Differences in virulence and drug resistance between Clostridioides difficile ST37 and ST1 isolates

One of the most common hospital-acquired infections is caused by toxigenic Clostridioides difficile. Although C. difficile ST37 only produces a functional toxin B, it causes disease as severe as that caused by hypervirulent ST1. We aim to compare the differences in virulence and drug resistance between ST37 and ST1 isolates. We conducted whole-genome sequencing on ST37 and ST1 isolates, analyzing their type-specific genes, and the distribution and mutation of genes related to virulence and antibiotic resistance. We compared the in vitro virulence-related phenotypes of ST37 and ST1 isolates, including: TcdB concentration, number of spores formed, aggregation rate, biofilm formation, swimming diameter in semi-solid medium, motility diameter on the surface of solid medium, and their resistance to 14 CDI-related antibiotics. We detected 4 ST37-specific genes related to adherence, including lytC, cbpA, CD3246, and srtB. We detected 97 virulence-related genes in ST37 isolates that exhibit genomic differences compared to ST1. ST37 isolates showed increased aggregation, biofilm formation, and surface motility compared to ST1 in vitro. Chloramphenicol resistance gene catQ and tetracycline resistance gene tetM are present in ST37 but absent in ST1 strains. The resistance rates of ST37 to chloramphenicol and tetracycline were 45.4% and 81.8%, respectively, whereas ST1 isolates were sensitive to both antibiotics. ST1 was more resistant to rifaximin than ST37. ST37 isolates showed stronger aggregation, biofilm formation and surface motility, and had higher resistance rates to chloramphenicol and tetracycline. ST1 isolates showed stronger ability to produce toxin and sporulation, and was highly resistant to rifaximin.

Characterization of phage vB_EcoP_HC25 and its therapeutic effect on chicken colibacillosis

Bacteriophage therapy has proved to be an attractive candidate for decreasing drug-resistant bacteria. In this study, a novel E. coli phage vB_EcoP_HC25 was isolated from sewage. Phage vB_EcoP_HC25 has an elongated head and a short tail, exhibiting the typical features of the rare C3 morphotype. The burst size was approximately 105 PFU/cell. Phage vB_EcoP_HC25 exhibited good pH range (pH 5-11) and temperature tolerance (<60 °C). The genomic analysis revealed that phage vB_EcoP_HC25 does not carry any virulence factor genes or antibiotic resistance genes. Moreover, it was found that vB_EcoP_HC25 is a promising candidate phage for biocontrol against antibiotic-resistant E. coli in milk and chicken meat. In addition, the results of the mental state, behavior, serum inflammatory factors, and intestinal morphology analyses indicated that phage vB_EcoP_HC25 was effective to control colibacillosis in chicks infected with E. coli.

Strain-Specific Anti-Inflammatory Effects of Faecalibacterium prausnitzii Strain KBL1027 in Koreans

Faecalibacterium prausnitzii is one of the most dominant commensal bacteria in the human gut, and certain anti-inflammatory functions have been attributed to a single microbial anti-inflammatory molecule (MAM). Simultaneously, substantial diversity among F. prausnitzii strains is acknowledged, emphasizing the need for strain-level functional studies aimed at developing innovative probiotics. Here, two distinct F. prausnitzii strains, KBL1026 and KBL1027, were isolated from Korean donors, exhibiting notable differences in the relative abundance of F. prausnitzii. Both strains were identified as the core Faecalibacterium amplicon sequence variant (ASV) within the healthy Korean cohort, and their MAM sequences showed a high similarity of 98.6%. However, when a single strain was introduced to mice with dextran sulfate sodium (DSS)-induced colitis, KBL1027 showed the most significant ameliorative effects, including alleviation of colonic inflammation and restoration of gut microbial dysbiosis. Moreover, the supernatant from KBL1027 elevated the secretion of IL-10 cytokine more than that of KBL1026 in mouse bone marrow-derived macrophage (BMDM) cells, suggesting that the strain-specific, anti-inflammatory efficacy of KBL1027 might involve effector compounds other than MAM. Through analysis of the Faecalibacterium pan-genome and comparative genomics, strain-specific functions related to extracellular polysaccharide biosynthesis were identified in KBL1027, which could contribute to the observed morphological disparities. Collectively, our findings highlight the strain-specific, anti-inflammatory functions of F. prausnitzii, even within the same core ASV, emphasizing the influence of their human origin.

Genomic and phenotypic insights into Serratia interaction with plants from an ecological perspective

We investigated the plant growth-promoting potential of two endophytic strains of Serratia marcescens, namely SmCNPMS2112 and SmUFMG85, which were isolated from the roots of the same maize (Zea mays) plant. The strains were evaluated in vitro for their ability to produce siderophores and indoleacetic acid, form biofilm, solubilize iron phosphate (Fe-P) and Araxá rock phosphate (RP), mineralize phytate, and for their ability to adhere and colonize host roots. Additionally, their plant growth-promoting potential was tested in vivo under greenhouse conditions using millet grown in soil under two fertilization schemes (triple superphosphate, TSP, or commercial rock phosphate, cRP). Both strains improved at least five physiological traits of millet or P content in soil. In order to elucidate the genetic basis of the plant growth-promoting ability of these strains, their genomes were compared. While both genomes exhibited a similar overall functional profile, each strain had unique features. SmCNPMS2112 contained genes related to arsenic and aromatic hydrocarbons degradation, whereas SmUFMG85 harbored genes related to rhamnolipid biosynthesis and chromium bioremediation. Also, we observe a unique repertoire of genes related to plant growth-promotion (PGP) in the SmUFMG85 genome, including oxalate decarboxylase (OxdC), associated with the catabolism of oxalic acid, and aerobactin siderophore (lucD) in the genome of SmCNPMS2112. The alkaline phosphatase was observed on two strains, but acid phosphatase was exclusive to SmUFMG85. Eighteen secondary metabolic gene clusters, such as those involved in the biosynthesis of macrolides and bacillomycin, among others, occur in both strains. Moreover, both genomes contained prophages, suggesting that viral-mediated horizontal gene transfer may be a key mechanism driving genomic variability in the endophytic environment. Indeed, the most genes unique and accessory of SmUFMG85 and SmCNPMS2112 were localized in genomic islands, highlighting genome plasticity and its underlying drivers. To investigate the ecological distribution of plant-interaction traits in the genus Serratia, the genomes of SmUFMG85 and SmCNPMS2112 strains were compared with those of other 19 Serratia strains of different species, which were isolated from different environments. We observe that many features for PGP are present in all genomes, regardless of niche, for instance: formation of flagella, fimbriae and pili, chemotaxis, biosynthesis of siderophores, indole-3-acetic acid (IAA) and volatile organic (VOC) and inorganic (VIC) compounds, such as acetoin and HCN. Also, all the analyzed genomes show an antimicrobial resistance repertoire of genes that confer resistance to several antibiotics belonging to the groups of aminoglycosides and quinolones, for instance. Also, from a niche partitioning perspective, secretion system preference and the ability to produce exopolysaccharides involved in biofilm formation are among the features that vary the most among strains, and most likely influence niche adaptation in Serratia spp., even though only the latter seems to be a feature specifically associated with virulence in the analyzed strains. Our results show that populations of bacteria sharing the same niche can present significant physiological and genomic differences, and reveal the intraspecific metabolic plasticity that underlie plant-bacteria interactions. Also, this study reveals the potential of two Serratia marcescens strains as bioinoculants in agriculture. Considering that Serratia spp. are regarded as low risk biological agents, despite the fact that they can be associated with human disease, we suggest that strain biosafety be evaluated using a combination of genome and phenotypic analyses, as presented herein.

A novel gliding filamentous bacterium Herpetosiphon tianshanensis sp. nov. NSE202 is a promising biocontrol agent for fire blight

BACKGROUND

Fire blight (Erwinia amylovora), a devastating bacterial disease, has posed significant challenges to apple and pear production for more than a century. In recent years, the spread of fire blight to China via Xinjiang has heightened concerns among planters and government authorities, particularly given the region's distinct geography and climate, underscoring the urgent need for innovative biocontrol strategies.

RESULTS

This study introduced a predatory bacterium, Herpetosiphon tianshanensis sp. nov. NSE202, isolated from natural forest soil in Xinjiang, China, that could be a new type of promising biological control agent for the management of fire blight. Strain NSE202 differs from the five other reported Herpetosiphon species in terms of its physiological characteristics and genomic composition. Using morphological, 16S ribosomal RNA gene and whole-genome analysis, the NSE202 strain was assigned to H. tianshanensis sp. nov. Strain NSE202 demonstrated strong predatory capability against Erwinia amylovora (Ea) in vitro. The biocontrol capacity of NSE202 was assayed on isolated inflorescences of fragrant pear and biennial potted pear seedlings under greenhouse conditions. The protective control efficacy of NSE202 was 64.8% in the inflorescences assay. Bacterial spraying of NSE202 significantly reduced the incidence and disease index on pear seedlings with protective and therapeutic control efficacies of 71.9% and 61.5%, respectively. Strain NSE202 demonstrated stable colonization on pear blossoms and twigs under greenhouse conditions. The pathogen population was suppressed significantly in planta treated with NSE202, as shown by colony counts on plates, scanning electron microscopy, and quantitative polymerase chain reaction analysis. Further investigation demonstrated that secondary metabolites of strain NSE202, collected via macroporous resin, and extracellular proteins, precipitated using ammonium sulfate, had pronounced lytic activity against the fire blight pathogen. In addition, certain lipases, glycoside hydrolases, and peptidases secreted by strain NSE202 may contribute significantly to the predation process. These findings suggest that such components may serve as promising biocontrol factors.

CONCLUSIONS

The discovery of H. tianshanensis sp. nov. NSE202 provides a new and promising strategy for combating fire blight. The isolates' multiple capacities to colonize and exert antagonistic effects against Erwinia amylovora makes them highly promising candidates for an integrated biological solution. © 2025 Society of Chemical Industry.

Genomic profiling of Streptococcus agalactiae (Group B Streptococcus) isolates from pregnant women in northeastern Mexico: clonal complexes, virulence factors, and antibiotic resistance

Background

Streptococcus agalactiae (Group B Streptococcus, GBS) is an important pathogen associated with neonatal sepsis, pneumonia, and meningitis, which can be transmitted from colonized pregnant women to their newborns. This study aimed to determine the prevalence and characterize the genomic features of S. agalactiae isolates from pregnant women attending a referral hospital in Northeastern Mexico.

