Culturable microbiota of ranched southern bluefin tuna (Thunnus maccoyii Castelnau)
Article first published online: 19 JUL 2013
© 2013 The Society for Applied Microbiology
Journal of Applied Microbiology
Volume 115, Issue 4, pages 923–932, October 2013
How to Cite
Valdenegro-Vega, V., Naeem, S., Carson, J., Bowman, J.P., Tejedor del Real, J.L. and Nowak, B. (2013), Culturable microbiota of ranched southern bluefin tuna (Thunnus maccoyii Castelnau). Journal of Applied Microbiology, 115: 923–932. doi: 10.1111/jam.12286
- Issue published online: 16 SEP 2013
- Article first published online: 19 JUL 2013
- Accepted manuscript online: 24 JUN 2013 12:00AM EST
- Manuscript Accepted: 18 JUN 2013
- Manuscript Revised: 16 JUN 2013
- Manuscript Received: 8 MAY 2013
- Fisheries Research and Development Corporation
- Australian Southern Bluefin Industry Association
- fish (live);
- Photobacterium ;
- southern bluefin tuna;
- Thunnus macoyii ;
The Australian tuna industry is based on the ranching of wild southern bluefin tuna (SBT, Thunnus maccoyii). Within this industry, only opportunistic pathogens have been reported infecting external wounds of fish. This study aimed to identify different culturable bacteria present in three cohorts of SBT and to determine normal bacteria and potential pathogens in isolates from harvest fish and moribund/dead fish. Post-mortem changes in the microbiota were also studied.
Methods and Results
Moribund/dead showed a greater proportion of members from the family Vibrionaceae than harvested fish; the latter presented mainly non-Vibrio species. In harvested fish spleens, Vibrio splendidus I complex was the most commonly identified group among Vibrio isolates, while most groups from the family Vibrionaceae were isolated from gills. For moribund/dead, Vibrio chagasii and Photobacterium damselae subsp. damselae were common in gill, spleen and kidney samples. Non-Vibrio isolates from gills were characterized using 16S rRNA sequencing as Flavobacteriaceae and classes Gammaproteobacteria and Alphaproteobacteria, mainly from the genera Winogradskyella and Tenacibaculum. Post-mortem changes showed dynamic shifts in bacterial dominance in gills, with Vibrionaceae and non-Vibrio spp. found in similar proportions initially and types related to Pseudoalteromonas ruthenica prevailing after 27 h. Spleen samples showed little bacterial growth until 5 h post-mortem, while various Vibrio-associated species were isolated 27 h post-mortem.
Bacterial isolates found include a range of potentially pathogenic bacteria that should be monitored though most of them have yet to be associated with disease in tuna.
Significance and Impact of the Study
This study forms a foundation for future research into the bacterial population dynamics under different culture conditions of SBT. An understanding of the bacterial compositions in SBT is necessary to evaluate the effects of some bacterial species on their health.