MUTACIN IV PRODUCTION IN STREPTOCOCCUS MUTANS UA159: CHARACTERIZATION, REGULATION, AND MECHANISM OF SELF-IMMUNITY

Streptococcus mutans, an oral pathogen, is considered as a principle etiological agent of dental caries. To colonize successfully in the oral cavity, this organism encounters fierce competition with other oral microbiota and this process is facilitated by ribosomally synthesized small cationic peptides called mutacins (bacteriocins) secreted by S. mutans. Although for long time mutacins are regarded as important virulence factors, it is not clear how these peptides work, what is the mechanism of self-immunity, and how they are regulated. In this study, we have characterized the activity, mechanism of self-immunity, and regulation of expression of a well-known bacteriocin, mutacin IV. To clarify the activity of mutacin IV, we studied the contribution of NlmA and NlmB peptides to mutacin IV activity. Using genetic and biochemical approaches, we showed that the presence of both genes is required for optimum mutacin IV activity. We also showed that mutacin IV is active against multiple Streptococcus species. Our studies revealed that mutacin IV has comparatively broader inhibitory spectrum than mutacin V; and both of them can work synergistically to inhibit various microorganisms. Next, we investigated the immunity activity of a putative immunity protein, SMU.152, which lies just downstream of the nlmAB operon. We observed that heterologous expression of SMU.152 in two sensitive strains converted the strains to become resistant to mutacin IV. We identified that C-terminal charged residues of SMU.152 is indispensible for conferring immunity to susceptible cells. In addition, our studies demonstrated that in absence of cognate immunity protein, S. mutans can employ other paralogous proteins to prevent the self-toxicity, which implies the presence of cross-immunity or immune redundancy in S. mutans UA159. To get a clear understanding on regulation of mutacin IV production, we carried out pGh9:ISS1-mediated random transposon mutagenesis in a reporter strain containing the nlmAB promoter with a promoter less gusA (glucuronidase) gene. Mapping the position of transposon insertion sites revealed 22 unique genes of diverse cellular activities, which are involved in regulation of mutacins production. Highlight of our finding is that an extracellular ATP-independent Lon-like protease functions specifically on maturation of peptide pheromone, CSP. Here, we show that functional form of CSP (18-amino acids) is generated by a specific post export cleavage with this Lon-like protease. Our study suggests that ComDE two-component system is primarily involved in regulation of mutacins production in S. mutans UA159. We also show that both the peptide pheromone (CSP) and mutacins use the same ABC transporter, NlmTE, for secretion. During the course of this study, we discovered two more novel regulators for gene expression in this bacterium. We show that a small hypothetical protein, SMU.2137, is required for normal cellular processes in S. mutans UA159 and a protein, SMU.832, required for glucose side chain formation, can also regulate mutacin production in this organism. Collectively, our data encourage us to propose a new model for regulation of mutacins production in S. mutans UA159. According to our model, peptide pheromone (BipC) is secreted as 21-amino acids and a specific Lon-like protease cleaves the C-terminal three amino acids to generate functional peptide pheromone (18-residue). BipC activates a two-component signal transduction system (BipDE), which in turn stimulates the expression of mutacins encoding genes (such as nlmAB and nlmC). A common ABC transporter, BipTE (NlmTE), is required for both mutacins and BipC secretion and proteolytic cleavage of leader peptide after GG-motif. In sum, our study has unraveled new pathways of gene regulation in S. mutans and strengthened our understanding on overall biology of mutacins production in S. mutans

Genome-wide Analysis of for the Identification of Putative Therapeutic Targets

Ever increasing propensity of antibiotic resistance among pathogenic bacteria raises the demand for the development of novel therapeutic agents to control this grave problem. Advances in the field of bioinformatics, genomics, and proteomics have greatly facilitated the discovery of alternative drugs by swift identification of new drug targets. In the present study, we employed comparative genomics and metabolic pathway analysis with an aim of identifying therapeutic targets in Mycoplasma hominis. Our study has revealed 40 annotated metabolic pathways, including five unique pathways of M. hominis. Our study also identified 179 essential proteins, including 59 proteins having no similarity with human proteins. Further filtering by molecular weight, subcellular localization, functional analysis, and protein network interaction, we identified 57 putative candidates for which new drugs can be developed. Druggability analysis for each of the identified targets has prioritized 16 proteins as suitable for potential drug development