Methods

Vaginal-rectal swabs were collected from pregnant women during routine prenatal care between April 2017 and March 2020. Whole-genome sequencing was conducted to determine sequence type (ST), clonal complex (CC), capsular polysaccharide (Cps) genotype, virulence factors, and antibiotic resistance genes through comparative genome analysis.

Results

S. agalactiae colonization was detected in 51 (2.7%) of 1,924 pregnant women. The most common STs were ST8 (23.5%) and ST88 (15.7%). Cps genotyping showed high concordance between serological and molecular methods. Genes conferring resistance to tetracyclines (tetM, 60.1%) and macrolides (mreA, 100%) were identified. Key virulence factor genes, including cylE, bca, and scpB, were present in over 90% of the isolates.

Conclusion

Although GBS colonization prevalence was low, genomic analysis revealed the genetic diversity of S. agalactiae in Northeastern Mexico, emphasizing the importance of molecular techniques for epidemiological surveillance and infection control.

Genome Mining Reveals Rifamycin Biosynthesis in a Taklamakan Desert Actinomycete

Actinomycetes are recognized for producing diverse bioactive natural products, yet most biosynthetic gene clusters (BGCs) remain inactive under laboratory conditions. Rare actinomycetes from extreme environments represent underexplored reservoirs of metabolic potential. This study investigates Actinomadura sp. TRM71106, a rare actinomycete isolated from the Taklamakan Desert, through integrated genomic and metabolomic approaches. Genome sequencing revealed 45 secondary metabolic BGCs, including BGC38 showing 65% nucleotide similarity to the rifamycin BGC. Gene cluster networking and linear comparisons predicted its capacity to encode novel rifamycin analogs. Targeted activation strategies-overexpression of the pathway-specific regulator LuxR combined with metabolite isolation-mark the first activation of a rifamycin-like BGC in desert actinomycetes. This study highlights the untapped biosynthetic potential of rare actinomycetes in extreme environments and establishes Actinomadura sp. TRM71106 as a novel source for rifamycin production. These results provide a promising avenue for expanding the clinical pipeline of rifamycin-derived antibiotics.

The complete mitochondrial genomes of Macrostylophora euteles and Citellophilus tesquorum sungaris and the phylogenetics of known Siphonaptera mitogenomes

Fleas serve as hosts to a diverse array of pathogens, which present significant medical and veterinary concerns for human and livestock health. The mitochondrial genome (mtDNA) has long been regarded as a classical model in biogenetics and species evolution research. However, the availability of mitochondrial genome data for fleas remains scarce. In this study, we sequenced Macrostylophora euteles specimens collected from the Yunnan plague focus and Citellophilus tesquorum sungaris specimens from Jilin plague focus. The obtained sequences were compared to the sequences of 24 flea species retrieved from the NCBI database, focusing on base composition, evolution rates, nucleotide polymorphism and phylogenetic analysis. All fleas analyzed contained a total of 37 genes. Gene sequences exhibited remarkable stability, with no evidence of gene rearrangement. Additionally, the base composition demonstrated a pronounced AT bias. Results from both methodologies and across the two datasets consistently indicated strong monophyly for the superfamilies Ceratophylloidea and Pulicoidea, as well as for the family Pulicidae. In contrast, the superfamily Hystrichopsylloidea, along with the families Ceratophyllidae, Leptopsyllidae and Ctenophthalmidae, were identified as paraphyletic. This research provides valuable molecular data to support taxonomic and phylogenetic studies of fleas.

Genomic Repertoire of Twenty-Two Novel Vibrionaceae Species Isolated from Marine Sediments

The genomic repertoire of vibrios has been extensively studied, particularly regarding their metabolic plasticity, symbiotic interactions, and resistance mechanisms to environmental stressors. However, little is known about the genomic diversity and adaptations of vibrios inhabiting deep-sea marine sediments. In this study, we investigated the genomic diversity of vibrios isolated from deep-sea core sediments collected using a manned submersible off Japan. A total of 50 vibrio isolates were obtained and characterized phenotypically, and by genome sequencing. From this total, we disclosed 22 novel species examining genome-to-genome distance, average amino acid identity, and phenotypes (Alivibrio: 1; Enterovibrio: 1; Photobacterium: 8; Vibrio: 12). The novel species have fallen within known clades (e.g., Fisheri, Enterovibrio, Profundum, and Splendidus) and novel clades (JAMM0721, JAMM0388, JAMM0395). The 28 remainder isolates were identified as known species: Aliivibrio sifiae (2), A. salmonicida (1), Enterovibrio baiacu (1), E. norvegicus (1), Photobacterium profundum (3), P. angustum (1), P. chitiniliticum (1), P. frigidiphilum (1), Photobacterium indicum (1), P. sanguinicancri (1). P. swingsii (2), Vibrio alginolyticus (3), V. anguillarum (1), V. campbellii (1), V. fluvialis (1), V. gigantis (1), V. lentus (1), V. splendidus (4), and V. tasmaniensis (1). Genomic analyses revealed that all 50 vibrios harbored genes associated with high-pressure adaptation, including sensor kinases, chaperones, autoinducer-2 (AI-2) signaling, oxidative damage repair, polyunsaturated fatty acid biosynthesis, and stress response mechanisms related to periplasmic and outer membrane protein misfolding under heat shock and osmotic stress. Additionally, alternative sigma factors, trimethylamine oxide (TMAO) respiration, and osmoprotectant acquisition pathways were identified, further supporting their ability to thrive in deep-sea environments. Notably, the genomes exhibited a high prevalence of antibiotic resistance genes, with antibiotic efflux pumps being the most abundant group. The ugd gene expanded in number in some novel species (Photobacterium satsumensis sp. nov. JAMM1754: 4 copies; Vibrio makurazakiensis sp. nov. JAMM1826: 3 copies). This gene may confer antibiotic (polymyxin) resistance to these vibrios.

Diversity and genomics of bacteriome-associated symbionts in treehopper Darthula hardwickii (Hemiptera: Aetalionidae) and implications of their nutritional functions

Symbionts play important roles in insect nutritional ecology, and the phylogenies of some vertically transmitted symbionts mirror the host phylogeny. Here we report the diversity, distribution, transmission, and potential functions of symbionts harbored in the aetalionid treehopper Darthula hardwickii (Aetalionidae) using multiple methods and compare the potential functions of its obligate symbiont Karelsulcia with that of the related aetalionid Aetalion reticulatum. D. hardwickii harbors Karelsulcia in bacteriomes, a yeast-like fungal symbiont (YLS) in fat bodies, and Tisiphia in both the bacteriomes and fat bodies. Karelsulcia and YLS are vertically transmitted to the ovaries but do not cluster to form a "symbiont ball" in terminal oocytes, as is the case in other auchenorrhynchan insects. YLS harbored in D. hardwickii represents the first known instance of a fungal symbiont being associated with treehoppers. Phylogenetic analysis revealed that Aetalionidae are derived from within Membracidae. Gene truncation and absence were revealed in the tryptophan biosynthetic pathway of Karelsulcia from D. hardwickii, suggesting this symbiont is no longer capable of providing this essential amino acid (EAA) to its host. Tryptophan is presumed to be supplied to D. hardwickii by YLS since tryptophan-related genes are either absent or degraded in Karelsulcia and Tisiphia. No truncated genes were found in Karelsulcia from A. reticulatum, but it has lost genes related to the synthesis of other EAAs, as in some leafhoppers. This study sheds new light on the diversity and functions of the nutritional endosymbionts of Membracoidea and processes that may have precipitated symbiont replacement in this diverse insect lineage.IMPORTANCESymbionts in sap-feeding insects play important roles related to nutrition of their hosts, which may change through evolutionary time and vary across host and symbiont lineages. This comparative genomic study indicates that, compared to the related symbionts of other leaf- and treehoppers, the Karelsulcia symbiont of the treehopper Darthula hardwickii has lost the ability to provide the EAA tryptophan to its host. This function is apparently being performed by a coexisting yeast-like symbiont (YLS). This is the first report of a YLS in a species of treehopper, which suggests that the processes involved in symbiont replacement in treehoppers are similar to those observed in other sap-sucking auchenorrhynchan insects. Phylogenetic analyses of Karelsulcia lineages of Membracoidea largely mirror the host insect phylogeny but suggest that Aetalionidae may have originated from Membracidae, in contrast to some recent phylogenies based on the genomic data from the host insects.

Identification and genome sequence analysis of a novel alphabaculovirus isolated from sweet potato leaf worm, Aedia leucomelas

Sweet potato leaf worm (Aedia leucomelas; Lepidoptera: Noctuidae) adversely affects sweet potato quality and yield. We collected infected A. leucomelas larvae with typical symptoms of baculovirus infection in Fuzhou, China in 2023 and then isolated a baculovirus, which we named Aedia leucomelas nucleopolyhedrovirus (isolate Fuzhou;AeleNPV-FZ). Helicoverpa armigera and Spodoptera exigua larvae were also susceptible to AeleNPV-FZ in laboratory assays, suggesting that AeleNPV-FZ may be useful for controlling multiple noctuid pests under field conditions. The AeleNPV-FZ genome was sequenced and de novo assembled. The genome was 135,409 bp in length with 146 open reading frames (ORFs) and 12 homologous regions (hrs) annotated for the sequence. Phylogenetic relationships inferred from concatenated core gene amino acid sequence alignment and pairwise Kimura two-parameter distances indicated that AeleNPV-FZ may be a novel member of genus Alphabaculovirus.

