Search Results (37)

Fusarium oxysporum f. sp. vasinfectum (Fov) is a devastating cotton pathogen. Australian Fov strains are distinguished by their ability to infect plants without nematode interaction and are genetically distinct from global Fov, classified into two vegetative compatibility groups (VCG-01111 and VCG-01112). Here, we present chromosome-level genome assemblies of a historical isolate for each Australian Fov VCG. The end-to-end gapless genome assemblies demonstrate high contiguity and completeness, with 97.7% BUSCO completeness for both isolates. Phylogenetic analysis indicates that the Australian Fov lineages diverged from other known Fov genomes over 3.6 million years ago, while VCG-01111 and VCG-01112 separated approximately 1.1 million years ago. Comparative genomics analysis identified four accessory chromosomes unique to the Australian isolates. Functional annotations revealed 14,495 and 15,342 genes in VCG-01111 and VCG-01112, respectively, with accessory chromosomes containing significantly fewer genes than core chromosomes. Ortholog analysis uncovered unique gene clusters enriched in key metabolic pathways, pathogenicity, and cell division processes. Additionally, we identified several novel lineage-specific peptides unique to each Australian isolate. This comprehensive genomic characterization provides the first insights into the unique evolutionary history of Australian Fov, distinguishing them from global Fov races. Our findings lay the foundation for understanding the genetic factors underlying their exceptional virulence, which makes Australian Fov among the most aggressive cotton pathogens worldwide. Full article

An EBSL-encoding plasmid, pESBL-PH, was identified during a nosocomial outbreak of Klebsiella pneumoniae ST628 at a United Kingdom general district hospital in 2018. The plasmid from the earliest 2018 K. pneumoniae strain discovered during the outbreak was assembled using both Oxford nanopore long reads and illumina short reads, yielding a fully closed plasmid, pESBL-PH-2018. pESBL-PH-2018 was queried against the complete NCBI RefSeq Plasmid Database, comprising 93,823 plasmids, which was downloaded on 16 July 2024. To identify structurally similar plasmids, strict thresholds were applied, including a mash similarity ≥0.98. This returned 61 plasmids belonging to 13 unique sequence types (STs) hosts. The plasmids were detected from 13 unique countries, dating from 2012 to 2023. The AMR region of the plasmids varied. Interestingly IS26-mediated tandem amplification of resistance genes, including the ESBL gene bla_CTX-M-15 was identified in two independent strains, raising their copy number to three. Furthermore, the genomic background of strains carrying a pESBL-PH-2018-like plasmid were analyzed, revealing truncation of the chromosomal ompK36 porin gene and carbapenem resistance gene carriage on accessory plasmids in 17.85% and 26.78% of strains with a complete chromosome available. This analysis reveals the widespread dissemination of an ESBL-encoding plasmid in a background of resistance-encoding strains, requiring active surveillance. Full article

The host specificity of Fusarium oxysporum (Fox) formae speciales has been reported to be linked to effector proteins known as Secreted in Xylem (SIX). These genes are associated with the non-autonomous mobile element miniature impala (mimp), normally distributed on the accessory chromosomes. The pattern of mimp associated with effector genes has been used to predict candidate effector profiles which characterize Fox formae speciales. In this study, we demonstrate the pathogenicity of strains Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407 and Fusarium oxysporum f.sp. radicis-cucumerinum (Forc) V03-2g in a common host plant (cucumber) and compare their genomes. The Forl ZUM2407 genome lacks SIX genes and their homologs, in contrast to Forc V03-2g. We predicted the total number of mimp elements in the genome of Forl ZUM2407 to be three-fold less than that of Forc V03-2g (10 and 36 copies, respectively). The mimp distribution pattern in Forl ZUM2407 was completely different from that present in Forc V03-2g. Candidate effector profile analysis did not predict that Forl ZUM2407 was able to infect cucumber plants like Forc V03-2g. Therefore, we assume that Forl ZUM2407 has a different type of genome organization associated with pathogenicity, whose effector profile cannot be described using the mimp-based approach. Full article

