SEARCH · Search PubMed

Results for “average nucleotide identity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2026

Development of a Multiplex Polymerase Chain Reaction Assay for Differentiating Three Lactococcus Species Associated With Piscine Lactococcosis.

Piscine lactococcosis is an important bacterial disease of farmed fish. The causative agents, Lactococcus garvieae, Lactococcus petauri and Lactococcus formosensis, are closely related, which complicates species-level identification. We developed a conventional multiplex PCR assay targeting species-specific genes identified by comparative genomic analysis. Average nucleotide identity reassignment of 441 publicly available genome assemblies identified 111 L. garvieae, 255 L. petauri and 75 L. formosensis genomes. Species-specific primers and a tuf-based Lactococcus common control were evaluated using in silico polymerase chain reaction (PCR) against target genomes and 10,460 off-target assemblies representing 474 taxa in 12 genera. Experimental specificity was assessed using six target strains and 19 non-target fish pathogens. Distinct amplicons of 195, 333 and 500 bp were produced for L. garvieae, L. petauri and L. formosensis, respectively, together with a 132-bp control amplicon. No cross-amplification was observed. All target species were detected in mixed-DNA samples and spiked kidney and spleen homogenates from two fish species. Analytical detection limits were estimated based on microscopic cell counts of bacterial suspensions before DNA extraction and ranged from 0.956 to 8.55 cell equivalents per reaction. This assay represents a rapid, low-cost method for differentiating lactococcosis-causing Lactococcus species using standard PCR and agarose gel electrophoresis.

Lactococcus garvieae↗

PubMed2006

Toward a more robust assessment of intraspecies diversity, using fewer genetic markers.

Phylogenetic sequence analysis of single or multiple genes has dominated the study and census of the genetic diversity among closely related bacteria. It remains unclear, however, how the results based on a few genes in the genome correlate with whole-genome-based relatedness and what genes (if any) best reflect whole-genome-level relatedness and hence should be preferentially used to economize on cost and to improve accuracy. We show here that phylogenies of closely related organisms based on the average nucleotide identity (ANI) of their shared genes correspond accurately to phylogenies based on state-of-the-art analysis of their whole-genome sequences. We use ANI to evaluate the phylogenetic robustness of every gene in the genome and show that almost all core genes, regardless of their functions and positions in the genome, offer robust phylogenetic reconstruction among strains that show 80 to 95% ANI (16S rRNA identity, >98.5%). Lack of elapsed time and, to a lesser extent, horizontal transfer and recombination make the selection of genes more critical for applications that target the intraspecies level, i.e., strains that show >95% ANI according to current standards. A much more accurate phylogeny for the Escherichia coli group was obtained based on just three best-performing genes according to our analysis compared to the concatenated alignment of eight genes that are commonly employed for phylogenetic purposes in this group. Our results are reproducible within the Salmonella, Burkholderia, and Shewanella groups and therefore are expected to have general applicability for microevolution studies, including metagenomic surveys.

Bacterial Proteins↗

PubMed2026

Effectiveness of mass spectrometry and genomic analysis in the surveillance of nontuberculous Mycobacterium in Taiwan.