Gracilibacillus pellucidus sp. nov., a moderately halophilic bacterium isolated from saline soil in Xinjiang province, China

A motile, Gram-positive, moderately halophilic, catalase-positive and oxidase-negative, obligate aerobic, slender rod-shaped bacterium, strain S3-1-1T was isolated from the plant rhizosphere soil in saline soil of Xinjiang Uygur Autonomous Region. Strain S3-1-1T grew in the presence of 1-21% NaCl and at pH 7.0-9.0, with optimum growth at 3% NaCl and pH 7.5. It grew at 16-45 °C, with optimum growth at 40 °C.Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S3-1-1T should be placed within the genus Gracilibacillus and formed a separate branch. It exhibited highest similarities to Gracilibacillus ureilyticus MF38T (sequence similarity 97.7%), Gracilibacillus massiliensis Awa-1T (sequence similarity 97.5%), Gracilibacillus xinjiangensis J2T (sequence similarity 97.4%) and Gracilibacillus salitolerans SCU50T (sequence similarity 97.4%). Genomic comparisons revealed that strain S3-1-1T shares closest phylogenetic relationships with Gracilibacillus saliphilus YIM 91119T (ANI 77.4%, AAI 78.4%), Gracilibacillus thailandensis TP2-8T (ANI 77.2%, AAI 78.3%), and Gracilibacillus salitolerans SCU50T (ANI 77.3%, AAI 78.1%). However, the digital DNA-DNA hybridization (19.3-22.1%), average nucleotide identity (71.1-77.4%), and average amino acid identity (66.9-78.6%) values all fell below the recommended thresholds for species delineation, supporting its novel taxonomic status. The major cellular fatty acids were anteiso-C15:0, C16:0, iso-C15:0, and anteiso-C17:0. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and aminophospholipids. On the basis of their phenotypic, physiological, biochemical and phylogenetic characteristics, S3-1-1T represented a novel species of the genus Gracilibacillus, for which the name Gracilibacillus pellucidus sp. nov. is proposed, with S3-1-1T (= JCM 36422T = GDMCC 1.4017T) as the type strain.

Identification of a novel phage depolymerase against ST11 K64 carbapenem-resistant Klebsiella pneumoniae and its therapeutic potential

Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a clinical pathogen with a high mortality rate, and its clinical management and infection control have become a serious challenge. Phage-encoded depolymerase cleaves the capsular polysaccharide, a major virulence factor of K. pneumoniae. This study aimed to identify a phage depolymerase targeting ST11 K64 CRKP, evaluate its antimicrobial activity and therapeutic efficacy, and provide new alternative therapeutic strategies for K64 CRKP. Phages were screened from untreated hospital sewage using clinically isolated CRKP as the host bacterium. The host range, efficiency of plaque formation, optimal multiplicity of infection, adsorption efficiency, and one-step growth curve of phage vB_KpnP_IME1309 were determined by the double-layer agar plate culture method. The morphology of the phage was observed by transmission electron microscopy. Phage nucleic acids were extracted for whole-genome sequencing, and the phage-encoded depolymerase gene ORF37 was amplified by polymerase chain reaction. Next, a recombinant plasmid was constructed to induce depolymerase expression, which was verified using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In vitro bactericidal activity was determined using a combined serum assay, and the anti-K. pneumoniae biofilm effect of depolymerase was determined by crystal violet staining. Finally, a Galleria mellonella larvae infection model was established to investigate the therapeutic effect of depolymerase on larvae in vivo. Here, we isolated and characterized a phage vB_KpnP_IME1309 targeting ST11 K64 CRKP, which featured a latent period of 20 min and a burst size of approximately 290 plaque-forming units/cell. It contained 41 predicted open reading frames, of which ORF37 encoded depolymerase. The expressed and purified depolymerase Dep37 cleaved only ST11 K64 CRKP and formed a translucent halo on the agar plate. Dep37 increased the susceptibility of K. pneumoniae B1 to serum killing, inhibited CRKP biofilm formation, and degraded mature biofilms. The combination of Dep37 and kanamycin was significantly more effective in treating CRKP biofilms compared to either Dep37 or kanamycin alone. An injection of Dep37 at 5 min and 2 h after the CRKP infection of Galleria mellonella larvae increased their survival rates by up to 73% and 53%, respectively. Depolymerase Dep37 may be used as a potential method for capsule typing of K. pneumoniae, showing great promise for the development of novel alternative therapeutic strategies against ST11 K64 CRKP.

IMPORTANCE

A novel phage vB_KpnP_IME1309 targeting ST11 K64 carbapenem-resistant Klebsiella pneumoniae (CRKP) was isolated and characterized. The ORF37 encoding depolymerase gene of phage vB_KpnP_IME1309 was successfully expressed and purified. Depolymerase increases the susceptibility of CRKP to serum killing, inhibits CRKP biofilm formation, and degrades mature biofilms. The combination of depolymerase and kanamycin is significantly more effective than either depolymerase or kanamycin alone in the treatment of CRKP biofilm. Depolymerase injection at 5 min and 2 h after CRKP infection of Galleria mellonella larvae increased the survival rate of larvae by up to 73% and 53%, respectively. Depolymerase Dep37 may be used as a method for the development of novel alternative therapeutic strategies against ST11 K64 CRKP.

Aeromonas caviae subsp. aquatica subsp. nov., a New Multidrug-Resistant Subspecies Isolated from a Drinking Water Storage Tank

The increasing prevalence and dissemination of multidrug-resistant bacteria represent a serious concern for public health. Aeromonas caviae is a pathogenic microorganism that causes a wide spectrum of diseases in fish and humans and is often associated with aquatic environments and isolated from foods and animals. Here, we present the isolation and characterization of the V15T strain isolated from a drinking water storage tank in Rio de Janeiro, Brazil. The V15T strain has a genome length of 4,443,347 bp with an average G + C content of 61.78% and a total of 4028 open reading frames. Its genome harbors eight types of antibiotic resistance genes (ARGs) involving resistance to beta-lactamases, macrolides, and quinolones. The presence of blaMOX-6, blaOXA-427/blaOXA-504, and mutations in parC were detected. In addition, other ARGs (macA, macB, opmH, and qnrA) and multidrug efflux pumps (such as MdtL), along with several resistance determinants and 106 genes encoding virulence factors, including adherence (polar and lateral flagella), secretion (T2SS, T6SS), toxin (hlyA), and stress adaptation (katG) systems, were observed. The genome sequence reported here provides insights into antibiotic resistance, biofilm formation, evolution, and virulence in Aeromonas strains, highlighting the need for more public health attention and the further monitoring of drinking water systems. Also, the results of physiological and phylogenetic data, average nucleotide identity (ANI) calculation, and digital DNA-DNA hybridization (dDDH) analysis support the inclusion of the strain V15T in the genus Aeromonas as a new subspecies with the proposed name Aeromonas caviae subsp. aquatica subsp. nov. (V15T = P53320T). This study highlights the genomic plasticity and pathogenic potential of Aeromonas within household drinking water systems, calling for the revision of water treatment protocols to address biofilm-mediated resistance and the implementation of routine genomic surveillance to mitigate public health risks.

Genomic characteristics and phylogenetic analyses of colonization and infection with carbapenem-resistant Klebsiella pneumoniae in multicenter intensive care units: a cohort study

Carbapenem-resistant Klebsiella pneumoniae (CRKp) poses a major threat to global public health. This study aimed to investigate the genomic characteristics and phylogenetic relatedness of colonization and infection with CRKp among intensive care unit (ICU) patients. A total of 61 CRKp isolates, including 29 non-ICU-acquired and 32 ICU-acquired strains, were collected by active screening and infection culture from 16 ICUs through a multicenter cohort study. Following whole-genome sequencing (WGS), seven sequence types (STs) were identified, with ST11 (60.7%) being the most dominant, followed by ST15 (27.9%). Most strains (93.4%) carried the blaKPC-2 gene, while 9.8% and 3.3% of strains carried either the blaNDM-1 gene or both genes. A high abundance of virulence genes including iutA (55.7%), rmpA (18.0%), and rmpA2 (52.5%) were identified, with iutA +rmpA2 (37.7%) being the most common combination. The IncHI1B plasmid was identified in all of the 34 strains carrying the detected virulence genes. Furthermore, results from cgMLST analysis revealed 10 clusters with highly homogeneous CRKp strains, from which the potential interregional and intrahospital spread of CRKp were hypothesized. Here, this study reveals the widespread distribution of CRKp as well as locally specific strains in different regions of Anhui Province. The observed high abundance of virulence genes requires additional attention and continued monitoring. Taken together, these findings highlight the need for coordinated efforts between healthcare facilities and networks to aid CRKp control strategies and prevent spread. Moreover, we emphasize the importance of WGS in revealing additional insights, thus improving epidemiological studies and transmission control of CRKp.

IMPORTANCE

Carbapenem-resistant K. pneumoniae (CRKp) has spread rapidly to different parts of the world and poses a serious threat to global health. High genetic diversity in CRKp can introduce complexities in disease treatment and management. Intensive care unit (ICU) patients are more susceptible to acquire CRKp infections. However, most CRKp studies have focused on strains isolated from infections, rather than cases of asymptomatic CRKp colonization. This study analyzed clinical CRKp isolates from ICU patients as well as isolate cases of active colonization screening. Findings reveal the genetic diversity of CRKp in different regions of Anhui Province, emphasizing the necessity for a more comprehensive investigation of the genomic characteristics and phylogenetic relatedness of CRKp in different regions. Data regarding antimicrobial resistance genes, virulence genes, and genetic relatedness will improve the understanding of the potential risk of CRKp to public health and aid guidance for prevention and control of CRKp.

Genomic and proteomic characterization of four novel Schitoviridae family phages targeting uropathogenic Escherichia coli strain

BACKGROUND

Escherichia coli-associated urinary tract infections (UTIs) are among the most prevalent bacterial infections in humans. Typically, antibiotic medication is used to treat UTIs, but over the time, growth of multidrug resistance among these bacteria has created a global public health issue that necessitates other treatment modalities, such as phage therapy.

METHODS

The UPEC strain PSU-5266 (UE-17) was isolated from human urine samples, while phages were obtained from wastewater. These phages were characterized through host range analysis, stability studies, adsorption assays, and electron microscopy. Additionally, genomic, phylogenetic, and proteomic analyses were conducted to provide further insights.

