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Asset Tag: Novogene

September 22, 2019  |  

Basic characterization of natural transformation in a highly transformable Haemophilus parasuis strain SC1401.

Haemophilus parasuis causes Glässer’s disease and pneumonia, incurring serious economic losses in the porcine industry. In this study, natural competence was investigated in H. parasuis. We found competence genes in H. parasuis homologous to ones in Haemophilus influenzae and a high consensus battery of Sxy-dependent cyclic AMP (cAMP) receptor protein (CRP-S) regulons using bioinformatics. High rates of natural competence were found from the onset of stationary-phase growth condition to mid-stationary phase (OD600 from 0.29 to 1.735); this rapidly dropped off as cells reached mid-stationary phase (OD600 from 1.735 to 1.625). As a whole, bacteria cultured in liquid media were observed to have lower competence levels than those grown on solid media plates. We also revealed that natural transformation in this species is stable after 200 passages and is largely dependent on DNA concentration. Transformation competition experiments showed that heterogeneous DNA cannot outcompete intraspecific natural transformation, suggesting an endogenous uptake sequence or other molecular markers may be important in differentiating heterogeneous DNA. We performed qRT-PCR targeting multiple putative competence genes in an effort to compare bacteria pre-cultured in TSB++ vs. TSA++ and SC1401 vs. SH0165 to determine expression profiles of the homologs of competence-genes in H. influenzae. Taken together, this study is the first to investigate natural transformation in H. parasuis based on a highly naturally transformable strain SC1401.

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September 22, 2019  |  

Multidrug-resistant Escherichia albertii: Co-occurrence of ß-lactamase and MCR-1 encoding genes.

Escherichia albertii is an emerging member of the Enterobacteriaceae causing human and animal enteric infections. Antimicrobial resistance among enteropathogens has been reported to be increasing in the past years. The purpose of this study was to investigate antibiotic resistance and resistance genes in E. albertii isolated from Zigong city, Sichuan province, China. The susceptibility to 21 antimicrobial agents was determined by Kirby-Bauer disk diffusion method. The highest prevalence was tetracycline resistance with a rate of 62.7%, followed by resistance to nalidixic acid and streptomycin with a rate of 56.9 and 51.0%, respectively. All isolates were sensitive or intermediate susceptible to imipenem, meropenem, amoxicillin-clavulanic acid, and levofloxacin. Among 51 E. albertii isolates, 15 were extended-spectrum ß-lactamase-producing as confirmed by the double disk test. The main ß-lactamase gene groups, i.e., blaTEM, blaSHV, and blaCTX-M, were detected in17, 20, and 22 isolates, respectively. Furthermore, four colistin-resistant isolates with minimum inhibitory concentrations of 8 mg/L were identified. The colistin-resistant isolates all harbored mcr-1 and blaCTX-M-55. Genome sequencing showed that E. albertii strain SP140150 carried mcr-1 and blaCTX-M-55 in two different plasmids. This study provided significant information regarding antibiotic resistance profiles and identified the co-occurrence of ß-lactamase and MCR-1 encoding genes in E. albertii isolates.

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September 22, 2019  |  

Heterologous expression guides identification of the biosynthetic gene cluster of chuangxinmycin, an indole alkaloid antibiotic.

The indole alkaloid antibiotic chuangxinmycin, from Actinobacteria Actinoplanes tsinanensis, containing a unique thiopyrano[4,3,2- cd]indole scaffold, is a potent and selective inhibitor of bacterial tryptophanyl-tRNA synthetase. The chuangxinmycin biosynthetic gene cluster was identified by in silico analysis of the genome sequence, then verified by heterologous expression. Systemic gene inactivation and intermediate identification determined the minimum set of genes for unique thiopyrano[4,3,2- cd]indole formation and the concerted action of a radical S-adenosylmethionine protein plus an unknown protein for addition of the 3-methyl group. These findings set a solid foundation for comprehensively investigating the biosynthesis, optimizing yield, and generating new analogues of chuangxinmycin.

