Table 3.
Phage particles detection in inducible L. lactis lysates and correlation between flow cytometry and MmC growth profiles.
| L. lactis strains | MmC growth profile | Inducible prophage | L. lactis host | Plaque assays (pfu.ml-1) | Phage-group1 | Flow cytometry analysis (pfu.ml-1)∗ | Gate 3 (% fluorescence) | Electron microscopy# |
|---|---|---|---|---|---|---|---|---|
| Controls | ||||||||
| NZ9000 (TP901-1 erm) | B | TP901-1 | 3107 | 2.43e05 | P335 | 6.85e05 | 80.6 | nd |
| UC509.9 | A | Prophage-free | – | – | – | <1.0e04 | 16.3 | nd |
| Strains tested | ||||||||
| DS68567 | A | 56701 | SMQ-86 | 5.90e04 | P335 | 1.74e06 | 48.6 | nd |
| DS71865 | A | 86501 | 3107 | 8.53e03 | P335 | 9.12e05 | 75.0 | + |
| DS63633 | B | 63301 | 3107 | 2.07e05 | P335 | 1.79e05 | 29.7 | + |
| DS70282 | B | 28201 | SMQ-86 | 8.30e03 | P335 | 1.59e06 | 83.2 | nd |
| DS63625 | D | 62501 | SMQ-86 | 2.07e04 | P335 | 5.47e05 | 72.7 | nd |
| DS68509 | D | 50901 | SMQ-86 | 8.88e04 | P335 | 1.24e06 | 76.5 | + |
| DS64982 | D | 98201 | SMQ-86 | 6.55e04 | P335 | 1.12e06 | 55.9 | + |
| DS64964 | A | No prophage detected | – | – | nd | <1.0e04 | 0.37 | nd |
| DS601 | A | No prophage detected | – | – | nd | <1.0e04 | 2.92 | – |
| DS69067 | A | 06701 | – | – | nd | 2.07e07 | 99.79 | + |
| DS68498 | B | 49801 | – | – | nd | 5.22e06 | 99.13 | + |
| DS69059 | B | No prophage detected | – | – | nd | <1.0e04 | 2.86 | nd |
| DS68518 | B | 51801 | – | – | nd | 2.02e06 | 97.48 | nd |
| DS66563 | B | No prophage detected | – | – | nd | <1.0e04 | 5.28 | – |
| DS68569 | C | No prophage detected | – | – | nd | <1.0e04 | 11.14 | nd |
| DS72158 | C | No prophage detected | – | – | nd | <1.0e04 | 12.05 | – |
| DS70248 | D | 24801 | – | – | nd | 3.80e06 | 90.03 | + |
| DS68495 | D | 49501 | – | – | nd | 4.04e06 | 98.37 | nd |
Profile A: UC509.9 profile with a growth cessation at 3 μg.ml-1; Profile B: TP901-1 profile with an equal growth cessation (1.3 and 3 μg.ml-1); Profile C: No chemical effect; Profile D: Growth cessation at 1.3 μg.ml-1; nd, Not determined; 1 Phage-group was determined by Multiplex PCR; ∗Phage particles quantification was performed using the following equation: [(no. events detected/sample volume analyzed)∗10] (pfu.ml-1). #+: Presence of phage particles; #-: phage particles not detected.