RESULTS

The current study describes the isolation and characterization of four Escherichia coli phages designated as UE-S5a, UE-S5b, UE-M3 and UE-M6. Bactericidal assays depicted that all bacteriophages exhibited a strong lytic ability against uropathogenic E. coli (UPEC) strain PSU-5266 (UE-17). The phages displayed a broad host range (31-41%) among 104 tested isolates and adsorption rate of 15-20 min. They were stable within pH range of 5-11 and temperature range of 4 to 55 °C. Electron microscopy showed that all phages have icosahedral heads (70-74 nm) and short non-contractile tails, thus exhibiting a podovirus morphology. Sequencing results showed that they have linear double stranded DNA, genome of 73 to 76 kb in length, with GC content of 42% and short direct terminal repeats. Their genomes contain 84-88 predicted genes with putative functions predicted to 42-48% of gene products. The phylogenetic and comparative genomic analysis results depicted that these phages, sharing > 98% sequence similarity, are new members of genus Gamaleyavirus of subfamily Enquatrovirinae, in the Schitoviridae family. Mass spectrometric analysis of purified phage particles identified 44-56 phage particle-associated proteins (PPAPs) belonging to various functional groups such as lysis proteins, structural proteins, DNA packaging related proteins, and proteins involved in replication, metabolism and regulation. In addition, no genes encoding virulence factors, antibiotic resistance or lysogeny factors were identified.

CONCLUSION

The overall findings suggest that these bacteriophages are potential candidates for phage therapy in treating UTIs caused by UPEC strains.

Development of a lytic Ralstonia phage cocktail and evaluation of its control efficacy against tobacco bacterial wilt

Introduction

Bacterial wilt (BW) caused by Ralstonia pseudosolanacearum is a devastating soil-borne disease. Bacteriophages are important biocontrol resources that rapidly and specifically lyse host bacteria, showing good application potential in agricultural production.

Methods

This study isolated nine phages (YL1-YL9) and, using host range and pot experiments, identified two broader host range phages (YL1 and YL4) and two higher control efficacy phages (YL2 and YL3), which were combined to obtain five cocktails (BPC-1-BPC-5).

Results

Pot experiments showed that BPC-1 (YL3 and YL4) had the highest control efficacy (99.25%). Biological characterization revealed that these four phages had substantial thermal stability and pH tolerance. Whole genome sequencing and analysis showed that YL1, YL2, YL3, and YL4 belonged to the genus Gervaisevirus. AlphaFold 3 predictions of tail fiber protein II structures showed that YL1 differed significantly from the other phages. Amino acid sequence alignment revealed that the ORF66 (YL1) "tip domain" of contained a higher proportion of aromatic and positively charged amino acids. However, the surface of the ORF69 (YL4) "tip domain" exhibited more positively charged residues than ORF66 (YL2) and ORF70 (YL3). These characteristics are hypothesized to confer a broader host range to YL1 and YL4.

Discussion

This study demonstrates that phages assembling a broad host range and high control efficacy have better biocontrol potential, providing high-quality resources for the biological control of BW.

Surfactin: a novel Aphis gossypii killing surfactin produced by Bacillus australimaris TRM82479 of Taklamakan Desert origin

Introduction

The cotton aphid Aphis gossypii poses a global, serious threat to cotton yield and quality. Although chemical pesticides are effective, pollution and resistance are increasingly prominent, making development of new biopesticides a priority in the context of green agricultural development.

Methods

Given that reports on the activity of surfactins against A. gossypii are limited, here, 107 Bacillus strains isolated from the extreme environment of the Chinese Taklamakan Desert were screened for insecticidal activity against A. gossypii using the leaf-dip method. Active strains were characterized by morphological observation, 16S rRNA gene sequencing, and phylogenetic analysis. Secondary metabolite synthesis genes were identified by whole-genome sequencing and antiSMASH analysis.

Results

B. australimaris strain TRM82479 showed 75.00% 48-h mortality against A. gossypii. An antiSMASH analysis showed that this strain contains several gene clusters related to the synthesis of nonribosomal peptide (NRP) fengycin and lichenysin lipopeptide analogs. Cluster 1 has the highest similarity of 52% with the fengycin synthesis gene cluster, and Cluster 8 has the highest similarity of 92% with the lichenysin synthesis gene cluster. It is inferred that B. australimaris strain can produce lipopeptide analogs distinct from fengycin and lichenysin, so we isolated and identified its NRPs. The results showed that surfactin is the main insecticidal substance, with an LC50 of 0.857 mg/mL and an LC95 of 4.350 mg/mL against cotton aphids in aqueous solution. The results of the zebrafish acute toxicity experiment showed that surfactins are low-toxic to fish, indicating good biological safety.

Discussion

This study not only provides new strain resources for cotton aphid control but also demonstrates the potential of surfactins as biopesticides, laying a foundation for their future agricultural application.

Isolation and characterization of fMGyn-Pae01, a phiKZ-like jumbo phage infecting Pseudomonas aeruginosa

BACKGROUND

Pseudomonas aeruginosa is an opportunistic pathogen that causes a wide variety of infections, and belongs to the group of ESKAPE pathogens that are the leading cause of healthcare-associated infections and have high level of antibiotic resistance. The treatment of infections caused by antibiotic-resistant P. aeruginosa is challenging, which makes it a common target for phage therapy. The successful utilization of phage therapy requires a collection of well characterized phages.

METHODS

Phage fMGyn-Pae01 was isolated from a commercial phage therapy cocktail. The phage morphology was studied by transmission electron microscopy and the host range was analyzed with a liquid culture method. The phage genome was sequenced and characterized, and the genome was compared to closest phage genomes. Phage resistant bacterial mutants were isolated and whole genome sequencing and motility, phage adsorption and biofilm formation assays were performed to the mutants and host bacterium.

RESULTS

The genomic analysis revealed that fMGyn-Pae01 is a lytic, phiKZ-like jumbo phage with genome size of 277.8 kb. No genes associated with lysogeny, bacterial virulence, or antibiotic resistance were identified. Phage fMGyn-Pae01 did not reduce biofilm formation of P. aeruginosa, suggesting that it may not be an optimal phage to be used in monophage therapy in conditions where biofilm formation is expected. Host range screening revealed that fMGyn-Pae01 has a wide host range among P. aeruginosa strains and its infection was not dependent on O-serotype. Whole genome sequencing of the host bacterium and phage resistant mutants revealed that the mutations had inactivated either a flagellar or rpoN gene, thereby preventing the biosynthesis of a functional flagellum. The lack of functional flagella was confirmed in motility assays. Additionally, fMGyn-Pae01 failed to adsorb on non-motile mutants indicating that the bacterial flagellum is the phage-binding receptor.

CONCLUSION

fMGyn-Pae01 is a phiKZ-like jumbo phage infecting P. aeruginosa. fMGyn-Pae01 uses the flagellum as its phage-binding receptor, supporting earlier suggestions that flagellum might be utilized by phiKZ but differs from some other previous findings showing that phiKZ-like phages use the type-IV pili as the phage-binding receptor.

Genomic and taxonomic characterization of the Comamonas sp. nov., a bacterium isolated from Brazilian Cerrado soil

A novel strain identified as Comamonas sp. was isolated from the soil of the Brazilian savanna-like Cerrado biome, a global hotspot for biodiversity. Phylogenetic analysis based on 16 S rRNA gene sequences showed that this strain is classified as Betaproteobacteria from the family Comamonadaceae. The digital DNA-DNA hybridization (dDDH) and Average Nucleotide Identity (ANI) results, of respectively 48.6% and < 93%, indicated that Comamonas sp. consists in a new species with Comamonas testosteroni as its closest strain. Comamonas sp. is a Gram-negative, rod-shaped, and non-spore-forming bacterium. Its colonies typically exhibit a round, convex, and irregular shape with a clear color and spotted edges. It is characterized as non-fermenting, aerobic, and motile, presenting both oxidase and catalase activities. The optimal growth parameters for this bacterial strain are 30 °C, a pH range of 5-8, and 0% NaCl. In addition, its fatty acid profile included palmitic acid (C16:0) at 26.94%, 13-Methyltetradecanoic Acid (iso-C15:0) at 10.94%, myristic acid (C14:0) at 8.94%, and a summed feature comprising 16:1 ω7c, 16:1 ω6c, or 16:1 at 15.8%. Genomic analysis of Comamonas sp. revealed a GC content of 62.1% across its 5.6 Mb genome. Phylogenomic and pangenome analyses, along with in silico phenotypic characterization indicate that this strain represents a novel species within the Comamonas genus, which we propose to name Comamonas brasiliensis nov.

Pollution profiles, pathogenicity, and toxicity of bioaerosols in the atmospheric environment of urban general hospital in China

Airborne microorganisms in hospitals present significant health risks to both patients and employees. However, their pollution profiles and associated hazards in different hospital areas remained largely unknown during the extensive use of masks and disinfectants. This study investigated the characteristics of bioaerosols in an urban general hospital during the COVID-19 pandemic and found that airborne bacteria and fungi concentrations range from 87 ± 35 to 1037 ± 275 CFU/m3 and 21 ± 15 to 561 ± 132 CFU/m3, respectively, with the outpatient clinic and internal medicine ward showing the highest levels. The operating room (OR) and clinical laboratory (LA) had lower bioaerosol levels but higher microbial activities, suggesting that disinfection procedures used to clean bioaerosols may change them into a viable but non-culturable state. The dominant fungi were Cladosporium, Aspergillus, and Penicillium, while the most common viruses were human associated gemykibivirus 2 and human alpha herpesvirus 1. Besides, the dominant pathogens were Staphylococcus aureus, Salmonella enterica, and Pseudomonas aeruginosa. Bacitracin and macrolides resistance genes bacA and ermC were the most prevalent subtypes of antibiotic resistance genes. Compared to the control sample, hospital-acquired bioaerosols, particularly from the outpatient examination room and emergency room can trigger higher levels of inflammatory factors and cell toxicity but lower cell proliferation rates. Lower cell toxicity was observed in low-risk areas (intensive care unit, LA, and OR). This study provides a new method for assessing bioaerosol health risks and enhances understanding of nosocomial and opportunistic infections and their control.

The complete mitogenome of Torodora canaliculata (Yu & Wang, 2022) (Lepidoptera: Lecithoceridae) and its phylogenetic implications

The complete mitochondrial genome sequence of Torodora canaliculata has been obtained based on the Illumina next-generation sequencing technology, which is currently the first reported mitogenome in the subfamil Torodorinae. The mitogenome is 15,590 bp in length, consisting of 13 PCGs, 22 tRNAs, 2 rRNA genes and one non-coding A + T rich control region. The phylogenetic tree constructed based on the maximum likelihood (ML) methods using the whole genome sequences does well support for the sister branch relationship between T. canaliculata and Issikiopteryx taipingensis. The complete mitogenome of T. canaliculata will provide useful genetic information for the evolutionary relationship of the Gelechioidea.

