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. 2014 Dec 12;5:706. doi: 10.3389/fmicb.2014.00706

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Copyright © 2014 Quave and Horswill.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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Schematic representation of the X-GAL agar plate test, which can be used in QSI screening efforts of either individual compounds or more complex natural product extracts. QSIs are identified by presence of both a white ring in the hla::lacZ plate and blue ring on the spa::lacZ plate. (A) hla::lacZ plate: following incubation of the plate containing the hla reporter, a white clearing surrounding the hole punch containing the QSI candidate indicates reduced expression of hla (α-toxin). (B) spa::lacZ plate: following incubation of the plate containing the spa reporter, a blue zone surrounding the hole punch containing the QSI candidate indicates increased expression of spa (Protein A).