Journal of Microbiology

Journal Article

Exploring the Therapeutic Potential of Scorpion‑Derived Css54 Peptide Against Candida albicans: Jonggwan Park , Hyeongsun Kim , Da Dam Kang , Yoonkyung Park; J. Microbiol. 2024;62(2):101-112. Published online April 8, 2024; DOI: https://doi.org/10.1007/s12275-024-00113-4

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Abstract: Candida albicans (C. albicans) is one of the most common opportunistic fungi worldwide, which is associated with a high mortality rate. Despite treatment, C. albicans remains the leading cause of life-threatening invasive infections. Consequently, antimicrobial peptides (AMPs) are potential alternatives as antifungal agents with excellent antifungal activity. We previously reported that Css54, found in the venom of Centrurodies suffusus suffusus (C. s. suffusus) showed antibacterial activity against zoonotic bacteria. However, the antifungal activity of Css54 has not yet been elucidated. The obj!ective of this study was to identify the antifungal activity of Css54 against C. albicans and analyze its mechanism. Css54 showed high antifungal activity against C. albicans. Css54 also inhibited biofilm formation in fluconazole-resistant fungi. The antifungal mechanism of action of Css54 was investigated using membrane-related assays, including the membrane depolarization assay and analysis of the membrane integrity of C. albicans after treatment with Css54. Css54 induced reactive oxygen species (ROS) production in C. albicans, which affected its antifungal activity. Our results indicate that Css54 causes membrane damage in C. albicans, highlighting its value as a potential therapeutic agent against C. albicans infection.

Editorial

Editorial] Bacterial Regulatory Mechanisms for the Control of Cellular Processes: Simple Organisms’ Complex Regulation: Jin-Won Lee; J. Microbiol. 2023;61(3):273-276. Published online April 3, 2023; DOI: https://doi.org/10.1007/s12275-023-00036-6

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Abstract: Bacteria employ a diverse array of cellular regulatory mechanisms to successfully adapt and thrive in ever-changing environments, including but not limited to temperature changes, fluctuations in nutrient availability, the presence or absence of electron acceptors such as oxygen, the availability of metal ions crucial for enzyme activity, and the existence of antibiotics. Bacteria can virtually modulate any step of gene expression from transcr!ptional initiation to posttranslational modification of a protein for the control of cellular processes. Furthermore, one gene regulator often controls another in a complex gene regulatory network. Thus, it is not easy to fully understand the intricacies of bacterial regulatory mechanisms in various environments. In this special issue, while acknowledging the challenge of covering all aspects of bacterial regulatory mechanisms across diverse environments, seven review articles are included to provide insight into the recent progress in understanding such mechanisms from different perspectives: positive regulatory mechanisms by secondary messenger (cAMP receptor protein), two-component signal transduction mechanisms (Rcs and Cpx), diverse regulatory mechanisms by a specific environmental factor in specific bacteria (oxygen availability in Mycobacterium and manganese ion availability in Salmonella), diverse regulatory mechanisms by a specific environmental factor (temperature and antibiotics), and regulatory mechanisms by antibiotics in cell wall synthesis. Bacteria, as ubiquitous organisms that can be found in almost every environment, carry out complex cellular processes that allow them to survive and thrive in a variety of different conditions despite their small size and relative simplicity. One of the key factors that allows bacteria to carry out these complex processes is their ability to regulate gene expression through various mechanisms. Gene expression is a fundamental biological process by which the genetic information encoded in a gene is transcribed into an RNA molecule and subsequently translated into a functional gene product, often a protein. Furthermore, the activity levels of proteins may further be altered by posttranslational modification. Regulation of gene expression refers to the control of the amount and timing of gene expression, and thus it can be divided into transcr!ptional, translational, and posttranslational levels.

Journal Articles

Light affects picocyanobacterial grazing and growth response of the mixotrophic flagellate Poterioochromonas malhamensis: Thomas Weisse , Michael Moser; J. Microbiol. 2020;58(4):268-278. Published online January 28, 2020; DOI: https://doi.org/10.1007/s12275-020-9567-8

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Abstract: We measured the grazing and growth response of the mixotrophic chrysomonad flagellate Poterioochromonas malhamensis on four closely related picocyanobacterial strains isolated from subalpine lakes in central Europe. The picocyanobacteria represented different pigment types (phycoerythrin- rich, PE, and phycocyanin-rich, PC) and phylogenetic clusters. The grazing experiments were conducted with laboratory cultures acclimated to 10 μmol photon/m2/sec (low light, LL) and 100 μmol photon/m2/sec (moderate light, ML), either in the dark or at four different irradiances ranging from low (6 μmol photon/m2/sec) to high (1,500 μmol photon/m2/ sec) light intensity. Poterioochromonas malhamensis preferred the larger, green PC-rich picocyanobacteria to the smaller, red PE-rich picocyanobacterial, and heterotrophic bacteria. The feeding and growth rates of P. malhamensis were sensitive to the actual light conditions during the experiments; the flagellate performed relatively better in the dark and at LL conditions than at high light intensity. In summary, our
results
found strain-specific ingestion and growth rates of the flagellate; an effect of the preculturing conditions, and, unexpectedly, a direct adverse effect of high light levels. We conclude that this flagellate may avoid exposure to high surface light intensities commonly encountered in temperate lakes during the summer.

