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July 7, 2019

Mistranslation can enhance fitness through purging of deleterious mutations.

Phenotypic mutations are amino acid changes caused by mistranslation. How phenotypic mutations affect the adaptive evolution of new protein functions is unknown. Here we evolve the antibiotic resistance protein TEM-1 towards resistance on the antibiotic cefotaxime in an Escherichia coli strain with a high mistranslation rate. TEM-1 populations evolved in such strains endow host cells with a general growth advantage, not only on cefotaxime but also on several other antibiotics that ancestral TEM-1 had been unable to deactivate. High-throughput sequencing of TEM-1 populations shows that this advantage is associated with a lower incidence of weakly deleterious genotypic mutations. Our observations show that mistranslation is not just a source of noise that delays adaptive evolution. It could even facilitate adaptive evolution by exacerbating the effects of deleterious mutations and leading to their more efficient purging. The ubiquity of mistranslation and its effects render mistranslation an important factor in adaptive protein evolution.

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July 7, 2019

Isolation and genomic characterization of a Dehalococcoides strain suggests genomic rearrangement during culture.

We have developed and characterized a bacterial consortium that reductively dechlorinates trichloroethene to ethene. Quantitative PCR analysis for the 16S rRNA and reductive dehalogenase genes showed that the consortium is highly enriched with Dehalococcoides spp. that have two vinyl chloride reductive dehalogenase genes, bvcA and vcrA, and a trichloroethene reductive dehalogenase gene, tceA. The metagenome analysis of the consortium by the next generation sequencer SOLiD 3 Plus suggests that a Dehalococcoides sp. that is highly homologous to D. mccartyi 195 and equipped with vcrA and tceA exists in the consortium. We isolated this Dehalococcoides sp. and designated it as D. mccartyi UCH-ATV1. As the growth of D. mccartyi UCH-ATV1 is too slow under isolated conditions, we constructed a consortium by mixing D. mccartyi UCH-ATV1 with several other bacteria and performed metagenomic sequencing using the single molecule DNA sequencer PacBio RS II. We successfully determined the complete genome sequence of D. mccartyi UCH-ATV1. The strain is equipped with vcrA and tceA, but lacks bvcA. Comparison with tag sequences of SOLiD 3 Plus from the original consortium shows a few differences between the sequences. This suggests that a genome rearrangement of Dehalococcoides sp. occurred during culture.

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July 7, 2019

Complete genome sequence of Clostridium perfringens CBA7123 isolated from a faecal sample from Korea.

Clostridium perfringens is an opportunistic human pathogen that causes necrotic enteritis, mild diarrhea, clostridial myonecrosis or gas gangrene, sepsis, etc. In this study, we aim to determine the pathogenesis of this bacterium at the genomic level. The genome of strain CBA7123 was sequenced, and a comparative genomic analysis between strain CBA7123 and four other related C. perfringens strains was performed.The genome of strain CBA7123 consisted of one circular chromosome and one plasmid that were 3,088,370 and 46,640 bp long with 28.5 and 27.1 mol% G+C content, respectively. The genomic DNA was predicted to contain 2798 open reading frames (ORFs), 10 rRNA genes, and 94 tRNA genes. The genomic comparison analysis between the five strains revealed the distinctive virulence properties of strain CBA7123 by highlighting certain strain-specific genes.In this study, the C. perfringens CBA7123 genome was sequenced and compared with other C. perfringens genomes. Among the various genes sequenced, the detection of antimicrobial resistance genes and those encoding various virulence factors may extend the understanding of the pathogenesis of C. perfringens strains.

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July 7, 2019

Whole-genome sequence of endophytic plant growth-promoting Escherichia coli USML2.

Escherichia coli strain USML2 was originally isolated from the inner leaf tissues of surface-sterilized phytopathogenic-free oil palm (Elaeis guineensis Jacq.). We present here the whole-genome sequence of this plant-endophytic strain. The genome consists of a single circular chromosome of 4,502,758 bp, 4,315 predicted coding sequences, and a G+C content of 50.8%. Copyright © 2017 Tharek et al.

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July 7, 2019

Complete genome sequence of Vibrio coralliilyticus 58, isolated from Pacific oyster (Crassostrea gigas) larvae.

We report here the complete genome of Vibrio coralliilyticus strain 58, which was originally isolated from inactive Pacific oyster (Crassostrea gigas) larvae in Japan. The assembled genome consisted of two chromosomes and one plasmid. These data will provide valuable information and important insights into the biodiversity of this organism. Copyright © 2017 Kim et al.

