Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Streptococcus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2025

NrdR in Streptococcus and Listeria spp.: DNA Helix Phase Dependence of the Bacterial Ribonucleotide Reductase Repressor.

NrdR is a universal transcriptional repressor of bacterial genes coding for ribonucleotide reductases (RNRs), essential enzymes that provide DNA building blocks in all living cells. Despite its bacterial prevalence, the NrdR mechanism has been scarcely studied. We report the biochemical, biophysical, and bioinformatical characterization of NrdR and its binding sites from two major bacterial pathogens of the phylum Bacillota Listeria monocytogenes and Streptococcus pneumoniae. NrdR consists of a Zn-ribbon domain followed by an ATP-cone domain. We show that it forms tetramers that bind to DNA when loaded with ATP and dATP, but if loaded with only ATP, NrdR forms various oligomeric complexes unable to bind DNA. The DNA-binding site in L. monocytogenes is a pair of NrdR boxes separated by 15-16 bp, whereas in S. pneumoniae, the NrdR boxes are separated by unusually long spacers of 25-26 bp. This observation triggered a comprehensive binding study of four NrdRs from L. monocytogenes, S. pneumoniae, Escherichia coli, and Streptomyces coelicolor to a series of dsDNA fragments where the NrdR boxes were separated by 12-27 bp. The in vitro results were confirmed in vivo in E. coli and revealed that NrdR binds most efficiently when there is an integer number of DNA turns between the center of the two NrdR boxes. The study facilitates the prediction of NrdR binding sites in bacterial genomes and suggests that the NrdR mechanism is conserved throughout the bacterial domain. It sheds light on RNR regulation in Listeria and Streptococcus, and since NrdR does not occur in eukaryotes, opens a way to the development of novel antibiotics.

Ribonucleotide Reductases↗
PubMed1995

[Participation in causing O.M.E. with nasopharyngeal alpha-Streptococcus].

The role of normal pharyngeal flora in the defense mechanism against infections in the upper respiratory tract was studied in 50 children with otitis media with effusion (O.M.E.). In the bacteriological study of the nasopharynx, the incidence of H. influenzae, S. pneumoniae, S. aureus, M. catarrhalis and group A Streptococcus was about 46%, 24%, 20%, 12% and 8%, respectively. The incidence of these species in the cases with O.M.E. was higher than that in the cases with chronic tonsilitis or control cases. In 41 O.M.E. cases with alpha-streptococci (82%), the incidence of alpha-streptococci with inhibitory activity against 5 pathogens (H. influenzae, S. pneumoniae, S. aureus, M. catarrhalis, group A Streptococcus) was examined. The detection rate of alpha-streptococcal strains with inhibitory activity against 5 pathogens derived from the nasopharynx in the cases with O.M.E. was significantly lower than that of the strain in the chronic tonsilitis cases and the control cases. Moreover, the detection rate of inhibitory alpha-streptococci from the nasopharynx was lower than that of from the tonsil. These findings suggest that the decline of inhibitory activity against pathogens by normal flora in nasopharynx is one of the factors causing O.M.E.

Child↗
PubMed2002

[Streptococcus dysgalactiae subsp. equisimilis possessing Lancefield's group A antigen].

We isolated Streptococcus dysgalactiae subsp. equisimilis with Lancefield's group A antigen from a patient in Osaka City. This clinical isolate formed beta-hemolytic large colonies on sheep blood agar, and was catalase-negative gram-positive cocci carrying Lancefield's group A antigen. Therefore, Streptococcus pyogenes and this clinical isolate could not be classified by the conventional method on the basis of Lancefield's group antigen. In addition, the rapid detection system of group A streptococci based on group A antigen detection techniques could not divide into two species. Recently, S. dysgalactiae subsp. equisimilis with Lancefield's group G antigen has been isolated from severe invasive streptococcal infection in an increasing frequency in Japan. A possibility that group A S. dysgalactiae subsp. equisimilis cause a serious infection from now on cannot be denied. Thus the discrimination of S. pyogenes from group A S. dysgalactiae subsp. equisimilis is very important. To identify beta-hemolytic streptococci, it is necessary to consider a serogrouping test as one of characteristics of streptococci, and to identify by checking biochemical tests like the PYR test.

