TABLE 4.
Differences in the tet38, tetR21, and mgrA transcript levels in S. aureus strains following exposure to fatty acids and tetracycline
| Strain, compound (MIC [μg/ml]) | Fold MIC used for induction | Relative expression (mean fold change ± SD) ofa: |
||
|---|---|---|---|---|
| tet38 | tetR21 | mgrA | ||
| RN6390 (wild type) | No induction | 1.0 ± 0.1 | 1.0 ± 0.1 | 1.0 ± 0.1 |
| Tetracycline (0.06) | 0.5 | 2.8 ± 0.2 | 0.9 ± 0.2 | 1.0 ± 0.1 |
| 0.25 | 3.1 ± 0.2 | 1.0 ± 0.1 | 1.0 ± 0.2 | |
| 0.10 | 4.0 ± 0.3 | 1.0 ± 0.1 | 1.0 ± 0.1 | |
| Palmitoleic acid (500) | 0.5 | 2.0 ± 0.2 | 1.0 ± 0.2 | 1.0 ± 0.3 |
| 0.25 | 2.5 ± 0.3 | 1.0 ± 0.2 | 1.0 ± 0.1 | |
| 0.10 | 4.0 ± 0.3 | 1.0 ± 0.1 | 1.0 ± 0.2 | |
| Undecanoic acid (500) | 0.5 | 2.0 ± 0.2 | 1.0 ± 0.2 | 1.0 ± 0.1 |
| 0.25 | 1.5 ± 0.1 | 1.0 ± 0.1 | 1.0 ± 0.1 | |
| 0.10 | 4.1 ± 0.4 | 1.0 ± 0.1 | 1.0 ± 0.1 | |
| Linoleic acid (1,000) | 0.5 | 1.8 ± 0.4 | 1.0 ± 0.1 | 1.0 ± 0.1 |
| 0.25 | 2.5 ± 0.5 | 1.0 ± 0.1 | 1.0 ± 0.1 | |
| 0.10 | 3.0 ± 0.4 | 1.0 ± 0.2 | 1.0 ± 0.1 | |
| Palmitic acid (2,000) | 0.5 | 1.0 ± 0.1 | 1.0 ± 0.2 | 1.0 ± 0.1 |
| 0.25 | 1.0 ± 0.1 | 1.0 ± 0.1 | 1.0 ± 0.1 | |
| 0.10 | 1.0 ± 0.1 | 1.0 ± 0.2 | 1.0 ± 0.1 | |
| QT1 (ΔmgrA) | No induction | 5.0 ± 0.5 | 0.9 ± 0.1 | |
| Tetracycline (4.0) | 0.5 | 5.2 ± 0.4 | 0.8 ± 0.2 | |
| 0.25 | 5.1 ± 0.4 | 0.7 ± 0.2 | ||
| 0.10 | 5.0 ± 0.3 | 0.9 ± 0.1 | ||
| Palmitoleic acid (1,500) | 0.5 | 5.0 ± 0.2 | 0.9 ± 0.4 | |
| 0.25 | 5.1 ± 0.4 | 1.0 ± 0.1 | ||
| 0.10 | 5.2 ± 0.5 | 1.2 ± 0.3 | ||
| Undecanoic acid (1,500) | 0.5 | 5.0 ± 0.5 | 1.1 ± 0.1 | |
| 0.25 | 4.5 ± 0.3 | 0.8 ± 0.3 | ||
| 0.10 | 5.1 ± 0.4 | 0.9 ± 0.1 | ||
| Linoleic acid (2,500) | 0.5 | 5.0 ± 0.4 | 0.9 ± 0.1 | |
| 0.25 | 5.1 ± 0.3 | 1.1 ± 0.1 | ||
| 0.10 | 5.1 ± 0.4 | 1.0 ± 0.2 | ||
| Palmitic acid (5,000) | 0.5 | 5.0 ± 0.2 | 1.0 ± 0.1 | |
| 0.25 | 5.0 ± 0.2 | 1.0 ± 0.2 | ||
| 0.10 | 5.0 ± 0.1 | 1.0 ± 0.2 | ||
| QT21 (ΔtetR21) | No induction | 5.0 ± 0.5 | 1.0 ± 0.1 | |
| Tetracycline (0.5) | 0.5 | 4.8 ± 0.5 | 1.0 ± 0.1 | |
| 0.25 | 5.1 ± 0.3 | 1.0 ± 0.2 | ||
| 0.10 | 5.0 ± 0.4 | 1.0 ± 0.1 | ||
| Palmitoleic acid (1,000) | 0.5 | 4.5 ± 0.4 | 1.0 ± 0.1 | |
| 0.25 | 4.5 ± 0.3 | 1.0 ± 0.2 | ||
| 0.10 | 5.0 ± 0.5 | 1.0 ± 0.2 | ||
