Protective action of reactivating factor of <Emphasis Type="Italic">Luteococcus japonicus</Emphasis> subsp. <Emphasis Type="Italic">casei</Emphasis> toward cells of <Emphasis Type="Italic">Escherichia coli</Emphasis> reparation mutants inactivated with UV-light

Reactivating factor (RF) from Luteococcus japonicus subsp. casei had a protective action on UV-irradiated cells of Escherichia coli AB1157 with a native reparation system and on cells of isogenic reparation mutants of E. coli UvrA⁻, RecA⁻, and PolA⁻: the effect resulted in multifold increase of survivability. Defense action of L. casei exometabolite is not connected with stimulating reparation systems in E. coli, and, probably, it is mediated by involvement of the exometabolite in the mechanism of cell division. RF did not provoke the reactivation of E. coli cells inactivated by UV-light.     

Lactobacillus casei DN-114 001 inhibits the ability of adherent-invasive Escherichia coli isolated from Crohn's disease patients to adhere to and to invade intestinal epithelial cells

Ileal lesions in 36.4% of patients with Crohn's disease are colonized by pathogenic adherent-invasive Escherichia coli. The aim of this study was to determine the in vitro inhibitory effects of the probiotic strain, Lactobacillus casei DN-114 001, on adhesion to and invasion of human intestinal epithelial cells by adherent-invasive E. coli isolated from Crohn's disease patients. The experiments were performed with undifferentiated Intestine-407 cells and with undifferentiated or differentiated Caco-2 intestinal epithelial cells. Bacterial adhesion to and invasion of intestinal epithelial cells were assessed by counting CFU. The inhibitory effects of L. casei were determined after coincubation with adherent-invasive E. coli or after preincubation of intestinal cells with L. casei prior to infection with adherent-invasive E. coli. Inhibitory effects of L. casei on adherent-invasive E. coli adhesion to differentiated and undifferentiated intestinal epithelial cells reached 75% to 84% in coincubation and 43% to 62% in preincubation experiments, according to the cell lines used. Addition of L. casei culture supernatant to the incubation medium increased L. casei adhesion to intestinal epithelial cells and enhanced the inhibitory effects of L. casei. The inhibitory effects on E. coli invasion paralleled those on adhesion. This effect was not due to a bactericidal effect on adherent-invasive E. coli or to a cytotoxic effect on epithelial intestinal cells. As Lactobacillus casei DN-114 001 strongly inhibits interaction of adherent-invasive E. coli with intestinal epithelial cells, this finding suggests that the probiotic strain could be of therapeutic value in Crohn's disease.     

Extracellular protein metabolite of Luteococcus japonicus subsp. casei reactivates cells subjected to oxidative stress

A protein exometabolite isolated from the culture liquid of Luteococcus japonicus subsp. casei reactivates the cells of this microorganism, following H2O2 or paraquat-induced oxidative stress. The resistance of L. casei cells to these oxidizers is accounted for by the high activity of superoxide dismutase and catalase. The effect of the protein exometabolite is universal, in that it reactivates the cells after UV irradiation, heating, or oxidative stress. However, the cells subjected to oxidative stress are significantly less susceptible to the reactivating effect, as compared to their UV-irradiated or heated counterparts. Possible causes of these differences are discussed.     

Myocardium of mdx mice contains factor(s) that damage DNA structure and retard DNA reparation after gamma-irradiation (experiences in modeling system)

We studied the action of saline extracts of ventricle myocard (EM) of C57BL and mdx mice on DNA structure and repair of one-strand breaks of DNA in a modelling system. The system involves DNA repair in E. coli WP2 cells after gamma-irradiation. Using standard technique, DNA reparation was estimated on measuring the speed of E. coli DNA sedimentation in alkaline sucrose gradients. It was shown, that EM of C57BL or mdx mice exerted no influence on DNA repair, which was completely declined within 60 min with EM present in the growth medium of permeabilized E. coli. Addition of C57BL mice EM into lytic solution does not accelerate DNA sedimentation of nonirradiated E. coli. At the same time, EM of mdx mice sharply accelerates DNA sedimentation of nonirradiated E. coli reducing DNA molecular weight from 200 x 10(6) to 135 x 10(6) Da. At entering in the lytic solution the EM of mdx mice also slows down E. coli DNA repair after gamma-irradiation. It is supposed, that EM of mdx mice may contain a factor(s) damaging DNA in the E. coli lysate and presumably slowing down DNA reparation after gamma-irradiation. Russian Foundation of Basic Research Grants 99-04-49390, 02-04-49870 and 00-04-49390.     

