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Novel Pathway for Vanadium(V) Bio-Detoxification by Gram-Positive Lactococcus raffinolactis
Baogang Zhang1, Yi'na Li1, Yangmei Fei1
1School of Water Resources and Environment, MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, P. R. China.
Environmental Science & Technology
|January 25, 2021
Summary
Lactococcus raffinolactis, a Gram-positive bacterium, effectively removes vanadium(V) through bioremediation. This study reveals a new pathway for vanadium reduction and detoxification by this species.
Area of Science:
- Environmental microbiology
- Bioremediation
- Biochemistry
Background:
- Vanadium(V) [V(V)] contamination poses environmental risks.
- Bioremediation strategies are sought, but functional microbial species are limited, primarily Gram-negative bacteria.
- A need exists for identifying novel microbial candidates for vanadium bioremediation.
Purpose of the Study:
- To investigate the V(V) reduction capability of Lactococcus raffinolactis, a Gram-positive bacterium.
- To elucidate the mechanisms involved in V(V) bio-detoxification by this species.
- To explore the potential of L. raffinolactis as a microbial resource for vanadium-contaminated environments.
Main Methods:
- Cultivation of L. raffinolactis in a citrate-fed system.
- Monitoring of V(V) removal efficiency and rate over 10 days.
- Analysis of V(V) reduction products and cellular distribution.
- Identification of key enzymes (nitrite reductase, nirS) and cellular components (extracellular polymeric substances, antioxidant enzymes) involved in the process.
Main Results:
- L. raffinolactis achieved 86.5% V(V) removal with a rate of 4.32 mg/L·d.
- V(V) was bio-reduced to insoluble vanadium(IV), found intra- and extracellularly.
- Nitrite reductase (nirS) was identified as the primary catalyst for intracellular V(V) reduction.
- Enhanced antioxidant activities (superoxide dismutase, catalase) and extracellular polymeric substances contributed to V(V) detoxification and ROS scavenging.
Conclusions:
- L. raffinolactis demonstrates significant V(V) bioremediation potential, expanding the known functional species.
- A novel intracellular V(V) reduction pathway mediated by nirS in Gram-positive bacteria was identified.
- Extracellular polymeric substances and antioxidant systems play crucial roles in V(V) detoxification.
- This study provides valuable insights into Gram-positive bacteria for V(V) bioremediation and offers a promising microbial resource.
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