Mapping of a deleted gene region by StaphChip. Cy-5 labelled DNA of parental strain SA113 was co-hybridized with Cy-3 labelled DNA from its isogenic ica deletion mutant. Colored bars indicate the position of each probe used to map ica-related and adjacent ORFs. Background signals (green) were recorded from probes recognizing the ica- region known to be deleted in strain SA113ica (arrows), as opposed to positive red signals recorded in the wild-type strain. The tetracycline resistance marker used for the construction and selection of strain SA113ica is recorded in the green channel only. Dye swap experiments provided similar results (not shown). Data are raw signal intensities; background level is indicated by a dotted line.