Aged↗
PubMed1976

Ingestion of Streptococcus mutans induces secretory immunoglobulin A and caries immunity.

Ingestion of killed cells of a highly cariogenic strain of Streptococcus mutans induced specific antibodies in both saliva and milk but not in serum of gnotobiotic rats. These antibodies were associated with the immunoglobulin A class. When infected with Streptococcus mutans, orally immunized animals developed significantly fewer carious lesions than nonimmunized infected controls.

Administration, Oral↗
PubMed1962

Cell wall replication in Streptococcus pyogenes.

Group A streptococci (Streptococcus pyogenes) of several different serological types were grown in fluorescein-labeled homologous type or group-specific globulins, thereby labeling the antigen-containing cell walls. Specific precipitation or inhibition of the labeled antibody, followed by continued incubation and examination at intervals by ultraviolet, phase, and dark-field microscopy, showed that new cell wall was then nonfluorescent. These nonfluorescent portions were differentiated by a reverse technique of culture in unlabeled globulin, followed by antibody precipitation, further growth, and fluorescent-antibody staining. This technique of differential labeling of cell wall has permitted following, for the first time in a living system, the fate of cell wall formed at different times. The results suggest that cell wall synthesis in actively growing cultures usually occurs simultaneously at at least two sites per coccus, each site representing stages in successive divisions, and that cell wall growth in Streptococcus pyogenes is not by diffuse intercalation with old wall, but is initiated at and extends both peripherally and centripetally from the coccal equator.

Cell Division↗
PubMed2001

Activities of a new fluoroketolide, HMR 3787, and its (des)-fluor derivative RU 64399 compared to those of telithromycin, erythromycin A, azithromycin, clarithromycin, and clindamycin against macrolide-susceptible or -resistant Streptococcus pneumoniae and S. pyogenes.

Activities of HMR 3787 and RU 64399 were compared to those of three macrolides, telithromycin, and clindamycin against 175 Streptococcus pneumoniae isolates and 121 Streptococcus pyogenes isolates. HMR3787 and telithromycin were the most active compounds tested against pneumococci. Telithromycin and RU 64399 were equally active against macrolide-susceptible (MICs, 0.008 to 0.06 microg/ml) and -resistant S. pyogenes isolates, but HMR 3787 had lower MICs for ermB strains.

Anti-Bacterial Agents↗
PubMed1975

Production of bacteriocins in a liquid medium by Streptococcus mutans.

A sterile-filtered, liquid medium composed of one-half-strength APT broth and 4% (wt/vol) yeast extract was found to support the production of bacteriocins by Streptococcus mutans strains BHT and GS-5. Culture supernatants, adjusted to pH 7.0 and sterilized by filtration, contained bacteriocin-like activity, which could be demonstrated by spotting dilutions onto top agar lawns seeded with Streptococcus pyogenes as the sensitive indicator and by adding dilutions to log-phase indicator broth cultures. A quantitative assay was developed for BHT bacteriocin, based on its lethal effects. Bacteriocin production did not occur until after the log phase of growth had ceased and was not inducible by ultraviolet irradiation or treatment with mitomycin C. Non-bacteriocinogenic clones of strain BHT occurred spontaneously at high frequency, suggesting control by a plasmid, but this frequency was not increased by treatment with the plasmid-curing agents acridine orange and ethidium bromide.

Bacteriocins↗
PubMed1997

Application of the extracellular alpha-amylase gene from Streptococcus bovis 148 to construction of a secretion vector for yogurt starter strains.

