CLONING OF CITRATE PERMEASE GENE OF LACTOCOCCUS-LACTIS SUBSP LACTIS BIOVAR DIACETYLACTIS NIAI N-7 AND EXPRESSION IN CITRATE-NEGATIVE LACTOCOCCI

The putative citrate permease (Cit-P) plasmid DNA (pN7CP) from Lactoco ccus lactis subsp. lactis biovar diacetylactis (L. diacetylactis) NIAI N-7 was cloned. Cit-P+ transformants possessed pIL253 with a 3.8-kb f ragment (pKAK1) or a 2.0-kb fragment (pKAK7). No XbaI site was present in the 3.8-kb of Xbal-Xbal fragment from pN7CP. It may thus be possib le to obtain the 2.0-kb fragment by deleting the 3.8-kb fragment. Asse ssment was made of citrate-transporting activity in transformants KAK1 and KAK7. Several Cit(-) lactococci were transformed by pKAK7. Althou gh all their transformants except KK-7LM and KK-7SL of Lactococcus lac tis subsp. lactis (L. lactis) LM0230 and NIAI SLN were incapable of tr ansporting citrate, transformants KK-7LM and KK-7SL showed the Cit(+) phenotype and citrate-transporting activity. L. diacetylactis and L. l actis were classified under citrate metabolism. However, the present f indings strongly indicate some strains of L. lactis to quite likely be the original citrate utilizers but simply to have lost the Cit-P gene .