Nontuberculous mycobacteria (NTM) are diverse, and species-level identification remains challenging in routine diagnostics. We analyzed NTM isolates collected at three regional centers of the National Taiwan University Hospital (NTUH) from 2019 to 2024 to assess geographic variation and identification performance after implementation of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Among 3,188 cases meeting the microbiological criteria for probable pulmonary NTM disease, the species distribution differed by region: Mycobacterium avium complex predominated in central Taiwan (Yunlin, 47.3%), whereas M. abscessus complex (Taipei, 26.5%) and M. kansasii (Hsinchu, 12.4%) were more common in northern Taiwan. In 2019, 14.5% of isolates were reported to be unidentified by MALDI-TOF MS; with workflow optimization and database updates, this percentage decreased but plateaued at 4.5-4.8%. Whole-genome sequencing (WGS) of 61 randomly selected persistently unidentified isolates revealed eight average nucleotide identity (ANI)-defined clusters; 55 isolates (90.2%) could not be assigned to known species using current reference databases. Two clusters detected only in Hsinchu were phylogenetically closest to M. kyorinense, with ANI values below the species demarcation threshold. Overall, we observed marked regional heterogeneity of NTM in Taiwan and a persistent identification gap that remained after MALDI-TOF MS optimization and follow-up WGS.IMPORTANCEThis study characterized regional differences in the NTM species distribution across Taiwan, and the results highlight the limitations of current identification approaches. MALDI-TOF MS identifies most isolates, but locally circulating lineages represent a persistent gap in global reference libraries. Even with whole-genome sequencing (WGS), 90.2% (55/61) of persistently unresolved isolates could not be assigned to known species in the current reference databases despite the formation of clear ANI- and phylogeny-defined clusters. These findings show that both proteomic and genomic reference resources for clinical NTM remain incomplete. Expanding regionally representative databases and performing WGS for isolates that remain unresolved by MALDI-TOF MS will be necessary to improve species-level resolution for surveillance and clinical interpretation.

Taiwan↗

PubMed2026

Complete genome sequences of three co-occurring Pseudomonas isolates from California Botanic Garden topsoil.

We report the complete genome sequences of three Pseudomonas isolates recovered from topsoil at the California Botanic Garden. Two isolates share ~99.4% average nucleotide identity, enabling investigation of intraspecies microvariation; the third represents a co-occurring distinct species, together capturing species- and strain-level genomic diversity within a natural soil community.

Pseudomonas↗

PubMed2026

New purple sulfur bacteria genomes from Nebraska salt marsh enrichments.

Two genomes from a Winogradsky column enrichment from the Nebraska salt marshes were sequenced. The analysis of whole-genome phylogeny and average nucleotide identity comparisons indicated that these belong to species of purple sulfur bacteria, Halochromatium and Ectothiorhodospira marina, that have not been described before.

Ectothiorhodospira↗

PubMed2026

Isolation, genomic characterization, and safety assessment of an O-desmethylangolensin-producing Clostridium beijerinckii strain from Chinese Stinky Tofu.

The health benefits of dietary soy isoflavones are largely mediated by specific microbial metabolites, such as O-desmethylangolensin (O-DMA). However, the diversity and application potential of O-DMA-producing strains remain poorly explored, primarily due to the limited availability of isolated strains, narrow ecological sources, and a lack of practical applications. In this study, an O-DMA-producing bacterium, designated strain FRJF5, was isolated from Chinese stinky tofu under anaerobic conditions and was identified as Clostridium beijerinckii. The biosynthesized O-DMA exhibited an enantiomeric excess (e.e.) of 78.6%. Based on phylogenetic and average nucleotide identity analyses against 235 public C. beijerinckii genomes, the clustering of FRJF5 with strains from diverse habitats-including industrial fermentation settings, animal feces, and soil-highlights the broad ecological diversity within this species. Functional gene mining and intra-species comparative genomics revealed a unique flavonoid metabolism gene cluster in FRJF5. Using apigenin as a representative flavonoid, we confirmed the successful conversion to 3-(4-hydroxyphenyl)-propionic acid. Moreover, the strain was predicted and verified to possess a substantial butyrate-producing capacity. Genomic screening for virulence or antibiotic resistance genes, combined with phenotypic tests (hemolysis, antibiotic susceptibility, and mouse gavage), revealed a favorable safety profile for strain FRJF5. Finally, intervention experiments in a mouse model of colitis supported its potential in alleviating the disease. Collectively, this study identifies C. beijerinckii FRJF5 as a strain capable of simultaneously producing O-DMA and butyrate, highlighting its potential for future applications in functional foods.IMPORTANCESoy isoflavones require gut bacterial conversion into bioactive metabolites-such as the anti-inflammatory compound O-desmethylangolensin (O-DMA)-to exert health benefits. Yet O-DMA-producing strains remain scarce, largely confined to fecal sources, and poorly characterized. Here, we isolated Clostridium beijerinckii FRJF5 from Chinese stinky tofu, an unexplored ecological niche. This strain not only produces enantiomerically enriched O-DMA but also co-produces butyrate, a metabolite known to strengthen gut barrier function. Genomic mining uncovered a unique flavonoid metabolism gene cluster responsible for this dual activity. Combined with favorable safety profiles, FRJF5 emerges as a strong candidate for functional food applications. This work expands the known diversity of O-DMA producers and bridges traditional fermented foods with next-generation probiotic development.

