The complete genome sequences of three Xanthomonas citri strains isolated from lime trees in Texas were found to belong to the A(w) group. All carried nearly identical large plasmids with similarity to those of a citrus canker strain from India and to xanthomonads from Africa and Colombia. All three strains harbored unusual pthA homologs. Copyright © 2017 Munoz Bodnar et al.
The study of biological diversification of oomycetes has been a difficult task for more than a century. Pioneer researchers used morphological characters to describe this heterogeneous group, and physiological and genetic tools expanded knowledge of these microorganisms. However, research on oomycete diversification is limited by conflicting phylogenies. Using whole genomic data from 17 oomycete taxa, we obtained a dataset of 277 core orthologous genes shared among these genomes. Analyses of this dataset resulted in highly congruent and strongly supported estimates of oomycete phylogeny when we used concatenated maximum likelihood and coalescent-based methods; the one important exception was the position of Albugo. Our results supported the position of Phytopythium vexans (formerly in Pythium clade K) as a sister clade to the Phytophthora-Hyaloperonospora clade. The remaining clades comprising Pythium sensu lato formed two monophyletic groups. One group was composed of three taxa that correspond to Pythium clades A, B and C, and the other group contained taxa representing clades F, G and I, in agreement with previous Pythium phylogenies. However, the group containing Pythium clades F, G and I was placed as sister to the Phytophthora-Hyaloperonospora-Phytopythium clade, thus confirming the lack of monophyly of Pythium sensu lato. Multispecies coalescent methods revealed that the white blister rust, Albugo laibachii, could not be placed with a high degree of confidence. Our analyses show that genomic data can resolve the oomycete phylogeny and provide a phylogenetic framework to study the evolution of oomycete lifestyles. Copyright © 2017 Elsevier Inc. All rights reserved.
The genus Porphyrobacter belongs to aerobic anoxygenic phototrophic bacteria cluster. Porphyrobacter neustonensis DSM 9434 was isolated from a eutrophic freshwater pond in Australia, and is able to synthesize Bacteriochlorophyll a as well as grow under aerobic conditions. It is the type species of the genus Porphyrobacter. Here we describe the characteristics of the strain DSM 9434, including the genome sequence and annotation, synthesis of BChl a, and metabolic pathways of the organism. The genome of strain DSM 9434 comprises 3,090,363 bp and contains 2,902 protein-coding genes, 47 tRNA genes and 6 rRNA genes. Strain DSM 9434 encodes 46 genes which participate in BChl a synthesis and this investigation shed light on the evolution and functional implications regarding bacteriochlorophyll synthesis.
Malaria is caused by parasites of the genus Plasmodium. All human-infecting Plasmodium species can establish long-lasting chronic infections(1-5), creating an infectious reservoir to sustain transmission(1,6). It is widely accepted that the maintenance of chronic infection involves evasion of adaptive immunity by antigenic variation(7). However, genes involved in this process have been identified in only two of five human-infecting species: Plasmodium falciparum and Plasmodium knowlesi. Furthermore, little is understood about the early events in the establishment of chronic infection in these species. Using a rodent model we demonstrate that from the infecting population, only a minority of parasites, expressing one of several clusters of virulence-associated pir genes, establishes a chronic infection. This process occurs in different species of parasites and in different hosts. Establishment of chronicity is independent of adaptive immunity and therefore different from the mechanism proposed for maintenance of chronic P. falciparum infections(7-9). Furthermore, we show that the proportions of parasites expressing different types of pir genes regulate the time taken to establish a chronic infection. Because pir genes are common to most, if not all, species of Plasmodium(10), this process may be a common way of regulating the establishment of chronic infections.
