A specific mutation in the promoter region of the silent cel cluster accounts for the appearance of lactose-utilizing Lactococcus lactis MG1363.
The Lactococcus lactis laboratory strain MG1363 has been described to be unable to utilize lactose. However, in a rich medium supplemented with lactose as the sole carbon source, it starts to grow after prolonged incubation periods. Transcriptome analyses showed that L. lactis MG1363 Lac(+) cells expressed celB, encoding a putative cellobiose-specific phosphotransferase system (PTS) IIC component, which is normally silent in MG1363 Lac(-) cells. Nucleotide sequence analysis of the cel cluster of a Lac(+) isolate revealed a change from one of the guanines to adenine in the promoter region. We showed here that one particular mutation, taking place at increased frequency, accounts for the lactose-utilizing phenotype occurring in MG1363 cultures. The G-to-A transition creates a -10 element at an optimal distance from the -35 element. Thus, a fully active promoter is created, allowing transcription of the otherwise cryptic cluster. Nuclear magnetic resonance (NMR) spectroscopy results show that MG1363 Lac(+) uses a novel pathway of lactose utilization.
Department of Molecular Genetics, University of Groningen, Groningen Biomolecular Sciences and Biotechnology Institute, Groningen, Netherlands.
Ana
A
Solopova
Herwig
H
Bachmann
Bas
B
Teusink
Jan
J
Kok
Ana Rute
AR
Neves
Oscar P
OP
Kuipers
D002244:Carbon / Q000378:metabolism; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D020869:Gene Expression Profiling; D013294:Lactococcus lactis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D059467:Transcriptome
D003470:Culture Media; D004269:DNA, Bacterial; D002244:Carbon; D007785:Lactose