Protective effect of extracellular protein metabolite of Luteococcus japonicus subsp, casei on cells subjected to heating and UV irradiation

Extracellular protein metabolite isolated from the culture liquid of Luteococcus japonicus subsp. casei had reactivating and protective effects on UV-irradiated and heated cells. The extracellular metabolite, produced by cells in the logarithmic growth phase, was present in culture liquid in minuscule amounts. Mass spectral analysis showed that, along with the major component with a molecular weight of 7.6 kDa, the preparation contained low quantities of three minor proteins. Apparently, the biological activity of the exometabolite is determined by the major polypeptide component.     

The extracellular protein of Luteococcus japonicus subsp casei reactivates cells inactivated by ultraviolet radiation or heating

The culture liquid of Luteococcus japonicus subsp. casei was found to be able to reactivate cells of this bacterium inactivated by UV irradiation or heat shock. The antistress activity of the culture liquid was due to the presence of an extracellular exometabolite of a protein nature with a molecular mass of more than 10 kDa. When the bacterium was grown in nutrient broth or glucose-containing mineral medium, the antistress protein was secreted by cells in the logarithmic growth phase. The reactivating effect of the antistress protein was inversely proportional to the survival rate of stressed cells.     

Cloning and expression of the beta-D-phosphogalactoside galactohydrolase gene of Lactobacillus casei in Escherichia coli K-12.

Lactose metabolism in Lactobacillus casei 64H is associated with the presence of plasmid pLZ64. This plasmid determines both phosphoenolpyruvate-dependent phosphotransferase uptake of lactose and beta-D-phosphogalactoside galactohydrolase. A shotgun clone bank of chimeric plasmids containing restriction enzyme digest fragments of pLZ64 DNA was constructed in Escherichia coli K-12. One clone contained the gene coding for beta-D-phosphogalactoside galactohydrolase on a 7.9-kilobase PstI fragment cloned into the vector pBR322 in E. coli strain chi 1849. The beta-D-phosphogalactoside galactohydrolase enzyme isolated from E. coli showed no difference from that isolated from L. casei, and specific activity of beta-D-phosphogalactoside galactohydrolase was stimulated 1.8-fold in E. coli by growth in media containing beta-galactosides. A restriction map of the recombinant plasmid was compiled, and with that information, a series of subclones was constructed. From an analysis of the proteins produced by minicells prepared from transformant E. coli cells containing each of the recombinant subclone plasmids, it was found that the gene for the 56-kilodalton beta-D-phosphogalactoside galactohydrolase was transcribed from an L. casei-derived promoter. The gene for a second protein product (43 kilodaltons) was transcribed in the opposite direction, presumably under the control of a promoter in pBR322. The relationship of this second product to the lactose metabolism genes of L. casei is at present unknown.     

Reactivating effect of Escherichia coli exometabolites on UV-irradiated cells

Wild-type and mutant (AB 1157 and K-12) strains of Escherichia coli were shown to synthesize the logarithmic growth phase, exometabolites reactivating UV-irradiated cells of producer strains. The exometabolites of the strain K-12 were of protein nature and had a molecular weight of no more than 10 kDa. The reactivating activity of these exometabolites was inversely related to bacterial survival and slightly increased under the influence of stress factors. The reactivating factor of Luteococcus casei had a cross-reactivating and protective effect on UV-irradiated cells of E. coli strain K-12. Due to activation of the reactivating factor after UV irradiation and heating, the cross-protective effect increased more than threefold. The reactivating effect remained unchanged under these conditions. The protein exometabolites of E. coli did not induce cross-stress response in L. casei.     

