Streptococcus suis prophage lysin as a new strategy for combating streptococci-induced mastitis and Streptococcus suis infection.

OBJECTIVES: The genus Streptococcus contains species of important zoonotic pathogens such as those that cause bovine mastitis. Unfortunately, many Streptococcus species have developed antibiotic resistance. Phage lysins are considered promising alternatives to antibiotics because it is difficult for bacteria to develop lysin resistance. However, there remains a lack of phage lysin resources for the treatment of streptococci-induced mastitis. METHODS: We identified the prophage lysin Lys0859 from the genome of the Streptococcus suis SS0859 strain. Lys0859 was subsequently characterized to determine its host range, MIC, bactericidal activity in milk, and ability to clear biofilms in vitro. Finally, to determine the effects of Lys0859 on the treatment of both bovine mastitis and S. suis infection in vivo, we established models of Streptococcus agalactiae ATCC 13813-induced mastitis and S. suis serotype 2 SC19 systemic infection. RESULTS: Our results demonstrate that Lys0859 possesses broad-spectrum lytic activity against Streptococcus and Staphylococcus species isolated from animals with bovine mastitis and 15 serotypes of S. suis isolated from swine. Intramammary and intramuscular injection of Lys0859 reduced the number of bacteria in mammary tissue by 3.75 and 1.45 logs compared with the PBS group, respectively. Furthermore, 100 µg/mouse of Lys0859 administered intraperitoneally at 1 h post-infection protected 83.3% (5/6) of mice from a lethal dose of S. suis infection. CONCLUSIONS: Overall, our results enhance the understanding and development of new strategies to combat both streptococci-induced mastitis and S. suis infection.

Spectroscopic evidence for a large spot on the dimming Betelgeuse.

During October 2019 and March 2020, the luminous red supergiant Betelgeuse demonstrated an unusually deep minimum of its brightness. It became fainter by more than one magnitude and this is the most significant dimming observed in the recent decades. While the reason for the dimming is debated, pre-phase of supernova explosion, obscuring dust, or changes in the photosphere of the star were suggested scenarios. Here, we present spectroscopic studies of Betelgeuse using high-resolution and high signal-to-noise ratio near-infrared spectra obtained at Weihai Observatory on four epochs in 2020 covering the phases of during and after dimming. We show that the dimming episode is caused by the dropping of its effective temperature by at least 170 K on 2020 January 31, that can be attributed to the emergence of a large dark spot on the surface of the star.

[Research on the Distribution of Broad-Band Correlated Photon Spectra and the Measurement of Time-Correlation].

The correlated photon technique makes it possible to achieve a radiation calibration processing without chain transferring. The study of the spectral radiation character and time correlation of the photon is of great significance for broad-band radiometric calibration. To absolutely calibrate quantum efficiency of photoelectric detector, it is necessary to extend calibration band from single band to more bands. According to the phase-matching condition of the spontaneous parametric down-conversion, non-collinear angle formula of correlated photon in the crystal is derived. The distribution of the photon spectrum is simulated. Meanwhile, the phase-matching angle of the crystal is optimized. The photon generated by the spontaneous parameters down-conversion has a broad spectral distribution and the correlated photon wavelength is corresponding to its emission angle. Based on the result of the simulation, the experimental measurement system of the spectral distribution and time-correlation of the correlated photon is established. The spectral distribution, the time-correlation and the polarization properties of the four pair photon were measured by using this system. The experimental results show that, (1) the spectral distribution of the measurements is 633~808 nm, where the maximum spectral distribution measurement bias is 1.51 mm. The experiment result is highly consistent with theoretical ones; (2) the correlation time of four pairs correlated photon is measured, during which "three coincidence-peaks" is observed and the minimum correlation time was 0.32 ns; (3) single photon count rate along with coincidence count rate of correlated photon vary with the polarization direction of the pump as sine function. The experimental result is shown that the correlated photon pairs are ranging from the visible to near infrared band distribution, and that the spectrum has time-correlation and polarization characteristic. The research result is firstly reported at home and abroad, and the results are promising for the application of the photoelectric detector in the multi-band radiometric calibration.