Cross-Host Protection of Marine Bacteria Against Macroalgal Disease

Abstract

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.

The Diversity and Functional Capacity of Microbes Associated with Coastal Macrophytes

“…Blades of kelp and surfgrass were a locus of microbial diversity and function, a finding that is similar to many recent studies of macroalgal and seagrass microbiomes reporting high microbial diversity ( 6 , 8 , 9 , 51 – 53 ). The functional attributes of microbial taxa associated with marine macrophytes include pathogen resistance ( 54 ), the ability to provision the host with B vitamins ( 11 ), and enhanced host algal fitness ( 55 ), perhaps through some of the nitrogen or sulfur metabolisms we documented here ( 5 , 13 ).…”

Bacteria on the foundational kelp in kelp forest ecosystems: Insights from culturing, whole genome sequencing and metabolic assays

“…It may be that bacteria that use the surface of kelp are in a dynamic relationship that can segue into consumption by the host. We note that other strains within Pseudoalteromonas have also been shown to rescue the red seaweed Dilsea from a pathogenic bacterial taxon (Li et al, 2021 ) and still others have inhibitory effects on heterospecific bacteria (Thomas et al, 2008 ).…”

Naturally occurring beneficial bacteria Vibrio alginolyticus X-2 protects seaweed from bleaching disease

“…Microbiome manipulation through probiotics can mitigate or rebalance pathogen-induced microbiome dysbiosis, eventually promoting host fitness ( 3 - 5 ). Nevertheless, few studies have investigated seaweed probiotics ( 20 - 30 - 30 ) and little is known about their mechanisms of action. Here, we identified a beneficial bacterium, V. alginolyticus X-2, that can mitigate the occurrence of bleaching disease in commercially farmed S. japonica .…”