title: Regulation of expression of the Lactobacillus pentosus xylAB operon.
abstract: The xylose cluster of Lactobacillus pentosus consists of five genes, two of which, xylAB, form an operon and code for the enzymes involved in the catabolism of xylose, while a third encodes a regulatory protein, XylR. By introduction of a multicopy plasmid carrying the xyl operator and by disruption of the chromosomal xylR gene, it was shown that L. pentosus xylR encodes a repressor. Constitutive expression of xylAB in the xylR mutant is repressed by glucose, indicating that glucose repression does not require XylR. The xylR mutant displayed a prolonged lag phase compared to wild-type bacteria when bacteria were shifted from glucose to xylose medium. Differences in the growth rate in xylose medium at different stages of growth are not correlated with differences in levels of xylAB transcription in L. pentosus wild-type or xylR mutant bacteria but are positively correlated in Lactobacillus casei with a plasmid containing xylAB. Glucose repression was further investigated with a ccpA mutant. An 875-bp internal fragment of the ccpA gene of L. pentosus was isolated by PCR and used to construct a ccpA knockout mutant. Transcription analysis of L. pentosus xylA showed that CcpA is involved in glucose repression. CcpA was also shown to be involved in glucose repression of the alpha-amylase promoter of Lactobacillus amylovorus by demonstrating that glucose repression of the chloramphenicol acetyltransferase gene under control of the alpha-amylase promoter is strongly reduced in the L. pentosus ccpA mutant strain.
authors.affiliation: Department of Molecular Genetics and Gene-Technology, TNO Nutrition and Food Research Institute, Zeist, The Netherlands.
authors.forename: B C
authors.initials: BC
authors.lastname: Lokman
authors.forename: M
authors.initials: M
authors.lastname: Heerikhuisen
authors.forename: R J
authors.initials: RJ
authors.lastname: Leer
authors.forename: A
authors.initials: A
authors.lastname: van den Broek
authors.forename: Y
authors.initials: Y
authors.lastname: Borsboom
authors.forename: S
authors.initials: S
authors.lastname: Chaillou
authors.forename: P W
authors.initials: PW
authors.lastname: Postma
authors.forename: P H
authors.initials: PH
authors.lastname: Pouwels
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D005947:Glucose / Q000494:pharmacology; D007778:Lactobacillus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009875:Operator Regions, Genetic / Q000235:genetics; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics* / Q000502:physiology; D014994:Xylose / Q000378:metabolism*; D000516:alpha-Amylases / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C074322:XylR protein, Pseudomonas; C069286:catabolite control proteins, bacteria; D014994:Xylose; D000516:alpha-Amylases; D005947:Glucose