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Journal of Bacteriology May 1966
Topics: Actinomyces; Antigens; In Vitro Techniques
PubMed: 5937255
DOI: 10.1128/jb.91.5.2107-.1966 -
Molecular Microbiology Dec 2014Sortase, a cysteine-transpeptidase conserved in Gram-positive bacteria, anchors on the cell wall many surface proteins that facilitate bacterial pathogenesis and...
Sortase, a cysteine-transpeptidase conserved in Gram-positive bacteria, anchors on the cell wall many surface proteins that facilitate bacterial pathogenesis and fitness. Genetic disruption of the housekeeping sortase in several Gram-positive pathogens reported thus far attenuates virulence, but not bacterial growth. Paradoxically, we discovered that depletion of the housekeeping sortase SrtA was lethal for Actinomyces oris; yet, all of its predicted cell wall-anchored protein substrates (AcaA-N) were individually dispensable for cell viability. Using Tn5-transposon mutagenesis to identify factors that upend lethality of srtA deletion, we uncovered a set of genetic suppressors harbouring transposon insertions within genes of a locus encoding AcaC and a LytR-CpsA-Psr (LCP)-like protein. AcaC was shown to be highly glycosylated and dependent on LCP for its glycosylation. Upon SrtA depletion, the glycosylated form of AcaC, hereby renamed GspA, was accumulated in the membrane. Overexpression of GspA in a mutant lacking gspA and srtA was lethal; conversely, cells overexpressing a GspA mutant missing a membrane-localization domain were viable. The results reveal a unique glycosylation pathway in A. oris that is coupled to cell wall anchoring catalysed by sortase SrtA. Significantly, this novel phenomenon of glyco-stress provides convenient cell-based assays for developing a new class of inhibitors against Gram-positive pathogens.
Topics: Actinomyces; Aminoacyltransferases; Bacterial Proteins; Cell Wall; Cysteine Endopeptidases; Gene Deletion; Genes, Essential; Genes, Lethal; Glycosylation; Heat-Shock Proteins; Mutagenesis, Insertional; Signal Transduction
PubMed: 25230351
DOI: 10.1111/mmi.12780 -
Food and Chemical Toxicology : An... Jul 2017This study aimed to determine the bioactive compounds of actinomyces (ACT) isolated from the Egyptian environment (D-EGY) and to evaluate their protective activity...
Evaluation of the bioactive extract of actinomyces isolated from the Egyptian environment against aflatoxin B-induce cytotoxicity, genotoxicity and oxidative stress in the liver of rats.
This study aimed to determine the bioactive compounds of actinomyces (ACT) isolated from the Egyptian environment (D-EGY) and to evaluate their protective activity against AFB in female Sprague-Dawley rats. Six groups of animals were treated orally for 3 weeks included: C, the control group, T1, AFB-treated group (80 μg/kg b.w), T2 and T3, the groups received ACT extract at low (25 mg/kg b.w) or high (50 mg/kg b.w) doses, T4 and T5, the groups received AFB plus the low or high dose of ACT extract. Blood, bone marrow and tissue samples were collected for different analyses and histological examination. The results revealed the identification of 40 components, representing 99.98%. Treatment with AFB disturbs liver function parameters, oxidative stress markers, antioxidant gene expressions, DNA fragmentation and induced severe histological changes. ACT extract at the low or high doses did not induce significant changes in all the tested parameters or histological picture of the liver. Moreover, ACT extract succeeded to induce a significant protection against the toxicity of AFB. It could be concluded that the bioactive compounds in ACT are promise candidate for the development of food additive or drugs for the protection and treatment of liver disorders in the endemic area.
Topics: Actinomyces; Aflatoxin B1; Animals; Biological Factors; DNA Damage; DNA Fragmentation; Egypt; Female; Liver; Oxidative Stress; Rats; Rats, Sprague-Dawley; Soil Microbiology
PubMed: 28442411
DOI: 10.1016/j.fct.2017.04.024 -
Journal of Dental Research Jan 1976Actinomyces have a complex antigenic structure that includes neutral cell wall carbohydrate and some polypeptide containing charged antigens. Wall carbohydrate can be...
Actinomyces have a complex antigenic structure that includes neutral cell wall carbohydrate and some polypeptide containing charged antigens. Wall carbohydrate can be prepared in a relatively pure form from cell walls or by DEAE Sephadex chromatography of acid extracts and supernatant culture fluid. Charged antigens are generally eluted in groups by batch-elution from columns. Cell wall carbohydrate can be responsible for species-specific reactions and cross-reactions, and strains may possess more than one cell wall carbohydrate determinant. The charged antigens also can be species specific, but they cause some cross-reactions, particularly those between the A israelii serotypes. Autoclave extracts of strains, tested against antiserums reacting with cell wall carbohydrate, may be valuable in routine identification of isolates.
