Limits...
Aerobic and anaerobic reduction of birnessite by a novel Dietzia strain.

Zhang H, Li Y, Wang X, Lu A, Ding H, Zeng C, Wang X, Wu X, Nie Y, Wang C - Geochem. Trans. (2015)

Bottom Line: Microbial reduction of Mn oxides is an important process found in many different environments including marine and freshwater sediments, lakes, anoxic basins, as well as oxic-anoxic transition zone of ocean.In contrast to anaerobic experiments, addition of AQDS decreased Mn reduction rate from 25 to 6%.Meanwhile, Mn(IV) bioreduction extent and suspension conditions determined the insoluble mineral products.

View Article: PubMed Central - PubMed

Affiliation: The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, 100871 People's Republic of China.

ABSTRACT

Background: Mn oxides occur in a wide variety of geological settings and exert considerable influences on the components and chemical behaviors of sediments and soils. Microbial reduction of Mn oxides is an important process found in many different environments including marine and freshwater sediments, lakes, anoxic basins, as well as oxic-anoxic transition zone of ocean. Although the pathway of Mn anaerobic reduction by two model bacteria, Geobacter and Shewanella, has been intensively studied, Mn bio-reduction is still the least well-explored process in nature. Particularly, reduction of Mn oxides by other bacteria and in the presence of O2 has been fewly reported in recent publishes.

Results: A series of experiments were conducted to understand the capability of Dietzia DQ12-45-1b in bioreduction of birnessite. In anaerobic systems, Mn reduction rate reached as high as 93% within 4 weeks when inoculated with 1.0 × 10(10) cells/mL Dietzia DQ12-45-1b strains. Addition of AQDS enhanced Mn reduction rate from 53 to 91%. The anaerobic reduction of Mn was not coupled by any increase in bacterial protein concentration, and the reduction rate in the stable stage of day 2-14 was found to be in good proportion to the protein concentration. The anaerobic reduction of birnessite released Mn(II) either into the medium or adsorbed on the mineral or bacteria surface and resulted in the dissolution of birnessite as indicated by XRD, SEM and XANES. Under aerobic condition, the reduction rate was only 37% with a cell concentration of 1.0 × 10(10) cells/mL, much lower than that in parallel anaerobic treatment. Bacterial growth under aerobic condition was indicated by time-course increase of protein and pH. In contrast to anaerobic experiments, addition of AQDS decreased Mn reduction rate from 25 to 6%. The reduced Mn(II) combined with carbon dioxide produced by acetate metabolism, as well as an alkaline pH environment given by cell growth, finally resulted in the formation of Mn(II)-bearing carbonate (kutnohorite), which was verified by XRD and XANES results. The system with the highest cell concentration of 1.0 × 10(10) cells/mL gave rise to the most amount of kutnohorite, while concentration of Mn(II) produced with cell concentration of 6.2 × 10(8) cells/mL was too low to thermodynamically favor the formation of kutnohorite but result in the formation of aragonite instead.

Conclusion: Dietzia DQ12-45-1b was able to anaerobically and aerobically reduce birnessite. The rate and extent of Mn(IV) reduction depend on cell concentration, addition of AQDS or not, and presence of O2 or not. Meanwhile, Mn(IV) bioreduction extent and suspension conditions determined the insoluble mineral products.

No MeSH data available.


Reduction potential of O2, birnessite (at 2 × 10−5 and 2 × 10−6 M Mn2+ activity) [42] and AQDS (at 5 × 10−5 M AQDS plus 5 × 10−5 M AH2DS and 10−4 AQDS M plus 10−7 M AH2DS activity) [43] as a function of pH.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4528715&req=5

Fig5: Reduction potential of O2, birnessite (at 2 × 10−5 and 2 × 10−6 M Mn2+ activity) [42] and AQDS (at 5 × 10−5 M AQDS plus 5 × 10−5 M AH2DS and 10−4 AQDS M plus 10−7 M AH2DS activity) [43] as a function of pH.

Mentions: It is believed that AQDS could enhance the rate and extent of microbial metal reduction by shuttling electrons from bacteria to mineral surfaces and thus eliminating the requirement for direct contact of bacteria with electron acceptors [18, 37–40]. The possible reduction of AQDS by cells gave rise to biogenic AH2DS (reduced state of AQDS), which then undertook chemical reduction of Mn(IV) [38, 40]. This mechanism could explain the observed increase in both the rate and extent of Mn reduction under anaerobic condition. Under aerobic condition, electrons were transferred to AQDS prior to birnessite and O2 [41]. Birnessite and O2 competed to accept electrons from biogenic AH2DS. At neutral to alkaline environment, the redox potential of O2 was higher than that of birnessite, especially at alkaline pH (Fig. 5). So the biogenic AH2DS may be preferentially to be oxidized by O2. In aerobic bio-treatment, AQDS as an electron shuttle essentially accelerated electron transfer between bacteria and O2, which finally lead to the inhibition of Mn(IV) reduction.Fig. 5


Aerobic and anaerobic reduction of birnessite by a novel Dietzia strain.

