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C. M. Toutain-Kidd, M. E. Zegans; Inhibition of Biofilm Formation of Pseudomonas aeruginosa by Polysorbate 80: A role of the Secretin, XcpQ. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3104.
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Bacterial infections are a common problem in ophthalmology as bacteria, like Pseudomonas aeruginosa, can attach and form biofilms on biotic surfaces such as the cornea, but also on abiotic surfaces such as intraocular or contact lenses. We have previously reported that the non ionic detergent, polysorbate 80 (PS80), commonly used in eye drops, is able to inhibit biofilm formation of P. aeruginosa on various abiotic surfaces including contact lenses. We now present evidence that the secretin, XcpQ, may be involved in PS80 mediated inhibition of biofilm formation.
All genetic, biochemical and microbiologic assays were performed following previously published protocols. PS80 was used at 0.01% unless noted otherwise.
A transposon library of P. aeruginosa PA14 was screened to look for mutants able to form biofilms in presence of PS80 which led to the isolation of a strain containing a transposon inserted early in the secretin-encoding gene xcpQ. Expression of xcpQ as measured by RT-PCR was absent in this mutant. PS80 did not effect planktonic growth of this mutant. XcpQ is a major player in the Type 2 Secretion System (T2SS), as it allows the secretion of proteins, many of which are virulence factors, outside of the cell. As expected this mutant demonstrated decreased secretion of proteases as measured on a milk plate lysis assay. Importantly, the xcpQ mutant does not inactivate or degrade PS80.
Our data indicate that the xcpQ mutant is resistant to PS80 through a mechanism that does not involve the direct cleavage of PS80 by a lipase as we have previously reported in other mutants. We hypothesize that PS80 interacts directly with XcpQ in order to inhibit biofilm formation or, that the deletion of XcpQ from the outer membrane has an effect on the bacterial envelope rendering it resistant to the action of PS80.
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