Ontario's COVID-19 Modelling Consensus Table: mobilizing scientific expertise to support pandemic response.

SETTING: COVID-19 has highlighted the need for credible epidemiological models to inform pandemic policy. Traditional mechanisms of commissioning research are ill-suited to guide policy during a rapidly evolving pandemic. At the same time, contracting with a single centre of expertise has been criticized for failing to reflect challenges inherent in specific modelling approaches. INTERVENTION: This report describes an alternative approach to mobilizing scientific expertise. Ontario's COVID-19 Modelling Consensus Table (MCT) was created in March 2020 to enable rapid communication of credible estimates of the impact of COVID-19 and to accelerate learning on how the disease is spreading and what could slow its transmission. The MCT is a partnership between the province and academic modellers and consists of multiple groups of experts, health system leaders, and senior decision-makers. Armed with Ministry of Health data, the MCT meets once per week to share results from modelling exercises, generate consensus judgements of the likely future impact of COVID-19, and discuss decision-makers' priorities. OUTCOMES: The MCT has enabled swift access to data for participants, a structure for developing consensus estimates and communicating these to decision-makers, credible models to inform health system planning, and increased transparency in public reporting of COVID-19 data. It has also facilitated the rapid publication of research findings and its incorporation into government policy. IMPLICATIONS: The MCT approach is one way to quickly draw on scientific advice outside of government and public health agencies. Beyond speed, this approach allows for nimbleness as experts from different organizations can be added as needed. It also shows how universities and research institutes have a role to play in crisis situations, and how this expertise can be marshalled to inform policy while respecting academic freedom and confidentiality.

RéSUMé: LIEU: La COVID-19 a mis en évidence le besoin de modèles épidémiologiques crédibles pour éclairer la politique pandémique. Les mécanismes habituels pour commander des travaux de recherche sont peu propices à orienter les politiques lors d'une pandémie qui évolue rapidement. En même temps, la passation de contrats avec un seul centre d'expertise est critiquée, car elle ne tient pas compte des difficultés inhérentes de certaines approches de modélisation. INTERVENTION: Le présent rapport décrit une approche de rechange pour mobiliser le savoir scientifique. L'Ontario a créé en mars 2020 une Table de concertation sur la modélisation (TCM) qui permet de communiquer de façon rapide et fiable les estimations des effets de la COVID-19 et d'apprendre plus vite comment la maladie se propage et ce qui pourrait en ralentir la transmission. La TCM, un partenariat entre les modélisateurs de la province et des milieux universitaires, est composée de plusieurs groupes d'experts, de dirigeants du système de santé et de décideurs de haut niveau. Armée des données du ministère de la Santé, la TCM se réunit une fois par semaine pour partager les résultats d'exercices de modélisation, générer des jugements consensuels sur les futurs effets probables de la COVID-19 et discuter des priorités des décideurs. RéSULTATS: La TCM rend possible un accès rapide aux données pour les participants, une structure pour élaborer des estimations consensuelles et les communiquer aux décideurs, des modèles fiables pour éclairer la planification du système de santé, ainsi qu'une transparence accrue dans la communication des données sur la COVID-19 au public. Elle facilite aussi la publication rapide des résultats de recherche et leur intégration dans la politique gouvernementale. CONSéQUENCES: L'approche de la TCM est un moyen d'obtenir rapidement des conseils scientifiques à l'extérieur du gouvernement et des organismes de santé publique. Au-delà de sa rapidité, cette approche offre une grande souplesse, car des experts de différents organismes peuvent être ajoutés au besoin. Elle montre aussi que les universités et les établissements de recherche ont un rôle à jouer dans les situations de crise, et qu'il est possible de mobiliser leurs compétences pour éclairer les politiques tout en respectant la liberté et la confidentialité des milieux de la recherche et de l'enseignement.

Quantifying the shift in social contact patterns in response to non-pharmaceutical interventions.