Colletotrichum lini is a pathogenic fungus that infects flax and causes significant yield losses. In this study, we assembled the genomes of four highly virulent C. lini strains using the Oxford Nanopore Technologies (ONT, R10.4.1 flow cells) and Illumina platforms. The performance of two tools developed for telomere-to-telomere (T2T) genome assembly was compared: Verkko and Hifiasm. Prior to the assembly, ONT reads were corrected using the HERRO algorithm. Verkko generated genome assemblies of high completeness but low contiguity, while Hifiasm allowed the generation of T2T assemblies. Despite significantly different genome coverage with ONT data (25–100×), four assemblies of equal contiguity were obtained: 53.6–54.7 Mb, ten core chromosomes, and two or three accessory chromosomes. A comparative analysis of different polishing tools showed that at a certain genome coverage with the corrected ONT data (≥35×), the additional polishing of the assembly did not improve its accuracy, even with the Illumina data. An analysis of the genome structures of the four C. lini strains revealed a high similarity between the core chromosomes. Thus, our approach enabled assembling T2T Colletotrichum genomes only from the ONT data obtained using R10.4.1 flow cells and may be promising for other fungal genera. These assemblies will allow the accurate identification of strain-specific differences at the chromosome level and will aid in the development of effective strategies to protect flax from anthracnose. Full article

Colletotrichum lini is a fungal pathogen of flax that can cause significant yield and quality losses. In this work, we obtained the first complete annotated genome assembly of the highly virulent C. lini strain #394-2. The nuclear genome consisted of ten core and two accessory chromosomes and had a length of 53.7 Mb. The mitochondrial genome was 39.1 kb. The assembly was obtained by the Canu–Racon ×2–Medaka–Polca algorithm using Oxford Nanopore Technologies and Illumina data. As a result of the annotation with the Illumina RNA-Seq data, 12,449 genes were identified. Potential signaling proteins were tested for effector functions and 550 effector proteins were predicted using EffectorP. The visualization of the effector protein localization revealed that the presence of effector proteins was associated with repeat-rich regions. A comparison of the genomic structure of C. lini with chromosome-level and complete assemblies of the genus Colletotrichum representatives revealed that the genomes of Colletotrichum species differed by the presence of chromosomal rearrangements. The obtained assembly expands the knowledge of the genomic structure of Colletotrichum species and provides the basis for further studies of C. lini, which will help to understand the virulence mechanisms and protect flax from anthracnose. Full article

There have been few reports regarding the long-term trends in the genotypes of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream isolates. Therefore, this study was performed to investigate the longitudinal trends in the genotypes of MRSA bloodstream isolates obtained from hospitalized patients during a 12-year study period from 2010 to 2021 at a tertiary care university hospital. Over the 12-year period from 2010 to 2021, we conducted a genetic investigation focusing on 245 MRSA strains isolated from the blood of hospitalized patients. The genotypes of the MRSA bloodstream isolates were determined by Staphylococcal Cassette Chromosome mec (SCCmec) typing, accessory gene regulator (agr) typing, PCR-based ORF typing (POT), and multilocus sequence typing (MLST). Strains with the same POT type detected in two or more isolates were designated as epidemic clones, while strains without a common POT type were classified as sporadic clones. Until 2015, isolates with SCCmec II/agr II were prevalent, but isolates with SCCmec IV/agr III increased from 2016. A total of 128 strains (52%) were identified as epidemic clones, while 117 strains (48%) were classified as sporadic clones. The detection rate of sporadic clones increased significantly since 2016 (p < 0.05). The epidemic clones were classified into three clusters, with MRSA of clonal complex (CC) 1 being prominent after 2016. This study showed that the genotypes of MRSA bloodstream isolates underwent a shift from SCCmec II/agr II type to SCCmec IV/agr III type, with a notable increase in MRSA of CC1, after 2016. There was a significant increase in the proportion of sporadic strains among the isolates, suggesting the diversification of genotypes. Full article