Streptococcus thermophilus ATCC 19258, Lactobacillus delbrueckii subsp. bulgaricus T-11, and Lactococcus lactis subsp. lactis IL1403 were transformed with the alpha-amylase gene (amyA) from Streptococcus bovis 148 by using a wide host-range vector, and all the transformants secreted the alpha-amylase successfully. Since the promoter and the secretion signal of the amyA gene were functional in these strains, we constructed a secretion vector using the expression elements of amyA. Trials to secrete foreign enzymes in yogurt starter strains were performed using this novel secretion vector.

Genetic Vectors↗
PubMed2001

Identification of bacteriocin-like inhibitors from rumen Streptococcus spp. and isolation and characterization of bovicin 255.

Streptococci obtained from rumen sources were tested for the production of antibacterial compounds using a deferred-antagonism plating assay. Of 35 isolates tested, 7 were identified that inhibited the growth of other streptococci. None of the inhibitory activity was due to bacteriophage. Three isolates, LRC0253, LRC0255, and LRC0476, were selected for further characterization. Analysis of 16S ribosomal DNA indicated that LRC0476 was a strain of Streptococcus bovis, while isolates LRC0253 and LRC0255 are likely strains of Streptococcus gallolyticus. The antibacterial compounds produced by these bacteria were protease sensitive, remained active in a pH range from 1 to 12, and did not lose activity after heating at 100 degrees C for 15 min. The inhibitory peptide from strain LRC0255 was purified using pH-dependent adsorption and desorption to bacterial cells, followed by ammonium sulfate precipitation and reversed-phase chromatography and gel filtration. The peptide was 6 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An oligonucleotide probe based on the N-terminal sequence of the purified peptide was used to identify the gene encoding the inhibitory peptide. The antibacterial peptide has characteristics that are very similar to those described for class II bacteriocins of gram-positive bacteria.

Amino Acid Sequence↗
PubMed1976

Unbalanced growth and macromolecular synthesis in Streptococcus mutans FA-1.

The continued synthesis of deoxyribonucleic acid, protein, cell wall peptidoglycan and intracellular iodophilic polysaccharide (IPS) by Streptococcus mutans strain FA-1 after several treatments intended to inhibit protein synthesis was studied. Exponential-phase cultures were: (i) simultaneously deprived of two required amino acids (cystine and leucine) that are not present in the cell wall peptidoglycan of this species; (ii) depreived of required amino acids (lysine or glutamate plus glutamine ) that are present in both peptidoglycan and protein; or (iii) treated with tetracycline. Each of these three types of treatment was accompanied by a different pattern of unbalanced growth. The patterns of unbalanced growth that accompanied treatments (i) or (ii) differed substantially from the patterns observed previously for Streptococcus faecalis ATCC 9790, a noncariogenic organism that does not contain IPS. In contrast to S. faecalis 9790, S. mutans FA-1 failed to accumulate peptidoglycan and thicken its wall when deprived of non-wall amino acids. Instead, S. mutans FA-1 continued to accumulate IPS to levels substantially higher than those found in exponential-phase cells. Again, in contrast to S. faecalis, S. mutans FA-1 failed to autolyze upon deprivation of essential precursors of wall peptidoglycan. Under conditions of lysine of glutamate/glutamine deprivation, S. mutans FA-1 continued to accumulate IPS to very high levels. Treatment with tetracycline did result in peptidoglycan accumulation and wall thickening in a manner very similar to that observed previously for inhibition of protein synthesis in S. faecalis. Realtively little IPS synthesis continued after tetracycline treatment. Accumulation of IPS appeared to occur when both ribonucleic acid and peptidoglycan synthesis were severely inhibited. The observations are discussed in terms of the survival of cariogenic organisms in the oral environment.

Amino Acids↗
PubMed1983

Platelet aggregation by Streptococcus pyogenes.