Social contact mixing plays a critical role in influencing the transmission routes of infectious diseases. Moreover, quantifying social contact mixing patterns and their variations in a rapidly evolving pandemic intervened by changing public health measures is key for retroactive evaluation and proactive assessment of the effectiveness of different age- and setting-specific interventions. Contact mixing patterns have been used to inform COVID-19 pandemic public health decision-making; but a rigorously justified methodology to identify setting-specific contact mixing patterns and their variations in a rapidly developing pandemic, which can be informed by readily available data, is in great demand and has not yet been established. Here we fill in this critical gap by developing and utilizing a novel methodology, integrating social contact patterns derived from empirical data with a disease transmission model, that enables the usage of age-stratified incidence data to infer age-specific susceptibility, daily contact mixing patterns in workplace, household, school and community settings; and transmission acquired in these settings under different physical distancing measures. We demonstrated the utility of this methodology by performing an analysis of the COVID-19 epidemic in Ontario, Canada. We quantified the age- and setting (household, workplace, community, and school)-specific mixing patterns and their evolution during the escalation of public health interventions in Ontario, Canada. We estimated a reduction in the average individual contact rate from 12.27 to 6.58 contacts per day, with an increase in household contacts, following the implementation of control measures. We also estimated increasing trends by age in both the susceptibility to infection by SARS-CoV-2 and the proportion of symptomatic individuals diagnosed. Inferring the age- and setting-specific social contact mixing and key age-stratified epidemiological parameters, in the presence of evolving control measures, is critical to inform decision- and policy-making for the current COVID-19 pandemic.

MtrA Response Regulator Controls Cell Division and Cell Wall Metabolism and Affects Susceptibility of Mycobacteria to the First Line Antituberculosis Drugs.

The biological processes regulated by the essential response regulator MtrA and the growth conditions promoting its activation in Mycobacterium tuberculosis, a slow grower and pathogen, are largely unknown. Here, using a gain-of-function mutant, MtrAY 102C, which functions in the absence of the cognate MtrB sensor kinase, we show that the MtrA regulon includes several genes involved in the processes of cell division and cell wall metabolism. The expression of selected MtrA targets and intracellular MtrA levels were compromised under replication arrest induced by genetic manipulation and under stress conditions caused by toxic radicals. The loss of the mtrA gene in M. smegmatis, a rapid grower and non-pathogen, produced filamentous cells with branches and bulges, indicating defects in cell division and cell shape. The ΔmtrA mutant was sensitized to rifampicin and vancomycin and became more resistant to isoniazid, the first line antituberculosis drug. Our data are consistent with the proposal that MtrA controls the optimal cell division, cell wall integrity, and susceptibility to some antimycobacterial drugs.

Amelioration of arsenic-induced oxidative stress in CHO cells by Ixora coccinea flower extract.

Chronic exposure to inorganic arsenic creates various health problems. Ixora coccinea flower extract was investigated for its ability to protect against arsenic-induced cytotoxicity and genotoxicity in CHO cell line. MTT assay confirmed the efficacy of the extract in ameliorating arsenic-induced cytotoxicity. The value (48 mM) of 24 h inhibitory concentration (IC50) of sodium arsenate for CHO cells was obtained by MTT assay. Various free radical scavenging assays like DPPH, ABTS and nitric oxide scavenging assay confirmed antioxidant activity of the Ixora coccinea flower extract. Pretreatment of the extract significantly inhibited the arsenic-induced DNA damage (p < 0.01) in CHO cells. The extract administration significantly (p < 0.01) inhibited the intracellular ROS and depolarization of mitochondrial membrane induced by sodium arsenate. Ixora coccinea flower extract reduced oxidative stress in cells. Antioxidant enzymes like catalase and SOD activity was restored significantly (p < 0.01) in pretreated CHO cells. Ixora coccinea flower extract also exhibited the anti-apoptotic potential by decreasing the percentage apoptotic index (p < 0.01). These results may expand the applications of Ixora coccinea flowers as an alternative food with antioxidant properties and protective functions against arsenic (iAs) induced toxicological effects.