Dickeya dadantii is a common pathogen of bacterial soft rot on a wide range of plants, including several crops. In this study, we present the complete genome sequence of the D. dadantii type strain DSM18020^T. The genome was assembled using PacBio technology, resulting in a 4,997,541 bp circular chromosome with a G+C content of 56.5%. Our sequence analyses predicted 4277 protein-encoding genes, including several associated with known bacterial virulence factors and secondary metabolites. Comparative genomics analysis between Dickeya revealed that the category of ‘metabolism’ is the most important in both the core and accessory genomes, while the category of ‘information storage and processing’ is the most dominant in unique genomes. These findings will not only help us to understand the pathogenic mechanisms of D. dadantii DSM18020^T, but also provide us with useful information for new control strategies against this phytopathogen. Full article

Quinolone resistance has been largely related to the presence of specific point mutations in chromosomal targets, with an accessory role of impaired uptake and enhanced pump-out. Meanwhile the relevance of transferable mechanisms of resistance able to protect the target of pump-out or inactivate quinolones has been increasingly reported since 1998. Nevertheless, bacteria have other strategies and mechanisms allowing them to survive and even proliferate in the presence of quinolones, which might be qualified as resistance or resilience mechanisms. These include decreasing levels of quinolone target production, transient amoeba protection, benthonic lifestyle, nutrient-independent slow growth, activation of stringent response, inactivation or degradation of quinolones as well as apparently unrelated or forgotten chromosomal mutations. These mechanisms have been largely overlooked, either because of the use of classical approaches to antibiotic resistance determination or due to the low increase in final minimum inhibitory concentration levels. This article is devoted to a review of a series of these mechanisms. Full article

Staphylococcus pseudintermedius is a frequent cause of infections in dogs. Infectious isolates of this coagulase-positive staphylococcal species are often methicillin- and multidrug-resistant, which complicates therapy. In staphylococci, methicillin resistance is encoded by determinants found on mobile genetic elements called Staphylococcal Chromosome Cassette mec (SCCmec), which, in addition to methicillin resistance factors, sometimes encode additional genes, such as further resistance factors and, rarely, virulence determinants. In this study, we analyzed SCCmec in a collection of infectious methicillin-resistant S. pseudintermedius (MRSP) isolates from predominant lineages in the United States. We found that several lineages characteristically have specific types of SCCmec elements and Agr types and harbor additional factors in their SCCmec elements that may promote virulence or affect DNA uptake. All isolates had SCCmec-encoded restriction–modification (R-M) systems of types I or II, and sequence types (STs) ST84 and ST64 had one type II and one type I R-M system, although the latter lacked a complete methylation enzyme gene. ST68 isolates also had an SCCmec-encoded CRISPR system. ST71 isolates had a psm-mec gene, which, in all but apparently Agr-dysfunctional isolates, produced a PSM-mec peptide toxin, albeit at relatively small amounts. This study gives detailed insight into the composition of SCCmec elements in infectious isolates of S. pseudintermedius and lays the genetic foundation for further efforts directed at elucidating the contribution of identified accessory SCCmec factors in impacting SCCmec-encoded and thus methicillin resistance-associated virulence and resistance to DNA uptake in this leading canine pathogen. Full article

