Cross-Host Protection of Marine Bacteria Against Macroalgal Disease

Despite an increasing awareness of disease impacts on both cultivated and native seaweed populations, the development of marine probiotics has been limited and predominately focused on farmed animals. Bleaching (loss of thallus pigmentation) is one of the most prevalent diseases observed in marine macroalgae. Endemic probiotic bacteria have been characterized to prevent bleaching disease in red macroalgae Agarophyton vermiculophyllum and Delisea pulchra; however, the extent to which probiotic strains provide cross-protection to non-endemic hosts and the influence of native microbiota remain unknown. Using A. vermiculophyllum as a model, we demonstrate that co-inoculation with the pathogen Pseudoalteromonas arctica G-MAN6 and D. pulchra probiotic strain Phaeobacter sp. BS52 or Pseudoalteromonas sp. PB2-1 reduced the disease risks compared to the pathogen only treatment. Moreover, non-endemic probiotics outperformed the endemic probiotic strain Ralstonia sp. G-NY6 in the presence of the host natural microbiota. This study highlights how the native microbiota can impact the effectiveness of marine probiotics and illustrates the potential of harnessing probiotics that can function across different hosts to mitigate the impact of emerging marine diseases.

Automated summary

The development of marine probiotics has been limited, with a focus on farmed animals rather than seaweeds. This study demonstrates that non-endemic probiotics may be more effective in preventing diseases in certain seaweeds compared to endemic probiotics. The potential of utilizing probiotics that can function across different hosts to mitigate the impact of emerging marine diseases is highlighted.