Boundaries of photosynthesis: adaptations of carbon fixation in extreme environments

Extreme environments challenge fundamental pillars of photosynthesis: light capture and carbon fixation. Organisms thriving in extreme conditions, such as high and low temperatures, extreme pH levels, and high salinity, have evolved remarkable adaptive mechanisms allowing them to sustain photosynthesis. Research into these adaptations has expanded our understanding of the limits and evolution of photosynthesis, while also providing promising biotechnological applications. In this review, we explore the adaptations that tolerant and extremophilic photosynthetic organisms have evolved, overcoming these environmental challenges while maintaining photosynthetic functionality. These adaptations include modifications in photosystems and electron transport chain components, the development of photoprotective mechanisms, the use of unique CO₂-concentrating mechanisms (CCMs), and fine-tuning of Rubisco's kinetic properties and concentration. Our aim is to provide the basis for future research in extremophile biology while highlighting its applications in biotechnology.