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PubMed1982

Folate assays--an alternative to microbiological assays and commercial kits.

A simple and reliable folate radioassay technique based on the principles of classic folate radioassays but incorporating several of the recently introduced technical innovations is presented as an alternative to the microbiological assays and commercial kits. Serum and red cell folate values from this method were compared with results from two commercial kits and a Lactobacillus casei (L. casei) assay. There was a good correlation with the L. casei assay for both serum and red cell folate (r = 0.95). The method uses N-methyltetrahydrofolate standards diluted in folate free serum, beta-lactoglobulin as a binder and an alkaline denaturation ('no-boil') of endogenous folate binding proteins. Low hematocrit lysates were best performed at a 1 in 10 rather than 1 in 20 dilution. A comparison of the boil and 'no-boil' kits from Diagnostic Products Corporation revealed that the 'no-boil' kit produced results closer to those obtained from the L. casei assay than the boil kit.

Biological Assay↗
PubMed1983

[Characteristics of subunit composition of H+-ATPase from the anaerobic bacterium Lactobacillus casei].

In the presence of Mg2+ or Ca2+ the membranes of the anaerobic glycolytic bacterium Lactobacillus casei hydrolyze 0.1-0.2 mumole ATP/min/mg of protein with a pH optimum 6.4. This activity is inhibited by N,N'-dicyclohexylcarbodiimide and is insensitive to oligomycin, ouabain, vanadate and hydroxylamine. A soluble ATPase was isolated and purified from L. casei membranes. The specific activity of this ATPase is 3.0-4.0 mumole ATP/min/mg of protein. The enzyme homogeneity was established by analytical polyacrylamide gel disc electrophoresis and by analytical centrifugation (S20, omega = 12 +/- 0,5). The molecular weight of the enzyme is 270 000. Polyacrylamide gel electrophoresis of ATPase denaturated by 1% SDS and 8 M urea in the presence of SDS revealed one type of subunits with Mr = 43 000. These subunits could not be separated by isoelectrofocusing in polyacrylamide gel in the presence of 8 M urea and migrated as a single peptide with pI at 4.2. The experimental results suggest that the soluble ATPase from L. casei consists of six identical subunits with Mr of 43 000.

Anaerobiosis↗
PubMed1976

[Sensitivity of the lactobacilli of the subgenus Streptobacterium to bacteriocins of lactobacilli of different species].

Sensitivity of 167 cultures of Lactobacilli of Streptobacterium to 39 bacteriocins produced by L. acidophilus, L. jugurti, L. salivarius, L. lactis, L. helveticus, L. casei, L. plantarum, L. fermenti, L. brevis and L. buchneri was studied. It was found that the cultures of L. casei were sensitive to 30 types of bacteriocins, while the cultures of L. plantarum were sensitive to 9 bacteriocin types. 89.6 per cent of the cultures of L. casei and all cultures of L. plantarum were sensitive to one or several bacteriocins produced by Lactobacilli of different species.

Bacteriocins↗
PubMed1990

Genetic transformation of Lactobacillus casei by electroporation.

Lactobacillus casei IAM1045 was transformed with a plasmid pAM beta 1-1, a tra deleted derivative of pAM beta 1, by electroporation. Effective transformation was achieved in electroporation buffers of a wide range of pH values, and in all phases of cell growth tested, with highest frequency in the early log phase. Polyethylene glycol increased the transformation frequency, whereas divalent cations such as Mg2+, Ca2+ and Mn2+ at 0.25 mM decreased the frequency by 2 to 3 orders. Highly efficient transformation of approximately 10(-4)/viable cell was achieved under optimal conditions. A plasmid harboring the trpD, C, F, B and A genes from L casei RNL7 was introduced by electroporation into tryptophan auxotrophic L casei JCM1053. The resulting transformant was found to express the trp genes introduced.

Calcium↗
PubMed1981

Reconstitution of the allosteric L-lactate dehydrogenase from Lactobacillus casei investigated by hybridization.

The reassociation process of the urea-denatured allosteric L-lactate dehydrogenase from Lactobacillus casei was investigated by hybridization experiments between the reassociating enzymes from L. casei and Lactobacillus curvatus. The quantitatively evaluated hybridization patterns indicate an assembly pathway from the unfolded subunits to the tetrameric state via dimers. The comparison of the kinetics of reassociation and reactivation of the L. casei L-lactate dehydrogenase shows that the tetramer is the only active form.

Allosteric Regulation↗
PubMed1994

[Influence of Lactobacillus casei on rat bladder carcinogenesis].

