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Critical Involvement of Environmental Carbon Dioxide Fixation to Drive Wax Ester Fermentation in Euglena

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ABSTRACT

Accumulation profiles of wax esters in Euglena gracilis Z were studied under several environmental conditions. The highest amount of total wax esters accumulated under hypoxia in the dark, and C28 (myristyl-myristate, C14:0-C14:0) was prevalent among all conditions investigated. The wax ester production was almost completely suppressed under anoxia in the light, and supplying exogenous inorganic carbon sources restored wax ester fermentation, indicating the need for external carbon sources for the wax ester fermentation. 13C-labeling experiments revealed specific isotopic enrichment in the odd-numbered fatty acids derived from wax esters, indicating that the exogenously-supplied CO2 was incorporated into wax esters via the propionyl-CoA pathway through the reverse tricarboxylic acid (TCA) cycle. The addition of 3-mercaptopicolinic acid, a phosphoenolpyruvate carboxykinase (PEPCK) inhibitor, significantly affected the incorporation of 13C into citrate and malate as the biosynthetic intermediates of the odd-numbered fatty acids, suggesting the involvement of PEPCK reaction to drive wax ester fermentation. Additionally, the 13C-enrichment pattern of succinate suggested that the CO2 assimilation might proceed through alternative pathways in addition to the PEPCK reaction. The current results indicate that the mechanisms of anoxic CO2 assimilation are an important target to reinforce wax ester fermentation in Euglena.

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Related in: MedlinePlus

Recovery of the inhibited wax ester fermentation in anoxia by inorganic carbon sources.The relative levels of C28 (14:0–14:0) are shown as representing the wax esters in E. gracilis Z. The cells were cultivated in the light under hypoxic and anoxic conditions in the presence of CO2 and/or NaHCO3 (either 10 mM or 20 mM). The inset indicates light-anoxic conditions without an exogenous carbon supply. Error bars indicate standard deviation from triplicate cultures.
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pone.0162827.g004: Recovery of the inhibited wax ester fermentation in anoxia by inorganic carbon sources.The relative levels of C28 (14:0–14:0) are shown as representing the wax esters in E. gracilis Z. The cells were cultivated in the light under hypoxic and anoxic conditions in the presence of CO2 and/or NaHCO3 (either 10 mM or 20 mM). The inset indicates light-anoxic conditions without an exogenous carbon supply. Error bars indicate standard deviation from triplicate cultures.

Mentions: Fig 4 compares the relative accumulation levels of C28 wax ester, representing the general wax ester profile in E. gracilis Z, under various conditions. C14:0-C14:0 wax ester was most abundant in all the samples investigated. Supplementing CO2 gas restored wax ester fermentation in light-grown anoxic E. gracilis Z cells (Fig 4). Supplementation of NaHCO3 (either 10 mM or 20 mM) to the CO2-aerated sample did not have additional influence on the wax ester accumulation (Fig 4). The amounts of wax esters accumulated in the CO2-aerated anoxic cells were slightly higher than that produced in the hypoxic culture (Fig 4). Distribution of the five major wax esters synthesized under these growth conditions is shown in Table 1.


Critical Involvement of Environmental Carbon Dioxide Fixation to Drive Wax Ester Fermentation in Euglena
Recovery of the inhibited wax ester fermentation in anoxia by inorganic carbon sources.The relative levels of C28 (14:0–14:0) are shown as representing the wax esters in E. gracilis Z. The cells were cultivated in the light under hypoxic and anoxic conditions in the presence of CO2 and/or NaHCO3 (either 10 mM or 20 mM). The inset indicates light-anoxic conditions without an exogenous carbon supply. Error bars indicate standard deviation from triplicate cultures.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036851&req=5

pone.0162827.g004: Recovery of the inhibited wax ester fermentation in anoxia by inorganic carbon sources.The relative levels of C28 (14:0–14:0) are shown as representing the wax esters in E. gracilis Z. The cells were cultivated in the light under hypoxic and anoxic conditions in the presence of CO2 and/or NaHCO3 (either 10 mM or 20 mM). The inset indicates light-anoxic conditions without an exogenous carbon supply. Error bars indicate standard deviation from triplicate cultures.
Mentions: Fig 4 compares the relative accumulation levels of C28 wax ester, representing the general wax ester profile in E. gracilis Z, under various conditions. C14:0-C14:0 wax ester was most abundant in all the samples investigated. Supplementing CO2 gas restored wax ester fermentation in light-grown anoxic E. gracilis Z cells (Fig 4). Supplementation of NaHCO3 (either 10 mM or 20 mM) to the CO2-aerated sample did not have additional influence on the wax ester accumulation (Fig 4). The amounts of wax esters accumulated in the CO2-aerated anoxic cells were slightly higher than that produced in the hypoxic culture (Fig 4). Distribution of the five major wax esters synthesized under these growth conditions is shown in Table 1.

View Article: PubMed Central - PubMed

ABSTRACT

Accumulation profiles of wax esters in Euglena gracilis Z were studied under several environmental conditions. The highest amount of total wax esters accumulated under hypoxia in the dark, and C28 (myristyl-myristate, C14:0-C14:0) was prevalent among all conditions investigated. The wax ester production was almost completely suppressed under anoxia in the light, and supplying exogenous inorganic carbon sources restored wax ester fermentation, indicating the need for external carbon sources for the wax ester fermentation. 13C-labeling experiments revealed specific isotopic enrichment in the odd-numbered fatty acids derived from wax esters, indicating that the exogenously-supplied CO2 was incorporated into wax esters via the propionyl-CoA pathway through the reverse tricarboxylic acid (TCA) cycle. The addition of 3-mercaptopicolinic acid, a phosphoenolpyruvate carboxykinase (PEPCK) inhibitor, significantly affected the incorporation of 13C into citrate and malate as the biosynthetic intermediates of the odd-numbered fatty acids, suggesting the involvement of PEPCK reaction to drive wax ester fermentation. Additionally, the 13C-enrichment pattern of succinate suggested that the CO2 assimilation might proceed through alternative pathways in addition to the PEPCK reaction. The current results indicate that the mechanisms of anoxic CO2 assimilation are an important target to reinforce wax ester fermentation in Euglena.

No MeSH data available.


Related in: MedlinePlus