Pathogenicity and virulence of bacterial strains associated with summer mortality in marine mussels (Perna...

Area of Science:

• Marine microbiology
• Aquaculture pathology
• Bacterial genomics

Background:

• Summer mortalities in Greenshell mussels (Perna canaliculus) are a significant issue in aquaculture.
• Pathogenic bacteria are increasingly suspected as a key cause of these mortalities.

Purpose of the Study:

• To identify and characterize bacterial pathogens associated with Greenshell mussel summer mortalities.
• To assess the virulence of identified bacterial isolates in laboratory challenge experiments.

Main Methods:

• Bacterial isolates from moribund mussels were identified using morpho-biochemical tests, MALDI-TOF MS, and whole genome sequencing.
• Laboratory challenge assays were conducted by injecting mussels with varying concentrations of bacterial isolates.
• Quantitative polymerase chain reaction (qPCR) was used to analyze virulence gene expression.

Main Results:

• Four bacterial species were confirmed: Vibrio celticus, Photobacterium swingsii, Photobacterium rosenbergii, and P. proteolyticum.
• Photobacterium swingsii induced the highest mortality in challenged mussels.
• Photobacterium rosenbergii and P. swingsii exhibited the highest expression of virulence genes.

Conclusions:

• Photobacterium species are identified as significant potential pathogens contributing to Perna canaliculus summer mortalities.
• Monitoring Photobacterium concentrations in farmed mussel populations is recommended to enhance industry resilience.
• Understanding the host-pathogen dynamics is crucial for managing aquaculture in a changing environment.