The inhibitory effect of Lactobacillus casei (L. casei) in superficial bladder tumors was investigated in an experimental study using N-butyl-N (4-hydroxybutyl) nitrosamine (BBN)-induced rat bladder cancer as an experimental system. The study consisted of two experiments; in a short-term experiment, the inhibitory effect of 6-week treatment with L. casei was assessed in vitro in terms of the capacity for agglutination by concanavalin A (Con A) of bladder epithelial cells in their incipient stage of malignant transformation induced by 1-week exposure to BBN. As a result, the number of bladder epithelial cell aggregates caused by Con A was significantly smaller in the L. casei-treated group than in the non-L. casei-treated group (p < 0.001). In a long-term experiment, treatment with L. casei of varying duration was investigated for effectiveness against bladder tumors induced by 7-weeks exposure to BBN that arose 22 weeks. The results indicate that both bladder weight and tumor volume per organ were significantly lower in the L. casei-treated than non-L. casei-treated group (p < 0.05). The inhibitory effect on these parameters was more pronounced with treatment with L. casei of longer duration. While there was no significant difference among the treatment groups in the degree of extension of induced malignancy, tumors with a high degree of extension (T1b, T2) developed only in the non-L. casei-treated group. The degree of malignancy of induced tumors was significantly lower in those groups receiving L. casei while BBN was being administered as compared to the non-L. casei-treated group (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Cryoprotected Lactobacillus casei: an approach to standardization of microbiological assay of folic acid in serum.

Folate-depleted, cryoprotected preparations of Lactobacillus casei are stable for at least eight months at -18 degrees C, capable of reproducible growth and suitable as a ready source of inoculum for measurement of folates in physiological fluids. Cryoprotected microorganisms can be a commercially available laboratory reagent, thus simplifying and further standardizing the microbiological assay of various nutriments. Standard folate growth curves of cryoprotected L. casei, prepared at intervals over eight months, are superimposable, have a low blank, and should eliminate the variations encountered with the continuous passages of microorganisms required for the classic microbiological assays. Serum folate values obtained by use of the cryoprotected L. casei fall into the same diagnostic groups as determined by the classic microbiological assay.

Biological Assay↗
PubMed1992

Construction and characterization of shuttle plasmids for lactic acid bacteria and Escherichia coli.

The chimeric plasmid pBN183 was first constructed in Escherichia coli by ligating the BamHI-digested E. coli plasmid pBR322 and a Bg/II-linearized streptococcal plasmid, pNZ18. The pBN183 transformed E. coli to ApR at a frequency of (8.2 +/- 1.2) x 10(5) colony forming units (CFU)/microgram DNA. Electrotransformation of Streptococcus thermophilus with pBN183 yielded CmR, ApS clones at a frequency of (2.6 +/- 0.3) x 10(1) CFU/microgram DNA. Plasmid screening with pBN183-transformed S. thermophilus clones revealed that ca. 70% of these transformants contained deleted plasmids. Plasmid pBN183A, a pBN183 deletion mutant lacking one copy of a tandemly arranged, highly homologous DNA sequence, was isolated for further study. It transformed E. coli to ApR and S. thermophilus to CmR with frequencies of (4.8 +/- 0.1) x 10(5) and (8.1 +/- 0.2) x 10(2) CFU/microgram DNA, respectively. Screening of S. thermophilus transformants did not show the presence of deleted plasmids. Based on the structure of pBN183A, a new shuttle plasmid, pDBN183, was constructed from pBN183 by removal of the small (1.2 kb) Sa/I fragment. Transformation frequencies of pDBN183 were (5.0 +/- 1.3) x 10(5) and (4.6 +/- 0.2) x 10(2) CFU/microgram DNA with E. coli and S. thermophilus, respectively. In contrast to the parent pBN183, only 17% of the pDBN183-transformed S. thermophilus contained deleted plasmids. Plasmid copy numbers of the three vectors in E. coli were estimated at 17-18 per chromosome. The three plasmids conferred ApR and CmR to E. coli, but only CmR to S. thermophilus. The insertion of a Streptomyces cholesterol oxidase gene (choA) into pDBN183 did not affect the plasmid's stability in Lactobacillus casei, but resulted in deletion of the recombinant DNA in S. thermophilus.

Cholesterol Oxidase↗
PubMed1982

Molecular cloning of the gene for dihydrofolate reductase from Lactobacillus casei.

The Lactobacillus casei gene for dihydrofolate reductase has been cloned in Escherichia coli using the multicopy vector pBR322. A restriction map of the cloned DNA has been prepared. The cloned DNA directs the synthesis of L. casei dihydrofolate reductase in E. coli and confers trimethoprim and methotrexate resistance.

Chromosome Mapping↗
PubMed1983

Trimethoprim binding to bacterial and mammalian dihydrofolate reductase: a comparison by proton and carbon-13 nuclear magnetic resonance.

