Abstract
Bacteria and other microorganisms play an important role for removal of pollutants released into the environment, either deliberately or accidentally. In particular, soils are reservoirs for microorganisms carrying the catalytic potential for breakdown of otherwise toxic and often recalcitrant compounds.
However, soil environments frequently undergo changes, for instance in nutrient and water availability, and microbial cells residing in soils are continuously exposed to various abiotic and biotic insults. Thriving in soil is therefore difficult and conditions are rarely optimal for the microbial biodegradative or catabolic performance.
To date, details concerning the physiology of degrader microorganisms and their ability to express the relevant catabolic genes in the context of a complex and stressful environment have yet to be elucidated. In order to fully exploit the catabolic potential of degrader microorganisms, that being indigenous populations already present in a given environment or specific microorganisms delivered to the environment for bioremediation purposes, a deeper understanding of the abovementioned characteristics is needed.
This PhD project aimed at studying the physiological responses of model degrader bacteria to nutrient- and oxidative stress, two highly relevant stress scenarios in natural environments, and at evaluating the impact of these environmental stress conditions on catabolic gene expression.
The results suggest that environmental bacteria, here represented by the toluene- and xylene degrading bacterium Pseudomonas putida mt-2 and the phenoxy acid herbicide degrading bacterium Cupriavidus pinatubonensis JMP134, have a high defense capacity towards archetypical environmental stressors. However, the results also showed that induction of a stress defense may have a cost in regard to expression of catabolic genes. Hence, even though environmental bacteria are able to deal with many stressful situations, environmental stressors can be bottlenecks for pollutant degradation by influencing directly on the level of catabolic gene expression.
Finally the study investigated whether findings on pollutant degradation from in vitro test tube conditions have any relevance when increasing the complexity to approach conditions that degrader bacteria encounter in the actual environment.
However, soil environments frequently undergo changes, for instance in nutrient and water availability, and microbial cells residing in soils are continuously exposed to various abiotic and biotic insults. Thriving in soil is therefore difficult and conditions are rarely optimal for the microbial biodegradative or catabolic performance.
To date, details concerning the physiology of degrader microorganisms and their ability to express the relevant catabolic genes in the context of a complex and stressful environment have yet to be elucidated. In order to fully exploit the catabolic potential of degrader microorganisms, that being indigenous populations already present in a given environment or specific microorganisms delivered to the environment for bioremediation purposes, a deeper understanding of the abovementioned characteristics is needed.
This PhD project aimed at studying the physiological responses of model degrader bacteria to nutrient- and oxidative stress, two highly relevant stress scenarios in natural environments, and at evaluating the impact of these environmental stress conditions on catabolic gene expression.
The results suggest that environmental bacteria, here represented by the toluene- and xylene degrading bacterium Pseudomonas putida mt-2 and the phenoxy acid herbicide degrading bacterium Cupriavidus pinatubonensis JMP134, have a high defense capacity towards archetypical environmental stressors. However, the results also showed that induction of a stress defense may have a cost in regard to expression of catabolic genes. Hence, even though environmental bacteria are able to deal with many stressful situations, environmental stressors can be bottlenecks for pollutant degradation by influencing directly on the level of catabolic gene expression.
Finally the study investigated whether findings on pollutant degradation from in vitro test tube conditions have any relevance when increasing the complexity to approach conditions that degrader bacteria encounter in the actual environment.
| Original language | English |
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| Publisher | Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen |
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| Number of pages | 133 |
| Publication status | Published - 2015 |