Journal of Microbiology

Journal Article

Tubulysins are Essential for the Preying of Ciliates by Myxobacteria: Uisang Yu , Jiha Kim , Seohui Park , Kyungyun Cho; J. Microbiol. 2023;61(6):627-632. Published online June 14, 2023; DOI: https://doi.org/10.1007/s12275-023-00056-2

Abstract: Tubulysins are bioactive secondary metabolites produced by myxobacteria that promote microtubule disassembly. Microtubules are required for protozoa such as Tetrahymena to form cilia and flagella. To study the role of tubulysins in myxobacteria, we co-cultured myxobacteria and Tetrahymena. When 4000 Tetrahymena thermophila and 5.0 × 108 myxobacteria were added to 1 ml of CYSE medium and co-cultured for 48 h, the population of T. thermophila increased to more than 75,000. However, co-culturing tubulysin-producing myxobacteria, including Archangium gephyra KYC5002, with T. thermophila caused the population of T. thermophila to decrease from 4000 to less than 83 within 48 h. Almost no dead bodies of T. thermophila were observed in the culture medium. Co-culturing of T. thermophila and the A. gephyra KYC5002 strain with inactivation of the tubulysin biosynthesis gene led to the population of T. thermophila increasing to 46,667. These results show that in nature, most myxobacteria are preyed upon by T. thermophila, but some myxobacteria prey on and kill T. thermophila using tubulysins. Adding purified tubulysin A to T. thermophila changed the cell shape from ovoid to spherical and caused cell surface cilia to disappear.

Review

Protective and pathogenic role of humoral responses in COVID-19: Uni Park , Nam-Hyuk Cho; J. Microbiol. 2022;60(3):268-275. Published online March 2, 2022; DOI: https://doi.org/10.1007/s12275-022-2037-8

Abstract: Since the advent of SARS-CoV-2 in Dec. 2019, the global endeavor to identify the pathogenic mechanism of COVID-19 has been ongoing. Although humoral immunity including neutralizing activity play an important role in protection from the viral pathogen, dysregulated antibody responses may be associated with the pathogenic progression of COVID-19, especially in high-risk individuals. In addition, SARS-CoV-2 spike-specific antibodies acquired by prior infection or vaccination act as immune pressure, driving continuous population turnover by selecting for antibody-escaping mutations. Here, we review accumulating knowledge on the potential role of humoral immune responses in COVID-19, primarily focusing on their beneficial and pathogenic properties. Understanding the multifaceted regulatory mechanisms of humoral responses during SARS-CoV-2 infection can help us to develop more effective therapeutics, as well as protective measures against the ongoing pandemic.

Journal Article

Differences in seroprevalence between epicenter and non-epicenter areas of the COVID-19 outbreak in South Korea: Hye Won Jeong , Hyun-Ha Chang , Eun Ji Kim , Yu Kyung Kim , Se-Mi Kim , Eun-Ha Kim , Young-Il Kim , Mark Anthony B. Casel , Seong-Gyu Kim , Rare Rollon , Seung-Gyu Jang , Kwang-Min Yu , Hee-Sung Kim , Hee Sue Park , Su-Jin Park , Yong-Dae Kim , Eung-Gook Kim , Young Ki Choi; J. Microbiol. 2021;59(5):530-533. Published online April 28, 2021; DOI: https://doi.org/10.1007/s12275-021-1095-7

Abstract: To compare the standardized severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence of high epicenter region with non-epicenter region, serological studies were performed with a total of 3,268 sera from Daegu City and 3,981 sera from Chungbuk Province. Indirect immunofluorescence assay (IFA) for SARS-CoV-2 IgG results showed a high seroprevalence rate in the Daegu City (epicenter) compared with a non-epicenter area (Chungbuk Province) (1.27% vs. 0.91%, P = 0.0358). It is noteworthy that the highest seroprevalence in Daegu City was found in elderly patients (70’s) whereas young adult patients (20’s) in Chungbuk Province showed the highest seroprevalence. Neutralizing antibody (NAb) titers were found in three samples from Daegu City (3/3, 268, 0.09%) while none of the samples from Chungbuk Province were NAb positive. These results demonstrated that even following the large outbreak, the seropositive rate of SARS-CoV-2 in the general population remained low in South Korea.

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