April 21, 2020  |  

Streptococcus gwangjuense sp. nov., Isolated from Human Pericoronitis.

A novel facultative anaerobic, Gram-stain-negative coccus, designated strain ChDC B345T, was isolated from human pericoronitis lesion and was characterized by polyphasic taxonomic analysis. The 16S ribosomal RNA gene (16S rDNA) sequence revealed that the strain belonged to the genus Streptococcus. The 16S rDNA sequence of strain ChDC B345T was most closely related to those of  Streptococcus mitis NCTC 12261T (99.5%) and Streptococcus pseudopneumoniae ATCC BAA-960T (99.5%). Complete genome of strain ChDC B345T was 1,972,471 bp in length and the G?+?C content was 40.2 mol%. Average nucleotide identity values between strain ChDC B345T and S. pseudopneumoniae ATCC BAA-960T or S. mitis NCTC 12261T were 92.17% and 93.63%, respectively. Genome-to-genome distance values between strain ChDC B345T and S. pseudopneumoniae ATCC BAA-960T or S. mitis NCTC 12261T were 47.8% (45.2-50.4%) and 53.0% (51.0-56.4%), respectively. Based on these results, strain ChDC B345T (=?KCOM 1679T?=?JCM 33299T) should be classified as a novel species of genus Streptococcus, for which we propose the name Streptococcus gwangjuense sp. nov.


July 19, 2019  |  

Genome modification in Enterococcus faecalis OG1RF assessed by bisulfite sequencing and Single-Molecule Real-Time Sequencing.

Enterococcus faecalis is a Gram-positive bacterium that natively colonizes the human gastrointestinal tract and opportunistically causes life-threatening infections. Multidrug-resistant (MDR) E. faecalis strains have emerged, reducing treatment options for these infections. MDR E. faecalis strains have large genomes containing mobile genetic elements (MGEs) that harbor genes for antibiotic resistance and virulence determinants. Bacteria commonly possess genome defense mechanisms to block MGE acquisition, and we hypothesize that these mechanisms have been compromised in MDR E. faecalis. In restriction-modification (R-M) defense, the bacterial genome is methylated at cytosine (C) or adenine (A) residues by a methyltransferase (MTase), such that nonself DNA can be distinguished from self DNA. A cognate restriction endonuclease digests improperly modified nonself DNA. Little is known about R-M in E. faecalis. Here, we use genome resequencing to identify DNA modifications occurring in the oral isolate OG1RF. OG1RF has one of the smallest E. faecalis genomes sequenced to date and possesses few MGEs. Single-molecule real-time (SMRT) and bisulfite sequencing revealed that OG1RF has global 5-methylcytosine (m5C) methylation at 5′-GCWGC-3′ motifs. A type II R-M system confers the m5C modification, and disruption of this system impacts OG1RF electrotransformability and conjugative transfer of an antibiotic resistance plasmid. A second DNA MTase was poorly expressed under laboratory conditions but conferred global N(4)-methylcytosine (m4C) methylation at 5′-CCGG-3′ motifs when expressed in Escherichia coli. Based on our results, we conclude that R-M can act as a barrier to MGE acquisition and likely influences antibiotic resistance gene dissemination in the E. faecalis species.The horizontal transfer of antibiotic resistance genes among bacteria is a critical public health concern. Enterococcus faecalis is an opportunistic pathogen that causes life-threatening infections in humans. Multidrug resistance acquired by horizontal gene transfer limits treatment options for these infections. In this study, we used innovative DNA sequencing methodologies to investigate how a model strain of E. faecalis discriminates its own DNA from foreign DNA, i.e., self versus nonself discrimination. We also assess the role of an E. faecalis genome modification system in modulating conjugative transfer of an antibiotic resistance plasmid. These results are significant because they demonstrate that differential genome modification impacts horizontal gene transfer frequencies in E. faecalis. Copyright © 2015, American Society for Microbiology. All Rights Reserved.


July 19, 2019  |  

Pangenome analysis of Bifidobacterium longum and site-directed mutagenesis through by-pass of restriction-modification systems.

