Evaluating the variation in the number and structure of the bacterial pathogens associated with A. muricata and the implications in coral health

- Theoretical results: There was a clear distinction between the number and structure of the heterogeneous and pathogenic microorganisms associated with healthy and diseased corals collected in nature and in laboratory experiment.
- The number of heterotrophic and pathogenic bacteria in diseased increased 66 and 40,000 times, respectively, compared to those in healthy corals.
- Vibrio sp., Enterobacteria group was not observed in healthy coral samples but high in diseased corals. Some species of pathogenic bacteria isolated from coral were found in natural conditions such as V. vilnificus, V. parahaemoliticus, V. cholera, V. communis, V. alginolyticus, Vibrio rotiferianus and Photobacterium rosenbergii. And under experimental conditions: Vibrio harveyi, Vibrio parahaemolyticus, Pseudomonas stutzeri, Vibrio coralliilyticus. Vibrio proteolyticus. Most of these strains are the previously reported as coral pathogens.
- Of the 11 bacterial isolates from healthy coral, 7 out of 11 strains have antimicrobial activity against some coral and human pathogens. There are 5 strains resistant to B. subtilis, four strains resistant to S. typhimurium, two strains resistant to S. marcesens, two strains resistant to E. coli and one resistant to V. parahaemoliticus. This is the first significant screening result in the study of coral disease resistance and the production of drugs for human medicine.
- There was a remarked differences in functional and genetic diversity of the bacterial communities associated with healthy coral and coral disease. In particular, bacteria in diseased corals showed the difference in the mechanism of assimilation of some important substrates. In the genetic structure, some new phylum appeared in diseased corals that were previously not found in healthy corals. Some bacterial phylum were only found in diseased corals: BD1-5 (1.29%) and Verrucomicrobia (3.5%), Candidate-divsion SR1 and Candidate-division WS3.

Some images of the project:

This is the first study to compare the number and structure of bacterial communities associated with healthy and diseased corals in both natural and laboratory conditions. The results showed that when corals change their health status under the influence of environmental changes (increased temperature over a long period of time), the number of heterotrophic bacteria, and pathogenic bacteria increased dramatically in diseased corals compared to healthy corals. Some strains of Vibrio, Enterobacteria, Samonella and Shigella were only found in diseased corals. The result from this study is important for future studies regarding the role of pathogens, mechanisms and conditions of pathogenic bacteria in coral diseases.

Scientific papers in referred journals (list):

1. Nguyễn Kim Hạnh, Phạm Thị Miền, Bùi Hữu Hưng, Võ Hải Thi. 2016. Isolation and screening of bacteria associated with scleractinian coral Acropora muricata and their antibacterial activities. Collection of Marine Research Works. 22: 83-95.
2. Nguyễn Kim Hạnh, Phạm Thị Miền, Đoàn Như Hải. 2018. Life cycles of coral associated viruses related to different health states collected in Hang Rai-Ninh Thuan, Vietnam. Academia Journal of Biology. 40(2): 223-232.
3. Hedberg N., Stenson I., Nitz Pettersson M., Warshan D., Nguyen-Kim H., Tedengren M., Kautsky N. 2018. Antibiotic use in Vietnamese fish and lobster sea cage farms; implications for coral reefs and human health. Aquaculture. 495: 366-375.

- Technological products (describe in details: technical characteristics, place):
- Report about pathogenic bacteria associated with coral A. muricata collected at the Nha Trang bay
- Documentation of some coral associated pathogens for future research on coral diseases.
Support master trainning: 1 graduated master
- Other products (if applicable): Support master trainning: 1 graduated master