Identification and functional characterisation of cellobiose and lactose transport systems in Lactococcus lactis IL1403
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ORIGINAL PAPER
Identification and functional characterisation of cellobiose and lactose transport systems in Lactococcus lactis IL1403 Magdalena Kowalczyk Æ Muriel Cocaign-Bousquet Æ Pascal Loubiere Æ Jacek Bardowski
Received: 11 May 2007 / Revised: 2 August 2007 / Accepted: 13 September 2007 / Published online: 2 October 2007 Springer-Verlag 2007
Abstract Physiological, biochemical and macroarray analyses of Lactococcus lactis IL1403 and its ccpA and bglR single and double mutants engaged in lactose and b-glucosides catabolism were performed. The kinetic analysis indicated the presence of different transport systems for salicin and cellobiose. The control of salicin catabolism was found to be mediated by the transcriptional regulator BglR and the CcpA protein. The transcriptional analysis by macroarray technology of genes from the PEP:PTS regions showed that several genes, like ybhE, celB, ptcB and ptcA, were expressed at higher levels both in wild type cells exposed to cellobiose and in the ccpA mutant. We also demonstrated that in L. lactis IL1403 cultured on medium with cellobiose and lactose as carbon sources, after the first phase of cellobiose consumption and then co-metabolism of the two sugars, when cellobiose is exhausted the strain uses lactose as the only carbon source. These data could indicate that lactose and cellobiose are transported by a unique system—a PTS carrier induced by the presence of cellobiose, and negatively controlled by the CcpA regulator.
Communicated by Erko Stackebrandt. M. Kowalczyk J. Bardowski (&) Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5a, 02-106 Warsaw, Poland e-mail: [email protected] M. Cocaign-Bousquet P. Loubiere Laboratoire Biotechnologie et Bioproce´de´s, UMR CNRS 5504, UMR INRA 792, INSA, 135 Avenue de Rangueil, 31077 Toulouse Cedex 4, France
Keywords CcpA Sugar catabolism Cellobiose Lactose PTS
Abbreviations LAB Lactic acid bacteria CDM Chemically defined medium
Introduction Lactococcus lactis is a lactic acid bacterium (LAB) that is used as a dairy starter in the production of fermented milk products, particularly cheeses. From an industrial point of view the main role of lactococci is the conversion of sugar into lactic acid. Efficient internalisation and catabolism of lactose are important for growth of lactococci in milk as well as for generation of dairy products with low lactose concentration. On the other hand, LAB used in vegetable fermentations are exposed to various carbon sources, including b-glucosides like cellobiose, salicin, esculin or arbutin. L. lactis converts rapidly metabolised sugars to lactate, while poorly metabolised substrates are converted to mixedacid products, formate, acetate and ethanol (CocaignBousquet et al. 1996; Garriques et al. 1997). Moreover, these observations clearly show that the central metabolic pathways, i. e., glycolysis and pyruvate oxidation pathways, are strongly regulated by several factors, one of which is the speed of sugar consumption. In addition to regulation
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