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July 7, 2019

MHC class I diversity in chimpanzees and bonobos.

Major histocompatibility complex (MHC) class I genes are critically involved in the defense against intracellular pathogens. MHC diversity comparisons among samples of closely related taxa may reveal traces of past or ongoing selective processes. The bonobo and chimpanzee are the closest living evolutionary relatives of humans and last shared a common ancestor some 1 mya. However, little is known concerning MHC class I diversity in bonobos or in central chimpanzees, the most numerous and genetically diverse chimpanzee subspecies. Here, we used a long-read sequencing technology (PacBio) to sequence the classical MHC class I genes A, B, C, and A-like in 20 and 30 wild-born bonobos and chimpanzees, respectively, with a main focus on central chimpanzees to assess and compare diversity in those two species. We describe in total 21 and 42 novel coding region sequences for the two species, respectively. In addition, we found evidence for a reduced MHC class I diversity in bonobos as compared to central chimpanzees as well as to western chimpanzees and humans. The reduced bonobo MHC class I diversity may be the result of a selective process in their evolutionary past since their split from chimpanzees.

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July 7, 2019

Complete genome sequence of a Legionella longbeachae serogroup 1 strain isolated from a patient with Legionnaires’ disease.

Legionella longbeachae serogroup 1, predominantly found in soil and composted plant material, causes the majority of cases of Legionnaires’ disease (LD) in New Zealand. Here, we report the complete genome sequence of an L. longbeachae serogroup 1 (sg1) isolate derived from a patient hospitalized with LD in Christchurch, New Zealand. Copyright © 2017 Slow et al.

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July 7, 2019

Complete genome sequence of Stenotrophomonas sp. KCTC 12332, a biotechnological potential bacterium.

Hydroxy fatty acids are used in various industries due to their availability, and in particular, Stenotrophomonas sp. has been regarded as a potential candidate for biotechnological applications, including biotransformation that hydrate unsaturated fatty acids into their derivatives. Here we complete the genome sequence of Stenotrophomonas sp. KCTC 12332 which has a size of 4,541,594bp (G+C content of 63.83%) with 3790 coding DNA sequences (CDSs), 67 tRNA and 3 rRNA operons. The genome contains gene encoding oleate hydratase that can convert oleic acid into 10-hydroxyoctadecanoic acid. Copyright © 2017 Elsevier B.V. All rights reserved.

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July 7, 2019

Untangling heteroplasmy, structure, and evolution of an atypical mitochondrial genome by PacBio Sequencing.

The highly compact mitochondrial (mt) genome of terrestrial isopods (Oniscidae) presents two unusual features. First, several loci can individually encode two tRNAs, thanks to single nucleotide polymorphisms at anticodon sites. Within-individual variation (heteroplasmy) at these loci is thought to have been maintained for millions of years because individuals that do not carry all tRNA genes die, resulting in strong balancing selection. Second, the oniscid mtDNA genome comes in two conformations: a ~14 kb linear monomer and a ~28 kb circular dimer comprising two monomer units fused in palindrome. We hypothesized that heteroplasmy actually results from two genome units of the same dimeric molecule carrying different tRNA genes at mirrored loci. This hypothesis, however, contradicts the earlier proposition that dimeric molecules result from the replication of linear monomers-a process that should yield totally identical genome units within a dimer. To solve this contradiction, we used the SMRT (PacBio) technology to sequence mirrored tRNA loci in single dimeric molecules. We show that dimers do present different tRNA genes at mirrored loci; thus covalent linkage, rather than balancing selection, maintains vital variation at anticodons. We also leveraged unique features of the SMRT technology to detect linear monomers closed by hairpins and carrying noncomplementary bases at anticodons. These molecules contain the necessary information to encode two tRNAs at the same locus, and suggest new mechanisms of transition between linear and circular mtDNA. Overall, our analyses clarify the evolution of an atypical mt genome where dimerization counterintuitively enabled further mtDNA compaction. Copyright © 2017 by the Genetics Society of America.

