1 research outputs found
Stable-Isotope Probing Reveals the Activity and Function of Autotrophic and Heterotrophic Denitrifiers in Nitrate Removal from Organic-Limited Wastewater
Combined
heterotrophic and autotrophic denitrification (HAD) is
a sustainable and practical method for removing nitrate from organic-limited
wastewater. However, the active microorganisms responsible for denitrification
in wastewater treatment have not been clearly identified. In this
study, a combined microelectrolysis, heterotrophic, and autotrophic
denitrification (CEHAD) process was established. DNA-based stable
isotope probing was employed to identify the active denitrifiers in
reactors fed with either <sup>13</sup>C-labeled inorganic or organic
carbon sources. The total nitrogen removal efficiencies reached 87.2–92.8%
at a low organic carbon concentration (20 mg/L COD). Real-time polymerase
chain reaction of the <i>nirS</i> gene as a function
of the DNA buoyant density following the ultracentrifugation of the
total DNA indicated marked <sup>13</sup>C-labeling of active denitrifiers.
High-throughput sequencing of the fractionated DNA in H<sup>13</sup>CO<sub>3</sub><sup>–</sup>/<sup>12</sup>CH<sub>3</sub><sup>12</sup>COO<sup>–</sup>-fed and H<sup>12</sup>CO<sub>3</sub><sup>–</sup>/<sup>13</sup>CH<sub>3</sub><sup>13</sup>COO<sup>–</sup>-fed reactors revealed that <i>Thermomonas</i>-like phylotypes were labeled by <sup>13</sup>C-bicarbonate, while <i>Thauera</i>-like and <i>Comamonas</i>-like phylotypes
were labeled by <sup>13</sup>C-acetate. Meanwhile, <i>Arenimonas</i>-like and <i>Rubellimicrobium</i>-like phylotypes were
recovered in the “heavy” DNA fractions from both reactors.
These results suggest that nitrate removal in CEHAD is catalyzed by
various active microorganisms, including autotrophs, heterotrophs,
and mixotrophs. Our findings provide a better understanding of the
mechanism of nitrogen removal from organic-limited water and wastewater
and can be applied to further optimize such processes