FIG. 6.

Analysis of target gene transcription (A, B, and D) and expression (C) in different isogenic single- and double-mutant strains of RN6390. (A) Northern blots of spa (protein A) transcript in the RN6390 wild-type (wt), sarZ mutant, and single-copy (cps) complemented strains from the mid-exponential (OD₆₀₀, ∼1.1) phase of growth. (B) Northern blots of cysteine protease (sspB) transcript in the wild-type and isogenic single- and double-mutant strains, as indicated, from the postexponential phase of growth (OD₆₀₀, ∼1.7). A 1.0-kb DNA fragment containing the sspB ORF was used for hybridization. In S. aureus, the V8 protease gene (sspA), the cysteine protease gene (sspB), and an unknown gene (sspC) are in a single transcriptional unit (39). (C) Gelatin zymogram of culture supernatants from various S. aureus RN6390 strains as indicated. Equal amounts of culture supernatant (OD₆₀₀, ∼1.7) were used for all strains, except sarX and the sarZ sarX mutant, where one-fifth volume was applied. (D) Northern blot analysis for α-hemolysin (hla) transcript in assorted S. aureus RN6390 strains, as indicated, from the postexponential phase of growth. The Northern blot was hybridized with an hla fragment containing the coding region of the hemolysin gene. The region of 23S rRNA of the ethidium bromide-stained gel used for blotting is also shown as a loading control in panels A, B, and D.