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September 22, 2019  |  

Precise control of SCRaMbLE in synthetic haploid and diploid yeast.

Compatibility between host cells and heterologous pathways is a challenge for constructing organisms with high productivity or gain of function. Designer yeast cells incorporating the Synthetic Chromosome Rearrangement and Modification by LoxP-mediated Evolution (SCRaMbLE) system provide a platform for generating genotype diversity. Here we construct a genetic AND gate to enable precise control of the SCRaMbLE method to generate synthetic haploid and diploid yeast with desired phenotypes. The yield of carotenoids is increased to 1.5-fold by SCRaMbLEing haploid strains and we determine that the deletion of YEL013W is responsible for the increase. Based on the SCRaMbLEing in diploid strains, we develop a strategy called Multiplex SCRaMbLE Iterative Cycling (MuSIC) to increase the production of carotenoids up to 38.8-fold through 5 iterative cycles of SCRaMbLE. This strategy is potentially a powerful tool for increasing the production of bio-based chemicals and for mining deep knowledge.

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September 22, 2019  |  

Genome-wide analysis of Mycoplasma bovirhinis GS01 reveals potential virulence factors and phylogenetic relationships.

Mycoplasma bovirhinis is a significant etiology in bovine pneumonia and mastitis, but our knowledge about the genetic and pathogenic mechanisms of M. bovirhinis is very limited. In this study, we sequenced the complete genome of M. bovirhinis strain GS01 isolated from the nasal swab of pneumonic calves in Gansu, China, and we found that its genome forms a 847,985 bp single circular chromosome with a GC content of 27.57% and with 707 protein-coding genes. The putative virulence determinants of M. bovirhinis were then analyzed. Results showed that three genomic islands and 16 putative virulence genes, including one adhesion gene enolase, seven surface lipoproteins, proteins involved in glycerol metabolism, and cation transporters, might be potential virulence factors. Glycerol and pyruvate metabolic pathways were defective. Comparative analysis revealed remarkable genome variations between GS01 and a recently reported HAZ141_2 strain, and extremely low homology with others mycoplasma species. Phylogenetic analysis demonstrated that M. bovirhinis was most genetically close to M. canis, distant from other bovine Mycoplasma species. Genomic dissection may provide useful information on the pathogenic mechanisms and genetics of M. bovirhinis. Copyright © 2018 Chen et al.

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September 22, 2019  |  

Clinical Staphylococcus argenteus develops to small colony variants to promote persistent infection.

Staphylococcus argenteus is a novel staphylococcal species (also considered as a part of Staphylococcus aureus complex) that is infrequently reported on, and clinical S. argenteus infections are largely unstudied. Here, we report a persistent and recurrent hip joint infection case in which a S. argenteus strain and its small colony variants (SCVs) strain were successively isolated. We present features of the two S. argenteus strains and case details of their pathogenicity, explore factors that induce S. argenteus SCVs formation in the course of anti-infection therapy, and reveal potential genetic mechanisms for S. argenteus SCVs formation. S. argenteus strains were identified using phenotypic and genotypic methods. The S. argenteus strain XNO62 and SCV strain XNO106 were characterized using different models. S. argenteus SCVs were induced by the administration of amikacin and by chronic infection course based on the clinical case details. The genomes of both strains were sequenced and aligned in a pair-wise fashion using Mauve. The case details gave us important insights on the characteristics and therapeutic strategies for infections caused by S. argenteus and its SCVs. We found that strain XNO62 and SCV strain XNO106 are genetically-related sequential clones, the SCV strain exhibits reduced virulence but enhanced intracellular persistence compared to strain XNO62, thus promoting persistent infection. The induction experiments for S. argenteus SCVs demonstrated that high concentrations of amikacin greatly induce S. argenteus XNO62 to form SCVs, while a chronic infection of S. argenteus XNO62 slightly induces SCVs formation. Potential genetic mechanisms for S. argenteus SCVs formation were revealed and discussed based on genomic alignments. In conclusion, we report the first case of infection caused by S. argenteus and its SCVs strain. More attention should be paid to infections caused by S. argenteus and its SCVs, as they constitute a challenge to current therapeutic strategies. The problem of S. argenteus SCVs should be noticed, in particular when amikacin is used or in the case of a chronic S. argenteus infection.

