Meromictic Lake Cadagno is a permanently redox-stratified lake in the Swiss Alps. This environment supports the growth of a dense community of anoxygenic phototrophic sulfur bacteria that form a distinct bacterial layer (BL) between the two layers, in the chemocline.

The study aimed to investigate the eco-physiological consequences of bioconvection, a phenomenon of self-sustaining transport driven by motile microorganisms in response to light and oxygen.

Our research included laboratory and field experiments that revealed phenotypic cell changes and metabolic activity in response to fluctuations in various physicochemical parameters between the wild and lab-grown bacterial populations. The seasonal dynamics of bioconvection and its impact on microbial ecophysiology were also investigated. The results highlight how bioconvection affects fitness and ecological niches within the bacterial community. Overall, the results indicate that bioconvection provides a competitive advantage to the responsible species, the motile bacterium Chromatium okenii, over the other anoxygenic phototrophs in the BL.