O-desmethylangolensin↗

PubMed2026

Proposal to validate Listeria swaminathanii sp. nov. and reassign the type strain to UTK S2-0008.

Listeria swaminathanii UTK S2-0008, isolated from soil collected in the Nantahala National Forest in North Carolina, USA, is the only L. swaminathanii strain eligible to serve as the type strain, which is needed to achieve valid status. The previously effectively published type, L. swaminathanii FSL L7-0020T, and previously described strains UTK C1-0015 and UTK C1-0024 do not conform to the International Code of Nomenclature of Prokaryotes' rules for type strains. Additionally, the currently designated type strain (FSL L7-0020T = ATCC TSD-239T) is an atypical representative of L. swaminathanii as it is the only strain lacking catalase activity. Therefore, it is proposed to reassign the type to L. swaminathanii (UTK S2-0008T = CCUG 77280T = LMG 33255T). Whole-genome sequence-based average nucleotide identity (ANI) showed that this strain clustered with the three previously described L. swaminathanii strains (FSL L7-0020 = ATCC TSD-239, UTK C1-0015, and UTK C1-0024; pairwise ANI ranged from 98.71% to 98.83%). All four strains, including the one described here, could not be classified as any validly published Listeria species and showed the highest similarity to Listeria marthii (maximum ANI of 93.92%, in silico DNA-DNA hybridization of 56.2%). L. swaminathanii exhibits the phenotypic characteristics that are currently expected of the Listeria sensu stricto species. This species lacks phenotypic characteristics associated with Listeria pathogenicity (non-hemolytic and negative for phosphatidylinositol-specific phospholipase C activity); the genomes lack genes associated with virulence (all genes found on the Listeria pathogenicity island 1 [LIPI-1], as well as the internalin genes inlA and inlB), which support L. swaminathanii is nonpathogenic.IMPORTANCEThe genus Listeria includes species of significant relevance to food safety, environmental microbiology, and public health. Accurate species identification is critical because misidentification of nonpathogenic species as pathogenic ones can lead to unnecessary recalls and regulatory complications. The validation of Listeria swaminathanii sp. nov. will ensure that this species is formally recognized and has a type strain (UTK S2-0008T) that is representative of the species. This work strengthens diagnostic accuracy by enabling the inclusion of this species in reference databases and inclusivity studies, reducing the risk of false identification. Furthermore, the identification and characterization of Listeria swaminathanii sp. nov. expands our understanding of the genetic and ecological diversity within the genus Listeria, particularly among soil-dwelling strains.

Listeria↗

PubMed2026

Whole genome sequence of a superbug-Escherichia coli strain KAB-AI-497 isolated from the vagina of a 20 year old pregnant woman with premature rupture of membrane (PROM) in a resource limited setting, Kabale Regional Referral Hospital, in Uganda.

OBJECTIVES: The objective of the study is to sequence the whole genome of multidrug resistant E. coli strain KAB-AI-497 that causes bacterial vaginosis and implicated in premature rupture of membrane in pregnant woman. DATA DESCRIPTION: The DNA of the E. coli strain KAB-AI-497 was extracted using the MagAttract HMW DNA Kit, and the extracted DNA was sequenced using an MGI DNBSEQ G99ARS platform. FastQC was used to perform quality control analysis and the reads were trimmed by Trimmomatic. De novo genome assembly was performed by SPAdes and it resulted to a draft assembled genome that has 5.1 Mb genome size, 153 contigs, and 50.5% GC content. Quality analysis of the assembled genome revealed it has 98.46% completeness and 0.97% contamination. The closest E. coli strain to this strain KAB-AI-497 in terms of similarity was Escherichia coli SMS-3-5 with an average nucleotide identity of 98.43% and genome coverage of 86.19%, which confirmed the species level identity of the strain. The assembled genome was annotated using the NCBI Prokaryotic Genome Annotation Pipeline which identified 4,726 protein coding genes in the strain genome. Furthermore, the annotation revealed the genome has resistant genes responsible for resistance against many antibiotic classes such as tetracycline, fluoroquinolone, and penicillin.

