Progress 08/01/03 to 07/31/05
Outputs
A key challenge to understanding microbial community dynamics in soil is our ability to predict the adhesion/de-adhesion behavior and resulting movement of both indigenous and introduced bacteria in soil systems. Adhesion is mediated by the bacterial outer membrane, the composition of which varies with nutrient status, attachment state and environmental stressors such as extreme drying. We have developed the protocol to use a Surface Forces Apparatus to measure the adhesive and elastic properties of bacteria deposited on surfaces. To minimize cell surface changes due to the influence of solution composition and bacterial growth, initial force measurements have been conducted on bacterial monolayers in ambient humidity. Force measurements can be used not only to understand bacterial adhesion but also to understand how bacteria withstand the extreme stress of air drying and subsequent rewetting that occurs on plant surface and in unsaturated soils. Our measurements show
that it takes four to six days for the bacterial layer to reach equilibrium with the surroundings with respect to water. This is contrary to the commonly held idea that bacteria come into equilibrium with the surroundings in a relatively short period of time of minutes to hours. Additionally, the bacteria become more adhesive with repeated contacts and finally become very adhesive as they die and lyse. A number of presentations have been made and several publications are in preparation.
Impacts
This research will be important for understanding biofilm formation in medical, environmental and industrial applications. In soil systems in particular, bacterial adhesion is the key event that retards movement of bacteria in soils. A quantitative understanding of bacterial movement in soil is critical to several areas important in agriculture. One such area is the prediction of dissemination of pathogenic bacteria in the environment, e.g., from biosolids-amended crops, or root infecting plant pathogens. A second area is the movement of bacteria in response to environmental perturbation, e.g., application of pesticides or other cropping procedures that disturb the natural soil environment.
Publications
- Directly measuring bacteria-surface interactions with the Surface Forces Apparatus, C.H. Heo, J.G. Dorn, R.M. Maier and J.E. Curry (2006) Langmuir, in preparation.
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Progress 01/01/04 to 12/31/04
Outputs
A key challenge to understanding microbial community dynamics in soil is our ability to predict the adhesion/de-adhesion behavior and resulting movement of both indigenous and introduced bacteria in soil systems. Adhesion is mediated by the bacterial outer membrane, the composition of which varies with nutrient status, attachment state and environmental stressors such as extreme drying. We have developed the protocol to use a Surface Forces Apparatus to measure the adhesive and elastic properties of bacteria deposited on surfaces. To minimize cell surface changes due to the influence of solution composition and bacterial growth, initial force measurements have been conducted on bacterial monolayers in ambient humidity. Force measurements can be used not only to understand bacterial adhesion but also to understand how bacteria withstand the extreme stress of air drying and subsequent rewetting that occurs on plant surfaces and in unsaturated soils. Our measurements
show that it takes four to six days for the bacterial layer to reach equilibrium with the surroundings with respect to water. This is contrary to the commonly held idea that bacteria come into equilibrium with the surroundings in a relative short time period of minutes to hours. Additionally, the bacteria become more adhesive with repeated contacts and finally become very adhesive as they die and lyse (> 400 hours). Several presentations have been made and our first paper will be submitted in early 2005.
Impacts
This research will be important for understanding biofilm formation in medical, environmental and industrial applications. In soil systems in particular, bacterial adhesion is the key event that retards movement of bacteria in soils. A quantitative understanding of bacterial movement in soil is critical to several areas important in agriculture. One such area is the prediction of dissemination of pathogenic bacteria in the environment, e.g., from biosolids-amended crops, or root infecting plant pathogens. A second area is the movement of bacteria in response to environmental perturbation, e.g., application of pesticides or other cropping procedures that disturb the natural soil environment.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The aim of this project is to develop the technology that allows use of the surface forces apparatus to make direct force measurements of the adhesive properties of bacteria. A macroscopic-level examination of bacterial adhesion in natural systems has so far been insufficient to understand the factors that control the initial events in microbial attachment to natural surfaces. The surfaces forces apparatus offers a unique opportunity to directly measure bacteria-surface interactions that will complement existing technologies and ultimately allow absolute quantitation of the forces involved in microbial adhesion. As a first step it is necessary to deposit a monolayer of bacteria on a mica surface. We have systematically studied deposition times and conditions and have developed a protocol that results in reproducible monolayer bacterial films. These films have been characterized with scanning electron microscopy. Additionally, we have successfully measured forces
between a bacteria coated surface and a bare mica surface in ambient humidity in the surface forces apparatus. Initial results show that the adhesive force is directly proportional to the applied force and that a minimum applied force is necessary to achieve measurable bacteria-surface adhesion.
Impacts
This research will be important for understanding biofilm formation in medical, environmental and industrial applications. In soil systems in particular, bacterial adhesion is the key event that retards movement of bacteria in soils. A quantitative understanding of bacterial movement in soil is critical to several areas important in agriculture. One such area is the prediction of dissemination of pathogenic bacteria in the environment, e.g., from biosolids-amended crops, or root infecting plant pathogens. A second area is the movement of bacteria in response to environmental perturbation, e.g., application of pesticides or other cropping procedures that disturb the natural soil environment.
Publications
- No publications reported this period
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