Abstract
Marennine, the water-soluble blue pigment produced by the marine diatom Haslea ostrearia, is known to display antibacterial activities. Previous studies have demonstrated a prophylactic effect of marennine on bivalve larvae challenged with a pathogenic Vibrio splendidus, suggesting that the blue Haslea is a good candidate for applications in aquaculture as a source of a natural antimicrobial agent. Indeed, the genus Vibrio is ubiquitous in aquaculture ecosystems, and regular events of pathogenic invasion cause some of the biggest losses worldwide. To better characterize the effects of marennine on Vibrios, a panel of 30 Vibrio strains belonging to 10 different species was tested, including bivalve pathogenic species (e.g., Vibrio crassostreae and Vibrio harveyi). Vibrio strains were first exposed to 10 and 25 µg mL−1 of Blue Water (BW), a concentrated culture supernatant of H. ostrearia containing marennine. This screening evidenced a great diversity in responses, from growth stimulation to a total inhibition, at both the interspecific or intraspecific level. In a second series of experiments, 10 Vibrio strains were exposed to BW at concentrations ranging from 5 to 80 µg mL−1. The highest concentrations of BW did not systematically result in the highest growth inhibition as hormetic responses—opposite effects regarding the concentration—were occasionally evidenced. The relationships between marennine and Vibrio strains appear more complex than expected and justify further study—in particular, on the mechanisms of action—before considering applications as a natural prophylactic or antibiotic agent in aquaculture.
Highlights
The marine diatom Haslea ostrearia is characterized by the production of a specific blue-green pigment, named marennine
The growth curves of the 30 Vibrio strains exposed to Blue Water (BW) at 0 μg mL−1, 10 μg mL−1, or 25 μg mL−1 were recorded for 24 h (Supplementary Figure S1)
As BW solution was used in the present work, and not a purified form of the pigment, it could be questioned if the observed effects were induced by marennine or by other molecules possibly present in the non-axenic culture medium (e.g., exopolysaccharides (EPS) from Haslea or epibiont bacteria)
Summary
The marine diatom Haslea ostrearia is characterized by the production of a specific blue-green pigment, named marennine. Blue diatoms other than H. ostrearia have been identified in the last decade, such as Haslea karadagensis (Black Sea; [2]), Haslea provincialis (Mediterranean Sea; [3]), and more recently, Haslea nusantara (Java Sea; [4]). All these species produce blue pigments whose spectral characteristics slightly differ from marennine, and are.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
