Journal of Microbiology最新文献

Yeast prion [PSI+], an amyloid form of the translation termination factor Sup35p/eRF3, causes translational stop codon readthrough by sequestering functional Sup35p. This unique phenotype may be analyzed via [PSI+]-suppressible nonsense alleles, and has greatly contributed to the advancement in yeast prion research. For comparing canonical reporters, like chromosomal ade1-14 or ade2-1, and plasmid-borne ura3-14, the de novo generation and characteristics of [PSI+] was investigated across common yeast laboratory strains (BY4741, 74D-694, and 779-6A). The results showed significant variability in [PSI+] induction frequency among strains. [PSI+] was successfully induced in BY4741 and frequently in 74D-694 (via Ade+ selection), but not in 779-6A. Notably, [PSI+] clones, even from identical genetic backgrounds, displayed vastly different nonsense suppression phenotypes depending on the reporter allele used; resulting in diverse growth patterns and suppression levels. Quantitative analyses revealed that prion seed counts fluctuated significantly based on the detection allele and observed phenotype. Furthermore, Sup35p aggregate visualization revealed distinct structural patterns between BY4741 and 74D-694, indicating strain-specific differences. Transferring [PIN+] prion variants from different strains into a common [psi-][pin-] background yielded similar [PSI+] inducibility and seed numbers, suggesting that the observed phenotypic and quantitative diversities of [PSI+] prions stem primarily from the interplay between the specific reporter detection system and the host strain's genetic background rather than solely from inherent differences in the initial [PIN+] prion or fundamental changes in the [PSI+] protein itself. This study underscores the crucial need to consider both the detection methodology and host genetic context for accurate prion variant characterization.

Dual specificity phosphatases (DUSPs), a subfamily of the protein tyrosine phosphatase (PTP) family, dephosphorylate not only phosphotyrosine but also phosphoserine and phosphothreonine residues. Beyond the 26 members of this family in humans, DUSPs represent the only type of PTPs found across a wide range of microorganisms, including bacteria, archaea, and viruses. This review presents a comprehensive structural analysis of human and microbial DUSPs. These proteins commonly share core features, such as a typical DUSP fold, shallow active site pocket, signature active site motif known as the P-loop, and conserved aspartate residue that acts as a general acid/base. However, DUSPs from diverse microorganisms also display unique structural and functional characteristics. Pseudomonas aeruginosa TpbA is the only bacterial DUSP identified to date, while a second candidate was proposed in this review. Archaeal DUSPs are hyperthermostable, contain a unique motif in their P-loops, and employ dual general acid/base residues. Poxviral DUSPs are characterized by the formation of domain-swapped homodimers. The presence of DUSPs across all domains of life and viruses, along with their low specificity for phosphorylated amino acids and structural similarity to classical PTPs, suggests that DUSPs represent the ancestral form of PTPs.

Pyroptosis a lytic form of programmed cell death, is a crucial host defense mechanism against bacterial pathogens. While caspase-mediated pathways are central to pyroptosis, the involvement of apoptotic regulators such as Bak, Bax, and MCL-1 in bacterial infection-induced pyroptosis remains unclear. Here, we investigated how these BCL-2 family proteins modulate pyroptosis induced by Vibrio vulnificus and Salmonella enterica serovar Typhimurium in murine cells. In mouse embryonic fibroblasts (MEFs), both pathogens strongly induced Gbp2 expression and activated caspase‑11, whereas activation of caspase‑1 occurred only in macrophages, indicating engagement of both non-canonical and canonical pyroptosis pathways. Importantly, Bak-/- and Bax-/- MEFs exhibited significantly reduced Gbp2 upregulation and caspase-11 activation-an effect most pronounced in Bak-deficient cells leading to attenuated pyroptotic cell death. These data suggest that pro-apoptotic proteins, Bak and Bax, act as positive regulators that amplify the Gbp2-caspase-11 axis. Conversely, overexpression of the anti-apoptotic protein MCL‑1 had no significant impact on Gbp2 expression, caspase activation, membrane integrity, or LDH release, indicating that pyroptosis proceeds independently of MCL‑1 regulation. Collectively, our findings uncover a novel role for Bak and Bax in promoting Gbp2-driven pyroptosis during Gram-negative bacterial infections, while MCL‑1 does not impede this process. This work expands our understanding of the crosstalk between apoptotic and pyroptotic pathways in innate immune responses.

CRISPR-Cas9-based gene editing enables precise genetic modifications. However, its application to human cytomegalovirus (HCMV) remains challenging due to the large size of the viral genome and the essential roles of key regulatory genes. Here, we establish an optimized CRISPR-Cas9 system for precise labeling and functional analysis of HCMV immediate early (IE) genes. By integrating a multifunctional cassette encoding an auxin-inducible degron (AID), a self-cleaving peptide (P2A), and GFP into the viral genome via homology-directed repair (HDR), we achieved efficient knock-ins without reliance on bacterial artificial chromosome (BAC) cloning, a labor-intensive and time-consuming approach. We optimized delivery strategies, donor template designs, and component ratios to enhance HDR efficiency, significantly improving knock-in success rates. This system enables real-time fluorescent tracking and inducible protein degradation, allowing temporal control of essential viral proteins through auxin-mediated depletion. Our approach provides a powerful tool for dissecting the dynamic roles of viral proteins throughout the HCMV life cycle, facilitating a deeper understanding of viral pathogenesis and potential therapeutic targets.