Zhang H, Li Y, Wang X, Lu A, Ding H, Zeng C, Wang X, Wu X, Nie Y, Wang C - Geochem. Trans. (2015)

Reduction potential of O2, birnessite (at 2 × 10−5 and 2 × 10−6 M Mn2+ activity) [42] and AQDS (at 5 × 10−5 M AQDS plus 5 × 10−5 M AH2DS and 10−4 AQDS M plus 10−7 M AH2DS activity) [43] as a function of pH.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4528715&req=5

Fig5: Reduction potential of O2, birnessite (at 2 × 10−5 and 2 × 10−6 M Mn2+ activity) [42] and AQDS (at 5 × 10−5 M AQDS plus 5 × 10−5 M AH2DS and 10−4 AQDS M plus 10−7 M AH2DS activity) [43] as a function of pH.
Mentions: It is believed that AQDS could enhance the rate and extent of microbial metal reduction by shuttling electrons from bacteria to mineral surfaces and thus eliminating the requirement for direct contact of bacteria with electron acceptors [18, 37–40]. The possible reduction of AQDS by cells gave rise to biogenic AH2DS (reduced state of AQDS), which then undertook chemical reduction of Mn(IV) [38, 40]. This mechanism could explain the observed increase in both the rate and extent of Mn reduction under anaerobic condition. Under aerobic condition, electrons were transferred to AQDS prior to birnessite and O2 [41]. Birnessite and O2 competed to accept electrons from biogenic AH2DS. At neutral to alkaline environment, the redox potential of O2 was higher than that of birnessite, especially at alkaline pH (Fig. 5). So the biogenic AH2DS may be preferentially to be oxidized by O2. In aerobic bio-treatment, AQDS as an electron shuttle essentially accelerated electron transfer between bacteria and O2, which finally lead to the inhibition of Mn(IV) reduction.Fig. 5

Bottom Line: Microbial reduction of Mn oxides is an important process found in many different environments including marine and freshwater sediments, lakes, anoxic basins, as well as oxic-anoxic transition zone of ocean.In contrast to anaerobic experiments, addition of AQDS decreased Mn reduction rate from 25 to 6%.Meanwhile, Mn(IV) bioreduction extent and suspension conditions determined the insoluble mineral products.

View Article: PubMed Central - PubMed

Affiliation: The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing, 100871 People's Republic of China.

ABSTRACT

Background: Mn oxides occur in a wide variety of geological settings and exert considerable influences on the components and chemical behaviors of sediments and soils. Microbial reduction of Mn oxides is an important process found in many different environments including marine and freshwater sediments, lakes, anoxic basins, as well as oxic-anoxic transition zone of ocean. Although the pathway of Mn anaerobic reduction by two model bacteria, Geobacter and Shewanella, has been intensively studied, Mn bio-reduction is still the least well-explored process in nature. Particularly, reduction of Mn oxides by other bacteria and in the presence of O2 has been fewly reported in recent publishes.

Results: A series of experiments were conducted to understand the capability of Dietzia DQ12-45-1b in bioreduction of birnessite. In anaerobic systems, Mn reduction rate reached as high as 93% within 4 weeks when inoculated with 1.0 × 10(10) cells/mL Dietzia DQ12-45-1b strains. Addition of AQDS enhanced Mn reduction rate from 53 to 91%. The anaerobic reduction of Mn was not coupled by any increase in bacterial protein concentration, and the reduction rate in the stable stage of day 2-14 was found to be in good proportion to the protein concentration. The anaerobic reduction of birnessite released Mn(II) either into the medium or adsorbed on the mineral or bacteria surface and resulted in the dissolution of birnessite as indicated by XRD, SEM and XANES. Under aerobic condition, the reduction rate was only 37% with a cell concentration of 1.0 × 10(10) cells/mL, much lower than that in parallel anaerobic treatment. Bacterial growth under aerobic condition was indicated by time-course increase of protein and pH. In contrast to anaerobic experiments, addition of AQDS decreased Mn reduction rate from 25 to 6%. The reduced Mn(II) combined with carbon dioxide produced by acetate metabolism, as well as an alkaline pH environment given by cell growth, finally resulted in the formation of Mn(II)-bearing carbonate (kutnohorite), which was verified by XRD and XANES results. The system with the highest cell concentration of 1.0 × 10(10) cells/mL gave rise to the most amount of kutnohorite, while concentration of Mn(II) produced with cell concentration of 6.2 × 10(8) cells/mL was too low to thermodynamically favor the formation of kutnohorite but result in the formation of aragonite instead.

Conclusion: Dietzia DQ12-45-1b was able to anaerobically and aerobically reduce birnessite. The rate and extent of Mn(IV) reduction depend on cell concentration, addition of AQDS or not, and presence of O2 or not. Meanwhile, Mn(IV) bioreduction extent and suspension conditions determined the insoluble mineral products.

No MeSH data available.