Bifidobacterial genome analysis has provided insights as to how these gut commensals adapt to and persist in the human GIT, while also revealing genetic diversity among members of a given bifidobacterial (sub)species. Bifidobacteria are notoriously recalcitrant to genetic modification, which prevents exploration of their genomic functions, including those that convey (human) health benefits.PacBio SMRT sequencing was used to determine the whole genome seqeunces of two B. longum subsp. longum strains. The B. longum pan-genome was computed using PGAP v1.2 and the core B. longum phylogenetic tree was constructed using a maximum-likelihood based approach in PhyML v3.0. M.blmNCII was cloned in E. coli and an internal fragment if arfBarfB was cloned into pORI19 for insertion mutagenesis.In this study we present the complete genome sequences of two Bifidobacterium longum subsp. longum strains. Comparative analysis with thirty one publicly available B. longum genomes allowed the definition of the B. longum core and dispensable genomes. This analysis also highlighted differences in particular metabolic abilities between members of the B. longum subspecies infantis, longum and suis. Furthermore, phylogenetic analysis of the B. longum core genome indicated the existence of a novel subspecies. Methylome data, coupled to the analysis of restriction-modification systems, allowed us to substantially increase the genetic accessibility of B. longum subsp. longum NCIMB 8809 to a level that was shown to permit site-directed mutagenesis.Comparative genomic analysis of thirty three B. longum representatives revealed a closed pan-genome for this bifidobacterial species. Phylogenetic analysis of the B. longum core genome also provides evidence for a novel fifth B. longum subspecies. Finally, we improved genetic accessibility for the strain B. longum subsp. longum NCIMB 8809, which allowed the generation of a mutant of this strain.


July 7, 2019  |  

Complete genome sequence of Bifidobacterium adolesentis BBMN23, a probiotic strain from healthy centenarian.

Bifidobacterium adolesentis BBMN23 (CGMCC No. 2264) was a probiotic strain originated from the feces of a centenarian. It is an excellent model for the study of the adaptation of genus bifidobacteria to adult human gut, which is a key factor in bifidobacterial strains that allows them to persist in gut and become useful in the food and medical industries. In the present study the complete genome sequence of BBMN23 is presented to provide insight into this strain. Copyright © 2015 Elsevier B.V. All rights reserved.


July 7, 2019  |  

Complete genome sequence of Bifidobacterium animalis subsp. lactis A6, a probiotic strain with high acid resistance ability.

Bifidobacterium animalis subsp. lactis A6 (BAA6) (CGMCC No. 9273) was a probiotic strain isolated from the feces of a centenarian. Previous study showed that BAA6 had high acid resistance to low pH which is a critical factor influencing its healthy benefits. Elaborating the stress resistant mechanisms of bifidobacteria is important to extensively exploit this probiotic. Here, we reported the complete genome sequence of BAA6 that contains 1,958,651 bp encoding 1622 CDSs, 16 rRNA genes, 52 tRNA genes. Copyright © 2015 Elsevier B.V. All rights reserved.


July 7, 2019  |  

In silico analysis of protein toxin and bacteriocins from Lactobacillus paracasei SD1 genome and available online databases.

Lactobacillus paracasei SD1 is a potential probiotic strain due to its ability to survive several conditions in human dental cavities. To ascertain its safety for human use, we therefore performed a comprehensive bioinformatics analysis and characterization of the bacterial protein toxins produced by this strain. We report the complete genome of Lactobacillus paracasei SD1 and its comparison to other Lactobacillus genomes. Additionally, we identify and analyze its protein toxins and antimicrobial proteins using reliable online database resources and establish its phylogenetic relationship with other bacterial genomes. Our investigation suggests that this strain is safe for human use and contains several bacteriocins that confer health benefits to the host. An in silico analysis of protein-protein interactions between the target bacteriocins and the microbial proteins gtfB and luxS of Streptococcus mutans was performed and is discussed here.


July 7, 2019  |  

Genomic and functional analysis of Romboutsia ilealis CRIBT reveals adaptation to the small intestine.

The microbiota in the small intestine relies on their capacity to rapidly import and ferment available carbohydrates to survive in a complex and highly competitive ecosystem. Understanding how these communities function requires elucidating the role of its key players, the interactions among them and with their environment/host.The genome of the gut bacterium Romboutsia ilealis CRIBT was sequenced with multiple technologies (Illumina paired-end, mate-pair and PacBio). The transcriptome was sequenced (Illumina HiSeq) after growth on three different carbohydrate sources, and short chain fatty acids were measured via HPLC.We present the complete genome of Romboutsia ilealis CRIBT, a natural inhabitant and key player of the small intestine of rats. R. ilealis CRIBT possesses a circular chromosome of 2,581,778 bp and a plasmid of 6,145 bp, carrying 2,351 and eight predicted protein coding sequences, respectively. Analysis of the genome revealed limited capacity to synthesize amino acids and vitamins, whereas multiple and partially redundant pathways for the utilization of different relatively simple carbohydrates are present. Transcriptome analysis allowed identification of the key components in the degradation of glucose, L-fucose and fructo-oligosaccharides.This revealed that R. ilealis CRIBT is adapted to a nutrient-rich environment where carbohydrates, amino acids and vitamins are abundantly available.


