Journal of Microbiology

Review

Balancing Act of the Intestinal Antimicrobial Proteins on Gut Microbiota and Health: Ye Eun Ra, Ye‑Ji Bang; J. Microbiol. 2024;62(3):167-179. Published online April 17, 2024; DOI: https://doi.org/10.1007/s12275-024-00122-3

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Abstract: The human gut houses a diverse and dynamic microbiome critical for digestion, metabolism, and immune development, exerting profound efects on human health. However, these microorganisms pose a potential threat by breaching the gut barrier, entering host tissues, and triggering infections, uncontrolled infammation, and even sepsis. The intestinal epithelial cells form the primary defense, acting as a frontline barrier against microbial invasion. Antimicrobial proteins (AMPs), produced by these cells, serve as innate immune efectors that regulate the gut microbiome by directly killing or inhibiting microbes. Abnormal AMP production, whether insufcient or excessive, can disturb the microbiome equilibrium, contributing to various intestinal diseases. This review delves into the complex interactions between AMPs and the gut microbiota and sheds light on the role of AMPs in governing host-microbiota interactions. We discuss the function and mechanisms of action of AMPs, their regulation by the gut microbiota, microbial evasion strategies, and the consequences of AMP dysregulation in disease. Understanding these complex interactions between AMPs and the gut microbiota is crucial for developing strategies to enhance immune responses and combat infections within the gut microbiota. Ongoing research continues to uncover novel aspects of this intricate relationship, deepening our understanding of the factors shaping gut health. This knowledge has the potential to revolutionize therapeutic interventions, ofering enhanced treatments for a wide range of gut-related diseases.

Journal Articles

Description of Vagococcus coleopterorum sp. nov., isolated from the intestine of the diving beetle, Cybister lewisianus, and Vagococcus hydrophili sp. nov., isolated from the intestine of the dark diving beetle, Hydrophilus acuminatus, and emended description of the genus Vagococcus: Dong-Wook Hyun , Euon Jung Tak , Pil Soo Kim , Jin-Woo Bae; J. Microbiol. 2021;59(2):132-141. Published online December 23, 2020; DOI: https://doi.org/10.1007/s12275-021-0485-1

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Abstract: A polyphasic taxonomic approach was used to characterize two novel bacterial strains, HDW17AT and HDW17BT, isolated from the intestine of the diving beetle Cybister lewisianus, and the dark diving beetle Hydrophilus acuminatus, respectively. Both strains were Gram-positive and facultative anaerobic cocci forming cream-colored colonies. The isolates grew optimally at 25°C, pH 7, in the presence of 0.3% (wt/vol) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences and genome sequences showed that the isolates were members of the genus Vagococcus, and strain HDW17AT was closely related to Vagococcus fessus CCUG 41755T (98.9% of 16S rRNA gene sequence similarity and 74.3% of average nucleotide identity [ANI]), whereas strain HDW17BT was closely related to Vagococcus fluvialis NCFB 2497T (98.9% of 16S rRNA gene sequence similarity and 76.6% of ANI). Both strains contained C16:0, and C18:1 ω9c as the major cellular fatty acids, but C16:1 ω9c was also observed only in strain HDW17BT as the major cellular fatty acid. The respiratory quinone of the isolates was MK-7. The major polar lipid components were phosphatidylglycerol, phosphatidylethanolamine, and diphosphatidylglycerol. The genomic DNA G + C content of strains HDW17AT and HDW17BT were 36.6 and 34.4%, respectively. Both strains had cell wall peptidoglycan composed of the amino acids L-alanine, glycine, D-glutamic acid, L-tryptophan, L-lysine, and L-aspartic acid, and the sugars ribose, glucose, and galactose. Based on phylogenetic, phenotypic, chemotaxonomic, and genotypic analyses, strains HDW17AT and HDW17BT represent two novel species in the genus Vagococcus. We propose the name Vagococcus coleopterorum sp. nov. for strain HDW17AT (= KACC 21348T = KCTC 49324T = JCM 33674T) and the name Vagococcus hydrophili sp. nov. for strain HDW17BT (= KACC 21349T = KCTC 49325T = JCM 33675T).

Pten gene deletion in intestinal epithelial cells enhances susceptibility to Salmonella Typhimurium infection in mice: Cody Howe , Jonathon Mitchell , Su Jin Kim , Eunok Im , Sang Hoon Rhee; J. Microbiol. 2019;57(11):1012-1018. Published online September 25, 2019; DOI: https://doi.org/10.1007/s12275-019-9320-3

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Abstract: Although phosphatase and tensin homolog (PTEN) is typically considered a tumor-suppressor gene, it was recently suggested that PTEN regulates TLR5-induced immune and inflammatory responses in intestinal epithelial cells (IECs), suggesting an immunomodulatory function of PTEN in the gut. However, this alternative function of PTEN has not yet been evaluated in an in vivo context of protection against enteropathogenic bacteria. To address this, we utilized IECrestricted Pten knockout (PtenΔIEC/ΔIEC) and littermate Pten+/+ mice. These mice were subjected to the streptomycin-pretreated mouse model of Salmonella infection, and subsequently given an oral gavage of a low inoculum (2 × 104 CFU) of Salmonella enterica serovar Typhimurium (S. Typhimurium). This bacterial infection not only increased the mortality of PtenΔIEC/ΔIEC mice compared to Pten+/+ mice, but also induced deleterious gastrointestinal inflammation in PtenΔIEC/ΔIEC mice manifested by massive histological damage to the intestinal mucosa. S. Typhimurium infection upregulated pro-inflammatory cytokine production in the intestine of PtenΔIEC/ΔIEC mice compared to controls. Furthermore, bacterial loads were greatly increased in the liver, mesenteric lymph node, and spleen of PtenΔIEC/ΔIEC mice compared to controls. Together, these results suggest that IEC-restricted Pten deficiency renders the host greatly susceptible to Salmonella infection and support an immuneregulatory role of PTEN in the gut.

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