Phage vB_Kpn_HF0522: Isolation, Characterization, and Therapeutic Potential in Combatting K1 Klebsiella pneumoniae Infections

Purpose

Klebsiella pneumoniae is a globally prevalent pathogen responsible for severe hospital- and community-acquired infections, and presents significant challenges for clinical management. Current therapeutic strategies are no longer able to meet the clinical needs; therefore, there is an urgent need to develop novel therapeutic strategies. This study aimed to evaluate the efficacy of phage therapy in treating bacterial infections.

Methods

Isolated phage vB_Kpn_HF0522 and phage morphology were observed using transmission electron microscopy. Analysis of vB_Kpn_HF0522 characteristics, including optimal multiplicity of infection (MOI), one-step growth curve, host range, stability in different environments, and adsorption capacity. The phage genomic sequence was analyzed to explore evolutionary relationships. The effect of phage vB_Kpn_HF0522 on biofilms was assessed using crystal violet staining assay. The Galleria mellonella (G. mellonella) infection model and mouse infection models were established to evaluate the practical application potential of the phage and the fitness cost of phage-resistant bacteria.

Results

Phage was isolated from hospital sewage for experimental studies. Genome analysis revealed that vB_Kpn_HF0522 is a double-stranded linear DNA virus. Biological characterization demonstrated that this phage specifically targets serotype K1 K. pneumoniae with an optimal multiplicity of infection (MOI) of 0.01, effectively disrupting biofilms and inhibiting bacterial growth. The bacterial growth rate remained largely unchanged after the phage resistance mutation, but mice infected with the mutant strain showed significantly higher survival rates than those infected with the wild-type strain. vB_Kpn_HF0522 increased the survival rate of infected G. mellonella from 12.5% to 75%, inhibited incisional surgical site infections and alleviated inflammatory response in mice.

Conclusion

These findings indicate that vB_Kpn_HF0522 has significant potential for treating specific bacterial infections, and may serve as an antimicrobial agent for research and clinical anti-infective therapy.

Metabolites Discovery from Streptomyces xanthus: Exploring the Potential of Desert Microorganisms

The Taklamakan Desert is an extreme environment supporting a unique and diverse microbial community with significant potential for exploration. Strain TRM70308T, isolated from desert soil, shares 98.43% 16S rRNA gene sequence similarity with Streptomyces alkaliterrae OF1T. Polyphasic taxonomy confirmed TRM70308T as a novel species, named Streptomyces xanthus. Genomic analysis revealed that only one of the strain's 25 biosynthetic gene clusters (BGCs) formed a cluster of gene families (CGFs) within the MIBiG database, emphasizing its genomics uniqueness. LC-MS/MS and Feature-Based Molecular Networking (FBMN) identified 33 metabolites across various categories, including alkaloids, saponins, benzoic acids, and benzofurans, most of which remain uncharacterized. Further chemical investigation led to the isolation of one novel compound, aconicarpyrazine C, and four known compounds: thiolutin, dibutyl phthalate, bis(2-ethylhexyl) phthalate, and N-acetyltryptamine. Thiolutin exhibited strong activity against five local fungal pathogens that cause plant diseases, with a production yield of 270 mg/L. These results establish a foundation for pilot-scale thiolutin production and its potential development as an antifungal agent for agricultural applications. Our findings highlight deserts as a valuable source of novel actinomycetes and bioactive natural products with immense potential for future research and development.

The characterization of outer membrane vesicles (OMVs) and their role in mediating antibiotic-resistance gene transfer through natural transformation in Riemerella anatipestifer

Riemerella anatipestifer (R. anatipestifer, RA) is the etiological agent of duck serositis, an acute multisystemic disease in ducks that is globally distributed and causes serious economic losses in the duck industry. Despite exhibiting multidrug resistance, the transmission mechanism of its antibiotic resistance genes (ARGs) remains incompletely identified. To contribute to addressing this gap, in this study, outer membrane vesicles (OMVs) from the RA strain CH-1 were isolated and characterized to investigate their involvement in ARG transfer in RA. Sequencing and data analysis revealed that RA CH-1 OMVs had ∼2.04 Mb genomic size, representing 88.3 % of the RA CH-1 genomic length. Proteomic analysis showed that OMVs contained 577 proteins, representing 27.2 % of the bacterial proteins. Subsequent investigations demonstrated that OMVs from antibiotic-resistant strains transferred ARG fragments and plasmids to the sensitive strain RA ATCC11845, relying on the natural transformation system, and the transformants exhibited corresponding resistance. Overall, OMV-mediated horizontal transfer of ARGs serving as a significant mechanism for acquiring multiple resistance genes in R. anatipestifer.

Prevalence and Molecular Characterization of Porcine Parvovirus 2 in Southwest China During 2020-2023

Porcine parvovirus (PPV) is a non-enveloped, single-stranded linear DNA virus that induces reproductive disorders in sows, particularly abortions in primiparous sows. This study investigated the prevalence of PPV in the southwestern region and conducted molecular characterization of PPV strains. An epidemiological survey was conducted on 1534 aborted fetuses from the southwestern region between 2020 and 2023, revealing an abortion rate of 3.00% due to PPV2, with the highest rate of 3.77% in Sichuan. Additionally, 2973 blood samples from sows were tested using ELISA, showing a PPV2 antibody positivity rate of 73.03% to 90%. Through shotgun metagenomics, PPV2 SC2020 was identified in aborted fetal samples from a pig farm in Pengzhou, Sichuan. PCR sequencing analysis yielded seven PPV2 genomic sequences, and the phylogenetic analysis of eight PPV2 strains with thirty reference strains showed distinct evolutionary branches. The virus was successfully isolated from PPV2-positive samples, and the phylogenetic analysis of PPV2 SC2020 revealed ORF1 gene homology of 94.9% to 99.3% and the ORF2 gene homology of 93.1% to 98.0%, with 34 reference strains. Homologous recombination analysis indicated that SC2020 is a recombinant strain of HeB03 and S1.

Geographic variation in abundance and diversity of Acinetobacter baumannii Vieuvirus bacteriophages

Introduction

Prophages play a crucial role in the genomic diversity of Acinetobacter baumannii, contributing to its pathogenicity and adaptation.

Methods

In this study, we induced and sequenced seven prophages from five isolates of A. baumannii. These were analyzed with 967 prophages identified from various isolates worldwide, plus 21 genomes of other phages infecting A. baumannii previously reported in NCBI. To have an overview of the populations of the prophages infecting A. baumannii.

Results

Our analysis revealed 13 major prophage clusters within the analyzed A. baumannii isolates. Notably, prophages belonging to the Vieuvirus genus were the most prevalent. Specifically, Vieuvirus-related phages were frequently identified in isolates from Thailand, Mexico, China, and South Korea, which show the geographic prevalence of A. baumannii prophages.

Discussion

This study highlights the importance of considering geographic factors to fully understand prophage diversity and their significant role in the evolutionary dynamics of A. baumannii.

Phylogenetic and Codon Usage Bias Analysis Based on mt-DNA of Cyphochilus crataceus (Coleoptera: Melolonthinae) and Its Neighboring Species

Background/Objectives: In order to determine the basic structural characteristics of the mitochondrial genome of Cyphochilus crataceus and explore its phylogenetic status, as well as to understand the codon usage bias of Melolonthinae species, the next-generation sequencing was used to obtain the mitochondrial genome sequence of C. crataceus. Methods: Combined with 121 sequences of Scarabaeidae downloaded from GeneBank, a phylogenetic tree of the family was constructed using PhyloSuite v 1.2.3 software. Additionally, the codon composition and codon usage bias of the mitochondrial protein-coding genes of C. crataceus and 16 other Melolonthinae species were analyzed. Results: The results showed that the mitochondrial genome sequence of C. crataceus was 17,946 bp in length, with an A + T content of 71.82%, exhibiting a significant AT bias and a preference for ending with the base A/U, showed typical features of Scarabaeidae mitogenomes. The analysis of RSCU, ENC-plot, and neutrality plot revealed that factors such as nucleotide composition, gene mutations, and natural selection can have an impact on codon usage bias, but the intensity varies. For C. crataceus, codon usage preference is primarily influenced by gene mutations. The phylogenetic tree results indicated that, apart from Melolonthinae, all other subfamilies within Scarabaeidae were monophyletic. Conclusions: This study not only enriches the mitochondrial genome information of scarab beetles in the subfamily Melolonthinae but also provides important foundational information for molecular systematics, population genetics, and molecular ecology research in the family Scarabaeidae.

De novo transcriptome assembly and discovery of drought-responsive genes in white spruce (Picea glauca)

Forests face an escalating threat from the increasing frequency of extreme drought events driven by climate change. To address this challenge, it is crucial to understand how widely distributed species of economic or ecological importance may respond to drought stress. In this study, we examined the transcriptome of white spruce (Picea glauca (Moench) Voss) to identify key genes and metabolic pathways involved in the species' response to water stress. We assembled a de novo transcriptome, performed differential gene expression analyses at four time points over 22 days during a controlled drought stress experiment involving 2-year-old plants and three genetically distinct clones, and conducted gene enrichment analyses. The transcriptome assembly and gene expression analysis identified a total of 33,287 transcripts corresponding to 18,934 annotated unique genes, including 4,425 genes that are uniquely responsive to drought. Many transcripts that had predicted functions associated with photosynthesis, cell wall organization, and water transport were down-regulated under drought conditions, while transcripts linked to abscisic acid response and defense response were up-regulated. Our study highlights a previously uncharacterized effect of drought stress on lipid metabolism genes in conifers and significant changes in the expression of several transcription factors, suggesting a regulatory response potentially linked to drought response or acclimation. Our research represents a fundamental step in unraveling the molecular mechanisms underlying short-term drought responses in white spruce seedlings. In addition, it provides a valuable source of new genetic data that could contribute to genetic selection strategies aimed at enhancing the drought resistance and resilience of white spruce to changing climates.

