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Applied and Environmental Microbiology, December 2006, p. 7701-7710, Vol. 72, No. 12
0099-2240/06/$08.00+0     doi:10.1128/AEM.01294-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Escherichia coli Biofilms Formed under Low-Shear Modeled Microgravity in a Ground-Based System ^,

S. V. Lynch,^1, K. Mukundakrishnan,³ M. R. Benoit,¹ P. S. Ayyaswamy,² and A. Matin^1*

Department of Microbiology and Immunology, Sherman Fairchild Science Building, Stanford University School of Medicine, 299 Campus Drive, Stanford, California 94305,¹ Department of Mechanical Engineering and Applied Mechanics, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6315,² Department of Anesthesiology and Critical Care, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104³

Received 24 March 2006/ Accepted 25 September 2006

Bacterial biofilms cause chronic diseases that are difficult to control. Since biofilm formation in space is well documented and planktonic cells become more resistant and virulent under modeled microgravity, it is important to determine the effect of this gravity condition on biofilms. Inclusion of glass microcarrier beads of appropriate dimensions and density with medium and inoculum, in vessels specially designed to permit ground-based investigations into aspects of low-shear modeled microgravity (LSMMG), facilitated these studies. Mathematical modeling of microcarrier behavior based on experimental conditions demonstrated that they satisfied the criteria for LSMMG conditions. Experimental observations confirmed that the microcarrier trajectory in the LSMMG vessel concurred with the predicted model. At 24 h, the LSMMG Escherichia coli biofilms were thicker than their normal-gravity counterparts and exhibited increased resistance to the general stressors salt and ethanol and to two antibiotics (penicillin and chloramphenicol). Biofilms of a mutant of E. coli, deficient in ^s, were impaired in developing LSMMG-conferred resistance to the general stressors but not to the antibiotics, indicating two separate pathways of LSMMG-conferred resistance.

Published ahead of print on 6 October 2006.

Supplemental material for this article may be found at http://aem.asm.org/.

Present address: Department of Anesthesia and Perioperative Care, UCSF Medical School, 513 Parnassus Ave., San Francisco, CA 94143.