Copper-based antimicrobial compounds are widely used to control plant bacterial pathogens. Pathogens have adapted in response to this selective pressure. Xanthomonas citri pv. citri, a major citrus pathogen causing Asiatic citrus canker, was first reported to carry plasmid-encoded copper resistance in Argentina. This phenotype was conferred by the copLAB gene system. The emergence of resistant strains has since been reported in Réunion and Martinique. Using microsatellite-based genotyping and copLAB PCR, we demonstrated that the genetic structure of the copper-resistant strains from these three regions was made up of two distant clusters and varied for the detection of copLAB amplicons. In order to investigate this pattern more closely, we sequenced six copper-resistant X. citri pv. citri strains from Argentina, Martinique and Réunion, together with reference copper-resistant Xanthomonas and Stenotrophomonas strains using long-read sequencing technology. Genes involved in copper resistance were found to be strain dependent with the novel identification in X. citri pv. citri of copABCD and a cus heavy metal efflux resistance-nodulation-division system. The genes providing the adaptive trait were part of a mobile genetic element similar to Tn3-like transposons and included in a conjugative plasmid. This indicates the system’s great versatility. The mining of all available bacterial genomes suggested that, within the bacterial community, the spread of copper resistance associated with mobile elements and their plasmid environments was primarily restricted to the Xanthomonadaceae family.© 2017 John Wiley & Sons Ltd.
Primula vulgaris contains two GLOBOSA loci, one located adjacent to the style length determinant gene CYP734A50 which lies within the S -locus. Using a combination of BAC walking and PacBio sequencing, we have sequenced two substantial genomic contigs in and around the S-locus of Primula vulgaris. Using these data, we were able to demonstrate that two alleles of PvGlo (P) as well as PvGlo (T) can be present in the genome of a single plant, providing empirical evidence that these two forms of the MADS-box gene GLOBOSA are separate loci and not allelic as previously reported. We propose they should be renamed PvGLO1 and PvGLO2. BAC contigs extending from each GLOBOSA locus were identified and fully sequenced. No homologous genes were found between the contigs other than the GLOBOSA genes themselves, consistent with their identity as separate loci. Exons of the recently identified style-length determinant gene CYP734A50 were identified on one end of the contig containing PvGLO2 and these genes are adjacent in the genome, suggesting that PvGLO2 lies either within or at least very close to the S-locus. Current evidence suggests that both CYP734A50 and GLO2 are specific to the S-morph mating type and are hemizygous rather than heterozygous in the Primula genome. This finding contrasts classical models of the HSI locus, which propose that components of the S-locus are allelic, suggesting that these models may need to be reconsidered.
Single molecule, real-time (SMRT) sequencing was used to characterize mitochondrial (mt) genome of Ophiocordyceps sinensis and to analyze the mt genome-wide pattern of epigenetic DNA modification. The complete mt genome of O. sinensis, with a size of 157,539 bp, is the fourth largest Ascomycota mt genome sequenced to date. It contained 14 conserved protein-coding genes (PCGs), 1 intronic protein rps3, 27 tRNAs and 2 rRNA subunits, which are common characteristics of the known mt genomes in Hypocreales. A phylogenetic tree inferred from 14 PCGs in Pezizomycotina fungi supports O. sinensis as most closely related to Hirsutella rhossiliensis in Ophiocordycipitaceae. A total of 36 sequence sites in rps3 were under positive selection, with dN/dS >1 in the 20 compared fungi. Among them, 16 sites were statistically significant. In addition, the mt genome-wide base modification pattern of O. sinensis was determined in this study, especially DNA methylation. The methylations were located in coding and uncoding regions of mt PCGs in O. sinensis, and might be closely related to the expression of PCGs or the binding affinity of transcription factor A to mtDNA. Consequently, these methylations may affect the enzymatic activity of oxidative phosphorylation and then the mt respiratory rate; or they may influence mt biogenesis. Therefore, methylations in the mitogenome of O. sinensis might be a genetic feature to adapt to the cold and low PO2 environment at high altitude, where O. sinensis is endemic. This is the first report on epigenetic modifications in a fungal mt genome.
