Immunoinformatic Identification of Potential Epitopes Against Shigellosis

Diarrhoeal diseases due to Shigellosis account for deaths of ~1.5 million children every year in developing countries. Outer membrane proteins (OMPs) of Gram negative bacteria have been shown to be excellent subunit vaccine candidates against various pathogens. However, effective immune response can be generated using specific immunogenic determinants or peptides instead of whole protein or pathogen. In the present study, we chose six OMPs of Shigella flexneri 2a to predict peptides with good antigenic potential. Various tools were used in a systematic flow to predict B- and T-cell epitopes. Stringent selection criteria were used for epitope screening to ensure generation of both arms of immunity. These epitopes are predicted to be effective against a significantly large population of the diarrhoea afflicted countries in Southeast Asia. Most of the predicted epitopes are located towards the outer exposed region of proteins. The epitopes were docked with respective MHC Class I and II molecules to study peptide–MHC interactions. In conclusion, we have predicted an epitope ensemble against Shigellosis which can be experimentally validated for its immunogenic efficacy. We also propose a systematic workflow for immune-optimization to design effective peptide vaccines.     

Gram positivity induced in Escherichia coli by chloroform-methanol treatment

Summary Extraction of lipid by chloroform-methanol from Escherichia coli induces Gram positivity in the cells of this bacterium. It has been observed that approximately 1.5 times more lipid is extracted from Escherichia coli than from Staphylococcus aureus by this treatment. An increase of 1.5–1.8 fold in the retention of dye has been evident in the case of S. aureus where as this was 70–90 fold in the case of E. coli, which is 1/4th of the normal retention by S. aureus. The more lipid present in the cell wall or cell membrane, the less retention of dye seems to be exhibited by the bacteria. This also substantiates our model for Gram reaction presented in a previous communication.     

Behaviour of catalase in some members of Chlorophyceae and Cyanophyceae

Summary The activation energy of catalase revealed statistically significant variations in Chlorophyceae and Cyanophyceae. The differences in two classes of algae may suggest a close catalase-chlorophyll relationship.     

Treatment with 24-epibrassinolide,a brassinosteroid,increases the basic thermotolerance of Brassica napus and tomato seedlings

Brassinosteroids are plant growth-promoting compounds that exhibit structural similarities to animal steroid hormones. Recent studies have indicated that brassinosteroids are essential for proper plant development. In addition to a role in development, several lines of evidence suggest that brassinosteroids exert anti-stress effects on plants. However, the mechanism by which they modulate plant stress responses is not understood. We show here that Brassica napus and tomato seedlings grown in the presence of 24-epibrassinolide (EBR) are significantly more tolerant to a lethal heat treatment than are control seedlings grown in the absence of the compound. Since a preconditioning treatment of seedlings was not required to observe this effect, we conclude that EBR treatment increases the basic thermotolerance of seedlings. An analysis of heat shock proteins (HSPs) in B. napus seedlings by western blot analysis indicated that the HSPs did not preferentially accumulate in EBR-treated seedlings at the control temperature. However, after heat stress, HSP accumulation was higher in EBR-treated than in untreated seedlings. The results of the present study provide the first direct evidence for EBR-induced expression of HSPs. The higher accumulation of HSPs in EBR-treated seedlings raises the possibility that HSPs contribute, at least in part, to thermotolerance in EBR-treated seedlings. A search for factors other than HSPs, which may directly or indirectly contribute to brassinosteroid-mediated increase in thermotolerance, is underway.     

A Mouse Geneticist’s Practical Guide to CRISPR Applications

CRISPR/Cas9 system of RNA-guided genome editing is revolutionizing genetics research in a wide spectrum of organisms. Even for the laboratory mouse, a model that has thrived under the benefits of embryonic stem (ES) cell knockout capabilities for nearly three decades, CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)/Cas9 technology enables one to manipulate the genome with unprecedented simplicity and speed. It allows generation of null, conditional, precisely mutated, reporter, or tagged alleles in mice. Moreover, it holds promise for other applications beyond genome editing. The crux of this system is the efficient and targeted introduction of DNA breaks that are repaired by any of several pathways in a predictable but not entirely controllable manner. Thus, further optimizations and improvements are being developed. Here, we summarize current applications and provide a practical guide to use the CRISPR/Cas9 system for mouse mutagenesis, based on published reports and our own experiences. We discuss critical points and suggest technical improvements to increase efficiency of RNA-guided genome editing in mouse embryos and address practical problems such as mosaicism in founders, which complicates genotyping and phenotyping. We describe a next-generation sequencing strategy for simultaneous characterization of on- and off-target editing in mice derived from multiple CRISPR experiments. Additionally, we report evidence that elevated frequency of precise, homology-directed editing can be achieved by transient inhibition of the Ligase IV-dependent nonhomologous end-joining pathway in one-celled mouse embryos.     

Synthesis of fluorescent nucleoside analogs as probes for 2′-deoxyribonucleoside kinases

We are reporting on the synthesis of fluorescent nucleoside analogs with modified sugar moieties (e.g., sugars other than ribose and 2′-deoxyribose). Four novel derivatives of the fluorescent thymidine analog 6-methyl-3-(β-D-2′-deoxyribofuranosyl) furano-[2,3-d]pyrimidin-2-one were synthesized via Sonogashira reaction and subsequent copper-catalyzed cycloaddition. These compounds represent promising tools for studying nucleoside metabolism inside living cells, as well as for screening directed evolution libraries of 2′-deoxyribonucleoside kinases with new and improved activity for the corresponding nucleoside analogs.     

Optknock: a bilevel programming framework for identifying gene knockout strategies for microbial strain optimization

The advent of genome-scale models of metabolism has laid the foundation for the development of computational procedures for suggesting genetic manipulations that lead to overproduction. In this work, the computational OptKnock framework is introduced for suggesting gene deletion strategies leading to the overproduction of chemicals or biochemicals in E. coli. This is accomplished by ensuring that a drain towards growth resources (i.e., carbon, redox potential, and energy) must be accompanied, due to stoichiometry, by the production of a desired product. Computational results for gene deletions for succinate, lactate, and 1,3-propanediol (PDO) production are in good agreement with mutant strains published in the literature. While some of the suggested deletion strategies are straightforward and involve eliminating competing reaction pathways, many others suggest complex and nonintuitive mechanisms of compensating for the removed functionalities. Finally, the OptKnock procedure, by coupling biomass formation with chemical production, hints at a growth selection/adaptation system for indirectly evolving overproducing mutants.