Cong Huang,Qian Liu,Zhi-Ling Li,Xiao-dan Ma,Ya-Nan Hou,Nan-Qi Ren,Ai-Jie Wang
The denitrification desulfurization system can be used to remediate wastewater containing carbon, nitrogen, and sulfur. However, the relationship between autotrophic and heterotrophic bacteria remains poorly understood. To better understand the roles and relations of core bacteria, an expanded granular sludge bed (EGSB) reactor was continuously operated under autotrophic (stage I), heterotrophic (stage II) and mixotrophic (stages III–VII) conditions with a 490-day period. Stage IV represented the excellent S 0 recovery rate (69.5%). The different trophic conditions caused the obvious succession of dominant bacterial genera. Autotrophic environment (stage I) enriched mostly Thiobacillus , and heterotrophic environment (stage II) was dominated with Azoarcus and Pseudomonas. Thauera, Arcobacter and Azoarcus became the predominant genera under mixotrophic conditions (stage III-VII). Strains belonged to these core genera were further isolated, and all seven isolates were confirmed with denitrifying sulfur oxidation capacity. Heterotrophic strain HDD1 (genus of Thauera ) possessed both the highest sulfide degradation and S 0 recovery rates. Expression levels of cbbM and gltA genes were positively related with the autotrophic and heterotrophic conditions, respectively. NirK gene was highly expressed between log 3.7–log 4.3 during the entire run. Expression of both sqr and soxB genes were closely related with sulfur conversion. More than 57.5% of S 0 recovery rate could be obtained as sqr gene expression was greater than log 3.2, and while, sulfate was the primary form as soxB gene expression higher than log 3.9. The correlation between core microbial genera was very low from network, indicating a complex and non-specific mutualistic network between bacterial functional groups under each nutrient condition, and a stable coexistence state was possibly formed through utilizing each the secondary or waste metabolites in the mixotrophic conditions. This relationship was beneficial to the stability of the microbial community structure in the denitrification desulfurization system.
Weiqi Wang,Xuan Qiu,Min Li,Xinyue Zhang,Xiaoyan Liu,Yang Li,Jingwen Lei,Olli H. Tuovinen,Hongmei Wang
Microbial-mediated antimony (Sb) release from stibnite (Sb 2 S 3 ) threatens groundwater safety, yet how hydrological fluctuations regulate this biogenic process and its mechanism remain poorly understood. This study explored how hydrodynamic variations (simulating organic-oxygen recharge into anoxic aquifers) govern stibnite bio-weathering in Xikuangshan shallow groundwater through microcosms. The results revealed bacterial communities exhibit dual functionality under redox fluctuations: driving biofilm formation in anoxic phases and accelerating Sb release during oxic transitions. The AnH system (Anoxic-oxic-anoxic-oxic cycles with Na-lactate for Heterotrophs) demonstrated a maximum of Sb concentration at 0.63 mM after 16 days, primarily driven by Dechloromonas, Ferribacterium , and Thauera . Microbial metabolic byproduct nitrite activates oxygen to produce H 2 O 2 (maximum of 14.7 μM), which also contributes to the release and oxidation of antimony. Moreover, carbon source affects the pathway of bacterial antimony release. Na-lactate stimulated the expression of aioA (Sb-oxidation) in heterotrophs, while inorganic carbon (Na-bicarbonate) favored soxB (sulfur-oxidation) in autotrophic Thiobacillus and mixotrophic sulfur-oxidizers. In summary, oxygen and carbon sources regulate biofilm formation, aioA and soxB expression, and H₂O₂ generation, subsequently affecting Sb release/oxidation. This study deciphered how oxygen-carbon regimes govern microbial Sb mobilization, elucidating antimony biogeochemical dynamics under hydrological fluctuations.
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