An Intrathermocline Eddy and a tropical cyclone in the Bay of Bengal.

The Bay of Bengal, subjected to monsoonal forcing and tropical cyclones, displays a complex field of ocean eddies. On 5 December 2013 a sub-surface vortex or Intrathermocline Eddy (ITE) composed of water characteristic of the Andaman Sea was observed within the thermocline of the western Bay of Bengal. We propose that the ITE was the product of Tropical Cyclone Lehar interaction on 27 November 2013 with a westward propagating surface eddy from the eastern Bay of Bengal. While Lehar's interaction with the ocean initially removes heat from the upper layers of the eddy, air-sea flux is limited as the deeper portions of the eddy was subducted into the stratified thermocline, inhibiting further interaction with the atmosphere. The ITE core from 30 to 150 m is thus isolated from local air-sea fluxes by strong stratification at the mixed layer base, and its periphery is stable to shear instability, suggestive of longevity and the ability to carry water far distances with minimal modification.

Loss of PRDM1/BLIMP-1 function contributes to poor prognosis of activated B-cell-like diffuse large B-cell lymphoma.

PRDM1/BLIMP-1, a master regulator of plasma-cell differentiation, is frequently inactivated in activated B-cell-like (ABC) diffuse large B-cell lymphoma (DLBCL) patients. Little is known about its genetic aberrations and relevant clinical implications. A large series of patients with de novo DLBCL was effectively evaluated for PRDM1/BLIMP-1 deletion, mutation, and protein expression. BLIMP-1 expression was frequently associated with the ABC phenotype and plasmablastic morphologic subtype of DLBCL, yet 63% of the ABC-DLBCL patients were negative for BLIMP-1 protein expression. In these patients, loss of BLIMP-1 was associated with Myc overexpression and decreased expression of p53 pathway molecules. In addition, homozygous PRDM1 deletions and PRDM1 mutations within exons 1 and 2, which encode for domains crucial for transcriptional repression, were found to show a poor prognostic impact in patients with ABC-DLBCL but not in those with germinal center B-cell-like DLBCL (GCB-DLBCL). Gene expression profiling revealed that loss of PRDM1/BLIMP-1 expression correlated with a decreased plasma-cell differentiation signature and upregulation of genes involved in B-cell receptor signaling and tumor-cell proliferation. In conclusion, these results provide novel clinical and biological insight into the tumor-suppressive role of PRDM1/BLIMP-1 in ABC-DLBCL patients and suggest that loss of PRDM1/BLIMP-1 function contributes to the overall poor prognosis of ABC-DLBCL patients.

Mycobacterium tuberculosis oriC sequestration by MtrA response regulator.

The regulators of Mycobacterium tuberculosis DNA replication are largely unknown. Here, we demonstrate that in synchronously replicating M. tuberculosis, MtrA access to origin of replication (oriC) is enriched in the post-replication (D) period. The increased oriC binding results from elevated MtrA phosphorylation (MtrA∼P) as evidenced by reduced expression of dnaN, dnaA and increased expression of select cell division targets. Overproduction of gain-of-function MtrAY102C advanced the MtrA oriC access to the C period, reduced dnaA and dnaN expression, interfered with replication synchrony and compromised cell division. Overproduction of wild-type (MtrA+) or phosphorylation-defective MtrAD56N did not promote oriC access in the C period, nor affected cell cycle progression. MtrA interacts with DnaA signaling a possibility that DnaA helps load MtrA on oriC. Therefore, oriC sequestration by MtrA∼P in the D period may normally serve to prevent untimely initiations and that DnaA-MtrA interactions may facilitate regulated oriC replication. Finally, despite the near sequence identity of MtrA in M. smegmatis and M. tuberculosis, the M. smegmatis oriC is not MtrA-target. We conclude that M. tuberculosis oriC has evolved to be regulated by MtrA and that cell cycle progression in this organisms are governed, at least in part, by oscillations in the MtrA∼P levels.

