Characterization of a mobile clpL gene from Lactobacillus rhamnosus.
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.
[show abstract] [hide abstract]
ABSTRACT: Incorporation of 1.9% beta-disodium glycerophosphate (GP) into a complex medium resulted in improved growth by lactic streptococci at 30 C. The medium, called M17, contained: Phytone peptone, 5.0 g; polypeptone, 5.0 g; yeast extract, 2.5 g; beef extract, 5.0 g; lactose, 5.0 g; ascorbic acid, 0.5 g; GP, 19.0 g; 1.0 M MgSO(4).7H(2)O, 1.0 ml; and glass-distilled water, 1,000 ml. Based on absorbance readings and total counts, all strains of Streptococcus cremoris, S. diacetilactis, and S. lactis grew better in M17 medium than in a similar medium lacking GP or in lactic broth. Enhanced growth was probably due to the increased buffering capacity of the medium, since pH values below 5.70 were not reached after 24 h of growth at 30 C by S. lactis or S. cremoris strains. The medium also proved useful for isolation of bacterial mutants lacking the ability to ferment lactose; such mutants formed minute colonies on M17 agar plates, whereas wild-type cells formed colonies 3 to 4 mm in diameter. Incorporation of sterile GP into skim milk at 1.9% final concentration resulted in enhanced acid-producing activity by lactic streptococci when cells were inoculated from GP milk into skim milk not containing GP. M17 medium also proved superior to other media in demonstrating and distinguishing between lactic streptococcal bacteriophages. Plaques larger than 6 mm in diameter developed with some phage-host combinations, and turbid plaques, indicative of lysogeny, were also easily demonstrated for some systems.Applied microbiology 07/1975; 29(6):807-13.
Article: Stress response in Actinobacillus actinomycetemcomitans: induction of general and specific stress proteins.[show abstract] [hide abstract]
ABSTRACT: Stress proteins are highly conserved proteins that are essential for cell survival. In this study, the induction of general and specific stress proteins in Actinobacillus actinomycetemcomitans cells subjected to different stress conditions was evaluated by two-dimensional SDS-PAGE analysis. Twenty-eight (up- or down)regulated proteins, including DnaK and GroEL proteins, were identified as general stress proteins. In addition, eighteen regulated proteins were classified as pH stress-specific proteins, ten as acid stress-specific proteins, five as alkaline stress-specific proteins, three as heat stress-specific proteins, and ten as acid/heat stress-specific proteins. Further proteomic studies are required to determine the exact nature of the proteins regulated during the stress response of A. actinomycetemcomitans.Research in Microbiology 154(1):43-8. · 2.76 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: This study utilized inverse polymerase chain reactions to characterize a 2.7-kb region of the Lactobacillus helveticus LH212 chromosome that included two complete and one truncated open reading frames (ORFs). Protein homology searches showed that the first two ORFs encoded homologs to the universally conserved heat shock proteins GroES and GroEL. Amino acids encoded by the 5' end of the truncated ORF that was downstream of groEL showed good homology to the amino terminal end of the Streptococcus pneumoniae DNA mismatch repair enzyme HexA. Nucleotide sequence analysis identified a putative transcriptional promoter upstream of groES that was comprised of -35 and -10 hexamers flanked upstream and downstream by copies of the conserved Gram-positive heat shock gene regulatory sequence, CIRCE. A large inverted repeat that may function as a rho-independent transcriptional terminator was located between groEL and the third ORF. Northern hybridization of an LH212 groEL gene fragment to RNA isolated from cells that had been heat shocked at 52 degrees C for 0, 5, 10 or 15 min detected a 2.2-kb transcript in each of the cell preparations. Densitometry showed the concentration of this mRNA species was approximately 4-fold higher after heat shock for 5 or 10 min and 3-fold higher after 15 min of heat shock.Research in Microbiology 05/1998; 149(4):247-53. · 2.76 Impact Factor