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July 7, 2019

Genome assembly of Chryseobacterium sp. strain IHBB 10212 from glacier top-surface soil in the Indian trans-Himalayas with potential for hydrolytic enzymes

The cold-active esterases are gaining importance due to their catalytic activities finding applications in chemical industry, food processes and detergent industry as additives, and organic synthesis of unstable compounds as catalysts. In the present study, the complete genome sequence of 4,843,645 bp with an average 34.08% G + C content and 4260 protein-coding genes are reported for the low temperature-active esterase-producing novel strain of Chrysobacterium isolated from the top-surface soil of a glacier in the cold deserts of the Indian trans-Himalayas. The genome contained two plasmids of 16,553 and 11,450 bp with 40.54 and 40.37% G + C contents, respectively. Several genes encoding the hydrolysis of ester linkages of triglycerides into fatty acids and glycerol were predicted in the genome. The annotation also predicted the genes encoding proteases, lipases, amylases, ß-glucosidases, endoglucanases and xylanases involved in biotechnological processes. The complete genome sequence of Chryseobacterium sp. strain IHBB 10212 and two plasmids have been deposited vide accession numbers CP015199, CP015200 and CP015201 at DDBJ/EMBL/GenBank.

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July 7, 2019

Emergence and evolution of multidrug-resistant Klebsiella pneumoniae with both blaKPC and blaCTX-M integrated in the chromosome.

The extended-spectrum-ß-lactamase (ESBL)- and Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae represent serious and urgent threats to public health. In a retrospective study of multidrug-resistant K. pneumoniae, we identified three clinical isolates, CN1, CR14, and NY9, carrying both blaCTX-M and blaKPC genes. The complete genomes of these three K. pneumoniae isolates were de novo assembled by using both short- and long-read whole-genome sequencing. In CR14 and NY9, blaCTX-M and blaKPC were carried on two different plasmids. In contrast, CN1 had one copy of blaKPC-2 and three copies of blaCTX-M-15 integrated in the chromosome, for which the blaCTX-M-15 genes were linked to an insertion sequence, ISEcp1, whereas the blaKPC-2 gene was in the context of a Tn4401a transposition unit conjugated with a PsP3-like prophage. Intriguingly, downstream of the Tn4401a-blaKPC-2-prophage genomic island, CN1 also carried a clustered regularly interspaced short palindromic repeat (CRISPR)-cas array with four spacers targeting a variety of K. pneumoniae plasmids harboring antimicrobial resistance genes. Comparative genomic analysis revealed that there were two subtypes of type I-E CRISPR-cas in K. pneumoniae strains and suggested that the evolving CRISPR-cas, with its acquired novel spacer, induced the mobilization of antimicrobial resistance genes from plasmids into the chromosome. The integration and dissemination of multiple copies of blaCTX-M and blaKPC from plasmids to chromosome depicts the complex pandemic scenario of multidrug-resistant K. pneumoniae Additionally, the implications from this study also raise concerns for the application of a CRISPR-cas strategy against antimicrobial resistance. Copyright © 2017 American Society for Microbiology.

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July 7, 2019

Comparative genomic and phylogenetic analysis of a toxigenic clinical isolate of Corynebacterium diphtheriae strain B-D-16-78 from Malaysia.

In this study, we report the comparative genomics and phylogenetic analysis of Corynebacterium diphtheriae strain B-D-16-78 that was isolated from a clinical specimen in 2016. The complete genome of C. diphtheriae strain B-D-16-78 was sequenced using PacBio Single Molecule, Real-Time sequencing technology and consists of a 2,474,151-bp circular chromosome with an average GC content of 53.56%. The core genome of C. diphtheriae was also deduced from a total of 74 strains with complete or draft genome sequences and the core genome-based phylogenetic analysis revealed close genetic relationship among strains that shared the same MLST allelic profile. In the context of CRISPR-Cas system, which confers adaptive immunity against re-invading DNA, 73 out of 86 spacer sequences were found to be unique to Malaysian strains which harboured only type-II-C and/or type-I-E-a systems. A total of 48 tox genes which code for the diphtheria toxin were retrieved from the 74 genomes and with the exception of one truncated gene, only nucleotide substitutions were detected when compared to the tox gene sequence of PW8. More than half were synonymous substitution and only two were nonsynonymous substitutions whereby H24Y was predicted to have a damaging effect on the protein function whilst T262V was predicted to be tolerated. Both toxigenic and non-toxigenic toxin-gene bearing strains have been isolated in Malaysia but the repeated isolation of toxigenic strains with the same MLST profile suggests the possibility of some of these strains may be circulating in the population. Hence, efforts to increase herd immunity should be continued and supported by an effective monitoring and surveillance system to track, manage and control outbreak of cases. Copyright © 2017 Elsevier B.V. All rights reserved.

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