Journal of Microbiology

Reviews

The Role of Extracellular Vesicles in Pandemic Viral Infections.: Woosung Shim, Anjae Lee, Jung-Hyun Lee; J. Microbiol. 2024;62(6):419-427. Published online June 25, 2024; DOI: https://doi.org/10.1007/s12275-024-00144-x

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Abstract: Extracellular vesicles (EVs), of diverse origin and content, are membranous structures secreted by a broad range of cell types. Recent advances in molecular biology have highlighted the pivotal role of EVs in mediating intercellular communication, facilitated by their ability to transport a diverse range of biomolecules, including proteins, lipids, DNA, RNA and metabolites. A striking feature of EVs is their ability to exert dual effects during viral infections, involving both proviral and antiviral effects. This review explores the dual roles of EVs, particularly in the context of pandemic viruses such as HIV-1 and SARS-CoV-2. On the one hand, EVs can enhance viral replication and exacerbate pathogenesis by transferring viral components to susceptible cells. On the other hand, they have intrinsic antiviral properties, including activation of immune responses and direct inhibition of viral infection. By exploring these contrasting functions, our review emphasizes the complexity of EV-mediated interactions in viral pathogenesis and highlights their potential as targets for therapeutic intervention. The insights obtained from investigating EVs in the context of HIV-1 and SARS-CoV-2 provide a deeper understanding of viral mechanisms and pathologies, and offer a new perspective on managing and mitigating the impact of these global health challenges.

MAPK Cascades in Plant Microbiota Structure and Functioning: Thijs Van Gerrewey, Hoo Sun Chung; J. Microbiol. 2024;62(3):231-248. Published online April 8, 2024; DOI: https://doi.org/10.1007/s12275-024-00114-3

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Abstract: Mitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules that coordinate diverse biological processes such as plant innate immunity and development. Recently, MAPK cascades have emerged as pivotal regulators of the plant holobiont, infuencing the assembly of normal plant microbiota, essential for maintaining optimal plant growth and health. In this review, we provide an overview of current knowledge on MAPK cascades, from upstream perception of microbial stimuli to downstream host responses. Synthesizing recent fndings, we explore the intricate connections between MAPK signaling and the assembly and functioning of plant microbiota. Additionally, the role of MAPK activation in orchestrating dynamic changes in root exudation to shape microbiota composition is discussed. Finally, our review concludes by emphasizing the necessity for more sophisticated techniques to accurately decipher the role of MAPK signaling in establishing the plant holobiont relationship.

Journal Articles

Description of Fervidibacillus gen. nov. with Two Species, Fervidibacillus albus sp. nov., and Fervidibacillus halotolerans sp. nov., Isolated from Tidal Flat Sediments and Emendation of Misclassificed Taxa in the Genus Caldibacillus: Sung&# , Mi&# , Hyun&# , Kae Kyoung Kwon; J. Microbiol. 2023;61(2):175-187. Published online February 17, 2023; DOI: https://doi.org/10.1007/s12275-023-00022-y

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Abstract: Two Gram-stain-positive, motile, endospore-forming, facultatively anaerobic strains, designated MEBiC13591T and MEBiC13594T, were isolated from tidal flat sediment of the Incheon City on the west coast of Korea. Growth of both novel strains was observed at pH 5–9 (optimum, pH 7–7.5), and in 0–8% NaCl (optimum, 2% for MEBiC13591T and 3% for MEBiC13594T). Strains MEBiC13591T and MEBiC13594T grew optimally at 50 °C, (37.5–56.1 °C) and 44 °C (20.7–50.7 °C), respectively. The main cellular fatty acids of strain MEBiC13591T were iso-C15: 0, anteiso-C15: 0, iso-C16: 0, iso-C17: 0 and anteiso-C17: 0, while those for strain MEBiC13594T were C14: 0, iso-C14: 0, iso-C15: 0, anteiso-C15: 0 and C16: 0. In both taxa, the major isoprenoid was MK-7. The genomic DNA G + C contents were 34.1 and 37.0 mol% for MEBiC13591T and MEBiC13594T, respectively. A 16S rRNA gene sequence analysis revealed that the novel strains showed high similarity with members of the genera Aeribacillus (95.0%) and Caldibacillus (93.5–94.5%); however, showed lower than 90% with Caldibacillus debilis TfT. Phylogenetic and Phylogenomic analysis revealed that two novel strains comprised distinct phyletic line with members formerly assigned to Caldibacillus. Based on genomic indices, such as AAI and ANI, members formerly affiliated with Caldibacillus and Bacillus as well as the novel strains should be classified into five independent genera. Based on the phenotypic, genomic and biochemical data, strains MEBiC13591T and MEBiC13594T represent two novel species in the novel genus, for which the names Fervidibacillus albus gen. nov., sp. nov. ( MEBiC13591T [= KCCM 43317T = KCTC 43181T = JCM 33662T = MCCC 1K04565T]), and Fervidibacillus halotolerans sp. nov. ( MEBiC13594T [= KCTC 43182T = JCM 34001T]) are proposed. Three additional genera Caldifermentibacillus, Palidibacillus, and Perspicuibacillus are also proposed by reclassification of the several species with valid names that formerly affiliated with the genera Caldibacillus.

Non-mitochondrial aconitase regulates the expression of iron-uptake genes by controlling the RNA turnover process in fission yeast: Soo-Yeon Cho , Soo-Jin Jung , Kyoung-Dong Kim , Jung-Hye Roe; J. Microbiol. 2021;59(12):1075-1082. Published online October 26, 2021; DOI: https://doi.org/10.1007/s12275-021-1438-4

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Abstract: Aconitase, a highly conserved protein across all domains of life, functions in converting citrate to isocitrate in the tricarboxylic acid cycle. Cytosolic aconitase is also known to act as an iron regulatory protein in mammals, binding to the RNA hairpin structures known as iron-responsive elements within the untranslated regions of specific RNAs. Aconitase-2 (Aco2) in fission yeast is a fusion protein consisting of an aconitase and a mitochondrial ribosomal protein, bL21, residing not only in mitochondria but also in cytosol and the nucleus. To investigate the role of Aco2 in the nucleus and cytoplasm of fission yeast, we analyzed the transcriptome of aco2ΔN mutant that is deleted of nuclear localization signal (NLS). RNA sequencing revealed that the aco2ΔN mutation caused increase in mRNAs encoding iron uptake transporters, such as Str1, Str3, and Shu1. The half-lives of mRNAs for these genes were found to be significantly longer in the aco2ΔN mutant than the wild-type strain, suggesting the role of Aco2 in mRNA turnover. The three conserved cysteines required for the catalytic activity of aconitase were not necessary for this role. The UV cross-linking RNA immunoprecipitation analysis revealed that Aco2 directly bound to the mRNAs of iron uptake transporters. Aco2-mediated degradation of iron-uptake mRNAs appears to utilize exoribonuclease pathway that involves Rrp6 as evidenced by genetic interactions. These results reveal a novel role of non-mitochondrial aconitase protein in the mRNA turnover in fission yeast to fine-tune iron homeostasis, independent of regulation by transcriptional repressor Fep1.

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