The binding of trimethoprim to dihydrofolate reductase from L1210 mouse lymphoma cells has been studied by measuring the changes in chemical shift of nuclei of the ligand that accompanying binding. The 6- and 2',6'-proton chemical shifts of bound trimethoprim have been determined by transfer of saturation experiments, and the 2-carbon chemical shift has been determined by using [2-13C]trimethoprim. The changes in proton chemical shift are substantially smaller than those accompanying binding to bacterial dihydrofolate reductase [Cayley, P. J., Albrand, J. P., Feeney, J., Robert, G. C. K., Piper, E. A., & Burgen, A. S. V. (1979) Biochemistry 18, 3886]. It is shown that this difference arises largely from the fact that trimethoprim adopts different conformations when bound to mammalian and to bacterial dihydrofolate reductase. The proton chemical shifts are interpreted in terms of ring-current contributions from the two aromatic rings of trimethoprim itself and the nearby aromatic amino acid residues of the enzyme. The latter have been located by using the refined crystallographic coordinates of the Lactobacillus casei and Escherichia coli reductases in their complexes with methotrexate [Bolin, J. T., Filman, D. J., Matthews, D. A. & Kraut, J. (1982) J. Biol. Chem. 257, 13650], under the assumption that, as indicated by the 13C chemical shifts, the diaminopyrimidine ring of trimethoprim binds in the same way as does the corresponding part of methotrexate. With use of these assumptions, the conformation of trimethoprim bound to the dihydrofolate reductases from L. casei, E. coli, and L1210 cells has been calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Isolation and characterization of proteinase- and aminopeptidase-deficient mutants of Lactobacillus casei subsp. casei IFPL 731.

Proteinase-deficient (Prt-) and aminopeptidase-deficient (Amp-) variants of Lactobacillus casei subsp. casei IFPL 731 were isolated and characterized. The Prt- mutant was isolated from strains that developed poorly on glucose milk agar. The Amp- mutant was isolated on the basis of its inability to hydrolyse L-leucine-beta-naphtylamide. The Prt- variant developed poorly, while in milk the Amp- variant grew at about the same rate as the parental strain. The characterization of aminopeptidase activity in more detail showed that at least two enzymes are involved The results of the present study suggest that the proteolytic system of Lactobacillus casei is subjected to a regulatory system.

Aminopeptidases↗
PubMed2007

The phosphotransferase system of Lactobacillus casei: regulation of carbon metabolism and connection to cold shock response.

Genome sequencing of two different Lactobacillus casei strains (ATCC334 and BL23) is presently going on and preliminary data revealed that this lactic acid bacterium possesses numerous carbohydrate transport systems probably reflecting its capacity to proliferate under varying environmental conditions. Many carbohydrate transporters belong to the phosphoenolpyruvate:sugar phosphotransferase system (PTS), but all different kinds of non-PTS transporters are present as well and their substrates are known in a few cases. In L. casei regulation of carbohydrate transport and carbon metabolism is mainly achieved by PTS proteins. Carbon catabolite repression (CCR) is mediated via several mechanisms, including the major P-Ser-HPr/catabolite control protein A (CcpA)-dependent mechanism. Catabolite response elements, the target sites for the P-Ser-HPr/CcpA complex, precede numerous genes and operons. PTS regulation domain-containing antiterminators and transcription activators are also present in both L. casei strains. Their activity is usually controlled by two PTS-mediated phosphorylation reactions exerting antagonistic effects on the transcription regulators: P~EIIB-dependent phosphorylation regulates induction of the corresponding genes and P~His-HPr-mediated phosphorylation plays a role in CCR. Carbohydrate transport of L. casei is also regulated via inducer exclusion and inducer expulsion. The presence of glucose, fructose, etc. leads to inhibition of the transport or metabolism of less favorable carbon sources (inducer exclusion) or to the export of accumulated non-metabolizable carbon sources (inducer expulsion). While P-Ser-HPr is essential for inducer exclusion of maltose, it is not necessary for the expulsion of accumulated thio-methyl-beta-D-galactopyranoside. Surprisingly, recent evidence suggests that the PTS of L. casei also plays a role in cold shock response.

Biological Transport↗
PubMed1988

Lactobacillus casei microbiological assay of folic acid derivatives in 96-well microtiter plates.

Microbiological assay is still widely used for estimating folic acid derivatives in serum and other biological samples. We describe here a modification of this procedure involving use of 96-well microtiter plates. This procedure, used with modern, computer-interfaced microtiter-plate readers and data-reduction software, greatly shortens the time and minimizes reagent costs for this assay. Under the conditions of our assay procedures, all folic acid derivatives tested gave equal growth response for Lactobacillus casei. Results for assays of rat liver extracts showed excellent agreement between the standard bioassay and the 96-well procedure.

Animals↗