Journal of Microbiology

Volume 61(10); October 2023

Review

Prions in Microbes: The Least in the Most: Moonil Son , Sia Han , Seyeon Lee; J. Microbiol. 2023;61(10):881-889. Published online September 5, 2023; DOI: https://doi.org/10.1007/s12275-023-00070-4

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Abstract: Prions are infectious proteins that mostly replicate in self-propagating amyloid conformations (filamentous protein polymers) and consist of structurally altered normal soluble proteins. Prions can arise spontaneously in the cell without any clear reason and are generally considered fatal disease-causing agents that are only present in mammals. However, after the seminal discovery of two prions, [PSI+] and [URE3], in the eukaryotic model microorganism Saccharomyces cerevisiae, at least ten more prions have been discovered, and their biological and pathological effects on the host, molecular structure, and the relationship between prions and cellular components have been studied. In a filamentous fungus model, Podospora anserina, a vegetative incomparability-related [Het-s] prion that directly triggers cell death during anastomosis (hyphal fusion) was discovered. These prions in eukaryotic microbes have extended our understanding to overcome most fatal human prion/amyloid diseases. A prokaryotic microorganism (Clostridium botulinum) was reported to have a prion analog. The transcriptional regulators of C. botulinum-Rho can be converted into the self-replicating prion form ([RHO-X-C+]), which may affect global transcription. Here, we outline the major issues with prions in microbes and the lessons learned from the relatively uncovered microbial prion world.

Journal Articles

Flavobacterium psychrotrophum sp. nov. and Flavobacterium panacagri sp. nov., Isolated from Freshwater and Soil: Yong-Seok Kim , Eun-Mi Hwang , Chang-Myeong Jeong , Chang-Jun Cha; J. Microbiol. 2023;61(10):891-901. Published online October 18, 2023; DOI: https://doi.org/10.1007/s12275-023-00081-1

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Abstract: Two novel bacterial strains CJ74T and CJ75T belonging to the genus Flavobacterium were isolated from freshwater of Han River and ginseng soil, South Korea, respectively. Strain CJ74T was Gram-stain-negative, aerobic, rod-shaped, non-motile, and non-flagellated, and did not produce flexirubin-type pigments. Strain CJ75T was Gram-stain-negative, aerobic, rodshaped, motile by gliding, and non-flagellated, and produced flexirubin-type pigments. Both strains were shown to grow optimally at 30 °C in the absence of NaCl on R2A medium. Phylogenetic analysis based on 16S rRNA gene sequences showed that strains CJ74T and CJ75T belonged to the genus Flavobacterium and were most closely related to Flavobacterium niveum TAPW14T and Flavobacterium foetidum CJ42T with 96.17% and 97.29% 16S rRNA sequence similarities, respectively. Genomic analyses including the reconstruction of phylogenomic tree, average nucleotide identity, and digital DNA-DNA hybridization suggested that they were novel species of the genus Flavobacterium. Both strains contained menaquinone 6 (MK-6) as the primary respiratory quinone and phosphatidylethanolamine as a major polar lipid. The predominant fatty acids of both strains were iso-C15:0 and summed feature 3 ( C16:1 ω7c and/or C16: 1 ω6c). Based on the polyphasic taxonomic study, strains CJ74T and CJ75T represent novel species of the genus Flavobacterium, for which names Flavobacterium psychrotrophum sp. nov. and Flavobacterium panacagri sp. nov. are proposed, respectively. The type strains are CJ74T (=KACC 19819T =JCM 32889T) and CJ75T (=KACC 23149T =JCM 36132T).

Impact of Elevational Gradients and Chemical Parameters on Changes in Soil Bacterial Diversity Under Semiarid Mountain Region: Salman Khan , Chun Han , Awais Iqbal , Chao Guan , Changming Zhao; J. Microbiol. 2023;61(10):903-915. Published online November 23, 2023; DOI: https://doi.org/10.1007/s12275-023-00085-x

