Effect of lauric acid on spa transcription. RN6911 (agr-null mutant in which spa is overexpressed) was grown in broth either with or without lauric acid. Lauric acid was added at 0 min (15 μg/ml) and 65 min (7.5 μg/ml) and samples (10 ml) were collected at 0, 65, 110, and 220 min. Whole-cell lysates were prepared and used for RNA (Northern) blotting. The blot was hybridized overnight with spa-specific PCR-labelled probe, washed, and exposed to Kodak X-Omat AR film.