Mutagenesis of folylpolyglutamate synthetase indicates that dihydropteroate and tetrahydrofolate bind to the same site

The folylpolyglutamate synthetase (FPGS) enzyme of Escherichia coli differs from that of Lactobacillus casei in having dihydrofolate synthetase activity, which catalyzes the production of dihydrofolate from dihydropteroate. The present study undertook mutagenesis to identify structural elements that are directly responsible for the functional differences between the two enzymes. The amino terminal domain (residues 1-287) of the E. coli FPGS was found to bind tetrahydrofolate and dihydropteroate with the same affinity as the intact enzyme. The domain-swap chimera proteins between the E. coli and the L. casei enzymes possess both folate or pteroate binding properties and enzymatic activities of their amino terminal portion, suggesting that the N-terminal domain determines the folate substrate specificity. Recent structural studies have identified two unique folate binding sites, the omega loop in L. casei FPGS and the dihydropteroate binding loop in the E. coli enzyme. Mutants with swapped omega loops retained the activities and folate or pteroate binding properties of the rest of the enzyme. Mutating L. casei FPGS to contain an E. coli FPGS dihydropteroate binding loop did not alter its substrate specificity to using dihydropteroate as a substrate. The mutant D154A, a residue specific for the dihydropteroate binding site in E. coli FPGS, and D151A, the corresponding mutant in the L. casei enzyme, were both defective in using tetrahydrofolate as their substrate, suggesting that the binding site corresponding to the E. coli pteroate binding site is also the tetrahydrofolate binding site for both enzymes. Tetrahydrofolate diglutamate was a slightly less effective substrate than the monoglutamate with the wild-type enzyme but was a 40-fold more effective substrate with the D151A mutant. This suggests that the 5,10-methylenetetrahydrofolate binding site identified in the L. casei ternary structure may bind diglutamate and polyglutamate folate derivatives.     

乳酸杆菌对攻毒小鼠的保护作用和对肠道菌群的影响

将含有乳酸杆菌Lactobacillus casei Zhang的悬浮液分组饲喂小鼠,然后分别用E.coliO157和K88攻毒观察发病情况。攻毒4d后取对照组和喂菌组未死亡小鼠的肠内容物,用选择性培养基分离纯化大肠杆菌和乳酸菌,提取分离到菌株的总DNA,进行ERIC-PCR扩增分析。发现灌服L.casei Zhang可以降低攻毒后小鼠的死亡率,在停止饲喂乳酸菌的第4d从小鼠肠道内分离到L.casei Zhang,从饲喂组未分离到E.coliO157和K88,喂L.casei Zhang使小鼠肠道中大肠杆菌总数极显著低于对照组。表明所饲喂的乳杆菌可以在小鼠肠道内定殖并对小鼠起到保护作用。     

Regulation of the synthesis and activity of thymidine phosphorylase in Lactobacillus casei

Abstract: Lactobacillus casei cells grown on excess thymine or on folic acid contained low levels of thymidine phosphorylase. On the other hand, thymine starved cells and also cells of a thymidine-monophosphate-kinase-defective mutant grown on excess thymine, possessed derepressed levels. These results suggest that the synthesis of thymidine phosphorylase is regulated by the end product of the thymidine-triphosphate-biosynthetic pathway. L. casei cells lacked 2-deoxyribose-1-phosphate-mutase activity and did not grow on 2-deoxyribose or thymidine as the sole-carbon source. Growth in the presence of thymidine did not result in induction of thymidine-phosphorylase synthesis, probably due to the inability of the cell to convert it to 2-deoxyribose-5-phosphate, which is known to act as an inducer in E. coli cells. Thymidine triphosphate inhibited non-competitively the activity of thymidine phosphorylase. It was also inhibited by dihydrofolic acid.     

Prevention of pathogenic Escherichia coli infection in mice and stimulation of macrophage activation in rats by an oral administration of probiotic Lactobacillus casei I-5

Lactobacillus casei I-5 isolated from an alcohol fermentation broth enhanced immunity and prevented pathogenic infection as a probiotic. Mice fed with I-5 cells for 11 days prior to an intraperitoneal challenge with pathogenic Escherichia coli Juhl exhibited a high survival rate compared with the control group. Rats fed with I-5 cells for 10 days significantly increased the phagocytosis of peritoneal macrophages. In a cell culture system employing peritoneal macrophages from rats, the I-5 administration activated NF-kappaB stimulated by LPS. It also enhanced LPS-stimulated IL-12 and TNF-alpha production, but not IL-6 production. These results show that L. casei I-5 effectively prevented infection by pathogenic E. coli possibly through the activation of peritoneal macrophages. The strain would be useful to prevent pathogenic microbial infections in humans and farm animals.     

The possible role of probiotics as dietary antimutagen.