DNA double-strand breaks cooperate with loss of Ink4 and Arf tumor suppressors to generate glioblastomas with frequent Met amplification.

Glioblastomas (GBM) are highly radioresistant and lethal brain tumors. Ionizing radiation (IR)-induced DNA double-strand breaks (DSBs) are a risk factor for the development of GBM. In this study, we systematically examined the contribution of IR-induced DSBs to GBM development using transgenic mouse models harboring brain-targeted deletions of key tumor suppressors frequently lost in GBM, namely Ink4a, Ink4b, Arf and/or PTEN. Using low linear energy transfer (LET) X-rays to generate simple breaks or high LET HZE particles (Fe ions) to generate complex breaks, we found that DSBs induce high-grade gliomas in these mice which, otherwise, do not develop gliomas spontaneously. Loss of Ink4a and Arf was sufficient to trigger IR-induced glioma development but additional loss of Ink4b significantly increased tumor incidence. We analyzed IR-induced tumors for copy number alterations to identify oncogenic changes that were generated and selected for as a consequence of stochastic DSB events. We found Met amplification to be the most significant oncogenic event in these radiation-induced gliomas. Importantly, Met activation resulted in the expression of Sox2, a GBM cancer stem cell marker, and was obligatory for tumor formation. In sum, these results indicate that radiation-induced DSBs cooperate with loss of Ink4 and Arf tumor suppressors to generate high-grade gliomas that are commonly driven by Met amplification and activation.

Mycobacterium tuberculosis MtrB sensor kinase interactions with FtsI and Wag31 proteins reveal a role for MtrB distinct from that regulating MtrA activities.

The septal association of Mycobacterium tuberculosis MtrB, the kinase partner of the MtrAB two-component signal transduction system, is necessary for the optimal expression of the MtrA regulon targets, including ripA, fbpB, and ftsI, which are involved in cell division and cell wall synthesis. Here, we show that MtrB, irrespective of its phosphorylation status, interacts with Wag31, whereas only phosphorylation-competent MtrB interacts with FtsI. We provide evidence that FtsI depletion compromises the MtrB septal assembly and MtrA regulon expression; likewise, the absence of MtrB compromises FtsI localization and, possibly, FtsI activity. We conclude from these results that FtsI and MtrB are codependent for their activities and that FtsI functions as a positive modulator of MtrB activation and MtrA regulon expression. In contrast to FtsI, Wag31 depletion does not affect MtrB septal assembly and MtrA regulon expression, whereas the loss of MtrB increased Wag31 localization and the levels of PknA/PknB (PknA/B) serine-threonine protein kinase-mediated Wag31 phosphorylation. Interestingly, we found that FtsI decreased levels of phosphorylated Wag31 (Wag31∼P) and that MtrB interacted with PknA/B. Overall, our results indicate that MtrB interactions with FtsI, Wag31, and PknA/B are required for its optimal localization, MtrA regulon expression, and phosphorylation of Wag31. Our results emphasize a new role for MtrB in cell division and cell wall synthesis distinct from that regulating the MtrA phosphorylation activities.

Adsorption of Phenol from Aqueous Solution Using Lantana camara, Forest Waste: Kinetics, Isotherm, and Thermodynamic Studies.

The present work investigates the potential of Lantana camara, a forest waste, as an adsorbent for the phenol reduction in wastewater. Batch studies were conducted with adsorbent treated with HCl and KOH to determine the influence of various experimental parameters such as pH, contact time, adsorbent dosage, and phenol concentration. The experimental conditions were optimized for the removal of phenol from wastewater. Equilibrium isotherms for the adsorption of phenol were analyzed by Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich isotherm models. Thermodynamic parameters like the Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were also determined and they showed that the adsorption process was feasible, spontaneous, and exothermic in the temperature range of 298-328 K. The kinetic data were fitted with pseudo-second-order model. The equilibrium data that followed Langmuir model with the monolayer adsorption capacity was found to be 112.5 mg/g and 91.07 mg/g for adsorbent treated with HCl and KOH, respectively, for the concentration of phenol ranging from 25 to 250 mg/L. This indicates that the Lantana camara was a promising adsorbent for the removal of phenol from aqueous solutions.

