BackgroundAkkermansia muciniphila is an important bacterium that resides on the mucus layer of the intestinal tract. Akkermansia muciniphila has a high abundance in human feces and plays an important role in human health.ObjectiveIn this article, 23 whole genome sequences of the Akkermansia genus were comparatively studied.MethodsPhylogenetic trees were constructed with three methods: All amino acid sequences of each strain were used to construct the first phylogenetic tree using the web server of Composition Vector Tree Version 3. The matrix of Genome-to-Genome Distances which were obtained from GGDC 2.0 was used to construct the second phylogenetic tree using FastME. The concatenated single-copy core gene-based phylogenetic tree was generated through MEGA. The single-copy genes were obtained using OrthoMCL. Population structure was assessed by STRUCTURE 2.3.4 using the SNPs in core genes. PROKKA and Roary were used to do pan-genome analyses. The biosynthetic gene clusters were predicted using antiSMASH 4.0. IalandViewer 4 was used to detect the genomic islands.ResultsThe results of comparative genomic analysis revealed that: (1) The 23 Akkermansia strains formed 4 clades in phylogenetic trees. The A. muciniphila strains isolated from different geographic regions and ecological niches, formed a closely related clade. (2) The 23 Akkermansia strains were divided into 4 species based on digital DNA-DNA hybridization (dDDH) values. (3) Pan-genome of A. muciniphila is in an open state and increases with addition of new sequenced genomes. (4) SNPs were not evenly distributed throughout the A. muciniphila genomes. The genes in regions with high SNP density are related to metabolism and cell wall/membrane envelope biogenesis. (5) The thermostable outer-membrane protein, Amuc_1100, was conserved in the Akkermansia genus, except for Akkermansia glycaniphila PytT.ConclusionOverall, applying comparative genomic and pan-genomic analyses, we classified and illuminated the phylogenetic relationship of the 23 Akkermansia strains. Insights of the evolutionary, population structure, gene clusters and genome islands of Akkermansia provided more information about the possible physiological and probiotic mechanisms of the Akkermansia strains, and gave some instructions for the in-depth researches about the use of Akkermansia as a gut probiotic in the future.Electronic supplementary materialThe online version of this article (10.1007/s13258-019-00855-1) contains supplementary material, which is available to authorized users.
Bacillus velezensis strain WRN014 was isolated from banana fields in Hainan, China. Bacillus velezensis is an important member of the plant growth-promoting rhizobacteria (PGPR) which can enhance plant growth and control soil-borne disease. The complete genome of Bacillus velezensis WRN014 was sequenced by combining Illumina Hiseq 2500 system and Pacific Biosciences SMRT high-throughput sequencing technologies. Then, the genome of Bacillus velezensis WRN014, together with 45 other completed genome sequences of the Bacillus velezensis strains, were comparatively studied. The genome of Bacillus velezensis WRN014 was 4,063,541bp in length and contained 4,062 coding sequences, 9 genomic islands and 13 gene clusters. The results of comparative genomic analysis provide evidence that (i) The 46 Bacillus velezensis strains formed 2 obviously closely related clades in phylogenetic trees. (ii) The pangenome in this study is open and is increasing with the addition of new sequenced genomes. (iii) Analysis of single nucleotide polymorphisms (SNPs) revealed local diversification of the 46 Bacillus velezensis genomes. Surprisingly, SNPs were not evenly distributed throughout the whole genome. (iv) Analysis of gene clusters revealed that rich gene clusters spread over Bacillus velezensis strains and some gene clusters are conserved in different strains. This study reveals that the strain WRN014 and other Bacillus velezensis strains have potential to be used as PGPR and biopesticide.
Strain WRN001T, a Gram–staining–negative, strictly aerobic, non–motile bacterium was isolated from the natural saline-alkali wetland soil of Binhai new district, Tianjin, China (38°46′N, 117°13′E). Cells of strain WRN001T were 0.3-0.5 µm in width and 1.5-2.5 µm in length, and the growth occurred optimally at 33-37 °C, pH 7.5-8.0, and in the presence of 8-10% (w/v) NaCl. Based on 16S rRNA gene sequence analysis, the isolate could be affiliated to the genus Halomonas, and the highest 16S rRNA gene sequence similarity of strain WRN001T to its closest relative Halomonas qiaohouensis YIM QH88T was 97.47%. The size of the genome as presented here was 5,475,884 bp with a G+C content of 63.8 mol %. The major respiratory quinone of strainWRN001T was Q-9, and the dominant fatty acids were summed feature 8, summed feature 3, C10:0, C12:0, C12:0 3-OH, C16:0, and C17:0 cyclo. The major polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), phophatidylcholine (PC), two phospholipids (PL), aminolipid (AL), and three unidentified lipids (L). These data mentioned above combined with the low DDH values between strain WRN001T and the close relative, Halomonas alkalitolerans 1513T (42.20%) and base on comparisons with currently available genomes, the highest average nucleotide identity (ANIm) value was 91.39% to Halomonas alkalitolerans 1513T (GenBank accession No. GCA_001971685.1). Therefore, we propose a novel species in the genus Halomonas to accommodate this novel isolate: Halomonas salipaludis sp. nov. (type strain WRN001T = KCTC 52853T = ACCC 19974T).
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