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September 22, 2019  |  

Temperature responses of mutation rate and mutational spectrum in an Escherichia coli strain and the correlation with metabolic rate.

Temperature is a major determinant of spontaneous mutation, but the precise mode, and the underlying mechanisms, of the temperature influences remain less clear. Here we used a mutation accumulation approach combined with whole-genome sequencing to investigate the temperature dependence of spontaneous mutation in an Escherichia coli strain. Experiments were performed under aerobic conditions at 25, 28 and 37 °C, three temperatures that were non-stressful for the bacterium but caused significantly different bacterial growth rates.Mutation rate did not differ between 25 and 28 °C, but was higher at 37 °C. Detailed analyses of the molecular spectrum of mutations were performed; and a particularly interesting finding is that higher temperature led to a bias of mutation to coding, relative to noncoding, DNA. Furthermore, the temperature response of mutation rate was extremely similar to that of metabolic rate, consistent with an idea that metabolic rate predicts mutation rate.Temperature affects mutation rate and the types of mutation supply, both being crucial for the opportunity of natural selection. Our results help understand how temperature drives evolutionary speed of organisms and thus the global patterns of biodiversity. This study also lend support to the metabolic theory of ecology for linking metabolic rate and molecular evolution rate.

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September 22, 2019  |  

Draft genome of Glyptosternon maculatum, an endemic fish from Tibet Plateau.

Mechanisms for high-altitude adaption have attracted widespread interest among evolutionary biologists. Several genome-wide studies have been carried out for endemic vertebrates in Tibet, including mammals, birds, and amphibians. However, little information is available about the adaptive evolution of highland fishes. Glyptosternon maculatum (Regan 1905), also known as Regan or barkley and endemic to the Tibetan Plateau, belongs to the Sisoridae family, order Siluriformes (catfishes). This species lives at an elevation ranging from roughly 2,800 m to 4,200 m. Hence, a high-quality reference genome of G. maculatum provides an opportunity to investigate high-altitude adaption mechanisms of fishes.To obtain a high-quality reference genome sequence of G. maculatum, we combined Pacific Bioscience single-molecule real-time sequencing, Illumina paired-end sequencing, 10X Genomics linked-reads, and BioNano optical map techniques. In total, 603.99 Gb sequencing data were generated. The assembled genome was about 662.34 Mb with scaffold and contig N50 sizes of 20.90 Mb and 993.67 kb, respectively, which captured 83% complete and 3.9% partial vertebrate Benchmarking Universal Single-Copy Orthologs. Repetitive elements account for 35.88% of the genome, and ?22,066 protein-coding genes were predicted from the genome, of which 91.7% have been functionally annotated.We present the first comprehensive de novo genome of G. maculatum. This genetic resource is fundamental for investigating the origin of G. maculatum and will improve our understanding of high-altitude adaption of fishes. The assembled genome can also be used as reference for future population genetic studies of G. maculatum.

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September 22, 2019  |  

The pathogenic mechanisms of Tilletia horrida as revealed by comparative and functional genomics.