Size Distribution and Pathogenic Potential of Culturable Airborne Clostridium spp. in a Suburb of Toyama City, Japan

Clostridium spp. are anaerobic, Gram-positive, spore-forming bacteria comprising more than 150 species, some of which are important pathogens of humans and animals. Members of this genus have been isolated from a number of environments, but are rarely found in the atmosphere. In the present study, we exami-ned culturable airborne Clostridium spp. and clarified their pathogenicity. We obtained 19 culturable Clostridium isolates from size-fractionated samples collected at a suburban site in Toyama, central Japan. Culturable Clostridium spp. were detected in particles larger than 1.1‍ ‍μm, and the size distribution peaked at 2.1-3.3‍ ‍μm, corresponding to the spore size of Clostridium spp. More Clostridium spp. were detected in coarse particles >2.1‍ ‍μm not only by culture methods, but also by 16S rRNA gene amplicon sequencing. Whole-genome sequencing (WGS) identified seven Clostridium species, among which Clostridium perfringens was predominant. Moreover, WGS revealed that C. perfringens isolates harbored many virulence and antibiotic resistance genes with the potential to cause gas gangrene. The detection and characterization of potential airborne pathogens are crucial for preventing the spread of diseases caused by these pathogens. To the best of our knowledge, this is the first study to demonstrate that anaerobic Clostridium spp. may be transported under aerobic conditions in the atmosphere and pose potential risks to human health.

The complete mitochondrial genome and phylogenetic implications of Paradoxopsyllus custodis and Stenischia montanis yunlongensis

Fleas, which are ubiquitous small wingless parasitic insects, have a significant impact on human and animal health globally. In this study, we sequenced and analyzed the complete mitochondrial genomes of Paradoxopsyllus custodis and Stenischia montanis yunlongensis. The lengths of these genomes were 15,375 bp and 15,651 bp respectively, encompassing a total of 37 genes. Notably, all nucleotide combinations displayed a marked AT preference, with ATN as start codon for all 13 protein-coding genes in both species. Furthermore, only two genes in Paradoxopsyllus custodis were terminated with an incomplete stop codon T(AA). The five most frequently utilized codons among the 13 PCGs in both species ended with A / U, and their relative synonymous codon usage values surpassed 2. Phylogenetic relationships among fleas were assessed using maximum likelihood (ML) and Bayesian inference (BI), providing support for the paraphyletic of Leptopsyllidae. This study not only enhances our understanding of the mitochondrial genome within the genera Paradoxopsyllus and Stenischia, but also offers valuable genetic markers for the taxonomic identification and phylogenetic evolution within the order Siphonaptera.

Whole Genome Sequencing of a Non-O1/O139-Group Vibrio cholerae Isolated from a Patient with a Bloodstream Infection

Background

Diarrhea caused by non-O1/O139-group V. cholerae (NOVC) tends to be mild and can be readily overlooked. In this report, a NOVC strain designated XXM was isolated from the blood of a 68-year-old male undergoing surgical treatment for a bile duct malignancy in October 2023.

Methods

XXM was identified through a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Virulence genes were detected using a V. cholerae ctxA/ctxB virulence gene dual real-time fluorescent PCR kit. AST-GN13 and AST-GN334 cards were used to test the resistance against 16 antibiotics with a Vitek2 compact system. The genomic and phylogenetic characteristics of XXM were established through whole genome sequencing (WGS).

Results

Serum agglutination tests revealed the isolate to be a non-O1/non-O139 strain. The strain was sensitive to all 16 tested antibiotics and did not carry the ctxA/ctxB gene. MLST analyses identified the XXM strain as ST1538. WGS analyses identified 8 classes of virulence genes with different functions. A total of 3.541 bacterial genes, including 3.482 from V. cholerae, were annoted using the Non-Redundant Protein Sequence (NR) database. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses annotated 32 genes including 17 key proteins involved in the V. cholerae biofilm pathway. Comparative analyses using the Pathogen Host Interactions Database (PHI) identified the YbeY gene. Evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG) was used to annotate 3280 genes in 21 categories. Phylogenetic analyses revealed that strain XXM was closely related to V. cholerae strain Man9.

Conclusion

The XXM carries multiple virulence genes, and this genomic analysis of the XXM in comparison with other NOVC strains provides important information for an improved understanding of the pathogenicity of NOVC in clinical samples.

Genomic Diversity and Virulence Factors of Clostridium perfringens Isolated from Healthy and Necrotic Enteritis-Affected Broiler Chicken Farms in Quebec Province

Avian necrotic enteritis due to the Gram-positive bacterium Clostridium perfringens has re-emerged following the ban on antibiotic growth promoters in many poultry producing countries. The limited number of previous studies has left important gaps in our understanding of the genetic diversity and virulence traits of the pathogen. To address these knowledge gaps, in this study, we sequenced the genomes of 41 Clostridium perfringens isolates recovered from commercial broiler chicken flocks in Quebec, Canada, including isolates from healthy birds and those affected by necrotic enteritis. We sought to understand the pangenome diversity and interrogated the genomes for key virulence factors involved in necrotic enteritis pathogenesis. On average, the genomes had a GC content of 28% and contained 3206 coding sequences. A variable presence of toxins, degradative hydrolytic enzymes, and collagen-binding proteins was also found. Through pangenome analysis, we revealed a total of 10,223 genes, 652 (6.4%) of which formed the core genome. Additionally, we identified 17 different plasmids, 12 antibiotic resistance genes, and nine prophage regions. Overall, our results demonstrated a relatively high genetic diversity among chicken Clostridium perfringens isolates collected from the same geographical location, offering new insights into potential virulence mechanisms and adaptation of the pathogen within poultry populations.

Research Note: Comparison of Enterococcus cecorum genomes from broiler chickens with enterococcal spondylitis in Australian farms and strains from other countries

Chickens in Australia have recently been identified with symptoms and morphological findings including spondylitis attributed to pathogenic Enterococcus cecorum. Notably, there is limited information on clinical E. cecorum strains in Australia. The cpsO gene, located downstream of the capsular polysaccharide (cps) locus, was recently reported to successfully differentiate between pathogenic and commensal E. cecorum strains, as this gene is highly conserved in the pathogenic strains. In this study, pathogenic E. cecorum, with a conserved cpsO gene, was detected on 1 of the 2 farms studied in Australia. E. cecorum strains isolated from clinical sites of the diseased birds from the second farm did not have the cpsO gene and were distant from the isolates of the first farm. A cpsO PCR of the caecal content of the birds on this farm was positive, while cpsO PCR of washed culture plates where the tissue extracts were spread onto and incubated for bacterial growth was negative. This suggests that pathogenic E. cecorum with the cpsO gene, as detected in Farm 1 and reported in other countries, was present in the second farm but could not grow on the selective agar plates during the initial step of E. cecorum isolation. Nevertheless, E. cecorum isolated from the clinical sites on the second farm might represent the pathogenic strain, but further animal studies are required to validate this possibility. Phylogenetic analysis showed that the pathogenic strains in Australia were most closely related to the clinical strains in North America.

Genomic analysis of Salmonella Heidelberg isolated from the Brazilian poultry farms

The rapid expansion of broiler chicken production in Brazil has presented significant sanitation challenges within the poultry industry. Among these challenges, Salmonella enterica subsp. enterica serotype Heidelberg stands as a contributor to global salmonellosis outbreaks. This study analyzed 13 draft genomes of Salmonella Heidelberg isolated from the pre-slaughter broiler chickens farms in Brazil. By conducting in silico analysis of these genomes, the study investigated genome similarity based on single nucleotide polymorphisms (SNPs) and identified genes encoding resistance to antimicrobials, sanitizers, and virulence factors. Furthermore, mobile genetic elements (MGE) were identified to assess their potential role in propagating genes through horizontal gene transfer. A risk classification was also applied based on the resistomes. The genomes revealed a high prevalence of genes conferring resistance to aminoglycosides, fosfomycin, sulfonamides, tetracycline, and genes linked to quaternary ammonium resistance. The study also uncovered six Salmonella pathogenicity islands (SPI) and over 100 genes encoding virulence factors. The association of MGE with antibiotic-resistant genes sul2 and blaCMY-2 raised concerns about the potential transfer to other bacteria, posing a substantial risk for spreading resistance mechanisms according to established risk protocols. Additionally, SNP analysis indicated close phylogenetic relationships among some isolates, suggesting a common origin. This study enhances our understanding of Salmonella Heidelberg strains by identifying key risk factors for transmission and revealing the association between resistance genes and MGEs. This insight provides a foundation for developing and implementing effective control, monitoring, and treatment strategies in the poultry industry.

Genomic characteristics of Salmonella Montevideo and Pomona: impact of isolation source on antibiotic resistance, virulence and metabolic capacity

Salmonella enterica is known for its disease-causing serotypes, including Montevideo and Pomona. These serotypes have been found in various environments, including river water, sediments, food, and animals. However, the global spread of these serotypes has increased, leading to many reported infections and outbreaks. The goal of this study was the genomic analysis of 48 strains of S. Montevideo and S. Pomona isolated from different sources, including clinical. Results showed that environmental strains carried more antibiotic resistance genes than the clinical strains, such as genes for resistance to aminoglycosides, chloramphenicol, and sulfonamides. Additionally, the type 4 secretion system, was only found in environmental strains. .Also many phosphotransferase transport systems were identified and the presence of genes for the alternative pathway Entner-Doudoroff. The origin of isolation may have a significant impact on the ability of Salmonella isolates to adapt and survive in different environments, leading to genomic flexibility and a selection advantage.