Vibrio parahaemolyticus exhibits severe pathogenicity in humans and animals worldwide. In this study, genome sequencing and comparative analyses were conducted for in-depth characterization of the virulence factor (VF) repertoire of V. parahaemolyticus strain LC, which presented significant virulence to shrimp Litopenaeus vannamei. Strain LC, harboring two circular chromosomes and three linear plasmids, demonstrated ≥98.14% average nucleotide identities with 31 publicly available V. parahaemolyticus genomes, including 13, 11, and 7 shrimp-, human-, and non-pathogenic strains, respectively. Phylogeny analysis based on dispensable genes of pan-genome clustered 11 out of 14 shrimp-pathogenic strains and 7 out of 11 clinical strains into two distinct clades, indicating the close association between host-specific pathogenicity and accessory genes. The VFDB database revealed that 150 VFs of LC were mainly associated with the secretion system, adherence, antiphagocytosis, chemotaxis, motility, and iron uptake, whereas no homologs of the typical pathogenic genes pirA, pirB, tdh, and trh were detected. Four genes, mshB, wbfT, wbfU, and wbtI, were identified in both types of pathogenic strains but were absent in non-pathogens. Notably, a unique cluster similar to Yen-Tc, which encodes an insecticidal toxin complex, and diverse toxin–antitoxin (TA) systems, were identified on the mobile genetic elements (MGEs) of LC. Conclusively, in addition to the common VFs, various unique MGE-borne VFs, including the Yen-Tc cluster, TA components, and multiple chromosome-encoded chitinase genes, may contribute to the full spectrum of LC virulence. Moreover, V. parahaemolyticus demonstrates host-specific virulence, which potentially drives the origin and spread of pathogenic factors. Full article

Homologous recombination (HR) is the major mechanism of rescue of stalled replication forks or repair of DNA double-strand breaks (DSBs) during S phase or mitosis. In human cells, HR is facilitated by the BRCA2-BRCA1-PALB2 module, which loads the RAD51 recombinase onto a resected single-stranded DNA end to initiate repair. Although the process is essential for error-free repair, unrestrained HR can cause chromosomal rearrangements and genome instability. F-box DNA Helicase 1 (FBH1) antagonizes the role of BRCA2-BRCA1-PALB2 to restrict hyper-recombination and prevent genome instability. Here, we analyzed reported FBH1 mutations in cancer cells using the Catalogue of Somatic Mutations in Cancers (COSMIC) to understand how they interact with the BRCA2-BRCA1-PALB2. Consistent with previous results from yeast, we find that FBH1 mutations co-occur with BRCA2 mutations and to some degree BRCA1 and PALB2. We also describe some co-occurring mutations with RAD52, the accessory RAD51 loader and facilitator of single-strand annealing, which is independent of RAD51. In silico modeling was used to investigate the role of key FBH1 mutations on protein function, and a Q650K mutation was found to destabilize the protein structure. Taken together, this work highlights how mutations in several DNA damage repair genes contribute to cellular transformation and immortalization. Full article

The Fusarium oxysporum species complex (FOSC) includes both plant and human pathogens that cause devastating plant vascular wilt diseases and threaten public health. Each F. oxysporum genome comprises core chromosomes (CCs) for housekeeping functions and accessory chromosomes (ACs) that contribute to host-specific adaptation. This study inspects global transcription factor profiles (TFomes) and their potential roles in coordinating CC and AC functions to accomplish host-specific interactions. Remarkably, we found a clear positive correlation between the sizes of TFomes and the proteomes of an organism. With the acquisition of ACs, the FOSC TFomes were larger than the other fungal genomes included in this study. Among a total of 48 classified TF families, 14 families involved in transcription/translation regulations and cell cycle controls were highly conserved. Among the 30 FOSC expanded families, Zn2-C6 and Znf_C2H2 were most significantly expanded to 671 and 167 genes per family including well-characterized homologs of Ftf1 (Zn2-C6) and PacC (Znf_C2H2) that are involved in host-specific interactions. Manual curation of characterized TFs increased the TFome repertoires by 3% including a disordered protein Ren1. RNA-Seq revealed a steady pattern of expression for conserved TF families and specific activation for AC TFs. Functional characterization of these TFs could enhance our understanding of transcriptional regulation involved in FOSC cross-kingdom interactions, disentangle species-specific adaptation, and identify targets to combat diverse diseases caused by this group of fungal pathogens. Full article

