The rapid community-spread of novel human coronavirus 2019 (nCOVID19 or SARS-Cov2) and morbidity statistics has put forth an unprecedented urge for rapid diagnostics for quick and sensitive detection followed by contact tracing and containment strategies, especially when no vaccine or therapeutics are known. Currently, quantitative real-time polymerase chain reaction (qRT-PCR) is being used widely to detect COVID-19 from various types of biological specimens, which is time-consuming, labor-intensive and may not be rapidly deployable in remote or resource-limited settings. This might lead to hindrance in acquiring realistic data of infectivity and community spread of SARS-CoV-2 in the population. This review summarizes the existing status of current diagnostic methods, their possible limitations, and the advantages of biosensorbased diagnostics over the conventional ones for the detection of SARS-Cov-2. Novel biosensors used to detect RNA-viruses include CRISPR-Cas9 based paper strip, nucleic-acid based, aptamer-based, antigen-Au/Ag nanoparticles-based electrochemical biosensor, optical biosensor, and Surface Plasmon Resonance. These could be effective tools for rapid, authentic, portable, and more promising diagnosis in the current pandemic that has affected the world economies and humanity. Present challenges and future perspectives of developing robust biosensors devices for rapid, scalable, and sensitive detection and management of COVID-19 are presented in light of the test-test-test theme of the World Health Organization (WHO).
We purified osmoregulated periplasmic glucans (OPGs) from Salmonella enterica serovar Typhimurium and found them to be composed of 100 % glucose with 2-linked glucose as the most abundant residue, with terminal glucose, 2,3-linked and 2,6-linked glucose also present in high quantities. The two structural genes for OPG biosynthesis, opgG and opgH, form a bicistronic operon, and insertion of a kanamycin resistance gene cassette into this operon resulted in a strain devoid of OPGs. The opgGH mutant strain was impaired in motility and growth under low osmolarity conditions. The opgGH mutation also resulted in a 2 log increase in the LD 50 in mice compared to the wild-type strain SL1344. Inability to synthesize OPGs had no significant impact on the organism's lipopolysaccharide pattern or its ability to survive antimicrobial peptides-, detergent-, pH-and nutrient-stress conditions. We observed that the opgGH-defective strain respired at a reduced rate under acidic growth conditions (pH 5.0) and had lower ATP levels compared to the wild-type strain. These data indicate that OPGs of S. Typhimurium contribute towards mouse virulence as well as growth and motility under low osmolarity growth conditions.
Two Gram-negative-staining, aerobic, non-motile, rod-shaped bacteria, designated strains FFA1T and FFA3T, and belonging to the class Gammaproteobacteria were isolated from the gastrointestinal tract of adult flesh flies (Diptera: Sarcophagidae). Phylogenetic analysis of 16S rRNA gene sequence data placed these two strains within the genus Ignatzschineria with similarities of 98.6 % (FFA1T) and 99.35 % (FFA3T) to Ignatzschineria larvae L1/68T. The level of gene sequence similarity between strains FFA1T and FFA3T was 99 %, 97.15 % and 78.1 % based on the 16S rRNA, 23S rRNA and gyrB gene sequences, respectively. Strains FFA1T and FFA3T shared 24 % DNA–DNA relatedness. DNA–DNA hybridization revealed a very low level of relatedness between the novel strains (22 % for strain FFA1T and 44 % for strain FFA3T) and I. larvae L1/68T genomic DNA. The respiratory quinone was Q-8 in both novel strains. The DNA G+C contents were 41.1 mol% and 40.1 mol% for strains FFA1T and FFA3T, respectively. The cell membrane of both strains consisted of phosphatidylglycerol, phosphatidylethanolamine, phospholipids and aminophospholipid. The major fatty acids for both strains were C16 : 0, summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), CyC19 : 0ω8c and C14 : 0. The results of DNA–DNA hybridization between the two new strains and I. larvae L1/68T, in combination with phylogenetic, chemotaxonomic, biochemical and electron microscopic data, demonstrated that strains FFA1T and FFA3T represented two novel species of the genus Ignatzschineria for which the names Ignatzschineria indica sp. nov. (type strain FFA1T = DSM 22309T = KCTC 22643T = NCIM 5325T) and Ignatzschineria ureiclastica sp. nov. (type strain FFA3T = DSM 22310T = KCTC 22644T = NCIM 5326T) are proposed.
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