Introduction: Bioconvection, a phenomenon characterized by the collective upward swimming of motile microorganisms, has mainly been investigated within controlled laboratory settings, leaving a knowledge gap regarding its ecological implications in natural aquatic environments. This study aims to address this question by investigating the influence of bioconvection on the eco-physiology of the anoxygenic phototrophic sulfur bacteria community of meromictic Lake Cadagno.

Methods: Here we comprehensively explore its effects by comparing the physicochemical profiles of the water column and the physiological traits of the main populations of the bacterial layer (BL). The search for eco-physiological effects of bioconvection involved a comparative analysis between two time points during the warm season, one featuring bioconvection (July) and the other without it (September).

Results: A prominent distinction in the physicochemical profiles of the water column centers on light availability, which is significantly higher in July. This minimum threshold of light intensity is essential for sustaining the physiological CO ₂ fixation activity of Chromatium okenii , the microorganism responsible for bioconvection. Furthermore, the turbulence generated by bioconvection redistributes sulfides to the upper region of the BL and displaces other microorganisms from their optimal ecological niches.

Conclusion: The findings underscore the influence of bioconvection on the physiology of C. okenii and demonstrate its functional role in improving its metabolic advantage over coexisting phototrophic sulfur bacteria. However, additional research is necessary to confirm these results and to unravel the multiscale processes activated by C. okenii’s motility mechanisms.

Title	Published in	Year	Views	Downloads

Motile bacteria leverage bioconvection for eco-physiological benefits in a natural aquatic environment	Frontiers in microbiology	2023	59	44
Bioconvection-Mediated Microbial Ecophysiology in the Chemocline of Meromictic Lake Cadagno		2023	308	47
Anoxygenic photo- and chemo-synthesis of phototrophic sulfur bacteria from an alpine meromictic lake	FEMS microbiology ecology	2021	123	215

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Di Nezio, Francesco