Structural maintenance of chromosomes (SMC) complexes are essential proteins found in genomes of all cellular organisms. Essential functions of these proteins, such as mitotic chromosome formation and sister chromatid cohesion, were discovered a long time ago. Recent advances in chromatin biology showed that SMC proteins are involved in many other genomic processes, acting as active motors extruding DNA, which leads to the formation of chromatin loops. Some loops formed by SMC proteins are highly cell type and developmental stage specific, such as SMC-mediated DNA loops required for VDJ recombination in B-cell progenitors, or dosage compensation in Caenorhabditis elegans and X-chromosome inactivation in mice. In this review, we focus on the extrusion-based mechanisms that are common for multiple cell types and species. We will first describe an anatomy of SMC complexes and their accessory proteins. Next, we provide biochemical details of the extrusion process. We follow this by the sections describing the role of SMC complexes in gene regulation, DNA repair, and chromatin topology. Full article

Rare information is available on clinical Enterococcus faecium encountered in Sardinia, Italy. This study investigated the antimicrobial susceptibility profiles and genotypic characteristics of E. faecium isolated at the University Hospital of Sassari, Italy, using the Vitek2 system and PCR, MLST, or WGS. Vitek2 revealed two VanB-type vancomycin-resistant Enterococcus faecium (VREfm) isolates (MICs mg/L = 8 and ≥32) but failed to detect vancomycin resistance in one isolate (MIC mg/L ≤ 1) despite positive genotypic confirmation of vanB gene, which proved to be vancomycin resistant by additional phenotypic methods (MICs mg/L = 8). This vanB isolate was able to increase its vancomycin MIC after exposure to vancomycin, unlike the “classic” occult vanB-carrying E. faecium, becoming detectable by Vitek 2 (MICs mg/L ≥ 32). All three E. faecium had highly mutated vanB₂ operons, as part of a chromosomally integrated Tn1549 transposon, with common missense mutations in VanH and VanB₂ resistance proteins and specific missense mutations in the VanW accessory protein. There were additional missense mutations in VanS, VanH, and VanB proteins in the vanB₂-carrying VREfm isolates compared to Vitek2. The molecular typing revealed a polyclonal hospital-associated E. faecium population from Clade A1, and that vanB₂-VREfm, and nearly half of vancomycin-susceptible E. faecium (VSEfm) analyzed, belonged to ST117. Based on core genome-MLST, ST117 strains had different clonal types (CT), excluding nosocomial transmission of specific CT. Detecting vanB₂-carrying VREfm isolates by Vitek2 may be problematic, and alternative methods are needed to prevent therapeutic failure and spread. Full article

Fusarium oxysporum f. sp. phaseoli, the causal agent of cowpea fusarium wilt, is a serious threat to cowpea production in China. In this study, a sample of cowpea fusarium wilt was identified as Fusarium oxysporum f. sp. phaseoli using the methods of morphological characters and molecular detection. We further reported the first genome assembly for Fusarium oxysporum f. sp. phaseoli, with 53.7 Mb genome sequence comprising 14,694 genes. Comparative genomic analysis among five Fusarium oxysporum genomes showed that four accessory chromosomes in the five Fusarium oxysporum display similar characteristics, with low sequence similarity (55.35%, vs. overall average of 81.76%), low gene density (2.18 genes/10 kb vs. 3.02 genes/Mb) and highly transposable element density (TEs) (15.01/100 kb vs. 4.89/100 kb), indicating that variable accessory chromosomes are the main source of Fusarium oxysporum evolution. We identified a total of 100 Fusarium oxysporum f. sp. phaseoli-specific effectors in the genome and found 13 specific effector genes located in large insertion or deletion regions, suggesting that insertion or deletion events can cause the emergence of species-specific effectors in Fusarium oxysporum. Our genome assembly of Fusarium oxysporum f. sp. phaseoli provides a valuable resource for the study of cowpea fusarium wilt, and the comparative genomic study of Fusarium oxysporum could contribute to the knowledge of genome and effector-associated pathogenicity evolution in Fusarium oxysporum study. Full article