An intelligent trust sensing scheme with metaheuristic based secure routing protocol for Internet of Things

Cluster Computing - The Internet of Things (IoT) defines the network of physical objects, commonly used to interconnect and communicate with other devices through the internet. Security is highly...     

Functions of the duplicated hik31 operons in central metabolism and responses to light, dark, and carbon sources in Synechocystis sp. strain PCC 6803

There are two closely related hik31 operons involved in signal transduction on the chromosome and the pSYSX plasmid in the cyanobacterium Synechocystis sp. strain PCC 6803. We studied the growth, cell morphology, and gene expression in operon and hik mutants for both copies, under different growth conditions, to examine whether the duplicated copies have the same or different functions and gene targets and whether they are similarly regulated. Phenotype analysis suggested that both operons regulated common and separate targets in the light and the dark. The chromosomal operon was involved in the negative control of autotrophic events, whereas the plasmid operon was involved in the positive control of heterotrophic events. Both the plasmid and double operon mutant cells were larger and had division defects. The growth data also showed a regulatory role for the chromosomal hik gene under high-CO(2) conditions and the plasmid operon under low-O(2) conditions. Metal stress experiments indicated a role for the chromosomal hik gene and operon in mediating Zn and Cd tolerance, the plasmid operon in Co tolerance, and the chromosomal operon and plasmid hik gene in Ni tolerance. We conclude that both operons are differentially and temporally regulated. We suggest that the chromosomal operon is the primarily expressed copy and the plasmid operon acts as a backup to maintain appropriate gene dosages. Both operons share an integrated regulatory relationship and are induced in high light, in glucose, and in active cell growth. Additionally, the plasmid operon is induced in the dark with or without glucose.     

Rapid, sensitive and label-free detection of Shiga-toxin producing Escherichia coli O157 using carbon nanotube biosensors

An electronic platform to detect very small amounts of genomic DNA from bacteria without the need for PCR amplification and molecular labeling is described. The system uses carbon nanotube field-effect transistor (FET) arrays whose electrical properties are affected by minute electrical charges localized on their active regions. Two pathogenic strains of E. coli are used to evaluate the detection properties of the transistor arrays. Described herein are the results for detection of synthetic oligomers, unpurified and highly purified genomic DNA at various concentrations and their comparison against non-specific binding. In particular, the capture of genomic DNA of E. coli O157:H7 by a specific oligonucleotide probe coated onto the transistor array results in a significant shift in the threshold (gate-source) voltage (V(th)). By contrast the signal under the same procedure using a different strain, E. coli O45 that is non-complementary to the probe remained nearly constant. This work highlights the detection sensitivity and efficacy of this biosensor without stringent requirement for DNA sample preparation.     

Role of Interferon Gamma Release Assay in Active TB Diagnosis among HIV Infected Individuals

Background

A rapid and specific test is urgently needed for tuberculosis (TB) diagnosis especially among human immunodeficiency virus (HIV) infected individuals. In this study, we assessed the sensitivity of Interferon gamma release assay (IGRA) in active tuberculosis patients who were positive for HIV infection and compared it with that of tuberculin skin test (TST).

Methodology/Principal Findings

A total of 105 HIV-TB patients who were naïve for anti tuberculosis and anti retroviral therapy were included for this study out of which 53 (50%) were culture positive. Of 105 tested, QuantiFERON-TB Gold in-tube (QFT-G) was positive in 65% (95% CI: 56% to 74%), negative in 18% (95% CI: 11% to 25%) and indeterminate in 17% (95% CI: 10% to 24%) of patients. The sensitivity of QFT-G remained similar in pulmonary TB and extra-pulmonary TB patients. The QFT-G positivity was not affected by low CD4 count, but it often gave indeterminate results especially in individuals with CD4 count <200 cells/µl. All of the QFT-G indeterminate patients whose sputum culture were positive, showed ≤0.25 IU/ml of IFN-γ response to phytohemagglutinin (PHA). TST was performed in all the 105 patients and yielded the sensitivity of 31% (95% CI: 40% to 22%). All the TST positives were QFT-G positives. The sensitivity of TST was decreased, when CD4 cell counts declined.

Conclusions/Significance

Our study shows neither QFT-G alone or in combination with TST can be used to exclude the suspicion of active TB disease. However, unlike TST, QFT-G yielded fewer false negative results even in individuals with low CD4 count. The low PHA cut-off point for indeterminate results suggested in this study (≤0.25 IU/ml) may improve the proportion of valid QFT-G results.     

Strategies to target SARS-CoV-2 entry and infection using dual mechanisms of inhibition by acidification inhibitors

Many viruses utilize the host endo-lysosomal network for infection. Tracing the endocytic itinerary of SARS-CoV-2 can provide insights into viral trafficking and aid in designing new therapeutic strategies. Here, we demonstrate that the receptor binding domain (RBD) of SARS-CoV-2 spike protein is internalized via the pH-dependent CLIC/GEEC (CG) endocytic pathway in human gastric-adenocarcinoma (AGS) cells expressing undetectable levels of ACE2. Ectopic expression of ACE2 (AGS-ACE2) results in RBD traffic via both CG and clathrin-mediated endocytosis. Endosomal acidification inhibitors like BafilomycinA1 and NH₄Cl, which inhibit the CG pathway, reduce the uptake of RBD and impede Spike-pseudoviral infection in both AGS and AGS-ACE2 cells. The inhibition by BafilomycinA1 was found to be distinct from Chloroquine which neither affects RBD uptake nor alters endosomal pH, yet attenuates Spike-pseudovirus entry. By screening a subset of FDA-approved inhibitors for functionality similar to BafilomycinA1, we identified Niclosamide as a SARS-CoV-2 entry inhibitor. Further validation using a clinical isolate of SARS-CoV-2 in AGS-ACE2 and Vero cells confirmed its antiviral effect. We propose that Niclosamide, and other drugs which neutralize endosomal pH as well as inhibit the endocytic uptake, could provide broader applicability in subverting infection of viruses entering host cells via a pH-dependent endocytic pathway.     

Rapid and simple DNA extraction method for the detection of enterotoxigenic Staphylococcus aureus directly from food samples: comparison of PCR and LAMP methods

Aims: The study describes the development of simple and rapid DNA extraction method in combination with loop‐mediated isothermal amplification (LAMP) to detect enterotoxigenic Staphylococcus aureus in food samples. Methods and Results: In this study, isolation of genomic DNA of enterotoxigenic Staph. aureus from spiked milk, milk burfi, khoa, sugarcane juice and boiled rice was carried out by boiling the isolated sample pellets for 10 min with 1% Triton X‐100. The isolated DNA was evaluated by polymerase chain reaction (PCR) and LAMP method. The LAMP was found to be 100 times more sensitive than PCR. The LAMP assay was very specific for Staph. aureus, and the presence of other contaminating bacterial DNAs and food matrix did not interfere or inhibit the LAMP assay. Conclusions: The template DNA extraction method developed in this study for food samples is simple, rapid and cost‐effective. LAMP was found to be less sensitive to matrix effect of food, compared to PCR. Significance and Impact of the Study: The method is suitable for direct detection of Staph. aureus without any enrichment in contaminated food samples and hence finds its application in food safety analysis, in permutation with LAMP.