Determining the probiotic potential of Pseudoalteromonas rubra against native pathogens

Education Level

Undergraduate

Faculty Advisor(s)

Professor Koty Sharp

Academic Department(s)

Biology, Marine Biology and Environmental Science

Comments

This research was presented at the 2024 Rhode Island Summer Undergraduate Research Symposium, held on Friday, July 26, at the University of Rhode Island and supported by RI-INBRE.

Symposium Date

2024

Abstract

Tropical corals host diverse and specific microbiomes that modulate coral fitness, and many microbes play a protective role against pathogens. Two strains of the bacteria Pseudoalteromonas rubra (KB1 and CH007) were isolated from seawater and crustose coralline algae (CCA) in the temperate coral (Astrangia poculata) culturing tanks in Roger Williams University Wet Lab. P. rubra is thought to be protective to tropical corals, via production of the prodigiosins and N-acyl-homoserine lactones. Additionally, P. rubra induces larval settlement in at least one tropical coral species. P. rubra KB1 and CH007 inhibit growth of several species of Vibrio, including known coral, finfish, and shellfish pathogens. An exposure assay was conducted and P. rubra KB1 and CH007 were found to be not lethal to A. poculata. Exposure to P. rubra significantly altered the A. poculata microbiome composition, including increases in bacteria involved in sulfur cycling and likely antibacterial production. However, exposure also was correlated with decrease in known beneficial associates. Coral mucus and seawater microbiomes resembled one another at some, but not all, time points during exposure, and there was significant strain-dependent variation in the impact on A. poculata microbiome composition and diversity. These data lay the groundwork in developing P. rubra as a probiotic treatment and in understanding the molecular mechanisms of any benefit that P. rubra may confer to corals. Due to the resistance of A. poculata against V. coralliilyticus in the lab, the sea anemone, Exaiptasia diaphana, was selected as an experimental system to assess P. rubra’s capacity for disease prevention and/or mitigation. Exaiptasia diaphana was exposed to high concentrations (108 cells/ml) of the pathogen V. coralliilyticus, and dosed with P. rubra either before or after the V. coralliilyticus exposure. Preliminary data showed that pretreatment with P. rubra 12 hours before V. coralliilyticus did not reduce the Vibrio-induced mortality. However, anemones treated with P. rubra 12 hours after V. coralliilyticus exposure showed a decrease in mortality compared to those exposed to the pathogen alone.

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