Unveiling the genetic basis and metabolic rewiring behind the galactose-positive phenotype in a Streptococcus thermophilus mutant

Streptococcus thermophilus (S. thermophilus) is a widely used starter culture in dairy fermentation, but most strains are galactose-negative and only metabolize glucose from lactose hydrolysis. In this study, we aimed to uncover the mechanisms underlying the acquisition of a stable galactose-positive (Gal+) phenotype in a mutant strain of S. thermophilus IMAU10636. By treating the wild-type strain with the mutagenic agent N-methyl-N-nitro-N-nitrosoguanidine, we successfully isolated a Gal+ mutant, S. thermophilus IMAU10636Y. Comparative enzyme activity assays revealed that the mutant exhibited higher β-galactosidase and galactokinase activities, but lower glucokinase and pyruvate kinase activities compared to the wild-type. High-performance liquid chromatography analysis confirmed the mutant's enhanced ability to utilize lactose and galactose, leading to increased glucose secretion. Integrated genome and transcriptomics analyses provided deeper insights into the underlying genetic and metabolic mechanisms. We found that the metabolism regulatory network of the glycolysis / Leloir pathway was altered in the mutant, possibly due to the upregulation of the gene expression in the galR-galK intergenic region. This likely led to increased RNA polymerase binding and transcription of the gal operon, ultimately promoting the Gal+ phenotype. Additionally, we identified a mutation in the scrR gene, encoding a LacI family transcriptional repressor, which also contributed to the Gal+ phenotype. These findings offer new perspectives on the metabolic rewiring and regulatory mechanisms that enable S. thermophilus to acquire the ability to metabolize galactose. This knowledge can inform strategies for engineering and selecting Gal+ strains with desirable fermentation characteristics for dairy applications.

Comparative genomic analysis provides new insights into non-typhoidal Salmonella population structure in Peru

Non-typhoidal Salmonella (NTS) is one of the leading causes of foodborne outbreaks worldwide, especially in low- and middle-income countries such as Peru. To understand the dynamics of NTS serotypes circulating in the country, the whole genomes of 1122 NTS strains from 1998 to 2018 were analyzed using phylogenomic and comparative genomics tools. A total of 40 different Sequences Type (STs) were identified, the five most frequent being ST-32 (S. Infantis, 37.25%), ST-11 (S. Enteritidis, 23.8%), ST-19 (S. Typhimurium, 14.17%), ST-31 (S. Newport, 6.77%), and ST-413 (S. Mbandaka, 4.72%). Furthermore, the maximum likelihood phylogeny showed high clonality between strains from the same ST recovered from different isolation sources, as well as a variable recombination rate, when comparing each ST individually. Moreover, several virulence factors involved in adherence and invasion, as well as plasmids and prophages, are strongly associated with the most frequent STs, while multidrug resistance markers are mostly linked to ST-32. This work provides an overview of the main genomic characteristics linked to the high-frequency ST, which have undergone few genetic modifications over time, suggesting a high adaptation of these NTS circulating clones in Peru.

The complete mitochondrial genome of Dimorphopterus japonicus (Hidaka, 1959) (Hemiptera, Lygaeoidea) and phylogenetic relationships within the Lygaeoidea superfamily

Dimorphopterus japonicus is a kind of pest which seriously harms sorghum and millet. In this study, we sequenced the mitochondrial whole genome of D. japonicus (Hidaka, 1959), and characterized and analyzed the mitogenome. The D. japonicus genome length is 15,473 bp, and it exhibits a typical high A + T content (77.6%). The mitogenomic structure of D. japonicus is highly conservative and there are no gene rearrangements. The evolutionary rates of the PCGs are in the order of atp8 > nad3 > nad6 > nad2 > nad5 > atp6 > nad4 > nad4L > cox2 > nad1 > cytb > cox3 > cox1. By using the Bayesian inference and maximum likelihood methods, we inferred the phylogenetic relationships within Lygaeoidea and estimated their divergence times based on concatenated mitogenome genes. The stable clades of (Oxycarenidae + Piesmatidae), (Malcidae + Colobathristidae), (Meschiidae + Berytidae), and (Blissidae+(Cymidae + Ninidae)) were consistently recovered in all analyses. Estimated divergence times revealed that the divergence time of the Lygaeoidea was 99.4 Ma (95% HPD: 83.4-124.8 Ma), and most lygaeoid families diverged during the early Cretaceous to late Paleogene. Berytidae is the latest differentiation in the lygaeoid families, and the genus Dimorphopterus was differentiated in 45.9 Ma (95% HPD: 39.8-47.7 Ma). This study is of great significance for reconstructing the phylogeny of Lygaeoidea and providing insights into its evolutionary history.

Streptococcus suis strains with novel and previously undescribed capsular loci circulate in Europe

Streptococcus suis (S. suis) causes serious diseases in pigs, and certain serotypes also pose a risk to humans. The expression of capsular polysaccharides (CPS) is considered an important virulence property of the pathogen. Recently, some serotypes have been reclassified as other organisms, while novel S. suis serotypes are being described. Although the CPS can be typed by serological methods using antisera, the presence of unique sequences for each capsular polysaccharide synthesis locus (cps locus) enables convenient PCR-based serotyping. In this study, we characterized 33 non-serotypeable S. suis strains obtained from diseased pigs in the Czech Republic by sequencing and analyzing the cps locus. Phylogenetic analysis of cpn60 confirmed that all isolates belong to the S. suis species. Four isolates had cps loci similar to the previously described reference S. suis serotypes. Eleven isolates were classified as recently described novel cps loci (NCLs). Nine isolates had substitutions, insertions and/or deletions in their cps loci and showed only partial similarity to the already described NCLs. Another eight isolates had previously undescribed cps locus structures and were proposed as novel NCLs. One isolate had lost the genes encoding capsule biosynthesis. Only four sequence types (ST) had two isolates each; the rest had unique STs. Two isolates harbored the classical virulence associated genes (VAGs) mrp and sly. Another isolate had only the mrp gene, while a different isolate harbored only the sly gene. This study provides insight into untypeable isolates in the Czech Republic, highlighting the genetic diversity and potential for novel serotype identification.

Deciphering the Genetic Architecture of Staphylococcus warneri Prophage vB_G30_01: A Comprehensive Molecular Analysis

The current knowledge of Staphylococcus warneri phages is limited, with few genomes sequenced and characterized. In this study, a prophage, vB_G30_01, isolated from Staphylococcus warneri G30 was characterized and evaluated for its lysogenic host range. The phage was studied using transmission electron microscopy and a host range. The phage genome was sequenced and characterized in depth, including phylogenetic and taxonomic analyses. The linear dsDNA genome of vB_G30_01 contains 67 predicted open reading frames (ORFs), classifying it within Bronfenbrennervirinae. With a total of 10 ORFs involved in DNA replication-related and transcriptional regulator functions, vB_G30_01 may play a role in the genetics and transcription of a host. Additionally, vB_G30_01 possesses a complete set of genes related to host lysogeny and lysis, implying that vB_G30_01 may influence the survival and adaptation of its host. Furthermore, a comparative genomic analysis reveals that vB_G30_01 shares high genomic similarity with other Staphylococcus phages and is relatively closely related to those of Exiguobacterium and Bacillus, which, in combination with the cross-infection assay, suggests possible cross-species infection capabilities. This study enhances the understanding of Staphylococcus warneri prophages, providing insights into phage-host interactions and potential horizontal gene transfer.

Carbapenem-resistant Klebsiella oxytoca transmission linked to preoperative shaving in emergency neurosurgery, tracked by rapid detection via chromogenic medium and whole genome sequencing

Objectives

This study describes the detection and tracking of emergency neurosurgical cross-transmission infections with carbapenem-resistant Klebsiella oxytoca (CRKO).

Methods

We conducted an epidemiological investigation and a rapid screening of 66 surveillance samples using the chromogenic selective medium. Two CRKO isolates from infected patients and three from the preoperative shaving razors had similar resistance profiles identified by the clinical laboratory.

Results

The whole genome sequencing (WGS) results identified all isolates as Klebsiella michiganensis (a species in the K. oxytoca complex) with sequence type 29 (ST29) and carrying resistance genes bla KPC-2 and bla OXY-5, as well as IncF plasmids. The pairwise average nucleotide identity values of 5 isolates ranged from 99.993% to 99.999%. Moreover, these isolates displayed a maximum genetic difference of 3 among 5,229 targets in the core genome multilocus sequence typing scheme, and the razors were confirmed as the contamination source. After the implementation of controls and standardized shaving procedures, no new CRKO infections occurred.

Conclusion

Contaminated razors can be sources of neurosurgical site infections with CRKO, and standard shaving procedures need to be established. Chromogenic selective medium can help rapidly identify targeted pathogens, and WGS technologies are effective mean in tracking the transmission source in an epidemic or outbreak investigation. Our findings increase the understanding of microbial transmission in surgery to improve patient care quality.

Comparative genomic analysis of pathogenic factors of Listeria spp. using whole-genome sequencing

Listeria monocytogenes is an important foodborne pathogen known for causing listeriosis. To gain insights into the pathogenicity, genetic characterization, and evolution of various Listeria species, in vitro cell adhesion and invasion ability assays and whole-genome sequencing were performed using four Listeria strains isolated from livestock and poultry slaughterhouses. The four Listeria strains exhibited adhesion and invasion abilities in Caco-2 and RAW264.7 cells. Pathogenic Liv1-1 and Lm2-20 had higher adhesion ability, but non-pathogenic Lin4-99 was more invasive than Lm2-20 (p < 0.05). Genetic characterization revealed the presence of a single chromosome without plasmid across four strains with similar whole-genome sizes and G + C% content. Analysis of key pathogenic genes underscored the presence of multiple virulence genes among the four Listeria strains. In contrast, non-pathogenic Listeria lacked LIPI-1, LIPI-2, and LIPI-3 genes, which could possibly be the cause of their non-pathogenicity despite their in vitro cell adhesion and invasion abilities. Thus, genetic determinants of Listeria do not necessarily predict cell adhesion and/or invasive ability in vitro. This study presents a comprehensive comparative genome-wide analysis of four Listeria strains, offering invaluable insights into the pathogenesis of the Listeria genus.

