title: Alternative lactose catabolic pathway in Lactococcus lactis IL1403.
abstract: In this study, we present a glimpse of the diversity of Lactococcus lactis subsp. lactis IL1403 beta-galactosidase phenotype-negative mutants isolated by negative selection on solid media containing cellobiose or lactose and X-Gal (5-bromo-4-chloro-3-indolyl-beta-d-galactopyranoside), and we identify several genes essential for lactose assimilation. Among these are ccpA (encoding catabolite control protein A), bglS (encoding phospho-beta-glucosidase), and several genes from the Leloir pathway gene cluster encoding proteins presumably essential for lactose metabolism. The functions of these genes were demonstrated by their disruption and testing of the growth of resultant mutants in lactose-containing media. By examining the ccpA and bglS mutants for phospho-beta-galactosidase activity, we showed that expression of bglS is not under strong control of CcpA. Moreover, this analysis revealed that although BglS is homologous to a putative phospho-beta-glucosidase, it also exhibits phospho-beta-galactosidase activity and is the major enzyme in L. lactis IL1403 involved in lactose hydrolysis.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5a, 02-106 Warsaw, Poland.
authors.forename: Tamara
authors.initials: T
authors.lastname: Aleksandrzak-Piekarczyk
authors.forename: Jan
authors.initials: J
authors.lastname: Kok
authors.forename: Pierre
authors.initials: P
authors.lastname: Renault
authors.forename: Jacek
authors.initials: J
authors.lastname: Bardowski
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002475:Cellobiose / Q000378:metabolism; D003470:Culture Media; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005697:Galactosides / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism*; D007211:Indoles / Q000378:metabolism; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D009154:Mutation; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D004268:DNA-Binding Proteins; D005697:Galactosides; D007211:Indoles; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; D002475:Cellobiose; D006026:Glycoside Hydrolases; D001616:beta-Galactosidase; D007785:Lactose; C044888:5-bromo-4-chloro-3-indolyl beta-galactoside