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July 7, 2019

Complete genome sequence of Yersinia ruckeri strain CSF007-82, etiologic agent of red mouth disease in salmonid fish.

We present the complete, closed, and finished chromosomal and extrachromosomal genome sequences of Yersinia ruckeri strain CSF007-82, the etiologic agent of enteric red mouth disease in salmonid fish. The chromosome is 3,799,036 bp with a G+C content of 47.5% and encodes 3,530 predicted coding sequences (CDS), 7 ribosomal operons, and 80 tRNAs. Copyright © 2015 Nelson et al.


July 7, 2019

Genetic determinants of reutericyclin biosynthesis in Lactobacillus reuteri.

Reutericyclin is a unique antimicrobial tetramic acid produced by some strains of Lactobacillus reuteri. This study aimed to identify the genetic determinants of reutericyclin biosynthesis. Comparisons of the genomes of reutericyclin-producing L. reuteri strains with those of non-reutericyclin-producing strains identified a genomic island of 14 open reading frames (ORFs) including genes coding for a nonribosomal peptide synthetase (NRPS), a polyketide synthase (PKS), homologues of PhlA, PhlB, and PhlC, and putative transport and regulatory proteins. The protein encoded by rtcN is composed of a condensation domain, an adenylation domain likely specific for d-leucine, and a thiolation domain. rtcK codes for a PKS that is composed of a ketosynthase domain, an acyl-carrier protein domain, and a thioesterase domain. The products of rtcA, rtcB, and rtcC are homologous to the diacetylphloroglucinol-biosynthetic proteins PhlABC and may acetylate the tetramic acid moiety produced by RtcN and RtcK, forming reutericyclin. Deletion of rtcN or rtcABC in L. reuteri TMW1.656 abrogated reutericyclin production but did not affect resistance to reutericyclin. Genes coding for transport and regulatory proteins could be deleted only in the reutericyclin-negative L. reuteri strain TMW1.656?rtcN, and these deletions eliminated reutericyclin resistance. The genomic analyses suggest that the reutericyclin genomic island was horizontally acquired from an unknown source during a unique event. The combination of PhlABC homologues with both an NRPS and a PKS has also been identified in the lactic acid bacteria Streptococcus mutans and Lactobacillus plantarum, suggesting that the genes in these organisms and those in L. reuteri share an evolutionary origin. Copyright © 2015, American Society for Microbiology. All Rights Reserved.


July 7, 2019

Analysis of a draft genome sequence of Kitasatospora cheerisanensis KCTC 2395 producing bafilomycin antibiotics.

Kitasatospora cheerisanensis KCTC 2395, producing bafilomycin antibiotics belonging to plecomacrolide group, was isolated from a soil sample at Mt. Jiri, Korea. The draft genome sequence contains 8.04 Mb with 73.6% G+C content and 7,810 open reading frames. All the genes for aerial mycelium and spore formations were confirmed in this draft genome. In phylogenetic analysis of MurE proteins (UDP-N-acetylmuramyl-L-alanyl-D-glutamate:DAP ligase) in a conserved dcw (division of cell wall) locus, MurE proteins of Kitasatospora species were placed in a separate clade between MurEs of Streptomyces species incorporating LL-diaminopimelic acid (DAP) and MurEs of Saccharopolyspora erythraea as well as Mycobacterium tuberculosis ligating meso-DAP. From this finding, it was assumed that Kitasatospora MurEs exhibit the substrate specificity for both LL-DAP and meso-DAP. The bafilomycin biosynthetic gene cluster was located in the left subtelomeric region. In 71.3 kb-long gene cluster, 17 genes probably involved in the biosynthesis of bafilomycin derivatives were deduced, including 5 polyketide synthase (PKS) genes comprised of 12 PKS modules.


July 7, 2019

Characterization of the effect of the histidine kinase CovS on response regulator phosphorylation in group A Streptococcus.

Two-component gene regulatory systems (TCSs) are a major mechanism by which bacteria respond to environmental stimuli and thus are critical to infectivity. For example, the control of virulence regulator/sensor kinase (CovRS) TCS is central to the virulence of the major human pathogen group A Streptococcus (GAS). Here, we used a combination of quantitative in vivo phosphorylation assays, isoallelic strains that varied by only a single amino acid in CovS, and transcriptome analyses to characterize the impact of CovS on CovR phosphorylation and GAS global gene expression. We discovered that CovS primarily serves to phosphorylate CovR, thereby resulting in the repression of virulence factor-encoding genes. However, a GAS strain selectively deficient in CovS phosphatase activity had a distinct transcriptome relative to that of its parental strain, indicating that both CovS kinase and phosphatase activities influence the CovR phosphorylation status. Surprisingly, compared to a serotype M3 strain, serotype M1 GAS strains had high levels of phosphorylated CovR, low transcript levels of CovR-repressed genes, and strikingly different responses to environmental cues. Moreover, the inactivation of CovS in the serotype M1 background resulted in a greater decrease in phosphorylated CovR levels and a greater increase in the transcript levels of CovR-repressed genes than did CovS inactivation in a serotype M3 strain. These data clarify the influence of CovS on the CovR phosphorylation status and provide insight into why serotype M1 GAS strains have high rates of spontaneous mutations in covS during invasive GAS infection, thus providing a link between TCS molecular function and the epidemiology of deadly bacterial infections. Copyright © 2015, American Society for Microbiology. All Rights Reserved.