A Rare Case of Pyridoxine-dependent Seizures in Infancy.

Pyridoxine-dependent seizures is a rare cause of recurrent seizures in neonatal period and resistant to most of the antiepileptic medications, but respond to administration of pyridoxine. We report a male infant who had neonatal seizures which were initially responsive to anticonvulsants and later became unresponsive and presented at 45 days of life with seizures. These seizures were not responding to any anticonvulsant but responded to pyridoxine. After discharge parents inadvertently stopped pyridoxine and the infant presented with seizures once again. These seizures were promptly controlled with readministration of pyridoxine confirming the diagnosis of pyridoxine-dependant seizures.

The lack of L-PG production and the repercussions of it in regards to M. Tuberculosis interactions with mononuclear phagocytes.

The lysine connection with phosphatidylglycerol (PG) alters the M. tuberculosis(Mtb) surface charge, and consequently it may decrease the bacterial vulnerability to antimicrobial action of the immune cells. The aim of the study was to assess the significance of PG lysinylation in the Mtb interactions with mononuclear phagocytes. Both the Mtb strain with deletion of lysX gene (Mtb-lysX) which is responsible for PG lysinylation as well as the complemented strain (Mtb-compl) was used to infect human blood monocytes or THP-1 cells. The monocytes were obtained by MACS technique, or THP-1 cells. The Mtb-lysX strain has exhibited the enhanced sensitivity to HNP 1-3. However, it was not susceptible to bactericidal action of cathepsin G. The LysX deletion did not influence the Mtb ability of monocyte induction to IL-10 secretion. The intra- and extracellular expression of MHC-II was similarly reduced after the Mtb-lysX or Mtb-Rv infections. Noticeably significant is that the Mtb strain with deleted lysX has not affected the intensity of the gene expression of cathepsin G compared to the uninfected monocytes. That is the clear contrast to what the Mtb-Rv strain has proved. The obtained results suggest that the Mtb ability to lysinylate PG is a participatory element in mycobacterial strategy of survival inside phagocytic cells. However, the extended studies are needed to determine its influence on the other immune cells and define its role in the developing of Mtb infection.

Mycobacterium tuberculosis MtrAY102C is a gain-of-function mutant that potentially acts as a constitutively active protein.

The MtrAB histidine-aspartate signal transduction of mycobacteria includes the response regulator MtrA and sensor kinase MtrB. We recently showed that Mycobacterium smegmatis ΔmtrB is filamentous, defective for cell division, cell shape maintenance and shows compromised MtrA target gene expression. Interestingly, overproduction of phosphorylation competent M. tuberculosis MtrAY102C reverses the ΔmtrB mutant phenotype, although the genetic basis of phenotype reversal is unknown. Here we show that introduction of D56N mutation in MtrAY102C completely abolished its phosphorylation potential yet the double mutant protein retained a partial ability to reverse the mtrB mutant phenotype indicating that phosphorylation activity is not necessary for the function of MtrAY102C. The phosphorylation-defective MtrAD56N-Y102C protein bound its target promoters ripA and fbpB efficiently. Together, these results support a hypothesis that the gain-of-function phenotype of MtrAY102C is in part due to its ability to function as a constitutively active protein in the absence of phosphorylation.

Septal localization of the Mycobacterium tuberculosis MtrB sensor kinase promotes MtrA regulon expression.

