Investigating the action of the microalgal pigment marennine on Vibrio splendidus by in vivo 2H and 31P solid-state NMR

International audience; This work investigates the potential probiotic effect of ma rennine-a natural pigme nt produ ced by the diatom Haslea ostrearia-on Vibrio splendidus. These ma rine bacteria are often considered a threat for aquacu lture; therefore, ch em ical antibiotics can be required to redu ce bacterial outbreaks. In vi vo 2 H solid-state NMR was used to probe the effects of ma rennine on the bacterial me mbrane in the exponential and stationary ph ases. Comparisons were ma de with polymyxin B (PxB)-an antibiotic used in aquacu lture and known to interact with Gram (−) bacteria me mbranes. We also investigated the effect of ma rennine using 31 P solidstate NMR on model me mbranes. Our results show that ma rennine has little effect on ph osph olipid headgroups dynamics, bu t redu ces the acyl ch ain fluidity. Our data suggest that the two antimicrobial agents perturb V. splendidus me mbranes through different me ch anism s. While PxB would alter the bacterial outer and inner me mbranes, ma rennine would act through a me mbrane stiffening me ch anism , without affecting the bilayer integrity. Our stud y proposes this microalgal pigme nt, wh ich is harm less for hu ma ns, as a potential treatme nt against vibriosis.