Characterization of a cloned chromosomal fragment affecting the proteinase activity of Streptococcus lactis ssp. lactis.

Plasmid pVS8 (14.3 kbp) contains a 9.3 kbp fragment of Streptococcus lactis ssp. lactis SSL135 chromosomal DNA associated with the ability of this strain to grow in milk. In this study, it was found that pVS8 complements a defective plasmid-linked proteinase gene of SSL135. Using deletions and insertions, it was found that the size of the complementing region of pVS8 is approximately 6.0 kbp, and that its main part is located within a 5.7 kbp BglII fragment.