Possible antimutagenic actions of probiotics--mainly lactic acid bacteria--were examined using in vitro and in vivo test systems. In the Ames test with Salmonella typhimurium TA1538 beef extract and nitrosated beef extract were used as mutagens. L. casei showed high antimutagenic activity on mutagenicity induced by nitrosated beef extract only without S9 mix, whereas Omniflora (a lyophilized preparation of lactobacilli and E. coli) and its cell-free culture broth exhibited antimutagenic action only on beef extract. The actions of probiotics were more homogeneous when living animals were used in the tests. Using busulfan as a mutagen both the chromosome aberration test (with Chinese hamster bone marrow cells) and the micronucleus test (with bone marrow cells of Chinese hamsters and mice) showed strong anticlastogenic action when L. casei, Omniflora or yoghurt (with living bifiobacteria) were given orally at the same time as the mutagen. Lactobacilli were effective also after i.p. injection. Cell-free culture broths had no or only weak antimutagenic effects. Mutagen-induced chromosome aberrations and micronuclei were reduced by up to 80% by the lactobacilli.     

Expression of human thymidylate synthase in Escherichia coli

A cDNA clone encoding thymidylate synthase (TS) has been isolated from a human T-cell library and modified in the 5'-untranslated region to incorporate several unique cloning sites. The gene has been cloned as a cassette into several Escherichia coli expression vectors which did not provide detectable amounts of the enzyme. A successful approach used a constitutive E. coli expression vector developed for the enzyme from Lactobacillus casei. A 115-base pair 5'-untranslated region from the L. casei TS which contains a ribosomal binding site and other regulatory sequences has been fused to the coding region of the human TS gene to provide a construct that is expressed in E. coli. The level of expression was further enhanced by altering the nucleotide sequence of the first 90 base pairs to accommodate common codon use in E. coli. In our best expression system, catalytically active human TS is expressed to a level that represents about 1.6% of the total soluble protein. The recombinant human TS has been purified and characterized; except for the presence of an amino-terminal blocking group, the enzyme has physical and kinetic properties similar to the enzyme isolated from human cells.     

Replication of phi X174 dna with purified enzymes. I. Conversion of viral DNA to a supercoiled, biologically active duplex

Conversion of phi X174 viral, single-stranded circular DNA to the duplex replicative form (RF), previously observed with partially purified enzymes, has now been demonstrated with the participation of 12 nearly pure Escherichia coli proteins containing approximately 30 polypeptides. To complete the synthesis of a full length complementary strand, E. coli DNA polymerase I was needed to fill the short gap left by DNA polymerase III holoenzyme, and to remove the primer and replace it with DNA. Production of supercoiled RF required the further actions of E. coli DNA ligase and gyrase. Net synthesis of viral circles was obtained by coupling the formation of RF supercoils to the actions of the phi X174-encoded gene A protein and E. coli rep protein. Viral DNA circles produced from enzymatically synthesized supercoiled RF, serving as template-substrate, were indistinguishable from those produced from RF isolated from infected cells; synthetic RF and the viral circles generated from it by replication were as biologically active in transfection of spheroplasts as the forms obtained from infected cells and virions. The conversion of single-stranded circular DNA to RF is suggested here as a model for discontinuous synthesis of the lagging strand of the E. coli chromosome. The primosome, a complex of some of the replication proteins responsible for initiations of DNA chains, will be described elsewhere. Multiplication of RF supercoils, described in the succeeding paper, proceeds by a rolling-circle mechanism in which the synthesis of viral strands may have analogies to the continuous synthesis of the leading strand of the E. coli chromosome.     

Mutation of an essential glutamate residue in folylpolyglutamate synthetase and activation of the enzyme by pteroate binding

