Open AccessGenetics of l -Sorbose Transport and Metabolism in Lactobacillus casei
Author(s) -
Marı́a J. Yebra,
Ana Veyrat,
Mario Adriano Dos Santos,
Gaspar PérezMartínez
Publication year - 2000
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.182.1.155-163.2000
Subject(s) - biology , sorbose , catabolite repression , lactobacillus casei , operon , biochemistry , peptide sequence , gene , open reading frame , microbiology and biotechnology , genetics , mutant , fructose , fermentation
Genes encodingl -sorbose metabolism ofLactobacillus casei ATCC 393 have been identified on a 6.8-kb chromosomal DNA fragment. Sequence analysis revealed seven complete genes and a partial open reading frame transcribed as two units. The deduced amino acid sequences of the first transcriptional unit (sorRE ) showed high similarity to the transcriptional regulator and thel -sorbose-1-phosphate reductase of the sorbose (sor ) operon fromKlebsiella pneumoniae . The other genes are transcribed as one unit (sorFABCDG ) in opposite direction tosorRE . The deduced peptide sequence ofsorF showed homology with thed -sorbitol-6-phosphate dehydrogenase encoded in thesor operon fromK. pneumoniae andsorABCD to components of the mannose phosphotransferase system (PTS) family but especially to domains EIIA, EIIB, EIIC and EIID of the phosphoenolpyruvate-dependentl -sorbose PTS fromK. pneumoniae . Finally, the deduced amino acid sequence of a truncated gene (sorG ) located downstream ofsorD presented high similarity with ketose-1,6-bisphosphate aldolases. Results of studies on enzyme activities and transcriptional analysis revealed that the two gene clusters,sorRE andsorFABCDG , are induced byl -sorbose and subject to catabolite repression byd -glucose. Data indicating that the catabolite repression is mediated by components of the PTS elements and by CcpA, are presented. Results of sugar uptake assays inL. casei wild-type andsorBC mutant strains indicated thatl -sorbose is taken up byl -sorbose-specific enzyme II and thatL. casei contains an inducibled -fructose-specific PTS. Results of growth analysis of those strains and aman sorBC double mutant suggested thatl -sorbose is probably also transported by thed -mannose PTS. We also present evidence, from studies on asorR mutant, suggesting that thesorR gene encodes a positive regulator of the twosor operons. Sequence alignment of SorR, SorC (K. pneumoniae ), and DeoR (Bacillus subtilis ) revealed that they might constitute a new group of transcriptional regulators.