TABLE 3.
Inhibitory spectrum of S. thermophilus LMD-9 and derivatives
| Indicator species or strain | No. of strains tested | No. of indicator strains inhibited by the induced producer strainsa
|
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| LMD-9 (D U E F) + | Δ1 (−) + | Δ2 (D) + | Δ3 (E F) + | Δ4/Δ5 (U) + | Δ4 (U E F) + | Δ9 (−) + | Δ5 (D U) + | Δ6 (D E F) + | Δ7 (D U E F) −b | Δ8 (D U E F) −b | ||
| Streptococcus | ||||||||||||
| S. thermophilus | 8 | 7 | 0 | 7 | 0 | 0 | 0 | 0 | 7 | 7 | 7 | 7 |
| S. thermophilus SFi16 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
| S. thermophilus LMG18311 | 1 | 1 | 0 | 1 | 1d | 0 | 1d | 0 | 1 | 1 | 1 | 1 |
| S. salivarius | 3 | 3 | 0 | 3 | 0 | 0 | 0 | 0 | 3 | 3 | 3 | 3 |
| Enterococcus | ||||||||||||
| E. faecalis OG1X | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 |
| E. faecalis JH2-SS | 1 | 1 | 0 | 1d | 0 | 0 | 0 | 0 | 1d | 1 | 1d | 1d |
| E. faecalis JH2-2 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1d | 1d |
| Lactococcus | ||||||||||||
| L. lactis | 3 | 3 | 0 | 3 | 0 | 0 | 0 | 0 | 3 | 3 | 3 | 3 |
| L. lactis IL-1403 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 |
| L. lactis MG1363 | 1 | 1 | 0 | 1d | 0 | 0 | 0 | 0 | 1d | 1d | 1d | 1d |
| Bacillus | ||||||||||||
| B. coagulans | 4 | 3 | 0 | 3 | 0 | 0 | 0 | 0 | 3 | 3 | 3 | 3 |
| B. coagulans NCIB8523 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1d | 1d |
| B. fusiformis SI0056 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 |
| Listeria | ||||||||||||
| L. monocytogenes | 3 | 3 | 0 | 3 | 0 | 0 | 0 | 0 | 3 | 3 | 0 | 0 |
| L. monocytogenes IHE-92 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1d | 1d |
| L. ivanovii IHE-3 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 |
| L. innocua IHE-2 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 |
| L. seeligeri | 2 | 2 | 0 | 2 | 0 | 0 | 0 | 0 | 2 | 2 | 0 | 0 |
| L. welshimeri | 3 | 0 | NTc | NT | NT | NT | NT | NT | NT | NT | NT | NT |
| Lactobacillus | ||||||||||||
| L. delbrueckii subsp. bulgaricus | 2 | 0 | NT | NT | NT | NT | NT | NT | NT | NT | NT | NT |
| L. helveticus | 3 | 0 | NT | NT | NT | NT | NT | NT | NT | NT | NT | NT |
Antimicrobial activity was assayed using the overlay protocol in the presence of 400 ng/ml D9C-30. Growth of the indicator strain was considered inhibited when the radius of the inhibitory zone was at least 1.5 mm. Each experiment was repeated at least three times. The letters in parentheses indicate the content in bacSt genes of the producer strain: D, blpDSt; U, blpUSt; E, blpESt; F, blpFSt. “−” denotes the absence of bacSt genes. The presence (+) or absence (−) of blpGSt, encoding the putative disulfide oxidase, is also indicated.
In strain Δ7, the blpGSt-blpXSt operon is deleted, while blpGSt alone is deleted in strain Δ8.
NT, not tested.
Highly significant difference in the size of the inhibitory zone produced by the LMD-9 derivative compared to the wild-type LMD-9 strain (Student's t test with a P value of <0.01).