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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

Ordination plots of elements for cytotoxic Chlorella sp. (strain 15) cultures responding to the addition of new iron. Red lines indicate the relative contribution of sampling time to the positioning of the elements in the ordination. Iron levels were fully restored for Treatment 4 Chlorella cultures (A); i.e., 0.1 mg/L Fe(III)-EDTA and 1.3 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Iron-replete conditions were established for the Treatment 5 Chlorella cultures (B); i.e., 40 mg/L Fe(III)-EDTA and 520 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Relative cytotoxic activity was inferred by in vivo bioassay and is denoted as highly active (+++), low level of activity (+), and no activity detected (ND).
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Figure 3: Ordination plots of elements for cytotoxic Chlorella sp. (strain 15) cultures responding to the addition of new iron. Red lines indicate the relative contribution of sampling time to the positioning of the elements in the ordination. Iron levels were fully restored for Treatment 4 Chlorella cultures (A); i.e., 0.1 mg/L Fe(III)-EDTA and 1.3 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Iron-replete conditions were established for the Treatment 5 Chlorella cultures (B); i.e., 40 mg/L Fe(III)-EDTA and 520 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Relative cytotoxic activity was inferred by in vivo bioassay and is denoted as highly active (+++), low level of activity (+), and no activity detected (ND).

Mentions: Figure 3 shows the elemental responses of Chlorella sp. (strain 15) cultures following the addition of iron as a function of time. Relative cytotoxicological activity responded in a time dependent manner in all cultures for both treatments following the addition to iron. Cytotoxicity in Treatment 4 (Figure 3A) cultures was just detectable after 7 days and no activity could be detected at 14 days. Interestingly, ordination plots of elements revealed that cellular contents of potassium (K), sulfur (S), and phosphorous (P) most strongly distinguished these time dependent samples, and that time had the greatest effect on S and P concentration, not K, at 14 days.


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)

Ordination plots of elements for cytotoxic Chlorella sp. (strain 15) cultures responding to the addition of new iron. Red lines indicate the relative contribution of sampling time to the positioning of the elements in the ordination. Iron levels were fully restored for Treatment 4 Chlorella cultures (A); i.e., 0.1 mg/L Fe(III)-EDTA and 1.3 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Iron-replete conditions were established for the Treatment 5 Chlorella cultures (B); i.e., 40 mg/L Fe(III)-EDTA and 520 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Relative cytotoxic activity was inferred by in vivo bioassay and is denoted as highly active (+++), low level of activity (+), and no activity detected (ND).
© Copyright Policy
Related In: Results  -  Collection

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

Figure 3: Ordination plots of elements for cytotoxic Chlorella sp. (strain 15) cultures responding to the addition of new iron. Red lines indicate the relative contribution of sampling time to the positioning of the elements in the ordination. Iron levels were fully restored for Treatment 4 Chlorella cultures (A); i.e., 0.1 mg/L Fe(III)-EDTA and 1.3 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Iron-replete conditions were established for the Treatment 5 Chlorella cultures (B); i.e., 40 mg/L Fe(III)-EDTA and 520 mg/L Fe(II)SO4 × 7H2O was added to the cultures. Relative cytotoxic activity was inferred by in vivo bioassay and is denoted as highly active (+++), low level of activity (+), and no activity detected (ND).
Mentions: Figure 3 shows the elemental responses of Chlorella sp. (strain 15) cultures following the addition of iron as a function of time. Relative cytotoxicological activity responded in a time dependent manner in all cultures for both treatments following the addition to iron. Cytotoxicity in Treatment 4 (Figure 3A) cultures was just detectable after 7 days and no activity could be detected at 14 days. Interestingly, ordination plots of elements revealed that cellular contents of potassium (K), sulfur (S), and phosphorous (P) most strongly distinguished these time dependent samples, and that time had the greatest effect on S and P concentration, not K, at 14 days.

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