Escherichia coli↗

PubMed2025

Comparative genomic analysis of a novel heat-tolerant and euryhaline strain of unicellular marine cyanobacterium Cyanobacterium sp. DS4 from a high-temperature lagoon.

BACKGROUND: Cyanobacteria have diversified through their long evolutionary history and occupy a wide range of environments on Earth. To advance our understanding of their adaptation mechanisms in extreme environments, we performed stress tolerance characterizations, whole genome sequencing, and comparative genomic analyses of a novel heat-tolerant and euryhaline strain of the unicellular cyanobacterium Cyanobacterium sp. Dongsha4 (DS4). This strain was isolated from a lagoon on Dongsha Island in the South China Sea, a habitat with fluctuations in temperature, salinity, light intensity, and nutrient supply. RESULTS: DS4 cells can tolerate long-term high-temperature up to 50 ℃ and salinity from 0 to 6.6%, which is similar to the results previously obtained for Cyanobacterium aponinum. In contrast, most mesophilic cyanobacteria cannot survive under these extreme conditions. Based on the 16S rRNA gene phylogeny, DS4 is most closely related to Cyanobacterium sp. NBRC102756 isolated from Iwojima Island, Japan, and Cyanobacterium sp. MCCB114 isolated from Vypeen Island, India. For comparison with strains that have genomic information available, DS4 is most similar to Cyanobacterium aponinum strain PCC10605 (PCC10605), sharing 81.7% of the genomic segments and 92.9% average nucleotide identity (ANI). Gene content comparisons identified multiple distinct features of DS4. Unlike related strains, DS4 possesses the genes necessary for nitrogen fixation. Other notable genes include those involved in photosynthesis, central metabolisms, cyanobacterial starch metabolisms, stress tolerances, and biosynthesis of novel secondary metabolites. CONCLUSIONS: These findings promote our understanding of the physiology, ecology, evolution, and stress tolerance mechanisms of cyanobacteria. The information is valuable for future functional studies and biotechnology applications of heat-tolerant and euryhaline marine cyanobacteria.

Cyanobacteria↗

PubMed2026

Two worlds beneath: Distinct microbial strategies of the rock-attached and planktonic subsurface biosphere.

BACKGROUND: Microorganisms in groundwater ecosystems exist either as planktonic cells or as attached communities on aquifer rock surfaces. Attached cells outnumber planktonic ones by at least three orders of magnitude, suggesting a critical role in aquifer ecosystem function. However, particularly in consolidated carbonate aquifers, where research has predominantly focused on planktonic microbes, the metabolic potential and ecological roles of attached communities remain poorly understood. RESULTS: To investigate the differences between attached and planktonic communities, we sampled the attached microbiome from passive samplers filled with crushed carbonate rock exposed to oxic and anoxic groundwater in the Hainich Critical Zone Exploratory and compared it to a previously published, extensive dataset of planktonic communities from the same aquifer ecosystem. Microbial lifestyle (attached vs. planktonic) explained more variance in community composition than redox conditions, prompting us to further investigate its role in shaping functional and activity profiles. Metagenomic analysis revealed a striking taxonomic and functional segregation: the 605 metagenome-assembled genomes (MAGs) from attached communities were dominated by Proteobacteria (358 MAGs) and were enriched in genes for biofilm formation, chemolithoautotrophy, and redox cycling (e.g., iron and sulfur metabolism). In contrast, the 891 MAGs from planktonic communities were dominated by Cand. Patescibacteria (464 MAGs) and Nitrospirota (60 MAGs) and showed lower functional versatility. Only a few genera were shared, and even closely related MAGs (> 90% average nucleotide identity) differed in assembly size and metabolic traits, demonstrating lifestyle-specific functional adaptation. Analysis of active replication indicated that the active fraction of the attached community was primarily represented by the most abundant MAGs. Planktonic communities featured a higher fraction of active MAGs compared to attached communities, but overall with lower relative abundances. CONCLUSIONS: The high abundance, metabolic specialization, and carbon fixation potential of attached microbes suggest that they are key drivers of subsurface biogeochemical processes. Carbonate aquifers may act as much larger inorganic carbon sinks than previously estimated based on CO2 fixation rates of the planktonic communities alone. Our findings underscore the need to incorporate attached microbial communities into models of subsurface ecosystem function. Video Abstract.

