Fig 2. Responses of known osmoprotectants to sustained hyperosmotic salt stress.

(A) Fold changes relative to unstressed control conditions of 54 detected metabolites with confirmed osmoprotective activity listed in the DEOP database [36], as well as of additional relevant polyprenyl quinones. For each species, only osmoprotectants showing a significant response (|log₂ fold-change| ≥ 1, P < 0.05, multiple-testing corrected two-sided unpaired t-tests) in at least one stress intensity were considered. Duplicate names represent different ions of the same metabolite because accurate mass annotation was ambiguous; refer to S1 Data for complete annotations. Osmoprotectants were grouped based on their main chemical characteristics. (B) Baseline abundances of osmoprotectants at IC₀ (unstressed control condition). Data are represented as Z-scores to compare relative abundances between species. Small Z-scores (|Z| < 1) are not colored.