The mechanisms responsible for activation of the MtrAB two-component regulatory signal transduction system, which includes sensor kinase MtrB and response regulator MtrA, are unknown. Here, we show that an MtrB-GFP fusion protein localized to the cell membrane, the septa, and the poles in Mycobacterium tuberculosis and Mycobacterium smegmatis. This localization was independent of MtrB phosphorylation status but dependent upon the assembly of FtsZ, the initiator of cell division. The M. smegmatis mtrB mutant was filamentous, defective for cell division, and contained lysozyme-sensitive cell walls. The mtrB phenotype was complemented by either production of MtrB protein competent for phosphorylation or overproduction of MtrA(Y102C) and MtrA(D13A) mutant proteins exhibiting altered phosphorylation potential, indicating that either MtrB phosphorylation or MtrB independent expression of MtrA regulon genes, including those involved in cell wall processing, are necessary for regulated cell division. In partial support of this observation, we found that the essential cell wall hydrolase ripA is an MtrA target and that the expression of bona fide MtrA targets ripA, fbpB, and dnaA were compromised in the mtrB mutant and partially rescued upon MtrA(Y102C) and MtrA(D13A) overproduction. MtrB septal assembly was compromised upon FtsZ depletion and exposure of cells to mitomycin C, a DNA damaging agent, which interferes with FtsZ ring assembly. Expression of MtrA targets was also compromised under the above conditions, indicating that MtrB septal localization and MtrA regulon expression are linked. We propose that MtrB septal association is a necessary feature of MtrB activation that promotes MtrA phosphorylation and MtrA regulon expression.

Review of various treatment methods for the abatement of phenolic compounds from wastewater.

Phenol and its derivatives are considered among the most hazardous organic pollutants from industrial wastewater and they are toxic even at low concentrations. Besides the existence of phenol in natural water source it can lead to the formation of other toxic substituted compounds. So this has led to growing concern on setting up of rigid limits on the acceptable level of phenol in the environment. The various methods for the treatment of phenol from wastewater streams are briefly reviewed. The various technologies like distillation, liquid-liquid extraction with different solvents, adsorption over activated carbons and polymeric and inorganic adsorbents, membrane pervaporation and membrane-solvent extraction, have been elucidated. The advantages and disadvantages of the various methods are illustrated and their performances are compared.

Phrenic nerve palsy: A rare cause of respiratory distress in newborn.

Birth injury is defined as an impairment of a newborn's body function or structure due to adverse influences that occurred at birth. Phrenic nerve palsy may result from birth trauma during a traumatic neonatal delivery from a stretch injury due to lateral hyperextension of the neck at birth. This could be a rare cause of respiratory distress in the newborn period with irregular respiration. Respiratory distress due to phrenic nerve damage leading to paralysis of the ipsilateral diaphragm may require continuous positive airway pressure or mechanical ventilation and if unresponsive, surgical plication of diaphragm. Herein, we report a case of phrenic nerve palsy in a newborn presenting with respiratory distress.

Control of CydB and GltA1 expression by the SenX3 RegX3 two component regulatory system of Mycobacterium tuberculosis.

Two component regulatory systems are used widely by bacteria to coordinate changes in global gene expression profiles in response to environmental signals. The SenX3-RegX3 two component system of Mycobacterium tuberculosis has previously been shown to play a role in virulence and phosphate-responsive control of gene expression. We demonstrate that expression of SenX3-RegX3 is controlled in response to growth conditions, although the absolute changes are small. Global gene expression profiling of a RegX3 deletion strain and wild-type strain in different culture conditions (static, microaerobic, anaerobic), as well as in an over-expressing strain identified a number of genes with changed expression patterns. Among those were genes previously identified as differentially regulated in aerobic culture, including ald (encoding alanine dehydrogenase) cyd,encoding a subunit of the cytochrome D ubiquinol oxidase, and gltA1, encoding a citrate synthase. Promoter activity in the upstream regions of both cydB and gltA1 was altered in the RegX3 deletion strain. DNA-binding assays confirmed that RegX3 binds to the promoter regions of ald, cydB and gltA1 in a phosphorylation-dependent manner. Taken together these data suggest a direct role for the SenX-RegX3 system in modulating expression of aerobic respiration, in addition to its role during phosphate limitation.