| Undecanoic acid (1,500) | 0.5 | 4.8 ± 0.2 | 1.0 ± 0.1 | |
| 0.25 | 4.5 ± 0.3 | 1.0 ± 0.1 | ||
| 0.10 | 4.8 ± 0.3 | 1.0 ± 0.1 | ||
| Linoleic acid (2,000) | 0.5 | 5.0 ± 0.4 | 1.0 ± 0.1 | |
| 0.25 | 4.5 ± 0.5 | 1.0 ± 0.1 | ||
| 0.10 | 4.8 ± 0.3 | 1.0 ± 0.1 | ||
| Palmitic acid (5,000) | 0.5 | 5.0 ± 0.2 | 1.0 ± 0.2 | |
| 0.25 | 4.8 ± 0.4 | 1.0 ± 0.2 | ||
| 0.10 | 5.0 ± 0.4 | 1.0 ± 0.1 | ||
| RN6390(pLI50) | No induction | 1.0 ± 0.1 | 1.0 ± 0.1 | 1.0 ± 0.1 |
| Tetracycline | 0.10 | 3.9 ± 0.4 | 1.0 ± 0.1 | 1.0 ± 0.1 |
| Palmitoleic acid | 0.10 | 4.0 ± 0.4 | 1.0 ± 0.2 | 1.0 ± 0.1 |
| Undecanoic acid | 0.10 | 3.8 ± 0.3 | 1.0 ± 0.1 | 1.0 ± 0.2 |
| Linoleic acid | 0.10 | 2.6 ± 0.3 | 1.0 ± 0.1 | 1.0 ± 0.2 |
| Palmitic acid | 0.10 | 1.0 ± 0.2 | 1.0 ± 0.2 | 1.0 ± 0.1 |
| QT1(pLI50-mgrA) | No induction | 1.0 ± 0.2 | 1.0 ± 0.2 | 6.0 ± 0.5 |
| Tetracycline | 0.10 | 3.5 ± 0.4 | 1.0 ± 0.1 | 6.0 ± 0.4 |
| Palmitoleic acid | 0.10 | 3.7 ± 0.4 | 1.0 ± 0.1 | 6.0 ± 0.4 |
| Undecanoic acid | 0.10 | 3.2 ± 0.4 | 1.0 ± 0.1 | 6.0 ± 0.5 |
| Linoleic acid | 0.10 | 2.2 ± 0.4 | 1.0 ± 0.1 | 6.0 ± 0.3 |
| Palmitic acid | 0.10 | 1.0 ± 0.1 | 1.0 ± 0.1 | 6.0 ± 0.2 |
| QT21(pLI50-tetR21) | No induction | 1.0 ± 0.3 | 5.0 ± 0.2 | 1.0 ± 0.4 |
| Tetracycline | 0.10 | 3.5 ± 0.3 | 5.0 ± 0.5 | 1.0 ± 0.1 |
| Palmitoleic acid | 0.10 | 3.7 ± 0.4 | 5.0 ± 0.3 | 1.0 ± 0.1 |
| Undecanoic acid | 0.10 | 3.0 ± 0.3 | 5.0 ± 0.3 | 1.0 ± 0.2 |
| Linoleic acid | 0.10 | 2.0 ± 0.2 | 5.0 ± 0.5 | 1.0 ± 0.1 |
| Palmitic acid | 0.10 | 1.0 ± 0.1 | 5.0 ± 0.5 | 1.0 ± 0.1 |
The relative gene expression is determined as the ratio of gene transcripts of mutant versus wild-type strains and the ratio of transcripts with versus without induction by fatty acids or tetracycline. The gmk gene was used as an internal control. Each assay was done in triplicate, and RNAs were collected from three independent biological samples. All values represent the means of three independent experiments. Values in boldface represent differences that are statistically significant based on Student's t test (P < 0.05). The differences between wild-type and mutant genes and the increases in transcript levels for gene expression after induction versus without induction were calculated.