Comparative assessment of total polyphenols, antioxidant and antimicrobial activity of different tea varieties of Bangladesh

Objective: To determine the total polyphenol content, antioxidant activity and antibacterial properties of the extracts of different Bangladeshi tea varieties such as flowery broken orange pekoe, broken orange pekoe, red dust and green tea. Methods: Total phenolic and flavonoid contents were determined by Folin–Ciocalteu and aluminum chloride colorimetric assay, respectively. The antioxidant capacity was determined by ferric ion reducing antioxidant power and phosphomolybdenum method. Antibacterial activity was evaluated by disc diffusion method in agar plate and subsequently, the minimum inhibitory concentration was determined by broth dilution method. Results: Total phenolic and flavonoid contents were significantly higher (P < 0.05) in green tea compared to other three black tea varieties. The green tea also showed a higher free radical scavenging and antioxidant activities than all the other tea varieties tested (P < 0.05). In addition, the extracts of all four tea varieties showed inhibitory activity against several pathogenic bacteria and also the same trend of higher antimicrobial activity of green tea than other tea varieties was observed. Conclusions: Taken together, the results of this study demonstrated that Bangladeshi tea, especially the green tea, may act as a substitute for natural antioxidants and as a promising antibacterial agent for beneficial influence in human health

Mental health of young people amidst COVID-19 pandemic in Bangladesh

Background: The psychological burden of the coronavirus disease 2019 (COVID-19) outbreak and lockdown strategy among young people not diagnosed with COVID-19 in the general population remains unknown and often have been overlooked. The objective of the study was to assess the prevalence and predictors of anxiety, depression and stress among young people diagnosed with COVID-19 of Bangladesh amidst the pandemic. Methods: A cross-sectional online survey was conducted from 1 May to 30 May 2020 using an online Google form-based questionnaire posted on Facebook. A snowball sampling approach was used for data collection. A total of 974 self-declared healthy individuals not diagnosed with COVID-19 participated here. Anxiety, depression and stress were measured using Bangla validated Generalized Anxiety Disorder Scale-7 (GAD-7), Patient Health Questionnaire (PHQ-9) scale, and Perceived Stress Scale (PSS), respectively. Statistical software SPSS 20 was used for analysis. Result: Average age of the population was 25.86 ± 6.26 (SD) years with nearly half (48.6%) of them being young people (15 to ≤24 years). Most of the participants were male (76.3%). The overall prevalence of anxiety, depression and stress was found to be 64.1%, 73.3% and 69.4%, respectively. Young people had significantly higher proportion of anxiety (67.2% vs 61.1%), and depression (78.2% vs 68.7%) compared to adults (p = 0.045 and p < 0.001, respectively). However, most of the participants had mild depression (30.3%), minimal anxiety (31.4%), and moderate stress (67.5%), and severity of depression and anxiety was higher in the young participants. The mean GAD-7, PHQ-9 and PSS scores were 7.57 ± 5.61, 9.19 ± 6.15 and 16.02 ± 5.55 (SD), respectively. On multivariable logistic analysis, unemployment (Adjusted Odds Ratio [AOR] 3.642; Confidence Interval [CI]: 1.005–13.200; p < 0.05) was the single most important predictor of depression. For stress, unemployment (AOR 1.399; CI: 1.055–1.855), and female sex (AOR 1.638; CI: 1.158–2.317) were significant predictors. Conclusion: Anxiety, depression and stress were highly prevalent among young people (≤24 years) not diagnosed with COVID-19 in Bangladesh amidst the pandemic. Unemployment is the most common underlying determinant. Authorities should address the issue on a priority basis

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05-1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4-7 days or &gt;= 8 days of 1.25 (1.04-1.48), p = 0.015 and 1.31 (1.11-1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care