Selenium protects Emiliania huxleyi algae from a bacterial pathogen by modulating oxidative stress
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Abstract
Oxidative stress arises when cells fail to maintain redox balance, leading to the accumulation of reactive oxygen species (ROS) that can damage proteins, lipids, and DNA, causing cells to function poorly or die. In marine algae, oxidative stress is a hallmark of bacterial pathogenicity and usually appears before algae die. During the interaction of Emiliania huxleyi algae with Phaeobacter inhibens pathogenic bacteria, algae experience elevated levels of ROS that precede and likely drive cell death. Here, we tested whether antioxidants could improve algal survival by alleviating oxidative stress. Among several environmentally relevant antioxidants, we found that nanomolar concentrations of the trace metal selenium, in the form of H 2 SeO 3 , completely prevented algal death in co-cultures with P. inhibens . Measurements over time showed that selenium significantly lowered ROS levels in algal cells, reducing oxidative stress. This effect did not interfere with bacterial growth, suggesting that selenium acts by helping algae, not by harming bacteria. Our findings demonstrate that oxidative stress plays a central role in bacterial pathogenicity towards algae, and that selenium can protect algae by reducing this stress.
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To evaluate the impact of these antioxidants, E. huxleyi algae were cultured both axenically and in co-culture with P. inhibens bacteria, and algal survival was monitored (Fig. 2).
Very cool and interesting findings! The selectivity of selenium protection is striking - it's fascinating that only selenium prevented algal death while ascorbate, DMSP, and α-tocopherol were all ineffective. I noticed there's quite a concentration disparity in the screen: selenium at 10 nM versus the others at 20 μM. This actually makes selenium's effectiveness even more remarkable, but do you think it would still be effective at 20 µM concentrations? or would there be diminishing returns and increased toxicity? It would be interesting to see dose-response curves for each antioxidant to confirm whether this represents true mechanistic selectivity versus …
To evaluate the impact of these antioxidants, E. huxleyi algae were cultured both axenically and in co-culture with P. inhibens bacteria, and algal survival was monitored (Fig. 2).
Very cool and interesting findings! The selectivity of selenium protection is striking - it's fascinating that only selenium prevented algal death while ascorbate, DMSP, and α-tocopherol were all ineffective. I noticed there's quite a concentration disparity in the screen: selenium at 10 nM versus the others at 20 μM. This actually makes selenium's effectiveness even more remarkable, but do you think it would still be effective at 20 µM concentrations? or would there be diminishing returns and increased toxicity? It would be interesting to see dose-response curves for each antioxidant to confirm whether this represents true mechanistic selectivity versus concentration optimization differences. Also intriguing that selenium protects against ROS in axenic cultures too - suggesting it strengthens the algae's intrinsic antioxidant capacity independent of bacterial stress. Do you think there selenium would protect against chemically induced ROS? and given the naturally occuring ROS developed as the culture ages, do you think selenium supplementation would increase the lifespan of a culture of E. huxleyi before crashing out?
Very cool work and a really neat finding! Thanks for sharing!
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