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Streptococcus suis is an important zoonotic pathogen that causes severe infections and great economic losses worldwide. Understanding how this pathogen senses and responds to environmental signals during the infectious process can offer insight into its pathogenesis and may be helpful in the development of drug targets. Two-component regulatory systems (TCSs) play an essential role in this environmental response. In S. suis , at least 15 groups of TCSs have been predicted. Among them, several have been demonstrated to be involved in virulence and/or stress response. In this review, we discuss the progress in the study of TCSs in S. suis , focusing on the role of these systems in the virulence of this bacterium. [ABSTRACT FROM AUTHOR]

Metals are necessary elements for bacteria. Typically, vertebrate hosts restrict invading bacterial pathogens from accessing metals. Therefore, bacteria have evolved high-affinity metal importers to acquire metals. Streptococcus suis is a major swine pathogen and an emerging zoonotic agent that endangers the swine industry and human health worldwide. Herein, we aimed to identify the zinc acquisition systems in S. suis and evaluate their roles in bacterial virulence. Bioinformatic analyses revealed that S. suis encodes homologues of AdcA and AdcAII, two well-characterised Zn-binding lipoproteins in certain streptococci. Quantitative reverse transcription PCR (qRT-PCR) analysis revealed that the expressions of adcA and adcAII were significantly upregulated in response to Zn limitation, with a higher expression level of adcAII than adcA. Gene deletion mutants and complementation strains were constructed; their growth characteristics under Zn-deficient and Zn-replete conditions indicated that AdcA and AdcAII have overlapping functionality in Zn acquisition. A mouse infection model was used to evaluate the roles of AdcA and AdcAII in S. suis virulence. Mice infected with the double mutant Δ adcA Δ adcAII exhibited a significantly higher survival rate, decreased bacterial burden, and lower production of inflammatory cytokines compared to those infected with the wild type (WT) strain. Furthermore, Δ adcA Δ adcAII showed reduced competitiveness in infection establishment compared with the WT strain. RNA sequencing, qRT-PCR, and electrophoretic mobility shift assays revealed that AdcR negatively regulates the expressions of adcA and adcAII. Collectively, our results demonstrated that AdcA and AdcAII, which are negatively regulated by AdcR, contribute additively to zinc acquisition and virulence in S. suis. • The expressions of adcA and AadcAII are upregulated in response to Zn limitation. • AdcA and AdcAII have overlapping functionality in zinc acquisition in S. suis. • Simultaneous deletion of AdcA and AdcAII attenuates S. suis virulence in mice. • The expressions of adcA and adcAII are negatively regulated by AdcR in S. suis. [ABSTRACT FROM AUTHOR]

Toxin–antitoxin (TA) systems, composed of a stable toxin and a cognate unstable antitoxin, are ubiquitous in the genomes of bacteria and archaea. Under suitable growth conditions, an antitoxin prevents its cognate toxin from inducing toxicity; nonetheless, under stress or plasmid loss, it is either rapidly degraded or downregulated, thereby freeing the toxin to exert its activity toward various targets. Currently, TA systems are classified into eight types based on the nature and mode of action of antitoxins. TA expression is tightly regulated at multiple levels. These systems have various biological roles, including genetic element maintenance, virulence, stress resistance, and phage inhibition. Because of the toxic property of toxins, TA systems have been exploited for biotechnological (e.g., DNA cloning, plasmid maintenance, and counterselection) and medical (e.g., antibacterial drugs, antivirals, and anticancer therapies) applications. Herein, we provided an updated overview of TA systems by focusing on their classification, biological roles, and applications. We also described recent advances in research on TA systems and discussed research perspectives in this field. [ABSTRACT FROM AUTHOR]

Streptococcus suis serotype 2 ( S. suis 2) is an important zoonotic pathogen that can also cause epidemics of life-threatening infections in humans. Surface proteins of pathogens play a critical role in the interaction with host system or environment, as they take part in processes like virulence, cytotoxicity, adhesion, signaling or transport, etc. Thus, surface proteins identified by the screening of immunoproteomic techniques are promising vaccine candidates or diagnostic markers. In this study, four membrane associated proteins (MAP) identified by immunoproteomic method were cloned and expressed as recombinant proteins with his-tag. Screening for vaccine candidates were firstly performed by protection assay in vivo and immunization with Sbp markedly protected mice against systemic S. suis 2 infection. The immune responses and protective of Sbp were further evaluated. The results showed that Sbp could elicit a strong humoral antibody response and protect mice from lethal challenge with S. suis 2. The antiserum against Sbp could efficiently impede survival of bacterial in whole blood killing assay and conferred significant protection against S. suis 2 infection in passive immunization assays. The findings indicate that Sbp may serve as an important factor in the pathogenesis of S. suis 2 and would be a promising subunit vaccine candidate. [ABSTRACT FROM AUTHOR]

