Bacterial controlled mitigation of dysbiosis in a seaweed disease

Abstract

Disease in the marine environment is predicted to increase with anthropogenic stressors and already affects major habitat-formers, such as corals and seaweeds. Solutions to address this issue are urgently needed. The seaweed Delisea pulchra is prone to a bleaching disease, which is caused by opportunistic pathogens and involves bacterial dysbiosis. Bacteria that can inhibit these pathogens and/or counteract dysbiosis are therefore hypothesised to reduce disease. This study aimed to identify such disease-protective bacteria and investigate their protective action. One strain, Phaeobacter sp. BS52, isolated from healthy D. pulchra, was antagonistic towards bleaching pathogens and significantly increased the proportion of healthy individuals when applied before the pathogen challenge (pathogen-only vs. BS52 + pathogen: 41–80%), and to a level similar to the control. However, no significant negative correlations between the relative abundances of pathogens and BS52 on D. pulchra were detected. Instead, inoculation of BS52 mitigated pathogen-induced changes in the epibacterial community. These observations suggest that the protective activity of BS52 was due to its ability to prevent dysbiosis, rather than direct pathogen inhibition. This study demonstrates the feasibility of manipulating bacterial communities in seaweeds to reduce disease and that mitigation of dysbiosis can have positive health outcomes.

Functional Annotation and Characterization of a Hypothetical Protein from Pseudoalteromonas spp. Identify Potential Biomarker: An In-silico Approach

“…Bacteria are known to be the main component of more diverse seaweed epibionts, and they may have played a role in the disease's development (Largo et al, 1995). In recent years, many seaweed farms ceased to exist because of the "ice-ice" problem particularly in south east Asia (Li et al, 2022). Recent reports have linked disease in seaweeds, to opportunistic microbial pathogens and in some instances the causative agent (s) have been identified and virulence traits described (Li et al, 2022).…”

Cross-Host Protection of Marine Bacteria Against Macroalgal Disease

“…However, current disease management strategies, involving specific cultivation practices or chemical treatments [6,7], are often highly labor-intensive and impractical for the application to wild seaweed populations. The use of probiotics for disease control in industrial and natural systems is gaining interest [8][9][10][11][12], yet in the marine environment disease protective bacteria have predominately been characterized for aquaculture animals [13,14] with few attempts made to discover macroalgal probiotics [15][16][17]. To date, research has focused either on the isolation of endemic probiotic bacteria from the target hosts and their environment or on the use of wellcharacterized human/animal dietary probiotics such as Lactobacillus spp.…”

“…PB2-1 and Phaeobacter sp. BS52) that can reduce the pathogen-induced bleaching in vivo [15]. Similarly, endemic bacterial strains have been shown to reduce the risk of disease in A. vermiculophyllum in the presence of pathogens [16].…”

“…BS52 and Pseudoalteromonas sp. PB2-1 [15] could also alleviate the pathogen-induced bleaching in A. vermiculophyllum. Bacteria belonging to the genera Phaeobacter and Pseudoalteromonas have also been reported as probiotics in a variety of marine systems, including corals [28], shellfish [11,29,30], and fish larvae [31][32][33].…”

“…PB2-1 may not be sufficient to protect A. vermiculophyllum against disease. Rather PB2-1 may have an indirect mode of action for disease protection, such as mitigating pathogen-induced dysbiosis (e.g., see [15,37,38]), or acting in synergy with other members of the microbiota to afford protection to the host.…”