Plankton↗

PubMed2026

Bacillus subtilis isolated from medicinal plants rhizosphere effectively controls Cercospora leaf spot and improves plant growth in mung bean (Vigna radiata).

BACKGROUND: Mung bean is an important leguminous crop, which is reported to face devastating yield losses of up to 70% due to Cercospora leaf spot (CLS) disease. Traditional methods, such as the application of agrochemicals and fungicides, have been used to control CLS, but their intensive use has toxic effects on edible crops. METHODS: To find out a sustainable alternative, this study characterizes a strain, Bacillus subtilis Medicinal_04, isolated from Cannabis sativa rhizosphere and explores its role as an eco-friendly biofungicide and biostimulant. The species level identification of the isolate was confirmed by Average Nucleotide Identity (ANIb) and a digital DNA-DNA hybridization (dDDH). The antagonistic efficacy of B. subtilis Medicinal_04 against Cercospora canescens was evaluated in vitro as well as in planta assays. RESULTS: ANIb of 97.80% and a dDDH score of 85.90% against the reference B. subtilis str. 168. confirmed this isolate as B. subtilis. The in-vitro results showed that B. subtilis robustly inhibited C. canescens growth by 81.5%, strongly correlated with positive chitinolytic activity and a diverse genomic array of secondary metabolite biosynthetic gene clusters. The in planta results demonstrated that B. subtilis seed priming reduced disease incidence by 80 and 71.4%, while foliar application resulted in reductions of 90 and 85.7% for NM-51 and NM-20-21 varieties, respectively. Furthermore, fungicide application successfully reduced disease, however it caused noticeable phytotoxic reductions in root-shoot architecture and chlorophyll content. In contrast, biological interventions completely bypassed these trade-offs as B. subtilis application displayed improved root-shoot length, pod number, and chlorophyll content, while simultaneously enhancing antioxidative enzyme activities (SOD, POD, and CAT) and PR-1 gene expression. CONCLUSION: These findings demonstrate that B. subtilis Medicinal_04 has the potential to serve as a multifunctional biocontrol agent and is capable of securing high-level disease suppression and optimizing plant productivity, offering a valuable toolkit for climate-smart, sustainable agriculture.

Bacillus subtilis↗

PubMed2026

Genomic insights into Aeromonas infections in diarrheal patients: high diversity, emerging resistance, and potential outbreak in Beijing.

