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Journal of Bacteriology, April 2009, p. 2512-2520, Vol. 191, No. 8
0021-9193/09/$08.00+0     doi:10.1128/JB.01596-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Nanoscale Structural and Mechanical Properties of Nontypeable Haemophilus influenzae Biofilms

Fernando Terán Arce,^1* Ross Carlson,² James Monds,³ Richard Veeh,² Fen Z. Hu,^4,5 Philip S. Stewart,² Ratnesh Lal,¹ Garth D. Ehrlich,^4,5 and Recep Avci³

Center for Nanomedicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637,¹ Center for Biofilm Engineering, Montana State University, Bozeman, Montana 59717,² Department of Physics, Montana State University, Bozeman, Montana 59717,³ Center for Genomic Sciences, Allegheny Singer Research Institute/Allegheny General Hospital, Pittsburgh, Pennsylvania 15212,⁴ Departments of Microbiology and Immunology and Otolaryngology/Head and Neck Surgery, Drexel University College of Medicine, Allegheny Campus, Pittsburgh, Pennsylvania 15212⁵

Received 11 November 2008/ Accepted 4 February 2009

Nontypeable Haemophilus influenzae (NTHI) bacteria are commensals in the human nasopharynx, as well as pathogens associated with a spectrum of acute and chronic infections. Two important factors that influence NTHI pathogenicity are their ability to adhere to human tissue and their ability to form biofilms. Extracellular polymeric substances (EPS) and bacterial appendages such as pili critically influence cell adhesion and intercellular cohesion during biofilm formation. Structural components in the outer cell membrane, such as lipopolysaccharides, also play a fundamental role in infection of the host organism. In spite of their importance, these pathogenic factors are not yet well characterized at the nanoscale. Here, atomic force microscopy (AFM) was used in aqueous environments to visualize structural details, including probable Hif-type pili, of live NTHI bacteria at the early stages of biofilm formation. Using single-molecule AFM-based spectroscopy, the molecular elasticities of lipooligosaccharides present on NTHI cell surfaces were analyzed and compared between two strains (PittEE and PittGG) with very different pathogenicity profiles. Furthermore, the stiffness of single cells of both strains was measured and subsequently their turgor pressure was estimated.

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* Corresponding author. Mailing address: Center for Nanomedicine, Department of Medicine (Pulmonary and Critical Care Section), University of Chicago, 5841 S Maryland Ave., I-505, Chicago, IL 60637. Phone: (773) 702-0654. Fax: (773) 702-4941. E-mail: ftarce{at}uchicago.edu

Published ahead of print on 13 February 2009.

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Journal of Bacteriology, April 2009, p. 2512-2520, Vol. 191, No. 8
0021-9193/09/$08.00+0     doi:10.1128/JB.01596-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

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