Regulation of expression of the Lactococcus lactis subsp. lactis biovar diacetylactis citrate transport system.

PALOMA LOPEZ; DJAMEL DRIDER; NIÈVES GARCIA-QUINTANS; MARIA ANGELES CORRALES; CHRISTIAN MAGNI; MAURICIO MARTIN; DIEGO DE MENDOZA

DAIRY SCIENCE & TECHNOLOGY

EDP SCIENCES S A

Año: 1998 vol. 78 p. 11 - 16

1958-5586

Citrate metabolism performed by a number of lactic acid bacteria yields volatile com-pounds, such as diacetyl and acetaldehyde, which are important for flavour development in fermented milk products. Citrate uptake in Lactococcus lactis subsp. lactis biovar diacetylactis and Leuconostoc mesenteroides subsp. mesenteroides is catalyzed by a secondary carrier, the citrate permease P (CitP). The presence of CitP is essential for citrate utilization, since in its absence no citrate metabolism is observed although all enzymes involved in conversion of citrate are present inside the cells. In this review the genetic organization of the plasmid encoding the citrate transport system of lactococci is described, the posttranscriptional regulation of the citQRP operon is presented and the influence of external pH on citP transcription, citrate uptake and cometabolism of citrate and glucose is discussed. These last studies reveal a novel molecular mechanism that improves the adaptation of L diacetylactis to acidic pH.