July 7, 2019  |  

A commensal bacterium promotes virulence of an opportunistic pathogen via cross-respiration.

Bacteria rarely inhabit infection sites alone, instead residing in diverse, multispecies communities. Despite this fact, bacterial pathogenesis studies primarily focus on monoculture infections, overlooking how community interactions influence the course of disease. In this study, we used global mutant fitness profiling (transposon sequencing [Tn-seq]) to determine the genetic requirements for the pathogenic bacterium Aggregatibacter actinomycetemcomitans to cause disease when coinfecting with the commensal bacterium Streptococcus gordonii Our results show that S. gordonii extensively alters A. actinomycetemcomitans requirements for virulence factors and biosynthetic pathways during infection. In addition, we discovered that the presence of S. gordonii enhances the bioavailability of oxygen during infection, allowing A. actinomycetemcomitans to shift from a primarily fermentative to a respiratory metabolism that enhances its growth yields and persistence. Mechanistically, respiratory metabolism enhances the fitness of A. actinomycetemcomitans in vivo by increasing ATP yields via central metabolism and creating a proton motive force. Our results reveal that, similar to cross-feeding, where one species provides another species with a nutrient, commensal bacteria can also provide electron acceptors that promote the respiratory growth and fitness of pathogens in vivo, an interaction that we term cross-respiration.Commensal bacteria can enhance the virulence of pathogens in mixed-species infections. However, knowledge of the mechanisms underlying this clinically relevant phenomenon is lacking. To bridge this gap, we comprehensively determined the genes a pathogen needs to establish coinfection with a commensal. Our findings show that the metabolism of the pathogen is low-energy-yielding in monoinfection, but in coinfection, the commensal improves the fitness of the pathogen by increasing the bioavailability of oxygen, thereby shifting the pathogen toward a high-energy-yielding metabolism. Similar to cross-feeding, this interaction, which we term cross-respiration, illustrates that commensal bacteria can provide electron acceptors that enhance the virulence of pathogens during infection. Copyright © 2016 Stacy et al.


July 7, 2019  |  

Evolutionary architecture of the infant-adapted group of Bifidobacterium species associated with the probiotic function.

Bifidobacteria, often associated with the gastrointestinal tract of animals, are well known for their roles as probiotics. Among the dozens of Bifidobacterium species, Bifidobacterium bifidum, B. breve, and B. longum are the ones most frequently isolated from the feces of infants and known to help the digestion of human milk oligosaccharides. To investigate the correlation between the metabolic properties of bifidobacteria and their phylogeny, we performed a phylogenomic analysis based on 452 core genes of forty-four completely sequenced Bifidobacterium species. Results show that a major evolutionary event leading to the clade of the infant-adapted species is linked to carbohydrate metabolism, but it is not the only factor responsible for the adaptation of bifidobacteria to the gut. The genome of B. longum subsp. infantis, a typical bifidobacterium in the gut of breast-fed infants, encodes proteins associated with several kinds of species-specific metabolic pathways, including urea metabolism and biosynthesis of riboflavin and lantibiotics. Our results demonstrate that these metabolic features, which are associated with the probiotic function of bifidobacteria, are species-specific and highly correlate with their phylogeny. Copyright © 2016 Elsevier GmbH. All rights reserved.


July 7, 2019  |  

Comparative genomics analysis of Streptococcus tigurinus strains identifies genetic elements specifically and uniquely present in highly virulent strains.

