Publications

4891

An anaerobic, salt-tolerant, rod-shaped bacterium, strain JL216-2 T , was isolated from the shell of the hydrothermal gastropod Alviniconcha marisindica in the Tianxiu hydrothermal field on the Carlsberg Ridge, Indian Ocean. Cells of strain JL216-2 T were motile and 0.5×3–6 µm in size. Strain JL216-2 T grew at 10–32 °C (optimal 28 °C), pH 6.0–9.0 (optimal pH 7.0) and 0.5–12.0% (w/v) sodium chloride(NaCl, optimal 2.5%). Strain JL216-2 T exhibited metabolic versatility, being capable of heterotrophic growth on complex organic compounds. It also performed autotrophic growth by utilizing carbon dioxide (CO₂) fixation or sodium bicarbonate (NaHCO 3 ) as the sole carbon source, driven by hydrogen oxidation coupled with Fe(III) reduction. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain was most closely related to Helicovermis profundi S502 T (90.43% sequence similarity). The genome size of strain JL216-2 T was 4.91 Mb, with a G+C content of 39.54 mol%. Phylogenomic analysis and overall genome relatedness indices values indicated a close relatedness of strain JL216-2 T to H. profundi S502 T and Fusibacter spp. The combined genotypic and phenotypic data showed that strain JL216-2 T represents a novel genus within the order Eubacteriales . The type strain is JL216-2 T (=MCCC M30262 T =KACC 23553 T ).

Abstract Bdellovibrio are predatory bacteria with potential applications in treating multidrug-resistant bacterial infections. We isolated Bdellovibrio sp. kdesi from sewage in Reynosa, Mexico, and performed comprehensive genomic characterization. The complete genome (3,343,978bp; 48.5% GC content; 3,208 coding sequences) contains a single rRNA operon with two identical 16S rRNA genes at distinct loci. While 16S rRNA analysis showed 99.3% identity to B. bacteriovorus SSB218315, polyphasic genomic analysis revealed kdesi as a distinct species. Core-genome phylogeny, average nucleotide identity (ANI ~ 89%), average amino acid identity (AAI ~ 82%), and digital DNA-DNA hybridization (dDDH < 70%) clearly demonstrated that Kdesi along with several other strains currently classified as B. bacteriovorus represents novel genomospecies requiring formal taxonomic revision. Comparative genomic analysis of 29 Bdellovibrio genomes revealed an open pan-genome (~ 25,000 genes) with limited transposable elements, absence of SecB in the Sec secretion system, and strain-specific adaptations in Type IV secretion systems. These findings underscore the need for genome-based taxonomic revision of the genus and highlight the importance of using multiple molecular criteria beyond 16S rRNA for bacterial species delineation.

Abstract The Genome Taxonomy Database (GTDB; https://gtdb.ecogenomic.org) provides a phylogenetically consistent and rank normalized genome-based taxonomy for prokaryotic genomes sourced from the NCBI Assembly database. GTDB release 10 (R10-RS226) spans 715 230 bacterial and 17 245 archaeal genomes organized into 136 646 bacterial and 6968 archaeal species clusters. Fewer new major branches of prokaryotic life are being discovered with each release of GTDB, suggesting that we are beginning to saturate readily discoverable microbial diversity through culture-independent analyses. However, species discovery continues unabated as >95% of bacterial and archaeal species remain to be genomically elucidated based on conservative projections. We present additions to the GTDB website, methodological improvements, policy changes, notable nomenclatural updates, and user applications. We conclude with a summary of future plans for the resource including a fungal taxonomy and a nomenclatural extension to classify pathogens.

Abstract BACKGROUND Huanglongbing (HLB) is the most devastating citrus disease worldwide, with no resistant commercial citrus varieties identified and no effective chemical treatments currently available on the market. The main challenge in developing effective strategies for controlling HLB is the inability to culture its associated pathogen, the fastidious Candidatus Liberibacter asiaticus ( C Las), in defined media or axenic cultures. RESULTS In this study, we developed an effective method for screening antimicrobials against C Las using periwinkle as a model plant. Compared with citrus, periwinkle offers notable advantages, including reduced time, increased efficiency, and lower costs. This method consists of two main components: screening exogenously applied antimicrobials and evaluating overexpressed endogenous antimicrobial peptides. Using this method, we demonstrated that bromothalonil and cyproconazole effectively inhibit the proliferation of C Las in hydroponically grown periwinkle. Further analyses revealed that bromothalonil and cyproconazole were also highly toxic to other citrus pathogens, including Xanthomonas citri subsp. citri ( Xcc ), Alternaria alternata tangerine pathotype (Z7), and Penicillium digitatum (KH8). In addition, we established an Agrobacterium rhizogenes ‐mediated hairy root genetic transformation system for periwinkle and demonstrated that the proliferation of C Las was significantly inhibited in transgenic roots overexpressing antimicrobial peptide (SAMP). CONCLUSION An efficient antimicrobial screening system for C Las and several other citrus pathogens has been established. By addressing challenges such as high costs, prolonged experimental periods, and heavy workloads, we anticipate that this developed method will serve as a useful tool for the identification of antimicrobials effective against C Las and other citrus pathogens. © 2025 Society of Chemical Industry.