Pseudoalteromonas simplex sp. nov. Isolated from the Skin of Bandtail Puffer Fish (Sphoeroides spengleri)

A novel bacterial isolate A520T (A520T = CBAS 737T = CAIM 1944T) was obtained from the skin of bandtail puffer fish Sphoeroides spengleri (Tetraodontidae Family), collected in Arraial do Cabo (Rio de Janeiro, Brazil). A520T is Gram-stain-negative, flagellated and aerobic bacteria. Optimum growth occurs at 25-30 °C in the presence of 3% NaCl. The genome sequence of the novel isolate consisted of 4.5 Mb (4082 coding genes and G+C content of 41.1%). The closest phylogenetic neighbor was Pseudoalteromonas shioyasakiensis JCM 18891T (97.9% 16S rRNA sequence similarity, 94.8% Average Amino Acid Identity, 93% Average Nucleotide Identity and 51.8% similarity in Genome-to-Genome-Distance). Several in silico phenotypic features are useful to differentiate A520T from its closest phylogenetic neighbors, including trehalose, D-mannose, cellobiose, pyrrolidonyl-beta-naphthylamide, starch hydrolysis, D-xylose, lactose, tartrate utilization, sucrose, citrate, glycerol, mucate and acetate utilization, malonate, glucose oxidizer, gas from glucose, nitrite to gas, L-rhamnose, ornithine decarboxylase, lysine decarboxylase and yellow pigment. The genome of the novel species contains 3 gene clusters (~ 66.81 Kbp in total) coding for different types of bioactive compounds that could indicate ecological roles pertaining to the bandtail puffer fish host. Based on genome-based taxonomic approach, strain A520T (A520T = CBAS 737T = CAIM 1944T) is proposed as a new species, Pseudoalteromonas simplex sp. nov.

Molecular characterization of Streptococcus suis isolates recovered from diseased pigs in Europe

Streptococcus suis is a major swine pathogen and zoonotic agent, causing important economic losses to the porcine industry. Here, we used genomics approaches to characterize 251 S. suis isolates recovered from diseased pigs across Belgium, France, Germany, Hungary, the Netherlands, Spain, and the United Kingdom. We identified 13 serotypes, being serotypes 9 and 2 the most prevalent, and 34 sequence types (STs), including 16 novel STs, although ST16 and ST1 dominated the strain population. Phylogenetic analysis revealed complex genetic relationships, notable geographic clustering, and potential differential capacity for capsular switching among serotype 9 isolates. We found antimicrobial resistance (AMR) genes in 85.3% of the isolates, with high frequencies of genes conferring resistance to tetracyclines and macrolides. Specifically, 49.4% of the isolates harbored the tetO gene, and 64.9% possessed the ermB gene. Additionally, we observed a diverse array of virulence-associated genes (VAGs), including the classical VAGs mrp, epf, and sly, with variable presence across different genotypes. The high genetic diversity among European S. suis isolates highlights the importance of targeted antimicrobial use and flexible vaccine strategies. Rapid strain characterization is crucial for optimizing swine health management, enabling tailored interventions like the development of autovaccines to mitigate S. suis infections.

Genetic and phenotypic diversity of Flavobacterium psychrophilum isolates from Czech salmonid fish farms

BACKGROUND

The salmonid pathogen Flavobacterium psychrophilum poses a significant economic threat to global aquaculture, yet our understanding of its genetic and phenotypic diversity remains incomplete across much of its geographic range. In this study, we characterise the genetic and phenotypic diversity of 70 isolates collected from rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta m. fario) from fish farms in the Czech Republic between 2012 and 2019 to compare their genomic content with all draft or complete genomes present in the NCBI database (n = 187).

RESULTS

The Czech isolates underwent comprehensive evaluation, including multiplex PCR-based serotyping, genetic analysis, antimicrobial resistance testing, and assessment of selected virulence factors. Multiplex PCR serotyping revealed 43 isolates as Type 1, 23 as Type 2, with sporadic cases of Types 3 and 4. Multi-locus sequence typing unveiled 12 sequence types (ST), including seven newly described ones. Notably, 24 isolates were identified as ST329, a novel sequence type, while 22 were classified as the globally-distributed ST2. Phylogenetic analysis demonstrated clonal distribution of ST329 in the Czech Republic, with these isolates lacking a phage sequence in their genomes. Antimicrobial susceptibility testing revealed a high proportion of isolates classified as non-wild type with reduced susceptibility to oxolinic acid, oxytetracycline, flumequine, and enrofloxacin, while most isolates were classified as wild type for florfenicol, sulfamethoxazole-trimethoprim, and erythromycin. However, 31 isolates classified as wild type for florfenicol exhibited minimum inhibitory concentrations at the susceptibility breakpoint.

CONCLUSION

The prevalence of the Czech F. psychrophilum serotypes has evolved over time, likely influenced by the introduction of new isolates through international trade. Thus, it is crucial to monitor F. psychrophilum clones within and across countries using advanced methods such as MLST, serotyping, and genome sequencing. Given the open nature of the pan-genome, further sequencing of strains promises exciting discoveries in F. psychrophilum genomics.

Differences in Mitochondrial Cytochrome b Binding Mediate Selectivity of Bifenazate toward Phytophagous and Predatory Mites

Bifenazate, a potent acaricide that targets mitochondrial complex III, exhibits selective toxicity (>280-fold) toward phytophagous mites versus predatory mites. Here, a systematic study was conducted to clarify the selective mechanism. Nontarget factors were excluded through epidermal penetration tests and assessment of detoxification enzymes' activities. Quantification of IC50 values, ATP content, and reactive oxygen species (ROS) levels revealed that differences in drug-target binding determine the toxicity selectivity. Structural modeling and molecular docking revealed that variations in key amino acid sites within the cytochrome b (cytb) target might regulate this selectivity, which was validated through a microscale thermophoresis assay. Significant disparities were observed in the binding affinity between bifenazate and recombinant cytb proteins derived from phytophagous mites and predatory mites. Mutating isoleucine 139 to leucine notably reduced the binding affinity of bifenazate to cytb. Insights into bifenazate selectivity between phytophagous and predatory mites inform a basis for developing compounds that target cytochrome b.

Development of tools for the genetic manipulation of Campylobacter and their application to the N-glycosylation system of Campylobacter hepaticus, an emerging pathogen of poultry

Various species of campylobacters cause significant disease problems in both humans and animals. The continuing development of tools and methods for genetic and molecular manipulation of campylobacters enables the detailed study of bacterial virulence and disease pathogenesis. Campylobacter hepaticus is an emerging pathogen that causes spotty liver disease (SLD) in poultry. SLD has a significant economic and animal welfare impact as the disease results in elevated mortalities and significant decreases in egg production. Although potential virulence genes of C. hepaticus have been identified, they have not been further studied and characterized, as appropriate genetic tools and methods to transform and perform mutagenesis studies in C. hepaticus have not been available. In this study, the genetic manipulation of C. hepaticus is reported, with the development of novel plasmid vectors, methods for transformation, site-specific mutagenesis, and mutant complementation. These tools were used to delete the pglB gene, an oligosaccharyltransferase, a central enzyme of the N-glycosylation pathway, by allelic exchange. In the mutant strain, N-glycosylation was completely abolished. The tools and methods developed in this study represent innovative approaches that can be applied to further explore important virulence factors of C. hepaticus and other closely related Campylobacter species.

IMPORTANCE

Spotty liver disease (SLD) of layer chickens, caused by infection with Campylobacter hepaticus, is a significant economic and animal welfare burden on an important food production industry. Currently, SLD is controlled using antibiotics; however, alternative intervention methods are needed due to increased concerns associated with environmental contamination with antibiotics, and the development of antimicrobial resistance in many bacterial pathogens of humans and animals. This study has developed methods that have enabled the genetic manipulation of C. hepaticus. To validate the methods, the pglB gene was inactivated by allelic exchange to produce a C. hepaticus strain that could no longer N-glycosylate proteins. Subsequently, the mutation was complemented by reintroduction of the gene in trans, on a plasmid vector, to demonstrate that the phenotypic changes noted were caused by the mutation of the targeted gene. The tools developed enable ongoing studies to understand other virulence mechanisms of this important emerging pathogen.

De novo genome assembly and functional insights of the first commercial pink Auricularia cornea

A pioneering pink cultivar of Auricularia cornea, first commercially cultivated in 2022, lacks genomic data, hindering research in genetic breeding, gene discovery, and product development. Here, we report the de novo assembly of the pink A. cornea Fen-A1 genome and provide a detailed functional annotation. The genome is 73.17 Mb in size, contains 86 scaffolds (N50 ∼ 5.49 Mb), 59.09% GC content and encodes 19,120 predicted genes with a BUSCO completeness of 92.60%. Comparative genomic analysis reveals the phylogenetic relatedness of Fen-A1 and remarkable gene family dynamics. Putative genes were found mapped to 3 antibiotic-related, 36 light-dependent and 25 terpene metabolites. In addition, 789 CAZymes genes were classified, revealing the dynamics of quality loss due to postharvest refrigeration. Overall, our work is the first report on a pink A. cornea genome and provides a comprehensive insight into its complex functions.

Assessing a respiratory toxic infectious bronchitis virus (IBV) strain: isolation, identification, pathogenicity, and immunological failure insights

Infectious bronchitis virus (IBV) is caused by avian coronavirus and poses a global economic threat to the poultry industry. In 2023, a highly pathogenic IBV strain, IBV/CN/GD20230501, was isolated and identified from chickens vaccinated with IBV-M41 in Guangdong, China. This study comprehensively investigated the biological characteristics of the isolated IBV strain, including its genotype, whole genome sequence analysis of its S1 gene, pathogenicity, host immune response, and serum non-targeted metabolomics. Through the analysis of the S1 gene sequence, serum neutralization tests, and comparative genomics, it was proven that IBV/CN/GD20230501 belongs to the GI-I type of strain and is serotype II. One alanine residue in the S1 subunit of the isolated strain was mutated into serine, and some mutations were observed in the ORF1ab gene and the terminal region of the genome. Animal challenge experiments using the EID50 and TCID50 calculations showed that IBV/CN/GD20230501 possesses strong respiratory pathogenicity, with early and long-term shedding of viruses and rapid viral spread. Antibody detection indicated that chickens infected with IBV/CN/GD20230501 exhibited delayed expression of early innate immune genes, while those infected with M41 showed rapid gene induction and effective viral control. Metabolomics analysis demonstrated that this virus infection led to differential expression of 291 ions in chicken serum, mainly affecting the citric acid cycle (tricarboxylic acid cycle).IMPORTANCEThis study identified an infectious bronchitis virus (IBV) strain isolated from vaccinated chickens in an immunized population that had certain sequence differences compared to IBV-M41, resulting in significantly enhanced pathogenicity and host defense. This strain has the potential to replace M41 as a more suitable challenge model for drug research. The non-targeted metabolomics analysis highlighting the citric acid cycle provides a new avenue for studying this highly virulent strain.