TABLE 1.
Lactococcal strains used in this study
| Strain | Host | Plasmid | Presence of gene(s)a
|
mIL-2 concn (pg/ml)b | Reference or source | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| L-mIL-2 | mIL-2 | usp-mIL-2 | lcnCD | nis | Δnis | nisRK | |||||
| FI5876 | + | 0 | 6 | ||||||||
| FI7847 | + | 0 | 8 | ||||||||
| UKLc10 | + | 0 | 29 | ||||||||
| FI9955 | FI5876 | + | |||||||||
| pFI2398 | + | 160 | This study | ||||||||
| FI9957 | FI5876 | + | |||||||||
| pFI2398 | + | ||||||||||
| pFI2148 | + | 215 | This study | ||||||||
| FI9947 | FI7847 | + | |||||||||
| pFI2398 | + | 150 | This study | ||||||||
| FI9949 | FI7847 | + | |||||||||
| pFI2398 | + | ||||||||||
| pFI2148 | + | 180 | This study | ||||||||
| FI10537 | UKLc10 | + | |||||||||
| pFI2398 | + | 195 | This study | ||||||||
| FI10538 | UKLc10 | + | |||||||||
| pFI2398 | + | ||||||||||
| pFI2148 | + | 355 | This study | ||||||||
| FI10585 | FI5876 | + | |||||||||
| pFI2584 | + | 175 | This study | ||||||||
| FI10584 | FI7847 | + | |||||||||
| pFI2584 | + | 140 | This study | ||||||||
| FI10586 | UKLc10 | + | |||||||||
| pFI2584 | + | 285 | This study | ||||||||
| FI10608 | FI5876 | + | |||||||||
| pFI2593 | + | 490 | This study | ||||||||
L-mIL-2 contains the lcnA leader and mIL-2 genes preceded by the nisin promoter; mIL-2 contains the mIL-2 gene preceded by the nisin promoter; usp-mIL-2 contains the usp45 leader and mIL-2 genes preceded by the nisin promoter; nis is the nisin gene cluster; Δnis is the nisin gene cluster with a frameshift mutation in codon 16 of the nisin structural gene impeding nisin biosynthesis (the sequences of the downstream nisin cluster genes are not affected); nisRK is the nisRK genes integrated into the fivefold peptidase-deficient mutant IM16, a derivative of L. lactis MG1363.
The concentration of mIL-2 (pg ml−1) in culture supernatants of lactococcal strains was determined by a sandwich ELISA. The values are the means from quadruplicate samples (standard deviation, ≤8%).