Abstract: Streptococcus suis serotype 2 (S. suis 2) is an important porcine and human pathogen. Some proteins secreted by S. suis 2 are thought to play important roles in the pathogenesis of this organism and in its induced immune response. SsPepO has been previously identified as a secretary immunogenic protein using immunoproteomic techniques. In this study, we confirmed that the sequence of this protein is highly conserved in S. suis 2 and compared it with its homologues in other pathogens. To test the protective efficacy of SsPepO in animal models, the recombinant SsPepO protein was used to immunize mice and pigs. The results demonstrated that it could elicit a strong humoral antibody response and confer significant protection against challenge with a lethal dose of S. suis 2 in mice and pig models. In addition, the antisera against rSsPepO could efficiently inhibit bacterial growth in a whole blood assay and conferred significant protection against S. suis 2 infection in passive immunization experiments. Our findings suggest that SsPepO plays an important role in the pathogenesis of S. suis 2 and would be a promising subunit vaccine candidate. [Copyright &y& Elsevier]

Results of different researches prove that Fe content plays a major role on the obtained mechanical properties of the aluminum alloys. Due to the importance of fatigue properties for the application of Al-Zn-Mg-Cu alloys in aviation industry and lack of study on the topic, this research was focused on the effect of Fe content on the low cycle fatigue behavior of these alloys processed by squeeze casting. The experimental alloys processed with different Fe contents of 0.01, 0.33 and 0.55 wt% exhibited similar cyclic behaviorsWhile cyclic hardening, owing to the dislocation multiplication, entanglement, accumulation, interaction with the second phases, and stress induced precipitation, was understood as the ruling mechanism at higher strain amplitudes (0.4%–0.6%), all the studied alloys showed cyclic stabilization at strain amplitudes below 0.4%. The fatigue life of the alloy with 0.33 wt% Fe (B alloy) was better than that of the alloy with 0.55 wt% Fe (C alloy) at all specific strain amplitudes. For the specific strain amplitudes of below 0.5%, the fatigue life of B alloy was much superior to that of the alloy with 0.01 wt% Fe (A alloy). On the other hand, due to the difference existing between the fatigue fracture mechanisms occurred under high strain amplitudes and low strain amplitudes, the fatigue life of A alloy was a little longer than that of B alloy at strain amplitude of 0.6%. It was understood that Fe-rich phases had a great potential to alter the crack propagation path at low strain amplitudes. The crack propagation rate accelerated under conditions that the cyclic stress was large enough to break Fe-rich phases at high strain amplitudes of 0.6%. • The Al alloys with different Fe content have the same cyclic hardening behavior. • The Fe-rich phases favored the fatigue properties at low strain amplitudes. • Fatigue life and failure characteristics were investigated. • The effect of Fe-rich phases on the fatigue fracture mechanisms was discussed. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is a food borne pathogen causing listeriosis in humans and animals. L. monocytogenes can tolerate severe environments and food processing conditions by forming biofilms and becoming resistant to disinfectants. Thus, it is important to develop new strategies to control the contamination of L. monocytogenes and keep food safety. In the present study, a new L. monocytogenes phage vB-LmoM-SH3-3 (designated as phage SH3-3) was isolated from a food processing plant. The genome of phage SH3-3 shares homology with multiple non- Listeria phages, but shares low similarity with classical Listeria phages. Phage SH3-3 showed widely lytic activity to Listeria spp. including L. monocytogenes, L. innocua and L. welshimeri. With an efficient minimal inhibitory concentration, phage SH3-3 could also inhibit the formation of the dense and net-like structure of the L. monocytogenes biofilm. Moreover, phage SH3-3 showed high efficacy against L. monocytogenes in salmon meat and orange juice. Therefore, phage SH3-3 could be potentially used as a natural biocontrol preservative to reduce L. monocytogenes contamination in ready-to-eat food and during the processing stages of food production. • We isolated a broad host range phage SH3-3 that can lyse L. monocytogenes, L. innocua and L. welshimeri • The genome of phage SH3-3 shares homology with non- Listeria phages, but shares low similarity with classical Listeria phages • Phage SH3-3 can effectively inhibit biofilm formation and reduce contamination of L. monocytogenes in RTE food. [ABSTRACT FROM AUTHOR]