Isolation of a Novel Phage with Activity against Streptococcus mutans Biofilms

peer-reviewedStreptococcus mutans is one of the principal agents of caries formation mainly, because of its ability to form biofilms at the tooth surface. Bacteriophages (phages) are promising antimicrobial agents that could be used to prevent or treat caries formation by S. mutans. The aim of this study was to isolate new S. mutans phages and to characterize their antimicrobial properties. A new phage, ɸAPCM01, was isolated from a human saliva sample. Its genome was closely related to the only two other available S. mutans phage genomes, M102 and M102AD. ɸAPCM01 inhibited the growth of S. mutans strain DPC6143 within hours in broth and in artificial saliva at multiplicity of infections as low as 2.5x10-5. In the presence of phage ɸAPCM01 the metabolic activity of a S. mutans biofilm was reduced after 24 h of contact and did not increased again after 48 h, and the live cells in the biofilm decreased by at least 5 log cfu/ml. Despite its narrow host range, this newly isolated S. mutans phage exhibits promising antimicrobial properties

Pseudo-Riemannian Sasaki solvmanifolds

We study a class of left-invariant pseudo-Riemannian Sasaki metrics on solvable Lie groups, which can be characterized by the prop-erty that the zero level set of the moment map relative to the action of some one-parameter subgroup {exp tX} is a normal nilpotent subgroup commuting with {exp tX}, and X is not lightlike. We characterize this geometry in terms of the Sasaki reduction and its pseudo-Kähler quotient under the action generated by the Reeb vector field. We classify pseudo-Riemannian Sasaki solvmanifolds of this type in dimension 5 and those of dimension 7 whose Kähler reduction in the above sense is abelian

IMMUNE MECHANISMS IN PARABIOSIS INTOXICATION

When A strain mice are placed in parabiotic union with (A x C57Bl/1)F1 hybrid partners, the parental strain partners are polycythemic and the hybrids anemic from the 5th through the 16th parabiosis days. All hybrids develop clinical intoxication between the 7th and the 12th days, and no pairs survive to 1 month. Long-term survival of parabiotic pairs can be achieved if lethally irradiated or specifically tolerant parental strain mice are united to hybrid partners. Production of tolerance by either of these methods results in elimination of anemia-polycythemia by the 12th parabiosis day and prevents intoxication in the hybrid partners. Preimmunization of the parental strain partners against the C57Bl/1 component of the hybrid leads to a considerable intensification of day 5 anemia-polycythemia. Intoxication develops in the hybrid partners between the 4th and the 6th days after union. It is concluded that anemia is primarily responsible for the syndrome of clinical intoxication. Early anemia-polycythemia on day 5 does not depend upon an immunological mechanism, but the late anemia-polycythemia appearing between days 12 and 16 is a function of the ability of the parental strain mouse to react immunologically against its hybrid partner. When neonatally thymectomized A strain mice are joined to hybrid partners, anemia-polycythemia is sustained through the 16th day and the hybrid partners develop clinical intoxication. On the other hand, when both partners are neonatally thymectomized, late anemia-polycythemia is considerably reduced, and the hybrid partners apparently do not develop clinical intoxication. It is concluded that normal hybrid mice are capable of reconstituting the immunological capacity of their thymectomized partners, whereas thymectomized hybrid mice do not have this restorative capacity. These findings are discussed in terms of their possible application to the problem of the induction of immunological tolerance in adult mice by the parabiosis procedure

Supercritical biharmonic equations with power-type nonlinearity

The biharmonic supercritical equation $\Delta^2u=|u|^{p-1}u$, where $n>4$ and $p>(n+4)/(n-4)$, is studied in the whole space $\mathbb{R}^n$ as well as in a modified form with $\lambda(1+u)^p$ as right-hand-side with an additional eigenvalue parameter $\lambda>0$ in the unit ball, in the latter case together with Dirichlet boundary conditions. As for entire regular radial solutions we prove oscillatory behaviour around the explicitly known radial {\it singular} solution, provided $p\in((n+4)/(n-4),p_c)$, where $p_c\in ((n+4)/(n-4),\infty]$ is a further critical exponent, which was introduced in a recent work by Gazzola and the second author. The third author proved already that these oscillations do not occur in the complementing case, where $p\ge p_c$. Concerning the Dirichlet problem we prove existence of at least one singular solution with corresponding eigenvalue parameter. Moreover, for the extremal solution in the bifurcation diagram for this nonlinear biharmonic eigenvalue problem, we prove smoothness as long as $p\in((n+4)/(n-4),p_c)$

Development of a PCR assay for the detection of animal tissues in ruminant feeds.

The European Community ban on use of meat and bone meal in ruminant feed, as a consequence of the spread of bovine spongiform encephalopathy in Europe, has prompted a number of investigations about the possibility of detecting animal tissues in feedstuff. In this paper, a study on vertebrate primers, designed in the 16S rRNA gene of mitochondrial DNA, is described. These primers were able to amplify fragments that contained between 234 and 265 bp. The fragments were specific for bovine, porcine, goat, sheep, horse, rabbit, chicken, trout, and European pilchard and were confirmed by sequence analysis amplicons. The primers were used in a PCR assay applied to five samples of meat and blood meals of different species and subjected to severe rendering treatments (134.4 to 141.9 degrees C and 3.03 to 4.03 bar for 24 min). The presence of vertebrate tissues was detected in all samples. The assay proved to be rapid and sensitive (detection limit 0.0625%). It can be used as a routine method to detect animal-derived ingredients in animal feedstuff