[Protocol] Detecting Salmonella Type II flagella production by transmission electron microscopy and immunocytochemistry: Yoontak Han , Eun-Jin Lee; J. Microbiol. 2020;58(4):245-251. Published online November 23, 2019; DOI: https://doi.org/10.1007/s12275-020-9297-y

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Abstract: The bacterial flagellum is an appendage structure that provides a means for motility to promote survival in fluctuating environments. For the intracellular pathogen Salmonella enterica serovar Typhimurium to survive within macrophages, flagellar gene expression must be tightly regulated, and thus, is controlled at multiple levels, including DNA recombination, transcription, post-transcription, protein synthesis, and assembly within host cells. To understand the contribution of flagella to Salmonella pathogenesis within the host, it is critical to detect flagella production within macrophages via microscopy. In this paper, we describe two methods for detecting bacterial flagella by microscopy both in vitro and in vivo infection models.

Research Support, Non-U.S. Gov't

Structural and Functional Importance of Outer Membrane Proteins in Vibrio cholerae Flagellum: Wasimul Bari , Kang-Mu Lee , Sang Sun Yoon; J. Microbiol. 2012;50(4):631-637. Published online August 25, 2012; DOI: https://doi.org/10.1007/s12275-012-2116-3

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Abstract: Vibrio cholerae has a sheath-covered monotrichous flagellum that is known to contribute to virulence. Although the structural organization of the V. cholerae flagellum has been extensively studied, the involvement of outer membrane proteins as integral components in the flagellum still remains elusive. Here we show that flagella produced by V. cholerae O1 El Tor strain C6706 were two times thicker than those from two other Gram-negative bacteria. A C6706 mutant strain (SSY11) devoid of two outer membrane proteins (OMPs), OmpU and OmpT, produced thinner flagella. SSY11 showed significant defects in the flagella-mediated motility as compared to its parental strain. Moreover, increased shedding of the flagella-associated proteins was observed in the culture supernatant of SSY11. This finding was also supported by the observation that culture supernatants of the SSY11 strain induced the production of a significantly higher level of IL-8 in human colon carcinoma HT29 and alveolar epithelial A549 cells than those of the wild-type C6706 strain. These results further suggest a definite role of these two OMPs in providing the structural integrity of the V. cholerae flagellum as part of the surrounding sheath.

Review

REVIEW] Dinoflagellates, Diatoms, and Their Viruses: Keizo Nagasaki; J. Microbiol. 2008;46(3):235-243. Published online July 5, 2008; DOI: https://doi.org/10.1007/s12275-008-0098-y

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107 Citations

Abstract: Since the first discovery of the very high virus abundance in marine environments, a number of researchers were fascinated with the world of “marine viruses”, which had previously been mostly overlooked in studies on marine ecosystems. In the present paper, the possible role of viruses infecting marine eukaryotic microalgae is enlightened, especially summarizing the most up-to-the-minute information of marine viruses infecting bloom-forming dinoflagellates and diatoms. To author’s knowledge, ~40 viruses infecting marine eukaryotic algae have been isolated and characterized to different extents. Among them, a double-stranded DNA (dsDNA) virus “HcV” and a single-stranded RNA (ssRNA) virus “HcRNAV” are the only dinoflagellate-infecting (lytic) viruses that were made into culture; their hosts are a bivalve-killing dinoflagellate Heterocapsa circularisquama. In this article, ecological relationship between H. circularisquama and its viruses is focused. On the other hand, several diatom-infecting viruses were recently isolated and partially characterized; among them, one is infectious to a pen-shaped bloom-forming diatom species Rhizosolenia setigera; some viruses are infectious to genus Chaetoceros which is one of the most abundant and diverse diatom group. Although the ecological relationships between diatoms and their viruses have not been sufficiently elucidated, viral infection is considered to be one of the significant factors affecting dynamics of diatoms in nature. Besides, both the dinoflagellate-infecting viruses and diatom-infecting viruses are so unique from the viewpoint of virus taxonomy; they are remarkably different from any other viruses ever reported. Studies on these viruses lead to an idea that ocean may be a treasury of novel viruses equipped with fascinating functions and ecological roles.

rpoS mutation relieves biosynthesis of flagella in hns mutants of salmonella typhimurium UK1: Cho, Mi Ook , Bang, Ile Soo , Hong, Seong Karp , Bang, Seong Ho , Park, Yong Keun; J. Microbiol. 1998;36(3):184-188.

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Abstract: The biosynthesis and function of flagella is positively regulated by the cyclic AMP-catabolite activator protein (cAMP-CAP) complex and the nucleoid protein H-NS. In this report, we show that nonmotile Salmonella typhimurium hns mutants could recover its motility by introducing the rpoSmutation. In a swarm plate assay, rpoS/hns double mutants could woim while hns mutants could not. This regeneration of motility resulted from the flagella synthesis. Transmission electron microscopy analysis showed the capability of rpoS/hns double mutants for flagella synthesis. And rpoS mutation derepressed the transcription of flhD, the flagella master gene, in hns mutants.

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