Heat-killed group A Streptococcus pyogenes induced platelet aggregation in platelet-rich plasma. Aggregation was dependent upon the ratio of platelets to bacteria, with maximal aggregation occurring at 0.8 platelets per bacterium (final concentration, 300,000 per microliter). Inhibition of the reaction by 3 mM EDTA indicated it was a true aggregation and not merely adhesion and agglutination. Lactic acid dehydrogenase assays indicated lysis of platelets did not occur during a 6-min incubation period. Aggregation was inhibited in a dose-dependent manner by acetylsalicylic acid (100 microM to 10 mM) and quinacrine (15.6 to 250 microM), with no decrease in aggregation at the lowest concentration of inhibitor tested. S. pyogenes induced the release of [14C]serotonin, which was maximal (50%) at 2.4 min, when aggregation was nearly complete. Gel-filtered platelets were not aggregated unless fibrinogen (final concentration, 1.8 mg/ml) was included in the reaction mixture. Staphylococcus aureus, a group B streptococcus, and Escherichia coli were unable to induce aggregation in platelet-rich plasma under the conditions used for S. pyogenes.

Aspirin↗
PubMed1983

Effects of local immunization of hamsters with glucosyltransferase antigens on infection with Streptococcus sanguis.

The effects of immunization with antigens of the Streptococcus mutans glucosyltransferase (GTF) complex on oral challenge with two Streptococcus sanguis strains (H7PR3 and 34) in hamsters were studied. Antisera to S. mutans GTF complex were able to inhibit one-third (strain H7PR3) to one-half (strain 34) of the S. sanguis GTF activity which could be inhibited when these S. sanguis GTFs were incubated with antisera to S. sanguis GTF. Washed, intact cells of strains H7PR3 and 34 were able to remove a significant amount of enzyme inhibitory activity and immunoglobulin G antibody activity from antisera to S. mutans GTF. These results established the existence of an antigenic relationship between S. sanguis and S. mutans GTFs. The effect of injection of S. mutans strain 6715 GTF or phosphate-buffered saline, incorporated into complete Freund adjuvant, on oral challenge with S. sanguis was compared in 243 hamsters in nine experiments. Salivary and serum GTF inhibitory activity was present in all GTF-injected animals before challenge. After a 2- or 3-day challenge with S. sanguis H7PR3 (seven experiments) or 34 (two experiments), fewer bacteria were recovered from GTF-injected hamsters in every experiment. Significant differences were observed in six of the nine experiments. During the 7- to 21-day period after challenge, 33% of the phosphate-buffered saline-injected sham group (group I) still had S. sanguis recoverable from the molar surfaces, whereas only 19% of the S. mutans GTF-injected group (group II) remained infected with S. sanguis (P less than 0.01). These results suggest that immunization with GTF from S. mutans may influence the colonization potential of S. sanguis in the oral cavity.

Animals↗
PubMed1987

Metabolism of glycosylsucrose by oral microorganisms and its hydrolysis by Streptococcus salivarius fructosyltransferase.

Resting-cell suspensions of oral microorganisms grown in sucrose were studied for the production of acid from glucosylsucrose and maltosylsucrose. Most oral microorganisms fermented these sugars to only a limited extent. Streptococcus salivarius, however, metabolized glucosylsucrose as well as sucrose. We therefore looked for a specific enzyme in S. salivarius which was capable of hydrolyzing glucosylsucrose. Fructosyltransferase and invertase were purified from S. salivarius 13419, and the substrate specificities and hydrolytic activities of these enzymes were determined. Purified fructosyltransferase catalyzed fructan synthesis from glucosylsucrose or maltosylsucrose, whereas purified invertase barely hydrolyzed these sugars. These results suggest that the high fermentative efficiency of glycosylsucrose by S. salivarius is due to the hydrolysis of these sugars by fructosyltransferase, but not by invertase. The partially purified fructosyltransferases of Actinomyces viscosus NY1 and Streptococcus mutans NCIB 11723 catalyzed fructan synthesis from glucosylsucrose or maltosylsucrose. The fructosyltransferases of these oral microorganisms are also responsible for the hydrolysis of glycosylsucrose.

