Adaptive Laboratory Evolution of Kitasatospora sp. SeTe27 Enhances Selenite Tolerance and Alters Cellular Morphology and Redox Stability

The effects of oxyanions selenite (SeO₃²⁻) in soils raise significant concerns in ecotoxicology and microbiology due to their interactions with mineral particles and microorganisms1. The actinomycete Kitasatospora sp. SeTe27 was studied to assess its evolutionary response to selenite through Adaptive Laboratory Evolution (ALE), a technique that simulates natural evolution and enhances microbial fitness under specific growth conditions2. This strain, originally isolated from uncontaminated soil, represents a unique model system, having never encountered the prooxidant selenite oxyanions. Although the Kitasatospora wild-type (WT) strain exhibited intrinsic tolerance to selenite, its bacterial growth and oxyanion removal capacity were limited compared to other environmental isolates. A comparison between the WT strain and the ALE-derived variant revealed distinct morphological and physiological adaptations. While both strains exhibited similar fatty acid profiles, only WT cells displayed hyphae aggregation and extensive membrane-like vesicle production when exposed to selenite. In contrast, the ALE-derived variant strain exhibited hyphae morphological features similar to the WT under unchallenged conditions, indicating an enhanced resilience to selenite toxicity. Moreover, the ALE variant showed enhanced selenite uptake and redox stability. Whole-genome sequencing revealed specific missense mutations in genes linked to anion transport and primary and secondary metabolisms in the ALE variant. These genetic modifications suggest a metabolic shift, where energy-intensive processes are attenuated to prioritize selenite bioprocessing, improving bacterial survival under oxidative stress. These findings highlight key mechanisms involved in the adaptation of Kitasatospora sp. SeTe27 to selenite stress and provide insights into strategies for coping with selenium pollution. Furthermore, they underscore the potential of non-conventional bacterial genera, such as Kitasatospora, for biotechnological applications. 1. Cappelletti, M., Funari, V., Gasparotto, G., Dinelli, E., Zannoni, D. (2021). Selenium in the environment. In: Lens, P.N.L., Pakshirajan, K. (Eds.), Environmental Technologies to Treat Selenium Pollution: Principles and Engineering. IWA Publishing, UK. pp. 101–130. https://doi.org/ 10.2166/9781789061055_0003. 2. Sandberg, T.E., Salazar, M.J., Weng, L.L., Palsson, B.O., Feist, A.M. (2019). The emergence of adaptive laboratory evolution as an efficient tool for biological discovery and industrial biotechnology. Metab. Eng., 56, 1–16. https://doi.org/10.1016/J.YMBEN.2019.08.004.