Nucleotide sequence and functional analysis of the tet (M)-carrying conjugative transposon Tn5251 of Streptococcus pneumoniae

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Streptococcus pyogenes Φ1207.3 Is a Temperate Bacteriophage Carrying the Macrolide Resistance Gene Pair mef(A)-msr(D) and Capable of Lysogenizing Different Streptococci

Streptococcus pyogenes prophage phi 1207.3 (formerly Tn1207.3) carries the mef(A)-msr(D) resistance genes, responsible for type M macrolide resistance. To investigate if phi 1207.3 is a functional bacteriophage, we transferred the element from the original S. pyogenes host in a prophage-free and competence-deficient S. pneumoniae strain. Pneumococcal cultures of the phi 1207.3-carrying lysogen were treated with mitomycin C to assess if phi 1207.3 enters the lytic cycle. Mitomycin C induced a limited phage burst and a growth impairment, resulting in early entrance into the stationary phase. To determine if phi 1207.3 is able to produce mature phage particles, we prepared concentrated supernatants recovered from a mitomycin C-induced pneumococcal culture by sequential centrifugation and ultracentrifugation steps. Negative-staining transmission electron microscopy (TEM) of supernatants revealed the presence of phage particles with an icosahedral, electron-dense capsid and a long, noncontractile tail, typical of a siphovirus. Quantification of phi 1207.3 was performed by quantitative PCR (qPCR) and semiquantitatively by TEM. PCR quantified 3.34 x 10(4) and 6.06 x 10(4) excised forms of phage genome per milliliter of supernatant obtained from the untreated and mitomycin C-treated cultures, respectively. By TEM, we estimated 3.02 x 10(3) and 7.68 x 10(3) phage particles per milliliter of supernatant. The phage preparations of phi 1207.3 infected and lysogenized pneumococcal recipient strains at a frequency of 7.5 x 10(-6) lysogens/recipient but did not show sufficient lytic activity to form plaques. Phage lysogenization efficiently occurred after 30 min of contact of the phages with the recipient cells and required a minimum of 10(3) phage particles. © 2023 Santoro et al

Computing Period and Shape of Oscillations in Piecewise Linear Lur'e Systems: a Complementarity Approach

International audienceAutonomous piecewise linear systems in the Lur'e form may exhibit periodic steady-state oscillations. For many practical systems belonging to this class the period and the shape of the oscillation is difficult to be predicted a priori. In this paper the complementarity approach is used to tackle the issue. The complementarity formalism is used to represent the closed-loop system and a phase condition acting as an anchor equation for the periodic solution. By discretizing the dynamics a mixed complementarity problem is formulated. The corresponding solution provides an accurate prediction of the steady-state oscillation and its period. Numerical results show the effectiveness of the proposed technique for the computation of stable and sliding periodic solutions. The analysis of the steady-state solution of a Colpitts oscillator is considered as an illustration

Modeling and analysis of a flexible spinning Euler-Bernoulli beam with centrifugal stiffening and softening: A Linear Fractional Representation approach with application to spinning spacecraft

The derivation of a linear fractional representation (LFR) model for a flexible, spinning and uniform Euler-Bernoulli beam is accomplished using the {Lagrange} technique, fully capturing the centrifugal force generated by the spinning motion and accounting for its dependence on the angular velocity. This six degrees of freedom (DOF) model accounts for the behavior of deflection in the moving body frame, encompassing the bending, traction and torsion dynamics. The model is also designed to be compliant with the Two-Input-Two-Output Port (TITOP) approach, which offers the possibility to model complex multibody mechanical systems, while keeping the uncertain nature of the plant and condensing all the possible mechanical configurations in a single LFR. To evaluate the effectiveness of the model, various scenarios are considered and their results are tabulated. These scenarios include uniform beams with fixed root boundary conditions for different values of tip mass, root offset and angular velocity. The results from the analysis of the uniform cantilever beam are compared with solutions found in the literature and obtained from a commercial finite element software. Ultimately, this paper presents a multibody model for a spinning spacecraft mission scenario. A comprehensive analysis of the system dynamics is conducted, providing insights into the behavior of the spacecraft under spinning conditions

Excision and Circularization of Integrative Conjugative Element Tn5253 of Streptococcus pneumoniae

The integrative conjugative element (ICE) Tn5253 of Streptococcus pneumoniae, conferring resistance to tetracycline and chloramphenicol, was found integrated at a 83-bp specific target site (attB) located in the rbgA gene of the pneumococcal chromosome. PCR analysis of Tn5253-carrying strains showed evidence of precise excision of Tn5253 from the pneumococcal chromosome with production of (i) circular forms of the ICE in which the ends were joined by a 84-bp sequence (attTn), and (ii) reconstituted chromosomal attB. When integrated into the chromosome, Tn5253 was flanked by attL, identical to attB, and attR, identical to attTn. Circular forms of Tn5253 were present at a concentration of 3.8 × 10-4 copies per chromosome, whereas reconstituted attB sites were at 3.0 × 10-4 copies per chromosome. Deletion of int-xis of Tn5253 abolished production of circular forms (<7.1 × 10-6 copies per chromosome) and was associated to the lack of Tn5253 conjugal transfer suggesting, as expected, that Tn5253 circular form acts as a conjugation intermediate