Vibrio sp. causing Porites ulcerative white spot disease

Area of Science:

• Marine Microbiology
• Coral Pathology
• Bacterial Disease Agents

Background:

• Porites ulcerative white spot syndrome (PUWS) is a significant coral disease in the Indo-Pacific.
• The specific causative agent of PUWS has remained unidentified, hindering effective management strategies.

Purpose of the Study:

• To identify the bacterial agent responsible for PUWS.
• To fulfill Koch's postulates to confirm the pathogenicity of isolated bacteria.

Main Methods:

• Isolation and characterization of bacteria from infected Porites cylindrica tissue on thiosulphate citrate bile sucrose (TCBS) agar.
• Infection trials using different bacterial growth phases (exponential, stationary, starved) and inoculation methods (immersion, injection, smearing).
• Molecular identification using 16S rRNA gene sequencing and phenotypic analysis.

Main Results:

• A Gram-negative, motile, non-sucrose-fermenting Vibrio sp. was isolated and identified.
• Stationary phase cells at concentrations of 10(4) cells/ml applied via a 1-step immersion technique consistently induced PUWS symptoms.
• Infection led to tissue degradation and bleaching, particularly at elevated temperatures (>29°C).
• The isolate showed 99% 16S rRNA gene sequence similarity to Vibrio natriegens and Vibrio parahaemolyticus.

Conclusions:

• A specific Vibrio species is confirmed as the causative agent of Porites ulcerative white spot syndrome (PUWS).
• The findings provide crucial insights into the etiology of this coral disease, aiding in future prevention and treatment efforts.
• This research contributes to understanding coral disease dynamics and the role of Vibrio species in marine ecosystems.