Topics: Actinomyces; Animals; Antigens, Bacterial; Carbohydrates; Cell Wall; Cross Reactions; Culture Media; Immune Sera; Immunization; Male; Precipitin Tests; Rabbits
PubMed: 1060641
DOI: 10.1177/002203457605500112011 -
Oral Microbiology and Immunology Dec 2004A total of 991 isolates of Actinomyces naeslundii were obtained from sound approximal tooth sites in either caries-active (n = 35) or caries-free (n = 20) preschool...
A total of 991 isolates of Actinomyces naeslundii were obtained from sound approximal tooth sites in either caries-active (n = 35) or caries-free (n = 20) preschool children. From this group of isolates, 101 strains were chosen to study the genotypic diversity of A. naeslundii genospecies 1 (n = 30), catalase-positive (n = 30), and catalase-negative genospecies 2 (n = 41). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), with a pair of primers targeting the 16S ribosome RNA gene (16S rDNA), and MnlI digestion together with randomly amplified polymorphic DNA (RAPD) with eight arbitrary, single 10-mer primers were performed to generate genetic profiles of selected Actinomyces isolates. The hierarchic relationships of genetic profiles were finally analyzed using computerized dendrograms. There was no significant difference in the prevalence rates and proportions of either genospecies 1 or 2 between the caries-free and caries-active groups, although a higher prevalence of genospecies 2 was noted in the total population. Dendrogram analyses of the 16S rDNA PCR-RFLP profiles revealed that all strains belonging to A. naeslundii genospecies 1 could be subgrouped into three genotypes (T7, T18, and T19), with a single predominant genotype, T18 (27/30). Catalase-positive strains for genospecies 2 fell into three subtypes (T4, T7, and T17), whereas the catalase-negative counterparts were distributed amongst 16 subtypes. No specific genotype was significantly associated with caries activity. We conclude that heterogeneous subgroups of A. naeslundii genospecies 1 and 2, particularly the latter, are the constituent flora of dental plaque in children and may contribute to the pathogenesis of childhood caries.
Topics: Actinomyces; Bacterial Typing Techniques; Case-Control Studies; Child, Preschool; DNA, Bacterial; Dental Caries; Dental Plaque; Genetic Variation; Genotype; Humans; Polymerase Chain Reaction; Polymorphism, Restriction Fragment Length; Random Amplified Polymorphic DNA Technique; Statistics, Nonparametric
PubMed: 15491462
DOI: 10.1111/j.1399-302x.2004.00171.x -
MBio Jun 2017The Gram-positive actinobacteria spp. are key colonizers in the development of oral biofilms due to the inherent ability of to adhere to receptor polysaccharides on...
The Gram-positive actinobacteria spp. are key colonizers in the development of oral biofilms due to the inherent ability of to adhere to receptor polysaccharides on the surface of oral streptococci and host cells. This receptor-dependent bacterial interaction, or coaggregation, requires a unique sortase-catalyzed pilus consisting of the pilus shaft FimA and the coaggregation factor CafA forming the pilus tip. While the essential role of the sortase machine SrtC2 in pilus assembly, biofilm formation, and coaggregation has been established, little is known about -acting factors contributing to these processes. We report here a large-scale Tn transposon screen for mutants defective in coaggregation with We obtained 33 independent clones, 13 of which completely failed to aggregate with , and the remainder of which exhibited a range of phenotypes from severely to weakly defective coaggregation. The former had Tn insertions in , , or , as expected; the latter were mapped to genes coding for uncharacterized proteins and various genes encoding the NADH dehydrogenase subunits. Electron microscopy and biochemical analyses of mutants with nonpolar deletions of genes and , a menaquinone C-methyltransferase-encoding gene downstream of the locus, confirmed the pilus and coaggregation defects. Both and mutants were defective in oxidation of MdbA, the major oxidoreductase required for oxidative folding of pilus proteins. Furthermore, supplementation of the mutant with exogenous menaquinone-4 rescued the cell growth and pilus defects. Altogether, we propose that the electron transport chain is biochemically linked to pilus assembly via oxidative protein folding. The Gram-positive actinobacterium expresses adhesive pili, or fimbriae, that are essential to biofilm formation and interactions with other bacteria, termed coaggregation. While the critical role of the conserved sortase machine in pilus assembly and the disulfide bond-forming catalyst MdbA in oxidative folding of pilins has been established, little is known about other -acting factors involved in these processes. Using a Tn transposon screen for mutants defective in coaggregation with , we found that genetic disruption of the NADH dehydrogenase and menaquinone biosynthesis detrimentally alters pilus assembly. Further biochemical characterizations determined that menaquinone is important for reactivation of MdbA. This study supports the notion that the electron transport chain is biochemically linked to pilus assembly in via oxidative folding of pilin precursors.
Topics: Actinomyces; Bacterial Adhesion; Biofilms; DNA Transposable Elements; Electron Transport; Fimbriae, Bacterial; Genetic Testing; Mutagenesis, Insertional; Organelle Biogenesis; Streptococcus oralis
PubMed: 28634238
DOI: 10.1128/mBio.00399-17 -
Journal of Bacteriology Feb 1969In a previous serological study, we compared 14 isolates of Actinomyces israelii serotype 2 with 13 serotype 1 cultures. The present study reports the morphological,...
