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Coexisting bacterial populations responsible for multiphasic mineralization kinetics in soil
1Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder, Colorado 80309.
Applied and Environmental Microbiology
|September 1, 1990
Summary
Two bacterial populations in soil mineralize 2,4-dinitrophenol (DNP). Janthinobacterium sp. and Rhodococcus sp. exhibit distinct DNP mineralization kinetics, explaining multiphasic degradation observed in forest soil.
Area of Science:
- Environmental microbiology
- Bioremediation
- Soil science
Background:
- 2,4-dinitrophenol (DNP) is a persistent pollutant requiring microbial degradation.
- Previous studies suggested two microbial populations contribute to DNP mineralization in forest soil.
- Understanding these populations is crucial for effective bioremediation strategies.
Purpose of the Study:
- To identify and characterize the microbial populations responsible for 2,4-dinitrophenol (DNP) mineralization in forest soil.
- To elucidate the physiological differences between these DNP-mineralizing bacteria.
- To confirm the role of distinct bacterial populations in observed multiphasic DNP mineralization kinetics.
Main Methods:
- Microbial inhibitors (eukaryotic and prokaryotic) were used to determine the nature of the DNP-mineralizing populations.
- Most-probable-number (MPN) counts were performed using various DNP concentrations.
- Bacterial enrichments with different DNP concentrations and inhibitors were used for isolation.
- Isolates were identified, and their kinetic parameters (mu(max), K(m)) for DNP mineralization were determined in pure culture and compared to soil studies.
Main Results:
- Both DNP-mineralizing populations in forest soil were identified as bacteria, not fungi.
- Two bacterial species, Janthinobacterium sp. and Rhodococcus sp., were consistently isolated.
- Janthinobacterium sp. exhibited low DNP mineralization kinetics (low mu(max), low K(m)), while Rhodococcus sp. showed higher values.
- Observed kinetic differences in pure culture mirrored those seen in soil, supporting the multiphasic mineralization model.
Conclusions:
- Two distinct bacterial populations, Janthinobacterium sp. and Rhodococcus sp., are responsible for the observed multiphasic 2,4-dinitrophenol (DNP) mineralization in forest soil.
- Physiological differences in DNP metabolism between these species explain the complex mineralization kinetics.
- This study validates the hypothesis of distinct bacterial consortia driving soil contaminant degradation.