Impact of bacteriophages and nutrient environment on the metaorganism Hydra vulgaris AEP
I studied the metaorganism Hydra vulgaris AEP, its microbiota and response to phage treatments as well as varying nutrient conditions.
Using lytic bacteriophages, we targeted Hydra’s main colonizer Curvibacter sp. AEP1.3 and found that the bacterium was impervious to phage infection on Hydra and in liquid culture, even though phages had shown strong lytic capacity on solid medium. Through transcriptomic analysis, it became clear that Curvibacter adapted to its surrounding environment, resulting in varying degrees of susceptibility to phage infection. This trend continued when we exposed the whole metaorganism to various nutrient environments, whereby addition of simple nutrients resulted in significant shifts in microbial community composition, showcasing the metaorganism’s ability to adapt to environmental changes. Furthermore, we found that addition of L-Arginine caused Pseudomonas alcaligenes T3, a neutral associate within the Hydra microbiota, to induce a disease phenotype by producing toxins harmful to Hydra. Upon targeting P. alcaligenes with bacteriophages, we discovered the bacterium's ability of rapid resistance formation, which we attempted to overcome using phage cocktails, before determining that phage sequential treatment was more efficient in suppressing resistance formation. Finally, we applied our phage treatment to diseased Hydra, only to find that the treatment alleviated adverse nutrient effects short-term, but nutrient effects outweighed phage treatment in long-term experiments.
The environment and especially nutrients are, in conclusion, an important factor which can induce change in a metaorganism's microbiota (even to its detriment) as well as alter the metabolism of bacterial residents.
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