Alterations in phospholipid catabolism in Mycobacterium tuberculosis lysX mutant.

Mycobacterium tuberculosis lysX mutant, defective for production of lysinylated phosphatidylglycerol (L-PG), is sensitive to cationic antimicrobial peptides, is not proficient for proliferation in mice lungs and exhibits altered membrane potential (17). In the present study we show that a lysX complement strain expressing lysX from inducible tet promoter is proficient in restoring lysX phenotypes, confirming that the observed phenotypes are specific to lysX. To evaluate the correlation between changes in membrane potential and lysX activity, we visualized regions of cardiolipin (CL), one of the abundant phospholipids of mycobacteria, by staining with fluorescent dye 10-N-nonyl-acridine orange (NAO) and found that CL is localized as bright spots at septal regions and poles of actively dividing cells, but not in stationary phase cells. lysX mutants were elongated and showed more numerous and brighter CL staining at both midcell and quarter cell septa, compared with wild type, indicating a defect in the cell division process. Evaluation of (14)C-acetic acid incorporation into major phospholipids such as CL, phosphatidylethanolamine (PE), phosphatidylinositol and their degradation between lysX mutant and its parent revealed differences in the turnover of PE and PI. Our results favor a hypothesis that alterations in phospholipids metabolism could be contributing to changes in membrane potential, hence the observed phenotype of lysX mutant.

Mycobacterium tuberculosis mtrA merodiploid strains with point mutations in the signal-receiving domain of MtrA exhibit growth defects in nutrient broth.

The genetic and biochemical aspects of the essential Mycobacteriumtuberculosis MtrAB two-component regulatory signal transduction (2CRS) system have not been extensively investigated. We show by bacterial two-hybrid assay that the response regulator (RR) MtrA and the sensor kinase MtrB interact. We further demonstrate that divalent metal ions [Mg²+, Ca²+ or both] promote MtrB kinase autophosphorylation activity, but only Mg²+ promotes phosphotransfer to MtrA. Replacement of the conserved aspartic acid residues at positions 13 and 56 with alanine (D13A), glutamine (D56E) or asparagine (D56N) prevented MtrA phosphorylation, indicating that these residues are important for phosphorylation. The MtrA(D56E) and MtrA(D13A) proteins bound to the promoter of fbpB, the gene encoding antigen 85B protein, efficiently in the absence of phosphorylation, whereas MtrA(D56N) did not. We also show that M.tuberculosismtrA merodiploids overproducing MtrA(D13A), unlike cells overproducing wild-type MtrA, grow poorly in nutrient broth and show reduced expression of fbpB. These latter findings are reminiscent of a phenotype associated with MtrA overproduction during intramacrophage growth. Our results suggest that MtrA(D13A) behaves like a constitutively active response regulator and that further characterization of mtrA merodiploid strains will provide valuable clues to the MtrAB system.

Catharanthus roseus: a natural source for the synthesis of silver nanoparticles.

OBJECTIVE: To develop a simple rapid procedure for bioreduction of silver nanoparticles (AgNPs) using aqueous leaves extracts of Catharanthus roseus (C. roseus). METHODS: Characterization were determined by using UV-Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive X-ray and X-ray diffraction. RESULTS: SEM showed the formation of silver nanoparticles with an average size of 67 nm to 48 nm. X-ray diffraction analysis showed that the particles were crystalline in nature with face centered cubic geometry. CONCLUSIONS: C. roseus demonstrates strong potential for synthesis of silver nanoparticles by rapid reduction of silver ions (Ag(+) to Ag(0)). This study provides evidence for developing large scale commercial production of value-added products for biomedical/nanotechnology-based industries.