July 7, 2019

Gut symbionts from distinct hosts exhibit genotoxic activity via divergent colibactin biosynthetic pathways.

Secondary metabolites produced by nonribosomal peptide synthetase (NRPS) or polyketide synthase (PKS) pathways are chemical mediators of microbial interactions in diverse environments. However, little is known about their distribution, evolution, and functional roles in bacterial symbionts associated with animals. A prominent example is “colibactin”, a largely unknown family of secondary metabolites produced by Escherichia coli via a hybrid NRPS-PKS biosynthetic pathway, inflicting DNA damage upon eukaryotic cells and contributing to colorectal cancer and tumor formation in the mammalian gut. Thus far, homologs of this pathway have only been found in closely related Enterobacteriaceae, while a divergent variant of this gene cluster was recently discovered in a marine alphaproteobacterial Pseudovibrio strain. Herein, we sequenced the genome of Frischella perrara PEB0191, a bacterial gut symbiont of honey bees, and identified a homologous colibactin biosynthetic pathway related to those found in Enterobacteriaceae. We show that the colibactin genomic island (GI) has conserved gene synteny and biosynthetic module architecture across F. perrara, Enterobacteriaceae and the Pseudovibrio strain. Comparative metabolomics analyses of F. perrara and E. coli further reveal that these two bacteria produce related colibactin pathway-dependent metabolites. Finally, we demonstrate that F. perrara, like E. coli, causes DNA damage in eukaryotic cells in vitro in a colibactin pathway-dependent manner. Together, these results support that divergent variants of the colibactin biosynthetic pathway are widely distributed among bacterial symbionts, producing related secondary metabolites and likely endowing its producer with functional capabilities important for diverse symbiotic associations. Copyright © 2014, American Society for Microbiology. All Rights Reserved.


July 7, 2019

Complete sequences of six IncA/C plasmids of multidrug-resistant Salmonella enterica subsp. enterica serotype Newport.

Multidrug-resistant (MDR) Salmonella enterica subsp. enterica serotype Newport has been a long-standing public health concern in the United States. We present the complete sequences of six IncA/C plasmids from animal-derived MDR S. Newport ranging from 80.1 to 158.5 kb. They shared a genetic backbone with S. Newport IncA/C plasmids pSN254 and pAM04528. Copyright © 2015 Cao et al.


July 7, 2019

Convergent losses of decay mechanisms and rapid turnover of symbiosis genes in mycorrhizal mutualists.

To elucidate the genetic bases of mycorrhizal lifestyle evolution, we sequenced new fungal genomes, including 13 ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species, and five saprotrophs, which we analyzed along with other fungal genomes. Ectomycorrhizal fungi have a reduced complement of genes encoding plant cell wall-degrading enzymes (PCWDEs), as compared to their ancestral wood decayers. Nevertheless, they have retained a unique array of PCWDEs, thus suggesting that they possess diverse abilities to decompose lignocellulose. Similar functional categories of nonorthologous genes are induced in symbiosis. Of induced genes, 7-38% are orphan genes, including genes that encode secreted effector-like proteins. Convergent evolution of the mycorrhizal habit in fungi occurred via the repeated evolution of a ‘symbiosis toolkit’, with reduced numbers of PCWDEs and lineage-specific suites of mycorrhiza-induced genes.


July 7, 2019

Sequence analysis of Staphylococcus hyicus ATCC 11249T, an etiological agent of exudative epidermitis in swine, reveals a type VII secretion system locus and a novel 116-kilobase genomic island harboring toxin-encoding genes.

Staphylococcus hyicus is the primary etiological agent of exudative epidermitis in swine. Analysis of the complete genome sequence of the type strain revealed a locus encoding a type VII secretion system and a large chromosomal island harboring the genes encoding exfoliative toxin ExhA and an EDIN toxin homolog. Copyright © 2015 Calcutt et al.


July 7, 2019

A unique chromatin complex occupies young a-satellite arrays of human centromeres.