Streptococcus tigurinus is responsible for severe invasive infections such as infective endocarditis, spondylodiscitis and meningitis. As described, S. tigurinus isolates AZ_3aT and AZ_14 were highly virulent (HV phenotype) in an experimental model of infective endocarditis and showed enhanced adherence and invasion of human endothelial cells when compared to low virulent S. tigurinus isolate AZ_8 (LV phenotype). Here, we sought whether genetic determinants could explain the higher virulence of AZ_3aT and AZ_14 isolates. Several genetic determinants specific to the HV strains were identified through extensive comparative genomics amongst which some were thought to be highly relevant for the observed HV phenotype. These included i) an iron uptake and metabolism operon, ii) an ascorbate assimilation operon, iii) a newly acquired PI-2-like pilus islets described for the first time in S. tigurinus, iv) a hyaluronate metabolism operon, v) an Entner-Doudoroff pathway of carbohydrates metabolism, and vi) an alternate pathways for indole biosynthesis. We believe that the identified genomic features could largely explain the phenotype of high infectivity of the two HV S. tigurinus strains. Indeed, these features include determinants that could be involved at different stages of the disease such as survival of S. tigurinus in blood (iron uptake and ascorbate metabolism operons), initial attachment of bacterial pathogen to the damaged cardiac tissue and/or vegetation that formed on site (PI-2-like pilus islets), tissue invasion (hyaluronate operon and Entner-Doudoroff pathway) and regulation of pathogenicity (indole biosynthesis pathway).


July 7, 2019  |  

Complete genome sequence of Streptococcus sp. strain NPS 308.

Streptococcus sp. strain NPS 308, isolated from an 8-year-old girl diagnosed with infective endocarditis, likely presents a novel species of Streptococcus Here, we present a complete genome sequence of this species, which will contribute to better understanding of the pathogenesis of infective endocarditis. Copyright © 2016 Kondo et al.


July 7, 2019  |  

Whole genome sequence and phenotypic characterization of a Cbm+ serotype e strain of Streptococcus mutans.

We report the whole genome sequence of the serotype e Cbm+ strain LAR01 of Streptococcus mutans, a dental pathogen frequently associated with extra-oral infections. The LAR01 genome is a single circular chromosome of 2.1 Mb with a GC content of 36.96%. The genome contains 15 phosphotransferase system gene clusters, seven cell wall-anchored (LPxTG) proteins, all genes required for the development of natural competence and genes coding for mutacins VI and K8. Interestingly, the cbm gene is genetically linked to a putative type VII secretion system that has been found in Mycobacteria and few other Gram-positive bacteria. When compared with the UA159 type strain, phenotypic characterization of LAR01 revealed increased biofilm formation in the presence of either glucose or sucrose but similar abilities to withstand acid and oxidative stresses. LAR01 was unable to inhibit the growth of Strpetococcus gordonii, which is consistent with the genomic data that indicate absence of mutacins that can kill mitis streptococci. On the other hand, LAR01 effectively inhibited growth of other S. mutans strains, suggesting that it may be specialized to outcompete strains from its own species. In vitro and in vivo studies using mutational and heterologous expression approaches revealed that Cbm is a virulence factor of S. mutans by mediating binding to extracellular matrix proteins and intracellular invasion. Collectively, the whole genome sequence analysis and phenotypic characterization of LAR01 provides new insights on the virulence properties of S. mutans and grants further opportunities to understand the genomic fluidity of this important human pathogen.© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.


July 7, 2019  |  

Complete genome sequence of Fusobacterium vincentii KCOM 2931 isolated from a human periodontitis lesion

Recently, Fusobacterium nucleatum subsp. vincentii was reclassified as Fusobacterium vincentii based on the average nucleotide identity and genome-to-genome distance analyses. F. vincentii is a Gram-negative, anaerobic, and filament-shaped bacterium. F. vincentii is a member of normal flora of human oral cavity and plays a role in periodontal diseases. F. vincentii KCOM 2931 was isolated from a periodontitis lesion. Here, we present the complete genome sequence of F. vincentii KCOM 2931.


July 7, 2019  |  

Draft genome sequence of Olsenella sp. KGMB 04489 isolated from healthy Korean human feces

The genus of Olsenella has been isolated from vertebrate animal mouth, rumen, and feces. Olsenella sp. KGMB 04489 was isolated from fecal samples obtained from a healthy Korean. The whole-genome sequence of Olsenella sp. KGMB 04489 was analyzed using the PacBio Sequel platform. The genome comprises a 2,108,034 bp chromosome with a G + C content of 65.50%, 1,838 total genes, 13 rRNA genes, and 52 tRNA genes. Also, we found that strain KGMB 04489 had some genes for hydrolysis enzymes, and antibiotic biosynthesis and resistance in its genome based on the result of genome analysis.


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