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Infect. Immun. doi:10.1128/IAI.01347-06
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification of Gene Products Involved in Biofilm Production by Moraxella catarrhalis ETSU-9 In Vitro

Department of Microbiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390-9048

^* To whom correspondence should be addressed. Email: eric.hansen{at}utsouthwestern.edu.

	Abstract

Moraxella catarrhalis ETSU-9 was subjected to random transposon insertion mutagenesis to identify genes encoding products involved in the ability of this organism to form biofilms in vitro. Screening of approximately 3,000 transposon insertion mutants in the crystal violet-based biofilm assay system yielded six mutants which exhibited a greatly reduced ability to form biofilms. Three of these mutants had transposon insertions in the uspA2H gene which encodes a surface protein previously shown to be involved in the ability of M. catarrhalis to both attach to human cell lines in vitro and resist killing by normal human serum. Random insertion mutagenesis of the uspA2H gene, involving the introduction of a 15-nt fragment encoding five amino acids, was used to attempt to identify the domain(s) necessary for biofilm formation. Most of these insertions adversely affected biofilm formation whereas the ability of these same mutants to attach to Chang conjunctival epithelial cells in vitro was usually not reduced. Gain-of-function experiments showed that introduction of the M. catarrhalis ETSU-9 uspA2H gene into Escherichia coli conferred biofilm formation ability on this recombinant strain. Two of the other three M. catarrhalis ETSU-9 transposon insertion mutants that had a greatly reduced ability to form biofilms were shown to have insertions in genes encoding products predicted to be directly or indirectly involved in cell wall metabolism.

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