The intractability of homogeneous a-satellite arrays has impeded understanding of human centromeres. Artificial centromeres are produced from higher-order repeats (HORs) present at centromere edges, although the exact sequences and chromatin conformations of centromere cores remain unknown. We use high-resolution chromatin immunoprecipitation (ChIP) of centromere components followed by clustering of sequence data as an unbiased approach to identify functional centromere sequences. We find that specific dimeric a-satellite units shared by multiple individuals dominate functional human centromeres. We identify two recently homogenized a-satellite dimers that are occupied by precisely positioned CENP-A (cenH3) nucleosomes with two ~100-base pair (bp) DNA wraps in tandem separated by a CENP-B/CENP-C-containing linker, whereas pericentromeric HORs show diffuse positioning. Precise positioning is largely maintained, whereas abundance decreases exponentially with divergence, which suggests that young a-satellite dimers with paired ~100-bp particles mediate evolution of functional human centromeres. Our unbiased strategy for identifying functional centromeric sequences should be generally applicable to tandem repeat arrays that dominate the centromeres of most eukaryotes.


July 7, 2019

Do echinoderm genomes measure up?

Echinoderm genome sequences are a corpus of useful information about a clade of animals that serve as research models in fields ranging from marine ecology to cell and developmental biology. Genomic information from echinoids has contributed to insights into the gene interactions that drive the developmental process at the molecular level. Such insights often rely heavily on genomic information and the kinds of questions that can be asked thus depend on the quality of the sequence information. Here we describe the history of echinoderm genomic sequence assembly and present details about the quality of the data obtained. All of the sequence information discussed here is posted on the echinoderm information web system, Echinobase.org. Copyright © 2015 Elsevier B.V. All rights reserved.


July 7, 2019

Complete genome of Geobacter pickeringii G13T, a metal-reducing isolate from sedimentary kaolin deposits.

We used PacBio sequencing to assemble the genome of the pristine freshwater isolate Geobacter pickeringii G13(T) into a single 3,618,700-bp circular chromosome polished to 99.999% accuracy (quality value [QV], 50). This isolate shares several features with other Geobacter spp., including genes for degradation of aromatics and an abundance of multiheme c-type cytochromes. Copyright © 2015 Badalamenti and Bond.


July 7, 2019

Complete genome sequence of the cyclohexylamine-degrading Pseudomonas plecoglossicida NyZ12.

Pseudomonas plecoglossicida NyZ12 (CCTCC AB 2015057), a Gram-negative bacterium isolated from soil, has the ability to degrade cyclohexylamine. The complete genome sequence of this strain (6,233,254bp of chromosome length) is presented, with information about the genes of characteristic enzymes responsible for cyclohexylamine oxidation to cyclohexanone and the integrated gene cluster for the metabolic pathway of cyclohexanone oxidation to adipate. Copyright © 2015 Elsevier B.V. All rights reserved.


July 7, 2019

Genomes of Geoalkalibacter ferrihydriticus Z-0531Tand Geoalkalibacter subterraneus Red1T, two haloalkaliphilic metal-reducing Deltaproteobacteria.

We sequenced and annotated genomes of two haloalkaliphilic Deltaproteobacteria, Geoalkalibacter ferrihydriticus Z-0531(T) (DSM 17813) and Geoalkalibacter subterraneus Red1(T) (DSM 23483). During assembly, we discovered that the DSMZ stock culture of G. subterraneus was contaminated. We reisolated G. subterraneus in axenic culture and redeposited it in DSMZ and JCM. Copyright © 2015 Badalamenti et al.


July 7, 2019

Ceftriaxone-resistant Salmonella enterica serotype Typhimurium sequence type 313 from Kenyan patients is associated with the blaCTX-M-15 gene on a novel IncHI2 plasmid.

Multidrug-resistant bacteria pose a major challenge to the clinical management of infections in resource-poor settings. Although nontyphoidal Salmonella (NTS) bacteria cause predominantly enteric self-limiting illness in developed countries, NTS is responsible for a huge burden of life-threatening bloodstream infections in sub-Saharan Africa. Here, we characterized nine S. Typhimurium isolates from an outbreak involving patients who initially failed to respond to ceftriaxone treatment at a referral hospital in Kenya. These Salmonella enterica serotype Typhimurium isolates were resistant to ampicillin, chloramphenicol, cefuroxime, ceftriaxone, aztreonam, cefepime, sulfamethoxazole-trimethoprim, and cefpodoxime. Resistance to ß-lactams, including to ceftriaxone, was associated with carriage of a combination of blaCTX-M-15, blaOXA-1, and blaTEM-1 genes. The genes encoding resistance to heavy-metal ions were borne on the novel IncHI2 plasmid pKST313, which also carried a pair of class 1 integrons. All nine isolates formed a single clade within S. Typhimurium ST313, the major clone of an ongoing invasive NTS epidemic in the region. This emerging ceftriaxone-resistant clone may pose a major challenge in the management of invasive NTS in sub-Saharan Africa. Copyright © 2015, Kariuki et al.


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