Article

Characterization of a mobile clpL gene from Lactobacillus rhamnosus.

Division of Microbiology and Epidemiology, Department of Basic Veterinary Sciences, Faculty of Veterinary Medicine, University of Helsinki, University of Helsinki, Helsinki, Finland.
Applied and Environmental Microbiology (impact factor: 3.83). 04/2005; 71(4):2061-9. DOI:10.1128/AEM.71.4.2061-2069.2005 pp.2061-9
Source: PubMed

ABSTRACT Two genes encoding ClpL ATPase proteins were identified in a probiotic Lactobacillus rhamnosus strain, E-97800. Sequence analyses revealed that the genes, designated clpL1 and clpL2, share 80% identity. The clpL2 gene showed the highest degree of identity (98.5%) to a clpL gene from Lactobacillus plantarum WCFSI, while it was not detected in three other L. rhamnosus strains studied. According to Northern analyses, the expression of clpL1 and the clpL2 were induced during heat shock by > 20- and 3-fold, respectively. The functional promoter regions were determined by primer extension analyses, and the clpL1 promoter was found to be overlapped by an inverted repeat structure identical to the conserved CIRCE element, indicating that clpL1 belongs to the HrcA regulon in L. rhamnosus. No consensus binding sites for HrcA or CtsR could be identified in the clpL2 promoter region. Interestingly, the clpL2 gene was found to be surrounded by truncated transposase genes and flanked by inverted repeat structures nearly identical to the terminal repeats of the ISLpl1 from L. plantarum HN38. Furthermore, clpL2 was shown to be mobilized during prolonged cultivation at elevated temperature. The presence of a gene almost identical to clpL2 in L. plantarum and its absence in other L. rhamnosus strains suggest that the L. rhamnosus E-97800 has acquired the clpL2 gene via horizontal transfer. No change in the stress tolerance of the ClpL2-deficient derivative of E-97800 compared to the parental strain was observed.

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Keywords

clpL1 promoter
 
clpL2 gene
 
clpL2 promoter region
 
ClpL2-deficient derivative
 
consensus binding sites
 
conserved CIRCE element
 
functional promoter regions
 
genes encoding ClpL ATPase proteins
 
horizontal transfer
 
inverted repeat structure identical
 
inverted repeat structures
 
L. plantarum
 
L. plantarum HN38
 
L. rhamnosus strains
 
Lactobacillus plantarum WCFSI
 
parental strain
 
primer extension analyses
 
probiotic Lactobacillus rhamnosus strain
 
share 80% identity
 
truncated transposase genes