for predicting and managing the impacts on freshwater ecosystems.
Original publication: DOI: 10.1016/j.celrep.2025.115415