BACKGROUND: Aeromonas species are ubiquitous aquatic bacteria that have emerged as significant foodborne enteric pathogens worldwide, yet their genomic landscape in clinical settings remains poorly delineated, particularly in Beijing. METHODS: To address this gap, we performed active surveillance for Aeromonas among 691 consecutive diarrheal outpatients in a Beijing district from January to December 2024. Isolates were recovered using enrichment culture coupled with PCR screening and identified by MALDI-TOF MS. Antimicrobial susceptibility was tested against 17 agents. Whole-genome sequencing was conducted on all isolates, enabling average nucleotide identity (ANI) analysis, comprehensive annotation of antimicrobial resistance and virulence genes, multilocus sequence typing (MLST), and core-genome SNP (cgSNP)-based phylogenetics. RESULTS: Aeromonas was detected in 3.3% (23/691) of patients, with Aeromonas veronii (56.52%, 13/23) and Aeromonas caviae (26.09%, 6/23) predominating. Co-infections with other enteric pathogens occurred in 65.2% of positive cases. Resistance rates were notably high for ampicillin/ampicillin-sulbactam (78.26%), nalidixic acid (56.52%), and ertapenem (21.73%), and 65.21% of isolates were multidrug-resistant. Genotypic-phenotypic concordance was robust, with β-lactamase genes ampS (60.87%) and blaCEPH-A3 (47.83%) being most prevalent. Strikingly, mcr-3.25 and mcr-3.3, which belong to the mcr family (originally described as mobile colistin resistance genes), were identified in 8.70% of isolates, exhibiting perfect correlation with phenotypic resistance. Plasmer analysis suggested both mcr genes to be chromosomally encoded. Comparative genomic analysis of virulence-associated genes revealed striking species-specific specialization: A. veronii predominantly carried complete T3SS clusters (61.5%), A. caviae and Aeromonas enteropelogenes were enriched in T6SS genes, and a single A. dhakensis isolate possessed an extensive arsenal including T3SS, T6SS, and a full RTX toxin cluster. MLST resolved the 23 isolates into 22 sequence types, 18 of which were novel. Phylogenetic reconstruction identified a tight monophyletic cluster of three A. veronii isolates (9-27 SNP differences) recovered within a 96-h window, suggestive of a potential cluster that warrants further epidemiological investigation. Comparative genomic analysis of the rare species Aeromonas allosaccharophila demonstrated that the Beijing clinical isolate S14 differs from the U.S. clinical strain ATCC 35942 by 42,099 SNPs, confirming its distinct genetic lineage. CONCLUSION: Collectively, this study delineates high genetic diversity, emerging chromosomal colistin resistance, and species-specific virulence specialization among Aeromonas isolates from diarrheal patients in Beijing. The detection of a potential outbreak cluster and a rare clinical isolate underscores the power of genomics-based surveillance for detecting and mitigating foodborne pathogen threats.

Aeromonas↗

PubMed2026

Genome analysis and antagonistic activity of Streptomyces sp. strain J36 against Phytophthora cactorum.

The Phytophthora blight of Panax notoginseng, caused by Phytophthora cactorum, is a devastating oomycete disease. Biocontrol strategies hold immense potential for inhibiting the spread of P. cactorum. We isolated 72 actinobacteria from soil and screened their antagonistic activity against P. cactorum. Both strain J36 and its cell-free filtrate exhibited strong antagonistic activity against P. cactorum and were therefore selected. Based on the 16S rRNA gene phylogenetic tree, strain J36 formed a well supported subclade with Streptomyces zaomyceticus NRRL B-2038 (bootstrap value 100%). However, because 16S rRNA sequences often lack sufficient resolution for species-level discrimination, we performed multilocus sequence analysis (MLSA) using three housekeeping genes (rpoB, recA, and atpD). The MLSA results consistently placed strain J36 within the same cluster as S. zaomyceticus NRRL B-2038, with a bootstrap support of 99%, indicating a close phylogenetic relationship. To further clarify the taxonomic status, we calculated the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain J36 and the type strain of S. zaomyceticus NBC-00415T. The ANI value was 90.91% and the dDDH value was 39.30%, both well below the accepted thresholds for species demarcation (ANI < 95%, dDDH < 70%). These genomic indices therefore strongly support that strain J36 represents a novel species within the genus Streptomyces. Through whole-genome sequencing and CAZymes analysis, a total of 98 carbohydrate-active enzymes (CAZymes) were detected, including 2 cellulase and 2 β-1,3-glucanases. The cell-free filtrate, which exhibited strong antagonistic activity against P. cactorum, also showed high activities of cellulase and β-1,3-glucanase, suggesting that these enzymes may be involved in its anti-oomycete activity. These findings suggest that J36 has potential as a biocontrol candidate, although further in vivo evaluation is needed to confirm its efficacy against Phytophthora blight of P. notoginseng.

Panax notoginseng↗

PubMed2026

Comparative genomics reveals hidden biosynthetic diversity in Streptomyces spp. and metal-dependent regulatory features associated with untapped specialized metabolites.

