Pré-Publication, Document De Travail Année : 2023

Singlet oxygen-induced alteration of bacteria associated with phytodetritus: effect of bacterial pigments

Résumé

We sought to determine whether the presence of carotenoids actively protects bacteria associated with senescent phytoplankton cells from damage caused by singlet oxygen (1O2) resulting from the cessation of photosynthetic reactions. We irradiated senescent cells of the diatom Thalassiosira sp. associated with the bacterial strains Pseudomonas stutzeri (a ubiquitous planktonic unpigmented heterotrophic bacterium) or Dinoroseobacter shibae (an aerobic anoxygenic bacterium often associated with phytoplankton rich in the spheroidenone, carotenoid). The analysis focused on the photooxidation of bacterial membrane lipids (vaccenic acid) and the expression of genes involved in DNA repair systems. In P. stutzeri cells, 1O2 transferred from senescent algae was not completely scavenged by bacterial membrane MUFAs and reached the cytoplasm, allowing both 1O2 and UV radiation to cause DNA damage. In D. shibae, scavenging by bacterial membrane MUFAs quenching by spheroidenone allowed only a small fraction of 1O2 to reach the cytoplasm, where the efficient detoxifying activity of mutY limited their impact on the DNA of this strain, thus preventing oxidative stress. The fact that Rhodobacteriales is the dominant order in bacterioplankton communities associated with algal blooms could thus be due to the protective effect of its constituent carotenoids against 1O2- and UV-induced damage.

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hal-04286634 , version 1 (15-11-2023)

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Gwénola Simon, Laurie Casalot, Corinne Valette, Christopher Burot, Jean-François Rontani, et al.. Singlet oxygen-induced alteration of bacteria associated with phytodetritus: effect of bacterial pigments. 2023. ⟨hal-04286634⟩
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