Actinomyces↗
PubMed1992

Molecular analysis of a Streptococcus mutans strain exhibiting polymorphism in the tandem gtfB and gtfC genes.

Streptococcus mutans UA101, which was previously demonstrated to be highly cariogenic in gnotobiotic rats, exhibited much lower water-insoluble glucan (IG) synthetic activity compared with that of S. mutans GS5 and was unable to express sucrose-dependent colonization of smooth surfaces in vitro. On the basis of Southern and Western blot (immunoblot) analyses, it was demonstrated that, unlike most S. mutans strains, strain UA101 contained a single copy of a gene coding for IG synthesis. The gene was isolated from a clone bank constructed with the plasmid pTH10 clone bank in Escherichia coli and had apparently evolved after homologous recombination of the gtfB and gtfC genes present on the chromosome of a recent ancestor of strain UA101. The enzyme expressed from the gene, gtfBC, was purified to near homogeneity by utilizing a single-step preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis system and was characterized. A derivative of strain UA101, UA101LBS, containing a chromosomal insertion of the GS5 gtfC gene was constructed after transformation. UA101LBS exhibited high IG synthetic activity and colonized smooth surfaces in vitro. By utilizing a conventional rat model system involving animals fed a high-sucrose diet, strain UA101 exhibited low levels of smooth surface caries activity relative to Streptococcus sobrinus 6715. By contrast, UA101LBS was as cariogenic as strain 6715. However, sulcal caries occurred equally well with all of the strains tested. These results are evaluated relative to the role of gtf gene products in cariogenicity.

Animals↗
PubMed2000

M-like proteins of Streptococcus dysgalactiae.

Streptococcus dysgalactiae is one of the most important bacterial species isolated from bovine mastitis. To identify potential virulence factors of this species we prepared chromosomal DNA from strain 8215 and constructed a phage display library. By affinity selection of the library against fibrinogen (Fg), we isolated and characterized a gene, called demA, encoding a protein with the molecular mass of approximately 58 kDa, called DemA, displaying both plasma protein binding properties and sequence similarities with the M and M-like proteins of other streptococcal species. Purified recombinant DemA protein was found to completely inhibit Fg-binding to cells of S. dysgalactiae. A continued sequence analysis revealed that the demA gene was preceded by an open reading frame (dmgA) coding for a putative protein, called DmgA, with high similarities to the Mga proteins of Streptococcus pyogenes. By additional cloning, the corresponding dmgA and demA genes from another strain, called Epi9, were isolated and analyzed. These genes, called dmgB and demB, respectively, revealed a high degree of similarity to the corresponding genes in strain 8215. Increased binding of Fg by cells of strain Epi9, grown in an atmosphere with 10% CO(2), was correlated to an enhanced transcription of the demB gene as shown in a Northern blot. Strain 8215 did not respond to CO(2), which could be explained by a nonfunctional dmgA gene due to insertion of an insertion sequence element. Based on sequence similarities of the described proteins to Mga, M, and M-like proteins and the response to elevated level of CO(2), we suggest that the dmg and dem genes are members of a regulon similar to the described mga regulon in S. pyogenes, which encodes several virulence factors in this species.

Amino Acid Sequence↗
PubMed2000

Identification of a fibronectin binding protein from Streptococcus mutans.