Site-directed mutagenesis was performed on Glu143, an essential amino acid in Lactobacillus casei folylpolyglutamate synthetase (FPGS) and the structurally equivalent residue, Glu146, in Escherichia coli FPGS. Glu143 is positioned near the P-loop and interacts with the Mg(2+) of Mg NTP-binding proteins. We have solved the structure of the E143A mutant of L. casei FPGS in the presence of AMPPCP and Mg(2+). The structure showed a water molecule at the place where Mg(2+) bound to the wild type enzyme. Mutant proteins E143A, and even E143D and E143Q with conservative mutations, lacked enzyme activity and failed to complement the methionine auxotrophy of the E. coli folC mutant SF4, showing that Glu143 is an essential residue. Both the L. casei and the E. coli FPGS mutant proteins bound methylene-tetrahydrofolate diglutamate and dihydropteroate normally. The E. coli E146Q mutant FPGS bound ADP with the same affinity as the wild type enzyme but bound ATP with much lower affinity and had higher ATPase activity than the wild type enzyme. The mutant enzyme was defective in forming the acyl-phosphate reaction intermediate from ATP and dihydropteroate. The E. coli FPGS requires activation by dihydropteroate or tetrahydrofolate binding to allow full activity. In the absence of a pteroate substrate, only 30% of the total enzyme binds ATP. We suggest that dihydropteroate causes a conformational change to allow increased ATP binding. The mutant enzyme was similarly activated by dihydropteroate resulting in increased ADP binding.     

Oral probiotic bacterial administration suppressed allergic responses in an ovalbumin-induced allergy mouse model

This study investigated whether orally administered probiotic bacteria (Bifidobacterium bifidum and Lactobacillus casei) and a gram-negative bacterium (Escherichia coli) function as allergic immune modulators to prevent food allergy, according to the hygiene hypothesis. C3H/HeJ mice were sensitized with ovalbumin (OVA) and cholera toxin for 5 weeks. After sensitization, the OVA-induced mice that were not treated with bacteria had significantly increased levels of OVA-specific IgE, total IgE, and IgG1 in sera, as well as scab-covered tails. In comparison, groups treated with B. bifidum BGN4 (BGN4), L. casei 911 (L. casei), or Escherichia coli MC4100 (E. coli) had decreased levels of OVA-specific IgE, total IgE, and IgG1, and decreased levels of mast cell degranulation and tail scabs. OVA-specific IgA levels were decreased in BGN4- and L. casei-treated groups. In conclusion, administration of E. coli, BGN4, or L. casei decreased the OVA-induced allergy response. However, a normal increase in body weight was inhibited in the E. coli-treated mice and in the montreated mice groups during allergy sensitization. Thus, BGN4 and L. casei appear to be useful probiotic bacteria for the prevention of allergy.     

Nucleotide sequences and genomic constitution of five tryptophan genes of Lactobacillus casei

Five trp genes, trpD, trpC, trpF, trpB, and trpA, of Lactobacillus casei were cloned by transformation of tryptophan auxotrophic mutants of the respective trp genes in Escherichia coli. These trp genes appear to constitute an operon and are located in the above order in a segment of DNA of 6,468 base pairs. The entire nucleotide sequence of this DNA segment was determined. Five contiguous open reading frames in this segment can encode proteins consisting of 341, 260, 199, 406, and 266 amino acids, respectively, in the same direction. The amino acid sequences of these proteins exhibit 25.5-50.2% homology with the amino acid sequences of the corresponding trp enzymes of E. coli. Two trp genes, trpC and trpF, from L. casei can complement mutant alleles of the corresponding genes of E. coli. However, neither the trpA gene nor the trpB gene of L. casei can complement mutations in the E. coli trpA gene and the trpB gene, respectively, suggesting that the protein products of the L. casei and E. coli trpA and trpB genes, respectively, cannot form heterodimers of tryptophan synthetase with activity. Other features of the coding and flanking regions of the trp genes are also described.     

Quantitative approach in the study of adhesion of lactic acid bacteria to intestinal cells and their competition with enterobacteria

To describe the phenomena of bacterial adhesion to intestinal cells and the competition for adhesion between bacteria, mathematical equations based on a simple dissociation process involving a finite number of bacterial receptors on intestinal cell surface were developed. The equations allow the estimation of the maximum number of Lactobacillus sp. and Escherichia coli cells that can adhere to Caco-2 cells and intestinal mucus; they also characterize the affinity of the bacteria to Caco-2 cells and intestinal and fecal mucus and the theoretical adhesion ratio of two bacteria present in a mixed suspension. The competition for adhesion between Lactobacillus rhamnosus GG and E. coli TG1 appeared to follow the proposed kinetics, whereas the competition between Lactobacillus casei Shirota and E. coli TG1 may involve multiple adhesion sites or a soluble factor in the culture medium of the former. The displacement of the adhered Lactobacillus by E. coli TG1 seemed to be a rapid process, whereas the displacement of E. coli TG1 by the Lactobacillus took more than an hour.