CovR-Controlled Global Regulation of Gene Expression in Streptococcus mutans

CovR/S is a two-component signal transduction system (TCS) that controls the expression of various virulence related genes in many streptococci. However, in the dental pathogen Streptococcus mutans, the response regulator CovR appears to be an orphan since the cognate sensor kinase CovS is absent. In this study, we explored the global transcriptional regulation by CovR in S. mutans. Comparison of the transcriptome profiles of the wild-type strain UA159 with its isogenic covR deleted strain IBS10 indicated that at least 128 genes (∼6.5% of the genome) were differentially regulated. Among these genes, 69 were down regulated, while 59 were up regulated in the IBS10 strain. The S. mutans CovR regulon included competence genes, virulence related genes, and genes encoded within two genomic islands (GI). Genes encoded by the GI TnSmu2 were found to be dramatically reduced in IBS10, while genes encoded by the GI TnSmu1 were up regulated in the mutant. The microarray data were further confirmed by real-time RT-PCR analyses. Furthermore, direct regulation of some of the differentially expressed genes was demonstrated by electrophoretic mobility shift assays using purified CovR protein. A proteomic study was also carried out that showed a general perturbation of protein expression in the mutant strain. Our results indicate that CovR truly plays a significant role in the regulation of several virulence related traits in this pathogenic streptococcus

Srv Mediated Dispersal of Streptococcal Biofilms Through SpeB Is Observed in CovRS+ Strains

Group A Streptococcus (GAS) is a human specific pathogen capable of causing both mild infections and severe invasive disease. We and others have shown that GAS is able to form biofilms during infection. That is to say, they form a three-dimensional, surface attached structure consisting of bacteria and a multi-component extracellular matrix. The mechanisms involved in regulation and dispersal of these GAS structures are still unclear. Recently we have reported that in the absence of the transcriptional regulator Srv in the MGAS5005 background, the cysteine protease SpeB is constitutively produced, leading to increased tissue damage and decreased biofilm formation during a subcutaneous infection in a mouse model. This was interesting because MGAS5005 has a naturally occurring mutation that inactivates the sensor kinase domain of the two component regulatory system CovRS. Others have previously shown that strains lacking covS are associated with decreased SpeB production due to CovR repression of speB expression. Thus, our results suggest the inactivation of srv can bypass CovR repression and lead to constitutive SpeB production. We hypothesized that Srv control of SpeB production may be a mechanism to regulate biofilm dispersal and provide a mechanism by which mild infection can transition to severe disease through biofilm dispersal. The question remained however, is this mechanism conserved among GAS strains or restricted to the unique genetic makeup of MGAS5005. Here we show that Srv mediated control of SpeB and biofilm dispersal is conserved in the invasive clinical isolates RGAS053 (serotype M1) and MGAS315 (serotype M3), both of which have covS intact. This work provides additional evidence that Srv regulated control of SpeB may mediate biofilm formation and dispersal in diverse strain backgrounds

Thinking about Race: The Salience of Racial Identity at Two- and Four-Year Colleges and the Climate for Diversity

Racial identity salience is an important component of identity development that is associated with a number of educational outcomes. Using the Diverse Learning Environments Survey, this study identifies precollege and college experiences that contribute to a heightened salience of racial identity, and its relationship to perceptions of campus climate

Current status of liver surgery for non-colorectal non-neuroendocrine liver metastases: the NON.LI.MET. Italian Society for Endoscopic Surgery and New Technologies (SICE) and Association of Italian Surgeons in Europe (ACIE) collaborative international survey

Despite the increasing trend in liver resections for non-colorectal non-neuroendocrine liver metastases (NCNNLM), the role of surgery for these liver malignancies is still debated. Registries are an essential, reliable tool for assessing epidemiology, diagnosis, and therapeutic approach in a single hub, especially when data are dispersive and inconclusive, as in our case. The dissemination of this preliminary survey would allow us to understand if the creation of an International Registry is a viable option, while still offering a snapshot on this issue, investigating clinical practices worldwide. The steering committee designed an online questionnaire with Google Forms, which consisted of 37 questions, and was open from October 5th, 2022, to November 30th, 2022. It was disseminated using social media and mailing lists of the Italian Society of Endoscopic Surgery and New Technologies (SICE), the Association of Italian Surgeons in Europe (ACIE), and the Spanish Chapter of the American College of Surgeons (ACS). Overall, 141 surgeons (approximately 18% of the total invitations sent) from 27 countries on four continents participated in the survey. Most respondents worked in general surgery units (62%), performing less than 50 liver resections/year (57%). A multidisciplinary discussion was currently performed to validate surgical indications for NCNNLM in 96% of respondents. The most commonly adopted selection criteria were liver resectability, RECIST criteria, and absence of extrahepatic disease. Primary tumors were generally of gastrointestinal (42%), breast (31%), and pancreaticobiliary origin (13%). The most common interventions were parenchymal-sparing resections (51% of respondents) of metachronous metastases with an open approach. Major post-operative complications (Clavien-Dindo > 2) occurred in up to 20% of the procedures, according to 44% of respondents. A subset analysis of data from high-volume centers (> 100 cases/year) showed lower post-operative complications and better survival. The present survey shows that NCNNLM patients are frequently treated by surgeons in low-volume hospitals for liver surgery. Selection criteria are usually based on common sense. Liver resections are performed mainly with an open approach, possibly carrying a high burden of major post-operative complications. International guidelines and a specific consensus on this field are desirable, as well as strategies for collaboration between high-volume and low-volume centers. The present study can guide the elaboration of a multi-institutional document on the optimal pathway in the management of patients with NCNNLM