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Published on: July 10, 2015
Use of poisons in determination of microbial manganese binding rates in seawater
R A Rosson1, B M Tebo, K H Nealson
1Marine Science Institute, The University of Texas at Austin, Port Aransas, Texas 78373, and Marine Biology Research Division A-002, Scripps Institution of Oceanography, La Jolla, California 92093.
Abstract:
A method was developed to determine whether microorganisms mediate the precipitation of manganese(II) in the marine environment. Radioactive Mn(II) was used as a tracer to measure the precipitation (binding and oxidation) of Mn(II) [i.e., the Mn(II) trapped on 0.2-mum membrane filters] in the presence and absence of biological poisons. A variety of antibiotics, fixatives, and metabolic inhibitors were tested in laboratory control experiments to select poisons that did not interfere in the chemistry of manganese. The poisons were deemed suitable if (i) they did not complex Mn(II) more strongly than the ion-exchange resin Chelex 100, (ii) they did not interfere in the adsorption of Mn(II) onto synthetic deltaMnO(2) (manganate), (iii) they did not cause desorption of Mn(II) which had been preadsorbed onto synthetic manganate, and (iv) they did not solubilize synthetic manganate. In addition, several known chelators, reducing agents, and buffers normally added to microbiological growth media or used in biochemical assays were tested. Most additions interfered to some extent with manganese chemistry. However, at least one inhibitor, sodium azide, or a mixture of sodium azide, penicillin, and tetracycline was shown to be appropriate for use in field studies of Mn(II) binding. Formaldehyde could also be used in short incubations (1 to 3 h) but was not suitable for longer time course studies. The method was applied to studies of Mn(II) precipitation in Saanich Inlet, British Columbia, Canada. Bacteria were shown to significantly enhance the rate of Mn(II) removal from solution in the manganese-rich particulate layer which occurs just above the oxygen-hydrogen sulfide interface in the water column.
Insights
Marine microorganisms significantly accelerate manganese(II) precipitation. This study developed a method using radioactive manganese(II) to measure microbial influence on manganese binding and oxidation in seawater.
Area of Science:
- Marine microbiology
- Geochemistry
- Environmental science
Background:
- Manganese(II) precipitation is crucial in marine environments.
- The role of microorganisms in manganese(II) precipitation requires precise measurement techniques.
Purpose of the Study:
- To develop and validate a method for quantifying microbial mediation of manganese(II) precipitation in marine settings.
- To assess the impact of biological poisons on manganese chemistry.
Main Methods:
- Utilized radioactive manganese(II) as a tracer to measure precipitation rates.
- Tested various biological poisons (antibiotics, fixatives, inhibitors) for compatibility with manganese chemistry.
- Applied the validated method in field studies in Saanich Inlet.
Main Results:
- Identified suitable inhibitors (sodium azide, or a mixture with penicillin and tetracycline) for field studies.
- Demonstrated that bacteria significantly enhance manganese(II) removal rates in specific marine layers.
- Formaldehyde suitable for short-term incubations only.
Conclusions:
- Microorganisms, particularly bacteria, play a significant role in the precipitation of manganese(II) in marine environments.
- The developed method accurately quantifies microbial contributions to manganese cycling.
- Findings are relevant to understanding biogeochemical processes at the oxygen-hydrogen sulfide interface.