The pho regulon plays a critical role in maintaining phosphate homeostasis in bacteria, with the PhoU protein functioning as a regulator that bridges the PhoB/PhoR two-component system and the PstSCAB2 phosphate transporter. While PhoU is known to suppress PhoR autophosphorylation under high phosphate conditions via interaction with its PAS domain, its broader regulatory functions remain elusive. Here, we investigated the role of the PhoU Ala147 residue in Salmonella enterica serovar Typhimurium using a phoUA147E substitution mutant. Bacterial two-hybrid and immunoprecipitation assays confirmed that Ala147 is essential for PhoU-PhoR PAS domain interaction, and its substitution leads to derepression of pho regulon genes, even in high phosphate conditions. This disruption impaired Salmonella survival inside macrophages and mouse virulence, demonstrating the importance of PhoU-PhoR interaction in Salmonella pathogenesis. However, unlike the phoU deletion mutant, the phoUA147E mutant does not exhibit growth defects or polyphosphate accumulation, indicating that the PhoU-PhoR interaction is not involved in these phenotypes. Our findings reveal PhoU as a multifaceted regulator, coordinating phosphate uptake and pho regulon expression through distinct molecular interactions, and provide new insights into its role in bacterial physiology and virulence.

Actinobacteria, a phylum of Gram-positive bacteria, are renowned for their remarkable ability to produce antibacterial natural products. The National Institute of Biological Resources (NIBR) of Korea maintains a collection of Korean native actinobacteria. In this study, we explored the phylogenetic and biosynthetic diversity of the NIBR actinobacteria collection to assess its potential as a source of new antibacterial natural products. A 16S rDNA-based phylogenetic analysis revealed a high level of genetic diversity within the collection, with a predominance of Streptomyces, along with rare actinobacterial genera such as Kitasatospora and Micromonospora. Additionally, genetic network analysis of biosynthetic gene clusters (BGCs) from 15 sequenced NIBR actinobacterial strains demonstrated extensive BGC diversity, with many clusters identified as cryptic. Screening of culture extracts for antibacterial activity, followed by dereplication of active extracts, suggested the presence of potentially novel antibacterial natural products. Activity-guided isolation and whole-genome sequencing of the active strain KU57 led to the isolation of one new and three known svetamycin congeners along with their BGC. Overall, our findings highlight the NIBR actinobacteria collection as a valuable source for the discovery of new antibacterial natural products.

Condensin plays a central role in mitotic chromosome organization and segregation by mediating long-range chromatin interactions. However, the extent to which cellular metabolic status influences condensin function remains unclear. To gain insights into the relationship of metal ion homeostasis and the function of condensin, we conducted genome-wide chromatin immunoprecipitation sequencing (ChIP-seq) using Schizosaccharomyces pombe under iron- or zine-deficient conditions. Under iron- or zinc-deficient conditions, ChIP-seq results revealed a selective reduction in condensin binding at high-affinity target loci, particularly genes regulated by Ace2 and Ams2, while cohesin binding remained largely unaffected. Hi-C analysis showed that iron depletion weakened chromatin interactions at these condensin targets and centromeres, without disrupting global genome architecture. DNA fluorescence in situ hybridization (FISH) confirmed that iron deficiency impaired long-range associations between centromeres and Ace2 target loci at the single-cell level. Notably, iron deficiency led to chromosome segregation defects during mitosis, suggesting that diminished condensin occupancy compromised genome stability. These changes occurred without significant alterations in condensin protein levels or global transcription, indicating a direct effect of metal ion availability on condensin activity. Collectively, our findings revealed a previously unrecognized regulatory axis in which cellular metal ion homeostasis modulated condensin-dependent chromatin organization and mitotic chromosome segregation, offering new insights into the integration of metabolic state with genome maintenance.

Marine organisms often form symbiotic relationships with various microorganisms to adapt and thrive in harsh environments. These symbiotic microbes contribute to host survival by providing nutrition, modulating the hosts' immune system, and supporting overall physiological stability. Advances in high-throughput sequencing technologies have enabled a deeper understanding of the structure and function of symbiotic microbial communities, as well as host-microbe interactions. Notably, symbiotic bacteria associated with marine invertebrates such as corals and sponges are recognized as a potential source of useful bioactive compounds, including antibiotics and enzymes. However, obtaining high-quality microbial DNA from host tissues still remains a technical challenge due to the presence of unknown substances. This study focuses on optimizing sample preparation and DNA extraction procedures and additional purification to improve the recovery of microbial DNA while minimizing host DNA contamination. Comparison between several methods was conducted using sponge samples to evaluate DNA quality and microbial recovery. A sample designated as 2110BU-001 was collected from the east coast of the Republic of Korea and used for culture-independent microbial cell isolation. Total bacterial DNA was extracted by using a manual Phenol-Chloroform protocol and three commercial kits. DNA extracted using the standard manual method showed both the highest yield and the largest fragment size. However, PCR (Polymerase chain reaction) test showed that quality of manually extracted DNA was not enough for sequencing. Therefore, the quality of DNA was improved through additional purification steps. Briefly, host eukaryotic cells were removed by mechanical process and almost only bacterial DNA was successfully obtained by combination of manual extraction method and further purification processes. The established protocol was successfully introduced to extraction of metagenomic DNA from mussel and jellyfish microbiomes, indicating that it can be widely applied to various marine organisms.