The adaptation mechanism of desert soil cyanobacterium Chroococcidiopsis sp. to desiccation

Desiccation is a common stress for organisms living in desert soil. Chroococcidiopsis sp. is the dominant species in the soil microbial community of desert regions. Some species of Chroococcidiopsis sp. are highly tolerant to desiccation, making them a good biological system for soil restoration in desert regions, but their adaptation mechanisms to desiccation are not well understood. In this study, different desiccation levels of desert regions were simulated in terms of relative humidity to investigate the adaptation of desert cyanobacterium Chroococcidiopsis sp. ASB-02 to desiccation. Chroococcidiopsis sp. ASB-02 exhibited the ability to rapidly restore PSII activity under desiccation-rehydration conditions. Desiccation-induced oxidative stress is a common feature and the Chroococcidiopsis sp. ASB-02 activated diverse antioxidant genes to eliminate oxidative products. When exposed to desiccation-induced water stress, Chroococcidiopsis sp. ASB-02 can slow water loss and regulate osmotic pressure by enhancing the synthesis of exopolysaccharides and intracellular sucrose. However, under extreme desiccation stress, trehalose is crucial in regulating the osmotic potential of Chroococcidiopsis sp. ASB-02. When the relative humidity is ≤ 56%, with the continuous loss of cellular water, Chroococcidiopsis sp. ASB-02 responds to reduced metabolic activity in the cell by initiating energy-saving pathways and enhancing transcription mechanisms. This study provides a theoretical basis for understanding the adaptation mechanisms of desert cyanobacterium Chroococcidiopsis sp., which is important for soil restoration in desert regions.