CITRATE TRANSPORT IN LACTOCOCCUS-LACTIS BIOVAR DIACETYLACTIS - EXPRESSION OF THE PLASMID-BORNE CITRATE PERMEASE-P

The Lactococcus lactis subsp. lactis biovar diacetylactis citrate perm ease P is encoded by the citP gene borne by an 8.3-kb Cit(+) plasmid(F . Sesma, Gardiol, D., de Ruiz Holgado, A.P. and de Mendoza, D., Appl. Environ. Microbiol. 56 (1990) 2099-2103). By subcloning different DNA fragments from the Cite plasmid it was found that citP is the only pla smidic gene required for the transport of citrate. Northern blot analy sis revealed that citP is transcribed in two mRNA species with lengths of 2.9 and 1.9 kb. The transcriptional pattern, the total amount of c itP mRNAs and the transport of citrate were unaffected by the presence of citrate in the growth media. Our results support the conclusion th at transcription of citP as well as citrate transport are not induced by citrate in Lactococcus lactis subsp. lactis biovar diacetylactis.