Search Menu Abstract In both freshwater and marine ecosystems, phytoplankton are the most dominant primary producers, contributing substantially to aquatic food webs. Algicidal bacteria that can associate to microalgae from the phytoplankton have the capability to control the proliferation and even to lyse them. These bacteria thus play an important role in shaping species composition in pelagic environments. In this review, we discuss and categorise strategies used by algicidal bacteria for the attack on microalgae.
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Primary Contact s : marc. We characterized the activity of the algicidal agent and its impact on dinoflagellate physiology. We also evaluated the effect of the algicide on microbial community structure and function to determine which natural bacteria work best.
Why We Care Harmful blooms of toxic dinoflagellates cause a wide variety of environmental, economic, and human health problems in the United States. The growing frequency and magnitude of outbreaks has created a pressing need for ways to control or mitigate harmful algal bloom HAB impacts in coastal waters. Biological control agents like viruses or bacteria may play a natural role in controlling blooms.
Research is needed to understand this phenomenon and find specific compounds that can be adapted to HAB control mechanisms without harming the environment. IRI—and examined the effects of this compound on dinoflagellates and non-target species of plankton. The team characterized the mechanism of toxicity on several species of dinoflagellates and used mixed cultures to study the broader effects of this agent on community composition and function.
The investigators tested hypotheses regarding the effect of IRIAA on photosynthesis, cell cycle progression, and programmed cell death in target algal species. What We Found Results show the algicide causes autocatalytic non-necrotic cell death in dinoflagellates, while having no negative impacts on other phytoplankton species tested in laboratory culture experiments. Algicidal effects were greatest during active growth stages of dinoflagellates, with minimal mortality in the stationary S phase.
We also examined the biochemical and physiological changes in dinoflagellates exposed to the algicide. Our research points to the nucleus as the primary organelle targeted by the algicide, with a loss of chromosomal structure in all species examined. This may be due to interactions between the algicide and metal ions that stabilize chromosomes in dinoflagellate species. Analysis of cell cycle progression growth curve in dinoflagellates exposed to the algicide also revealed a loss of DNA content.
For those cells that retained DNA, there was an increase in the number of cells in the stationary S phase over time, suggesting that biochemical signals triggering progression to a second generation G2 were inhibited. We also observed effects on the cell chloroplast, resulting in a decrease in photochemical function, but these effects varied depending on species.
We conducted small-scale, natural community, microcosm experiments during dinoflagellate blooms to evaluate the effects of the algicide on the total microbial community. Our results from these experiments reveal a restructuring of the microbial community in response to the algicide, with decreases in dinoflagellate species abundance and increases in the abundance of heterotrophic protists. IRI in natural bacterioplankton communities with increased dinoflagellate abundance. IRI may be a natural phenomenon.
Our findings indicate that application of the algicidal compound for control of dinoflagellate HABs will likely have the greatest impact in the early stages of a bloom, with minimal impact on the environment.
More study is needed to confirm that the compound can be safely used in the environment as a means to control HABs. Additional Resources Click to expand resource list s.
D, an algicidal marine bacterium, guided by algal lethality assay using the raphidophyte, Chattonella antiqua, one of the causative organisms of harmful algal bloom. The structures of 1—4 were assigned on the basis of their spectrometric and spectroscopic data. Compounds 1 to 4 exhibited algicidal activity against C. Co-cultivation experiment revealed that 1 was produced only when the microalgae and the bacterium are in close contact, suggesting that some interactions between them trigger the biosynthesis of questiomycins. These results suggested that the algicidal bacteria such as Alteromonas sp. D can control microalgae chemically in marine ecosystem. Keywords: algicidal bacteria, questiomycins, phenoxazinone antibiotics, Alteromonas, Chattonella antiqua, harmful algal bloom, red tide 1.
Chitinase producing bacteria with direct algicidal activity on marine diatoms
Primary Contact s : marc. We characterized the activity of the algicidal agent and its impact on dinoflagellate physiology. We also evaluated the effect of the algicide on microbial community structure and function to determine which natural bacteria work best. Why We Care Harmful blooms of toxic dinoflagellates cause a wide variety of environmental, economic, and human health problems in the United States. The growing frequency and magnitude of outbreaks has created a pressing need for ways to control or mitigate harmful algal bloom HAB impacts in coastal waters. Biological control agents like viruses or bacteria may play a natural role in controlling blooms.