Tilletia horrida is a soil-borne, mononucleate basidiomycete fungus with a biotrophic lifestyle that causes rice kernel smut, a disease that is distributed throughout hybrid rice growing areas worldwide. Here we report on the high-quality genome sequence of T. horrida; it is composed of 23.2?Mb that encode 7,729 predicted genes and 6,973 genes supported by RNA-seq. The genome contains few repetitive elements that account for 8.45% of the total. Evolutionarily, T. horrida lies close to the Ustilago fungi, suggesting grass species as potential hosts, but co-linearity was not observed between T. horrida and the barley smut Ustilago hordei. Genes and functions relevant to pathogenicity were presumed. T. horrida possesses a smaller set of carbohydrate-active enzymes and secondary metabolites, which probably reflect the specific characteristics of its infection and biotrophic lifestyle. Genes that encode secreted proteins and enzymes of secondary metabolism, and genes that are represented in the pathogen-host interaction gene database genes, are highly expressed during early infection; this is consistent with their potential roles in pathogenicity. Furthermore, among the 131 candidate pathogen effectors identified according to their expression patterns and functionality, we validated two that trigger leaf cell death in Nicotiana benthamiana. In summary, we have revealed new molecular mechanisms involved in the evolution, biotrophy, and pathogenesis of T. horrida.

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September 22, 2019  |  

Whole-Genome Analysis of an Extensively Drug-Resistant Acinetobacter baumannii Strain XDR-BJ83: Insights into the Mechanisms of Resistance of an ST368 Strain from a Tertiary Care Hospital in China.

Acinetobacter baumannii is an important pathogen of nosocomial infections. Nosocomial outbreaks caused by antibiotic-resistant A. baumannii remain a significant challenge. Understanding the antibiotic resistance mechanism of A. baumannii is critical for clinical treatment. The purpose of this study was to determine the whole-genome sequence (WGS) of an extensively drug-resistant (XDR) A. baumannii strain, XDR-BJ83, which was associated with a nosocomial outbreak in a tertiary care hospital of China, and to investigate the antibiotic resistance mechanism of this strain. The WGS of XDR-BJ83 was performed using single-molecule real-time sequencing. The complete genome of XDR-BJ83 consisted of a 4,011,552-bp chromosome and a 69,069-bp plasmid. The sequence type of XDR-BJ83 was ST368, which belongs to clonal complex 92 (CC92). The chromosome of XDR-BJ83 carried multiple antibiotic resistance genes, antibiotic efflux pump genes, and mobile genetic elements, including insertion sequences, transposons, integrons, and resistance islands. The plasmid of XDR-BJ83 (pBJ83) was a conjugative plasmid carrying type IV secretion system. These results indicate that the presence of multiple antibiotic resistance genes, efflux pumps, and mobile genetic elements is likely associated with resistance to various antibiotics in XDR-BJ83.

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September 22, 2019  |  

Comparative genomic analysis revealed rapid differentiation in the pathogenicity-related gene repertoires between Pyricularia oryzae and Pyricularia penniseti isolated from a Pennisetum grass.

A number of Pyricularia species are known to infect different grass species. In the case of Pyricularia oryzae (syn. Magnaporthe oryzae), distinct populations are known to be adapted to a wide variety of grass hosts, including rice, wheat and many other grasses. The genome sizes of Pyricularia species are typical for filamentous ascomycete fungi [~?40 Mbp for P. oryzae, and ~?45 Mbp for P. grisea]. Genome plasticity, mediated in part by deletions promoted by recombination between repetitive elements [Genome Res 26:1091-1100, 2016, Nat Rev Microbiol 10:417-430,2012] and transposable elements [Annu Rev Phytopathol 55:483-503,2017] contributes to host adaptation. Therefore, comparisons of genome structure of individual species will provide insight into the evolution of host specificity. However, except for the P. oryzae subgroup, little is known about the gene content or genome organization of other Pyricularia species, such as those infecting Pennisetum grasses.Here, we report the genome sequence of P. penniseti strain P1609 isolated from a Pennisetum grass (JUJUNCAO) using PacBio SMRT sequencing technology. Phylogenomic analysis of 28 Magnaporthales species and 5 non-Magnaporthales species indicated that P1609 belongs to a Pyricularia subclade, which is genetically distant from P. oryzae. Comparative genomic analysis revealed that the pathogenicity-related gene repertoires had diverged between P1609 and the P. oryzae strain 70-15, including the known avirulence genes, other putative secreted proteins, as well as some other predicted Pathogen-Host Interaction (PHI) genes. Genomic sequence comparison also identified many genomic rearrangements relative to P. oryzae.Our results suggested that the genomic sequence of the P. penniseti P1609 could be a useful resource for the genetic study of the Pennisetum-infecting Pyricularia species and provide new insight into evolution of pathogen genomes during host adaptation.

