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Mobilization of manganese by basalt associated Mn(II)-oxidizing bacteria from the Indian Ridge System
P P Sujith1, B S Mourya, S Krishnamurthi
1Microbiology Laboratory, National Institute of Oceanography, Council of Scientific and Industrial Research, Dona Paula 403 004, Goa, India.
Chemosphere
|November 5, 2013
Summary
Microbes in basaltic rocks oxidize and mobilize manganese oxides. Adding organic carbon shifted microbial activity from manganese oxidation to reduction, confirming bacterial roles in manganese cycling.
Area of Science:
- Geomicrobiology
- Environmental Science
- Mineralogy
Background:
- Basaltic rocks in the Indian Ridge System host manganese (Mn)-oxide coatings, primarily todorokite and birnesite.
- Microorganisms associated with these basalts are hypothesized to play a role in Mn oxidation and mineral deposition.
Purpose of the Study:
- To investigate the role of microorganisms in the oxidation and mobilization of Mn in basaltic environments.
- To test the hypothesis that Mn-oxidizing microbes respond to organic carbon pulses by mobilizing Mn-oxides.
Main Methods:
- Enumeration of Mn-oxidizing and -reducing bacteria.
- Incubation of basalt fragments with and without glucose (organic carbon proxy) at 4±2 °C.
- Measurement of Mn mobilization rates.
- Control experiments using azide (poison) and heat-killed samples.
- Identification of culturable bacteria using 16S rRNA gene sequencing.
Main Results:
- The microbial community initially exhibited Mn(II)-oxidizing activity.
- Addition of glucose shifted the community towards Mn(IV)-reducing activity, significantly increasing Mn mobilization.
- Mn mobilization rates were substantially higher in the presence of glucose compared to its absence and controls.
- Bacterial counts increased significantly with glucose addition.
Conclusions:
- Microorganisms, including Bacillus, Exiguobacterium, Staphylococcus, Brevibacterium, and Alcanivorax species, actively participate in Mn mobilization in basaltic environments.
- The addition of organic carbon alters microbial metabolism, switching from Mn oxidation to reduction, thereby influencing Mn cycling.
- These findings highlight the dynamic interplay between microbial communities and mineral transformations in marine geological settings.
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