In a previous serological study, we compared 14 isolates of Actinomyces israelii serotype 2 with 13 serotype 1 cultures. The present study reports the morphological, physiological, and biochemical characteristics of these same 27 cultures. All of the isolates exhibited similar cellular morphology, and all but one produced the typical spider type microcolony on solid media. Twelve of 13 serotype 1 isolates produced the molar tooth type macrocolony, whereas only 2 of 14 serotype 2 cultures produced this type of rough colony. All of the serotype 1 isolates fermented arabinose with the production of acid; none of the serotype 2 cultures fermented this carbohydrate. All 27 cultures produced the greatest amount of growth when cultured under anaerobic conditions and grew poorly or not at all in air. Both groups of organisms produced similar reactions on other biochemical test media; these findings suggested that A. israelii serotype 2 should not be given a species designation.
Topics: Actinomyces; Arabinose; Bacteriological Techniques; Oxygen Consumption; Serotyping
PubMed: 4886287
DOI: 10.1128/jb.97.2.589-593.1969 -
Oral Microbiology and Immunology Aug 1999The definition of the genus Actinomyces relies heavily on traditional methods of taxonomy. This study sought to develop molecular tools for the identification of strains...
The definition of the genus Actinomyces relies heavily on traditional methods of taxonomy. This study sought to develop molecular tools for the identification of strains of Actinomyces israelii and Actinomyces gerencseriae. Oligonucleotide probes were designed and one of these successfully differentiated. A. gerencseriae from ten strains of A. israelii and three other Actinomyces species by DNA:DNA hybridization. However, probes based on known 16S rRNA sequences failed to hybridize to all the strains previously identified as A. israelii. Using the PCR technique, a region encoding a portion of the 16S rRNA was amplified from genomic DNA. The results showed that A. israelii can be divided into three different groups based on comparison of the amplified DNA sequences. This information should allow the development of probes that are specific for these newly identified groups of strains within the species A. israelii.
Topics: Actinomyces; Bacterial Typing Techniques; DNA Probes; DNA, Bacterial; Oligonucleotide Probes; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Sequence Analysis, RNA; Species Specificity
PubMed: 10551170
DOI: 10.1034/j.1399-302x.1999.140409.x -
International Endodontic Journal Sep 1996Actinomyces israelii has been repeatedly implicated as a cause of failure of endodontic therapy. This study investigated the antimicrobial effect of antibiotics as well...
Actinomyces israelii has been repeatedly implicated as a cause of failure of endodontic therapy. This study investigated the antimicrobial effect of antibiotics as well as intracanal medicaments, sodium hypochlorite solution and calcium hydroxide, on this important pathogen. Growth of A. israelii was inhibited by low concentrations of antibiotics, yet high concentrations were not bactericidal for A. israelii over 1 week. When A. israelii was exposed for 2-6 weeks at concentrations equivalent to clinical serum levels, the antibiotics were lethal. The results reveal a species-specific antibiotic tolerance for A. israelii. Both sodium hypochlorite solution and calcium hydroxide were found to be highly effective in killing A. israelii.
Topics: Actinomyces; Actinomycosis; Anti-Bacterial Agents; Bacterial Adhesion; Calcium Hydroxide; Drug Resistance, Microbial; Humans; Microbial Sensitivity Tests; Periapical Diseases; Root Canal Irrigants; Sodium Hypochlorite; Species Specificity; Time Factors
PubMed: 9206415
DOI: 10.1111/j.1365-2591.1996.tb01392.x -
Microbiological Research 2006Ammonia production from urea by ureolytic oral bacteria is believed to have a significant impact on oral health and ecological balance of oral microbial populations....
Ammonia production from urea by ureolytic oral bacteria is believed to have a significant impact on oral health and ecological balance of oral microbial populations. Actinomyces naeslundii is an important ureolytic organism in the oral cavity. In this study, we aimed to investigate the substrate affinity and pH optimum for ureolysis of A. naeslundii (ATCC12104), and expression of urease under different environmental factors. In addition, in vitro acid killing and pH drop experiments were used to detect the role of ureolysis in bacterial aciduricity and capacity to modulate pH homeostasis. We observed the K(s) value of the ureolytic activity was 7.5mM and a pH optimum near 6.5. Urease expression by A. naeslundii (ATCC12104) was affected by multiple factors, including environmental pH, glucose and nitrogen availability. The cells could be protected against acid killing through hydrolysis of physiologically relevant concentrations of urea. A. naeslundii (ATCC12104) demonstrated a significant capacity to temper glycolytic acidification in vitro at urea concentrations normally found in the oral cavity.
Topics: Actinomyces; Gene Expression Regulation, Enzymologic; Homeostasis; Hydrogen-Ion Concentration; Transcription, Genetic; Urease
PubMed: 16412620
DOI: 10.1016/j.micres.2005.11.002