The genus Streptomyces is one of the richest sources of bioactive natural products; however, a substantial proportion of its biosynthetic gene clusters (BGCs) remain cryptic and their metabolic products are unresolved. Advances in genome mining and computational prediction now enable comprehensive exploration of this hidden biosynthetic repertoire. In this study, whole-genome sequencing and comparative genomic analyses were performed on three three newly isolated Streptomyces strains to evaluate their specialized metabolic potential. Genome assemblies were annotated and systematically analyzed using antiSMASH, DeepBGC, GECCO, and PRISM to identify, cross-validate, and functionally characterize BGCs while predicting their associated secondary metabolite scaffolds. Taxonomic analyses based on Average Nucleotide Identity (ANI), phylogenomics, and BLAST identified the isolates as Streptomyces thinghirensis, Streptomyces novocaesareae, and Streptomyces griseorubens. Applying the consensus framework across the three Streptomyces genomes yielded 43 cryptic BGCs, lacking close similarity to reference BGCs in the MIBiG database, of which 26 were classified as HIGH, 10 as MEDIUM, and 7 as LOW confidence. Notably, numerous BGCs exhibited low abundance to characterized reference clusters, indicating a high potential for previously undescribed biosynthetic pathways and novel metabolite scaffolds. Comparative analyses further revealed strain-specific biosynthetic architectures together with putative metal-responsive regulatory systems; Fur, Zur, and Nur, which were frequently associated with specialized metabolite biosynthetic loci. Collectively, these findings demonstrate the effectiveness of integrated genome-mining strategies for prioritizing cryptic biosynthetic gene clusters and highlight the remarkable biosynthetic potential of newly identified Streptomyces isolates as a source of novel natural products.

comparative genomics↗

PubMed2026

Dechloromonas parva sp. nov., a Member of the Family Azonexaceae.

A Dechloromonas-like bacterial strain, designated HYN0024T, was isolated from lake water, and its taxonomic status was characterized in this study. Although the bacterium was isolated from an aerobic water sample, its cells were facultative anaerobes utilizing Fe(III) and oxygen as terminal electron acceptors. Phylogenetic analysis based on both genome and 16S rRNA gene sequences indicated that strain HYN0024T belongs to the family Azonexaceae and forms a monophyletic clade with the type strains of Ferribacterium limneticum, Quatrionicoccus australiensis, and 'Dechloromonas aromatica'. However, the type strains of the genera Ferribacterium and Quatrionicoccus are currently unavailable from any public culture collections. Among the available type strains with validly published names, Dechloromonas hortensis shared the highest 16S rRNA gene sequence similarity (98.35%) with strain HYN0024T, but their average nucleotide identity (80.13%) was below the threshold for species delineation. The biochemical and physiological features also supported the distinctiveness of the isolate from previously known species. The 16S rRNA gene sequence similarity, genomic relatedness, phylogenetic tree topology, and phenotypic characteristics supported the taxonomic independence of the isolate as a novel species in the genus Dechloromonas. Based on the phylogenetic and polyphasic taxonomic data presented in this study, we propose a novel species, Dechloromonas parva sp. nov., for strain HYN0024T (= KACC 19179T = NBRC 112737T).

RNA, Ribosomal, 16S↗

PubMed2026

Vibrio phycocola sp. nov. and Vibrio phycohabitans sp. nov., Isolated from the Phycosphere of Marine Algae.

