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Shigella: Insights into the Clinical Features, Pathogenesis, Diagnosis, and Treatment Strategies
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Periyanaina Kesika, Bhagavathi Sundaram Sivamaruthi, Krishnaswamy Balamurugan
Regulation of the microbial virulence mechanism is necessary to cause persistent infection. Microbial pathogenesis is regulated by several effectors, including riboregulators (RNA-mediated gene regulation). In Shigella, riboregulators are involved in the direct and indirect environmental adaptation of bacterium, and the combined regulation of pathogenesis. The regulators of carbon metabolism, CsrA, CsrB, and CsrC, in E. coli are conserved in Shigella, which are responsible for the activation and suppression of machinery required for glycolysis and gluconeogenesis, respectively. CsrA activity is directly linked to the pathogenicity of S. flexneri, and loss of function of CsrB and CsrC mutation increased the ability of the bacterium to invade the host cells effectively.116 Moreover, CsrA influences the structural changes of Shigella LPS and affects the T3SS.86
Applications of the CRISPR-Cas system for infectious disease diagnostics
Published in Expert Review of Molecular Diagnostics, 2021
Peipei Li, Li Wang, Junning Yang, Li-Jun Di, Jingjing Li
Pardee et al. developed nucleic acid sequence-based amplification (NASBA)-CRISPR to discriminate American and African strains of Zika virus as well as detect Zika virus from plasma [39]. The sensitivity of this technology can reach 1–3 fM. The principle of this approach is associated with toehold switch sensors and the specific cleavage ability of Cas9 (Figure 1). Toehold switch sensors are synthetic riboregulators that control LacZ translation by binding RNA. In the absence of binding RNA, the hairpin structure of riboregulators impedes LacZ translation through sequestering the start codon and the ribosome-binding site. While the trigger RNA is complemented to the riboregulator, the start codon and the ribosome-binding site are exposed, and the translation of LacZ is initiated. Finally, LacZ catalyses the conversion of a yellow substrate to a purple product. Double-stranded DNA is generated by the NASBA reaction. When CRISPR-Cas9 cleaves dsDNA, the RNA product transcribed from cleaved dsDNA cannot activate the toehold switch sensor due to the lack of a sensor trigger sequence. In their research, they amplified Zika virus RNA using isothermal amplification, targeting the binding RNA of riboregulators.
Synthetic biology-based portable in vitro diagnostic platforms
Published in Alexandria Journal of Medicine, 2018
Almando Geraldi, Ernawati Arifin Giri-Rachman
RNA-based biosensors consist of genetic circuits with riboregulators that act as a switch (Fig. 2A).17 The genetic circuit would be activated, expressing the reporter gene, upon the binding of target biomarker RNA to the riboregulator. Until recently, riboregulators relied on cis-repression sequence to sequester the ribosomal binding site (RBS) for controlling the translation of the downstream mRNA. In the presence of higher affinity RNA molecule (the transactivator), the RBS is exposed, and translation ensues. The application of RNA-based biosensors with this conventional riboregulator is very limited, mainly due to the sequence constraints of the transactivator (target biomarker RNA), which need to contain the RBS sequence.9