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Discovery of Bioactive Metabolites in Biofuel Microalgae That Offer Protection against Predatory Bacteria.

Bagwell CE, Abernathy A, Barnwell R, Milliken CE, Noble PA, Dale T, Beauchesne KR, Moeller PD - Front Microbiol (2016)

Bottom Line: Even though Chlorophytes are generally regarded safe for human consumption, there is still much we do not understand about the metabolic and biochemical potential of microscopic algae.Introduction of V. chlorellavorus resulted in a 72% decrease in algal biomass in the experimental controls after 7 days.Further study of this phenomenon could contribute to the development of new strategies to extend algal production cycles in open, outdoor systems while ensuring the protection of biomass from predatory losses.

View Article: PubMed Central - PubMed

Affiliation: Environmental Sciences and Biotechnology, Savannah River National Laboratory, Aiken SC, USA.

ABSTRACT
Microalgae could become an important resource for addressing increasing global demand for food, energy, and commodities while helping to reduce atmospheric greenhouse gasses. Even though Chlorophytes are generally regarded safe for human consumption, there is still much we do not understand about the metabolic and biochemical potential of microscopic algae. The aim of this study was to evaluate biofuel candidate strains of Chlorella and Scenedesmus for the potential to produce bioactive metabolites when grown under nutrient depletion regimes intended to stimulate production of triacylglycerides. Strain specific combinations of macro- and micro-nutrient restricted growth media did stimulate neutral lipid accumulation by microalgal cultures. However, cultures that were restricted for iron consistently and reliably tested positive for cytotoxicity by in vivo bioassays. The addition of iron back to these cultures resulted in the disappearance of the bioactive components by LC/MS fingerprinting and loss of cytotoxicity by in vivo bioassay. Incomplete NMR characterization of the most abundant cytotoxic fractions suggested that small molecular weight peptides and glycosides could be responsible for Chlorella cytotoxicity. Experiments were conducted to determine if the bioactive metabolites induced by Fe-limitation in Chlorella sp. cultures would elicit protection against Vampirovibrio chlorellavorus, an obligate predator of Chlorella. Introduction of V. chlorellavorus resulted in a 72% decrease in algal biomass in the experimental controls after 7 days. Conversely, only slight losses of algal biomass were measured for the iron limited Chlorella cultures (0-9%). This study demonstrates a causal linkage between iron bioavailability and bioactive metabolite production in strains of Chlorella and Scenedesmus. Further study of this phenomenon could contribute to the development of new strategies to extend algal production cycles in open, outdoor systems while ensuring the protection of biomass from predatory losses.

No MeSH data available.


Related in: MedlinePlus

triacylglycerides (TAG) induction in microalgal cultures. The arithmetic mean and standard deviation (n = 6) in fluorescence intensity per cell for (A)Scenedesmus sp. (strain 18B) and (B)Chlorella sp. (strain 15) treatment populations analyzed by multi-parameter flow cytometry. Cells were stained with BODIPY® 505/515 for TAG accumulation and auto-fluorescence was measured for chlorophyll content.
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Figure 2: triacylglycerides (TAG) induction in microalgal cultures. The arithmetic mean and standard deviation (n = 6) in fluorescence intensity per cell for (A)Scenedesmus sp. (strain 18B) and (B)Chlorella sp. (strain 15) treatment populations analyzed by multi-parameter flow cytometry. Cells were stained with BODIPY® 505/515 for TAG accumulation and auto-fluorescence was measured for chlorophyll content.

Mentions: Plots of the mean fluorescence intensity for TAGs (BODIPY 505/515 staining) and chlorophyll autofluorescence of Scenedesmus sp. (strain 18B) cultures, as measured by flow cytometry, between treatments are shown in Figure 2A. Treatment 1 resulted in high cell to cell variability as fluorescence signals for TAG (BODIPY®) and chlorophyll were both equally high. Cultures from Treatments 2, 3, and 5 showed low TAG accumulation as indicated by BODIPY® fluorescence relative to significantly higher chlorophyll content. Finally, Treatment 4 produced a highly chlorotic culture as indicated by the very low chlorophyll auto-fluorescence signal. The TAG induction response for Treatment 4, though, was strong and unanimous among cells in the culture, large lipid bodies were observed by microscopy.