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Abstract: Elevation gradients, often regarded as “natural experiments or laboratories”, can be used to study changes in the distribution of microbial diversity related to changes in environmental conditions that typically occur over small geographical scales. We obtained bacterial sequences using MiSeq sequencing and clustered them into operational taxonomic units (OTUs). The total number of reads obtained by the bacterial 16S rRNA sequencing analysis was 1,090,555, with an average of approximately 45,439 reads per sample collected from various elevations. The current study observed inconsistent bacterial diversity patterns in samples from the lowest to highest elevations. 983 OTUs were found common among all the elevations. The most unique OTUs were found in the soil sample from elevation_2, followed by elevation_1. Soil sample collected at elevation_6 had the least unique OTUs. Actinobacteria, Protobacteria, Chloroflexi were found most abundant bacterial phyla in current study. Ammonium nitrogen ( NH4 +-N), and total phosphate (TP) are the main factors influencing bacterial diversity at elevations_ 1. pH was the main factor influencing the bacterial diversity at elevations_2, elevation_3 and elevation_4. Our results provide new visions on forming and maintaining soil microbial diversity along an elevational gradient and have implications for microbial responses to environmental change in semiarid mountain ecosystems.

Quantitative Analysis of RNA Polymerase Slippages for Production of P3N‑PIPO Trans‑frame Fusion Proteins in Potyvirids: Dongjin Choi , Yoonsoo Hahn; J. Microbiol. 2023;61(10):917-927. Published online October 16, 2023; DOI: https://doi.org/10.1007/s12275-023-00083-z

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Abstract: Potyvirids, members of the family Potyviridae, produce the P3N-PIPO protein, which is crucial for the cell-to-cell transport of viral genomic RNAs. The production of P3N-PIPO requires an adenine (A) insertion caused by RNA polymerase slippage at a conserved GAA AAA A ( GA6) sequence preceding the PIPO open reading frame. Presently, the slippage rate of RNA polymerase has been estimated in only a few potyvirids, ranging from 0.8 to 2.1%. In this study, we analyzed publicly available plant RNA-seq data and identified 19 genome contigs from 13 distinct potyvirids. We further investigated the RNA polymerase slippage rates at the GA6 motif. Our analysis revealed that the frequency of the A insertion variant ranges from 0.53 to 4.07% in 11 potyviruses (genus Potyvirus). For the two macluraviruses (genus Macluravirus), the frequency of the A insertion variant was found to be 0.72% and 10.96% respectively. Notably, the estimated RNA polymerase slippage rates for 12 out of the 13 investigated potyvirids were reported for the first time in this study. Our findings underscore the value of plant RNA-seq data for quantitative analysis of potyvirid genome variants, specifically at the GA6 slippage site, and contribute to a more comprehensive understanding of the RNA polymerase slippage phenomenon in potyvirids.

Development of a Novel Korean H9‑Specific rRT‑PCR Assay and Its Application for Avian Influenza Virus Surveillance in Korea: Mingeun Sagong , Yong-Myung Kang , Na Yeong Kim , Eun Bi Noh , Gyeong-Beom Heo , Se-Hee An , Youn-Jeong Lee , Young Ki Choi , Kwang-Nyeong Lee; J. Microbiol. 2023;61(10):929-936. Published online November 27, 2023; DOI: https://doi.org/10.1007/s12275-023-00088-8

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Abstract: Since the 2000s, the Y439 lineage of H9N2 avian influenza virus (AIV) has been the predominant strain circulating in poultry in Korea; however, in 2020, the Y280 lineage emerged and spread rapidly nationwide, causing large economic losses. To prevent further spread and circulation of such viruses, rapid detection and diagnosis through active surveillance programs are crucial. Here, we developed a novel H9 rRT-PCR assay that can detect a broad range of H9Nx viruses in situations in which multiple lineages of H9 AIVs are co-circulating. We then evaluated its efficacy using a large number of clinical samples. The assay, named the Uni Kor-H9 assay, showed high sensitivity for Y280 lineage viruses, as well as for the Y439 lineage originating in Korean poultry and wild birds. In addition, the assay showed no cross-reactivity with other subtypes of AIV or other avian pathogens. Furthermore, the Uni Kor-H9 assay was more sensitive, and had higher detection rates, than reference H9 rRT-PCR methods when tested against a panel of domestically isolated H9 AIVs. In conclusion, the novel Uni Kor-H9 assay enables more rapid and efficient diagnosis than the “traditional” method of virus isolation followed by subtyping RT-PCR. Application of the new H9 rRT-PCR assay to AI active surveillance programs will help to control and manage Korean H9 AIVs more efficiently.

Published Erratum

Erratum to: UBCG2: Up‑to‑Date Bacterial Core Genes and Pipeline for Phylogenomic Analysis: Jihyeon Kim , Seong-In Na , Dongwook Kim , Jongsik Chun; J. Microbiol. 2023;61(10):937-937.; DOI: https://doi.org/10.1007/s12275-023-00074-0

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