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July 7, 2019  |  

Complete genome sequence of the aerobically denitrifying thermophilic bacterium Chelatococcus daeguensis TAD1

Chelatococcus daeguensis TAD1 is a themophilic bacterium isolated from a biotrickling filter used to treat NOx in Ruiming Power Plant, located in Guangzhou, China, which shows an excellent aerobic denitrification activity at high temperature. The complete genome sequence of this strain was reported in the present study. Genes related to the aerobic denitrification were identified through whole genome analysis. This work will facilitate the mechanism of aerobic denitrification and provide evidence for its potential application in the nitrogen removal.

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July 7, 2019  |  

Complete genome sequence of Bacillus subtilis J-5, a potential biocontrol agent.

Bacillus subtilis J-5 was isolated from tomato rhizosphere soil and exhibited strong inhibitory activity against Botrytis cinerea To shed light on the molecular mechanism underlying the biological control on phytopathogens, the whole genome of this strain was sequenced. Genes encoding antimicrobial compounds and the regulatory systems were identified in the genome. Copyright © 2017 Jia et al.

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July 7, 2019  |  

Complete genome sequence of a denitrifying bacterium, Pseudomonas sp. CC6-YY-74, isolated from Arctic Ocean sediment

Pseudomonas sp. CC6-YY-74, a psychrotrophic, denitrifying bacterium isolated from Arctic Ocean sediment, uses NO3- or NH4+ as the sole nitrogen source to grow at low temperatures. Here we described the complete genome of Pseudomonas sp. CC6-YY-74. The genome has one circular chromosome of 5,040,792 bp (61.73 mol% G + C content), consisting of 4747 coding genes, 68 tRNA genes, as well as six rRNA operons as 16S-23S-5S rRNA. According to the annotation results, strain CC6-YY-74 encodes 52 proteins related to nitrogen metabolism, including a complete denitrifying pathway, and more than 20 kinds of hydrolytic enzymes.

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July 7, 2019  |  

Complete genome sequencing and genomic characterization of two Escherichia coli strains co-producing MCR-1 and NDM-1 from bloodstream infection.

We previously described the discovery of two Escherichia coli isolates (EC1002 and EC2474) co-harbouring mcr-1 and bla NDM-1 genes, which were recovered from bloodstream infection in China. More importantly, these antibiotic resistance genes were located on different plasmids and signaling the potential spread of pandrug-resistant bacteria. Here, the complete genome sequences of both isolates were determined using Pacbio RS II and Illumina HiSeq2000 systems. The genome of EC1002 consists of a 5,177,501 base pair chromosome and four circular plasmids, while the genome of EC2474 consists of a 5,013,813 base pair chromosome and three plasmids. The plasmid replicon type of pEC1002_NDM and pEC2474_NDM were identified as IncA/C2 and IncF, respectively. The genetic environment of bla NDM-1 in this study was similar to bla NDM-carrying plasmids detected in China, although the overall nucleotide identity and query coverage were variable. The plasmid replicon type of pEC1002_MCR and pEC2474_MCR were identified as IncI2 and IncHI2, respectively. Two different genetic strategies for mcr-1 gene spread were observed in this study and bla NDM-1 genes were also found transferred by two different mobile genetic elements in two plasmids. The findings of this study further support that the diversified transfer mechanisms of bla NDM-1 and mcr-1 present in Enterobacteriaceae.

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