Discovery of Bioactive Metabolites in Biofuel Microalgae That Offer Protection against Predatory Bacteria.

Bagwell CE, Abernathy A, Barnwell R, Milliken CE, Noble PA, Dale T, Beauchesne KR, Moeller PD - Front Microbiol (2016)

triacylglycerides (TAG) induction in microalgal cultures. The arithmetic mean and standard deviation (n = 6) in fluorescence intensity per cell for (A)Scenedesmus sp. (strain 18B) and (B)Chlorella sp. (strain 15) treatment populations analyzed by multi-parameter flow cytometry. Cells were stained with BODIPY® 505/515 for TAG accumulation and auto-fluorescence was measured for chlorophyll content.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834574&req=5

Figure 2: triacylglycerides (TAG) induction in microalgal cultures. The arithmetic mean and standard deviation (n = 6) in fluorescence intensity per cell for (A)Scenedesmus sp. (strain 18B) and (B)Chlorella sp. (strain 15) treatment populations analyzed by multi-parameter flow cytometry. Cells were stained with BODIPY® 505/515 for TAG accumulation and auto-fluorescence was measured for chlorophyll content.
Mentions: Plots of the mean fluorescence intensity for TAGs (BODIPY 505/515 staining) and chlorophyll autofluorescence of Scenedesmus sp. (strain 18B) cultures, as measured by flow cytometry, between treatments are shown in Figure 2A. Treatment 1 resulted in high cell to cell variability as fluorescence signals for TAG (BODIPY®) and chlorophyll were both equally high. Cultures from Treatments 2, 3, and 5 showed low TAG accumulation as indicated by BODIPY® fluorescence relative to significantly higher chlorophyll content. Finally, Treatment 4 produced a highly chlorotic culture as indicated by the very low chlorophyll auto-fluorescence signal. The TAG induction response for Treatment 4, though, was strong and unanimous among cells in the culture, large lipid bodies were observed by microscopy.

Bottom Line: Even though Chlorophytes are generally regarded safe for human consumption, there is still much we do not understand about the metabolic and biochemical potential of microscopic algae.Introduction of V. chlorellavorus resulted in a 72% decrease in algal biomass in the experimental controls after 7 days.Further study of this phenomenon could contribute to the development of new strategies to extend algal production cycles in open, outdoor systems while ensuring the protection of biomass from predatory losses.

View Article: PubMed Central - PubMed

Affiliation: Environmental Sciences and Biotechnology, Savannah River National Laboratory, Aiken SC, USA.

ABSTRACT
Microalgae could become an important resource for addressing increasing global demand for food, energy, and commodities while helping to reduce atmospheric greenhouse gasses. Even though Chlorophytes are generally regarded safe for human consumption, there is still much we do not understand about the metabolic and biochemical potential of microscopic algae. The aim of this study was to evaluate biofuel candidate strains of Chlorella and Scenedesmus for the potential to produce bioactive metabolites when grown under nutrient depletion regimes intended to stimulate production of triacylglycerides. Strain specific combinations of macro- and micro-nutrient restricted growth media did stimulate neutral lipid accumulation by microalgal cultures. However, cultures that were restricted for iron consistently and reliably tested positive for cytotoxicity by in vivo bioassays. The addition of iron back to these cultures resulted in the disappearance of the bioactive components by LC/MS fingerprinting and loss of cytotoxicity by in vivo bioassay. Incomplete NMR characterization of the most abundant cytotoxic fractions suggested that small molecular weight peptides and glycosides could be responsible for Chlorella cytotoxicity. Experiments were conducted to determine if the bioactive metabolites induced by Fe-limitation in Chlorella sp. cultures would elicit protection against Vampirovibrio chlorellavorus, an obligate predator of Chlorella. Introduction of V. chlorellavorus resulted in a 72% decrease in algal biomass in the experimental controls after 7 days. Conversely, only slight losses of algal biomass were measured for the iron limited Chlorella cultures (0-9%). This study demonstrates a causal linkage between iron bioavailability and bioactive metabolite production in strains of Chlorella and Scenedesmus. Further study of this phenomenon could contribute to the development of new strategies to extend algal production cycles in open, outdoor systems while ensuring the protection of biomass from predatory losses.

No MeSH data available.


Related in: MedlinePlus