The complete genome sequence of Corynebacterium glutamicum strain R was determined to allow its comparative analysis with other corynebacteria. The biology of corynebacteria was explored by refining the definition of the subset of genes that constitutes the corynebacterial core as well as those characteristic of saprophytic and pathogenic ecological niches. In addition, the relative scarcity of corynebacterial sigma factors and the plasticity of their two-component system machinery reflect their relatively exacting nutritional requirements and reduced membrane-associated and secreted proteins. The conservation of key genes and pathways between corynebacteria, mycobacteria and Nocardia validates the use of C. glutamicum to study fundamental processes that are conserved in slow-growing mycobacteria, including pathogenesis-associated mechanisms. The discovery of 39 novel genes in C. glutamicum R that have not been previously reported in other corynebacteria supports the rationale for sequencing additional corynebacterial genomes to better define the corynebacterial pan-genome and identify previously undetected metabolic pathways in these organisms.

Comparative analysis of the Corynebacterium glutamicum group and complete genome sequence of strain R.

The ability of Actinomyces naeslundii to convert sucrose to extracellular homopolymers of fructose and to catabolize these types of polymers is suspected to be a virulence trait that contributes to the initiation and progression of dental caries and periodontal diseases. Previously, we reported on the isolation and characterization of the gene, ftf, encoding the fructosyltransferase (FTF) of A. naeslundii WVU45. Allelic exchange mutagenesis was used to inactivate ftf, revealing that FTF-deficient stains were completely devoid of the capacity to produce levan-type (beta2,6-linked) polysaccharides. A polyclonal antibody was raised to a histidine-tagged, purified A. naeslundii FTF, and the antibody was used to localize the enzyme in the supernatant fluid. A sensitive technique was developed to detect levan formation by proteins that had been separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the method was used to confirm that the levan-synthesizing activity of A. naeslundii existed predominantly in a cell-free form, that a small amount of the activity was cell associated, and that the ftf mutant was unable to produce levans. By using the nucleotide sequence of the levanase gene of a genospecies 2 A. naeslundii, formerly Actinomyces viscosus, a portion of a homologue of this gene (levJ) was amplified by PCR and inserted into a suicide vector, and the resulting construct was used to inactivate the levJ gene in the genospecies 1 strain WVU45. A variety of physiologic and biochemical studies were performed on the wild-type and LevJ-deficient strains to demonstrate that (i) this enzyme was the dominant levanase and sucrase of A. naeslundii; (ii) that LevJ was inducible by growth in sucrose; (iii) that the LevJ activity was found predominantly (>90%) in a cell-associated form; and (iv) that there was a second, fructose-inducible fructan hydrolase activity produced by these strains. The data provide the first detailed molecular analysis of fructan production and catabolism in this abundant and important oral bacterium.

https://iai.asm.org/content/iai/69/9/5395.full.pdf

Roles of Fructosyltransferase and Levanase-Sucrase of Actinomyces naeslundii in Fructan and Sucrose Metabolism

Effect of native levan on membrane permeability. I. Effect on the vascular membrane in acute nonspecific inflammation: a study with the light microscope.

INJECTION into animals of native levan, a high molecular polyfructoside of an average molecular weight of 2 x 107 daltons, is known to modify greatly several biological reactions. It delays the passage of colloids and cells across vascular barriers (Davies, Shilo and Hestion, 1955; Shilo, Wolman and Wolman, 1956; Behar and Shilo, 1969), and connective tissue barriers (Tesi, Behar and Forss-man, 1971), while systemic or local administration of levan inhibits the growth and development of malignant neoplasms in mice (Leibovici et al., 1975). In a recent study (Sandbank, Leibovici and Wolman, 1977), the destruction of tumour cells in levanised mice was associated with, and probably mediated by, mobilisation of macrophages surrounding and infiltrating the tumour mass. Possibly contact with the levan-containing macrophages caused degeneration and necrosis of the neoplastic cells. In another study (Katzap, Leibovici and Wolman, 1977), the mononuclear phagocytic system was found to exert a major role in determining levan levels in the blood of treated animals. It seems, therefore, that the biological effects of levan administration depends on two factors at least, its influence on vascular permeability and its action on macrophages. The

Effects of exposure of murine peritoneal exudate and resident macrophages to high molecular levan: A morphological study

(1)

As distinct from its effect on antibody in adult animals, endotoxin (ofEscherichia coli andSalmonella typhi) was not found to stimulate antibody formation in young animals, either against protein or bacterial antigen.




(2)

The administration of endotoxin to newborn young significantly increased their resistance to infection, however.




(3)

Endotoxin produced only slight morphological changes in the tissue of young animals as compared with adult animals.




(4)

The mechanism of the action of endotoxin in the organism is discussed. The possibility that the stimulant effect of endotoxin on antibody formation is related to elicitation of a hypersensitivity reaction in a sensitized organism is considered.

Effect of endotoxin on antibody response and resistance to infection in Newborn animals

Activities of bacterial levans and of lipopolysaccharides in the processes of inflammation and infection.

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Activities of bacterial levans and of lipopolysaccharides in the processes of inflammation and infection.