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Directly Measuring the Adhesive and Elastic Properties of Bacteria using a Surface Force Apparatus: Effect of Desiccation

Published online by Cambridge University Press:  01 February 2011

Cheol Ho Heo
Affiliation:
[email protected], The University of Arizona, Soil, Water, and Environmental Science, Department of Soil Water and Environmental Science, The University of Arizona, P.O. Box 210038, Tucson, AZ, 85721-0038, United States, (520)626-5266, (520) 621-1647
Raina M Maier
Affiliation:
[email protected], The University of Arizona, Soil, Water, and Environmental Science, Tucson, AZ, 85721-0038, United States
Joan E Curry
Affiliation:
[email protected], The University of Arizona, Soil, Water, and Environmental Science, Tucson, AZ, 85721-0038, United States
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Abstract

Bacterial adhesion is the first step in biofilm formation which impacts numerous environmental, industrial and medical processes. Examples of undesirable consequences of biofilm formation include metal rust, sewage sludge and bacteria-related diseases. Desirable consequences are biofiltration and bioremediation. Bacteria are resilient and can survive in harsh environments. A severe stress is desiccation since dehydration can damage DNA and change the properties of proteins. Some bacteria protect against dehydration by accumulating sugars such as sucrose and trehalose while others undergo a transformation from an active to a dormant state. Evaporative deposition of bacteria on a surface shows that some bacteria aggregate to form two dimensional patterns which may be important for nutrient sharing and survival in dry conditions. Since bacteria are increasingly being employed as components in biosensors and biofilm reactors, it is important to understand the material properties of bacteria in dry conditions for these applications. For a decade, Atomic Force Microscopy (AFM) has been the primary tool used to study the adhesion and elastic properties of individual bacteria. In this work we show it is possible to use a Surface Forces Apparatus (SFA) to measure elastic and adhesive properties of small collections of surface bound bacteria. The measurements are conducted with incomplete, patterned bacterial films and we have developed a protocol to image the contact area with AFM after the experiment. Using the SFA, we measured the force profile between a Pseudomonas aeruginosa PAO1 film and a bare mica surface. P. aeruginosa PAO1 is a ubiquitous gram-negative soil bacterium and is also an opportunistic pathogen. We repeated the measurement in the same contact position for six days to determine the effect of desiccation on the film material properties.

Type
Research Article
Copyright
Copyright © Materials Research Society 2006

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