Abstract
Blooms of the dinoflagellate Alexandrium tamarense have become worldwide phenomena and have detrimental impacts on aquatic ecosystems and human health. In this study, a culture supernatant of the marine actinomycete BS01 exerted a strong algicidal effect on A. tamarense (ATGD98-006). The target algicide from BS01 was separated by adsorption chromatography and identified by MALDI-TOF-MS and NMR analysis. The results suggested that the purified algicidal component corresponded to a hydrophobic compound (2-isobutoxyphenyl)amine (C10H15NO) with a molecular weight of 165 Da, which exhibited a significant algicidal effect (64.5%) on A. tamarense. After incubation in 5 μg/mL of (2-isobutoxyphenyl)amine for 24 h, the algae lost mobility and sank to the bottom of the flasks, and 56.5% of the algae cells lost vitality at a concentration of 20 μg/mL (p < 0.01) despite having intact cell profiles. Morphological analysis revealed that the cell structure of A. tamarense was altered by (2-isobutoxyphenyl)amine resulting in cytoplasm degradation and the loss of organelle integrity. The images following propidium iodide staining suggested that the algal nucleus was also severely damaged and eventually degraded due to exposure to the algicidal compound. All of the results indicate that (2-isobutoxyphenyl)amine from the actinomycete might be a candidate for the control of bloom-forming A. tamarense.
Highlights
Harmful algal blooms (HABs) occur around the world, causing significant, direct economic losses to seafood-based industries (Anderson, 1997; Geohab, 2001), and the consumption of seafood contaminated by the toxins produced by these algae pose potential threats to human health (Geohab, 2001)
Lee et al (2000) reported that an extracellular protease from strain A28 of the marine bacterium Pseudoalt eromonas was algicidal toward Skeletonema costatum, and algicidal compounds with lower molecular weight, such as the rhamnolipid biosurfactants from Pseudomonas aeruginosa or the prodigiosin pigment from the bacterium Hahella chejuensis, have been identified (Wang et al, 2005; Kwon et al, 2010)
This study focused on the algicidal compounds produced in the stationary phase (48 h) when the secondary metabolite, (2isobutoxyphenyl)amine, accumulated to some extent and exerted its algicidal effect on A. tamarense
Summary
Harmful algal blooms (HABs) occur around the world, causing significant, direct economic losses to seafood-based industries (Anderson, 1997; Geohab, 2001), and the consumption of seafood contaminated by the toxins produced by these algae pose potential threats to human health (Geohab, 2001). Lee et al (2000) reported that an extracellular protease from strain A28 of the marine bacterium Pseudoalt eromonas was algicidal toward Skeletonema costatum, and algicidal compounds with lower molecular weight, such as the rhamnolipid biosurfactants from Pseudomonas aeruginosa or the prodigiosin pigment from the bacterium Hahella chejuensis, have been identified (Wang et al, 2005; Kwon et al, 2010). Given the considerable recent attention to the field of harmful algae, other active compounds have been screened and subsequently identified; the algicidal DHQ25, which is affiliated with the γproteobacteria subclass, produced a P7 protein that kills the toxic dinoflagellate A. tamarense (Wang et al, 2012). With few exceptions, the identities of the compounds or enzymes responsible for the algicidal effects remain unknown, and most studies continue to focus on the isolation, identification or characterization of algicidal bacteria
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