Beneficial microorganisms for corals (BMCs), or probiotics, can enhance coral resilience against stressors in laboratory trials. However, the ability of probiotics to restructure the coral microbiome in situ is yet to be determined. As a first step to elucidate this, we inoculated putative probiotic bacteria (pBMCs) on healthy colonies of Pocillopora verrucosa in situ in the Red Sea, three times per week, during 3 months. pBMCs significantly influenced the coral microbiome, while bacteria of the surrounding seawater and sediment remained unchanged. The inoculated genera Halomonas, Pseudoalteromonas, and Bacillus were significantly enriched in probiotic-treated corals. Furthermore, the probiotic treatment also correlated with an increase in other beneficial groups (e.g., Ruegeria and Limosilactobacillus), and a decrease in potential coral pathogens, such as Vibrio. As all corals (treated and non-treated) remained healthy throughout the experiment, we could not track health improvements or protection against stress. Our data indicate that healthy, and therefore stable, coral microbiomes can be restructured in situ, although repeated and continuous inoculations may be required in these cases. Further, our study provides supporting evidence that, at the studied scale, pBMCs have no detectable off-target effects on the surrounding microbiomes of seawater and sediment near inoculated corals.

在实验室试验中，对珊瑚有益的微生物（BMC）或益生菌可以增强珊瑚抵抗压力源的能力。然而，益生菌原位重组珊瑚微生物组的能力仍有待确定。作为阐明这一点的第一步，我们将推定的益生菌 (pBMC) 接种到红海的健康疣状Pocillopora 菌落上，每周 3 次，持续 3 个月。 pBMC 显着影响珊瑚微生物组，而周围海水和沉积物的细菌则保持不变。经益生菌处理的珊瑚中，接种的盐单胞菌属、假交替单胞菌属和芽孢杆菌属显着富集。此外，益生菌治疗还与其他有益菌群（例如， Ruegeria和Limosilactobacillus ）的增加以及潜在珊瑚病原体（例如弧菌）的减少相关。由于所有珊瑚（经过处理和未经处理的）在整个实验过程中都保持健康，因此我们无法跟踪健康状况的改善或免受压力的保护。我们的数据表明，健康且稳定的珊瑚微生物组可以在原位重建，尽管在这些情况下可能需要重复和连续接种。此外，我们的研究提供了支持证据，表明在研究范围内，pBMC 对接种珊瑚附近的海水和沉积物周围的微生物组没有可检测到的脱靶效应。