Two Gram-stain-negative, facultatively aerobic, oxidase- and catalase-positive, motile (by means of a polar flagellum) rod-shaped bacterial strains, designated BS-M-Sm-2T and MA40-2T, were isolated from marine algae. Growth was optimal at pH 7.0-8.0 and 2.0-3.0% (w/v) NaCl, with temperature optima of 25°C for BS-M-Sm-2T and 25-30°C for MA40-2T. Ubiquinone-8 was the sole respiratory quinone. The major fatty acids common to both strains were C16:0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c), while BS-M-Sm-2T additionally contained C12:0 and C14:0. The predominant polar lipids were phosphatidylethanolamine and phosphatidylglycerol, with diphosphatidylglycerol also detected in strain MA40-2T. The DNA G+C contents of strains BS-M-Sm-2T and MA40-2T were 44.2 and 39.8 mol%, respectively. The 16S rRNA gene sequence similarity, average nucleotide identity (ANI), and digital DNA-DNA hybridization (dDDH) values between the two strains were 93.8%, 71.4%, and 23.2%, respectively. Phylogenetic and phylogenomic analyses placed both strains within the genus Vibrio, forming distinct lineages. Comparisons with closely related Vibrio type strains yielded ANI and dDDH values below 91.6% and 44.3%, respectively, further supporting their classification as novel species. Genome analyses revealed genes potentially involved in algal symbiosis, including those for polysaccharide degradation and vitamin biosynthesis. Based on comprehensive genomic, phylogenetic, phenotypic, and chemotaxonomic evidence, strains BS-M-Sm-2T and MA40-2T represent two novel species, for which the names Vibrio phycocola sp. nov. (BS-M-Sm-2T =KACC 24066T =DSM 119941T) and Vibrio phycohabitans sp. nov. (MA40-2T =KACC 24064T = DSM 119942T) are proposed.

RNA, Ribosomal, 16S↗

PubMed2026

Isolation and Characterization of Botulinum Neurotoxin-Producing Clostridium caccae from Meat and Soil - China, 1990-2025.

WHAT IS KNOWN ABOUT THIS TOPIC?: Botulinum neurotoxin (BoNT)-producing clostridia are categorized into six physiologically and phylogenetically distinct groups (Groups I-VI). Increasing genomic evidence indicates that bont genes are distributed across multiple clostridial lineages, highlighting the taxonomic complexity of BoNT-producing clostridia. Clostridium caccae (C. caccae), first described in 2020 from human stool, was originally described as a strain lacking the bont gene; however, its association with BoNT production has not been previously recognized. WHAT IS ADDED BY THIS REPORT?: Six isolates originally identified as Group II C. botulinum in China were assigned to C. caccae based on the average nucleotide identity (ANI) analysis. In addition, 140 publicly available genomes of C. caccae were analyzed. Among the 146 C. caccae strains, 63% carried bont genes (subtypes B4, E9, E12, and F6), with geographical distribution patterns differing by subtype. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE?: A subset of Group II C. botulinum strains should be considered as C. caccae, indicating that this species represents a previously under-recognized reservoir of multiple BoNT subtypes. To our knowledge, this is the first study to link BoNT-producing C. caccae to both soil contamination and human botulism, highlighting that BoNT-producing C. caccae may be an under-recognized contributor to the risk of botulism.

Botulinum neurotoxin↗

PubMed2003

High intron sequence conservation across three mammalian orders suggests functional constraints.

Several studies have demonstrated high levels of sequence conservation in noncoding DNA compared between two species (e.g., human and mouse), and interpreted this conservation as evidence for functional constraints. If this interpretation is correct, it suggests the existence of a hidden class of abundant regulatory elements. However, much of the noncoding sequence conserved between two species may result from chance or from small-scale heterogeneity in mutation rates. Stronger inferences are expected from sequence comparisons using more than two taxa, and by testing for spatial patterns of conservation in addition to primary sequence similarity. We used a Bayesian local alignment method to compare approximately 10 kb of intron sequence from nine genes in a pairwise manner between human, whale, and seal to test whether the degree and pattern of conservation is consistent with neutral divergence. Comparison of the three sets of conserved gapless pairwise blocks revealed the following patterns: The proportion of identical intron nucleotides averaged 47% in pairwise comparisons and 28% across the three taxa. Proportions of conserved sequence were similar in unique sequence and general mammalian repetitive elements. We simulated sequence evolution under a neutral model using published estimates of substitution rate heterogeneity for noncoding DNA and found pairwise identity at 33% and three-taxon identity at 16% of nucleotide sites. Spatial patterns of primary sequence conservation were also nonrandomly distributed within introns. Overall, segments of intron sequence closer to flanking exons were significantly more conserved than interior intron sequence. This level of intron sequence conservation is above that expected by chance and strongly suggests that intron sequences are playing a larger functional role in gene regulation than previously realized.

Animals↗