Polyunsaturated aldehydes induce distinct proteomic responses in two diatom-associated bacterial communities.

Diatom-derived polyunsaturated aldehydes (PUAs) significantly influence marine bacterial dynamics, yet the underlying proteomic mechanisms remain elusive. We employed high-resolution comparative proteomics to decipher the functional reprogramming of two bacterial communities-one naturally associated with a PUA-producing diatom (N-community) and another with a non-PUA producing (I-community)-under ecologically relevant PUA exposure. While growth rates and cell densities remained unaffected, indicating an absence of acute toxicity, proteomics revealed pronounced community-specific reorganization. N-community displayed stable, regulation-oriented adjustments consistent with physiological accommodation, whereas I-community exhibited dose-dependent stress responses at the endpoint of the growth curve, shifting toward protein repair and antioxidant defense. Our findings demonstrate that PUAs trigger profound proteomic reprogramming conditioned by the communities' prior ecological history. This functional divergence provides a molecular basis for understanding bacterial fitness and succession during diatom blooms, where PUA-mediated interactions could act as a selective filter shaping the phycosphere's microbial landscape.