The interaction of viridans streptococci with components of the extracellular matrix (ECM) plays an important role in the pathogenesis of infective endocarditis. We have identified a surface protein of Streptococcus mutans which binds the ECM constituent fibronectin (Fn). Initially, we found that S. mutans could adsorb soluble Fn in plasma, but with lower efficiency than Streptococcus pyogenes. In addition, S. mutans could bind immobilized Fn in a dose-dependent manner when tested using an enzyme-linked immunosorbent assay. Crude extracts of cell wall-associated proteins or extracellular proteins from S. mutans MT8148 specifically bound Fn through a protein with the molecular mass of ca. 130 kDa, as detected by far-Western immunoblotting. The candidate Fn binding protein (FBP-130) was purified to near homogeneity by using Fn coupled Sepharose 4B affinity column chromatography. A rabbit polyclonal antibody against FBP-130 reacted specifically with a protein of molecular mass of ca. 130 kDa in both cell wall and extracellular fractions, and the abundance of FBP was higher in the former than in the latter fractions. The purified FBP bound specifically to immobilized Fn, whereas the binding of soluble Fn to coated FBP could only be detected in the presence of high concentrations of Fn. The purified FBP, as well as anti-FBP immunoglobulin G, inhibited the adherence of S. mutans to immobilized Fn and endothelial cells (ECV304) in a dose-dependent manner. These results demonstrated that FBP-130 mediated the adherence of S. mutans specifically to Fn and endothelial cells in vitro. The characteristics of S. mutans and FBP-130 in binding Fn confirmed that viridans streptococci adopt different strategies in their interaction with ECM.

Adhesins, Bacterial↗
PubMed2001

Genetic loci of Streptococcus mitis that mediate binding to human platelets.

The direct binding of bacteria to platelets is a postulated major interaction in the pathogenesis of infective endocarditis. To identify bacterial components that mediate platelet binding by Streptococcus mitis, we screened a Tn916deltaE-derived mutant library of S. mitis strain SF100 for reduced binding to human platelets in vitro. Two distinct loci were found to affect platelet binding. The first contains a gene (pblT) encoding a highly hydrophobic, 43-kDa protein with 12 potential membrane-spanning segments. This protein resembles members of the major facilitator superfamily of small-molecule transporters. The second platelet binding locus consists of an apparent polycistronic operon. This region includes genes that are highly similar to those of Lactococcus lactis phage r1t and Streptococcus thermophilus phage 01205. Two genes (pblA and pblB) encoding large surface proteins are also present. The former encodes a 107-kDa protein containing tryptophan-rich repeats, which may serve to anchor the protein within the cell wall. The latter encodes a 121-kDa protein most similar to a tail fiber protein from phage 01205. Functional mapping by insertion-duplication mutagenesis and gene complementation indicates that PblB may be a platelet adhesin and that expression of PblB may be linked to that of PblA. The combined data indicate that at least two genomic regions contribute to platelet binding by S. mitis. One encodes a probable transmembrane transporter, while the second encodes two large surface proteins resembling structural components of lysogenic phages.

Amino Acid Sequence↗
PubMed2003

Two novel superantigens found in both group A and group C Streptococcus.

Two novel streptococcal superantigen genes (speL(Se) and speM(Se)) were identified from the Streptococcus equi genome database at the Sanger Center. Genotyping of 8 S. equi isolates and 40 Streptococcus pyogenes isolates resulted in the detection of the orthologous genes speL and speM in a restricted number of S. pyogenes isolates (15 and 5%, respectively). Surprisingly, the novel superantigen genes could not be found in any of the analyzed S. equi isolates. The results suggest that both genes are located on a mobile element that enables gene transfer between individual isolates and between streptococci from different Lancefield groups. S. equi pyrogenic exotoxin L (SPE-L(Se))/streptococcal pyrogenic exotoxin L (SPE-L) and SPE-M(Se)/SPE-M are most closely related to SMEZ, SPE-C, SPE-G, and SPE-J, but build a separate branch within this group. Recombinant SPE-L (rSPE-L) and rSPE-M were highly mitogenic for human peripheral blood lymphocytes, with half-maximum responses at 1 and 10 pg/ml, respectively. The results from competitive binding experiments suggest that both proteins bind major histocompatibility complex class II at the beta-chain, but not at the alpha-chain. The most common targets for both toxins were human Vbeta1.1 expressing T cells. Seroconversion against SPE-L and SPE-M was observed in healthy blood donors, suggesting that the toxins are expressed in vivo. Interestingly, the speL gene is highly associated with S. pyogenes M89, a serotype that is linked to acute rheumatic fever in New Zealand.

Amino Acid Sequence↗