Bacterial leaf streak caused by Xanthomonas translucens pv. undulosa (Xtu) is an important disease of wheat (Triticum aestivum) and barley (Hordeum vulgare) worldwide. Transcription activator-like effectors (TALEs) play determinative roles in many of the plant diseases caused by the different species and pathovars of Xanthomonas, but their role in this disease has not been characterized. ICMP11055 is a highly virulent Xtu strain from Iran. The aim of this study was to better understand genetic diversity of Xtu and to assess the role of TALEs in bacterial leaf streak of wheat by comparing the genome of this strain to the recently completely sequenced genome of a U.S. Xtu strain, and to several other draft X. translucens genomes, and by carrying out mutational analyses of the TALE (tal) genes the Iranian strain might harbor. The ICMP11055 genome, including its repeat-rich tal genes, was completely sequenced using single molecule, real-time technology (Pacific Biosciences). It consists of a single circular chromosome of 4,561,583 bp, containing 3,953 genes. Whole genome alignment with the genome of the United States Xtu strain XT4699 showed two major re-arrangements, nine genomic regions unique to ICMP11055, and one region unique to XT4699. ICMP110055 harbors 26 non-TALE type III effector genes and seven tal genes, compared to 25 and eight for XT4699. The tal genes occur singly or in pairs across five scattered loci. Four are identical to tal genes in XT4699. In addition to common repeat-variable diresidues (RVDs), the tal genes of ICMP11055, like those of XT4699, encode several RVDs rarely observed in Xanthomonas, including KG, NF, Y*, YD, and YK. Insertion and deletion mutagenesis of ICMP11055 tal genes followed by genetic complementation analysis in wheat cv. Chinese Spring revealed that Tal2 and Tal4b of ICMP11055 each contribute individually to the extent of disease caused by this strain. A largely conserved ortholog of tal2 is present in XT4699, but for tal4b, only a gene with partial, fragmented RVD sequence similarity can be found. Our results lay the foundation for identification of important host genes activated by Xtu TALEs as targets for the development of disease resistant varieties.
The Swiss wastewater isolate Klebsiella pneumoniae 704SK6, encoding OXA-48 and CTX-M-15 ß-lactamases, was fully sequenced. The assembly resulted in an open chromosome of 5,208,104 bp in size (G+C content, 57.6%) and four closed plasmid sequences of 209,651, 197,670, 65,998, and 63,605 bp in size. Copyright © 2017 Marti et al.
Isolates of the Mycobacterium tuberculosis lineage 2/East-Asian are considered one of the most successful strains due to their increased pathogenicity, hyper-virulence associated with drug resistance, and high transmission. Recent studies in Colombia have shown that the Beijing-like genotype is associated with multidrug-resistance and high prevalence in the southwest of the country, but the genetic basis of its success in dissemination is unknown. In contribution to this matter, we obtained the whole sequences of six genomes of clinical isolates assigned to the Beijing-like genotype. The genomes were compared with the reference genome of M. tuberculosis H37Rv and 53 previously published M. tuberculosis genomes. We found that the six Beijing-like isolates belong to a modern Beijing sub-lineage and share specific genomic variants: i.e. deletion in the PPE8 gene, in Rv3806c (ubiA) responsible of high ethambutol resistance and in Rv3862c (whiB6) which is involved in granuloma formation and virulence, are some of them. Moreover, each isolated has exclusively single nucleotide polymorphisms (SNPs) in genes related with cell wall processes and cell metabolism. We identified polymorphisms in genes related to drug resistance that could explain the drug-resistant phenotypes found in the six isolates from Colombia. We hypothesize that changes due to these genetic variations contribute to the success of these strains. Finally, we analyzed the IS6110 insertion sequences finding very low variance between them, suggesting that SNPs is the major cause of variability found in Beijing-like strains circulating in Colombia. Copyright © 2017 Elsevier B.V. All rights reserved.
A total of 31 sea otters Enhydra lutris nereis found dead or moribund (and then euthanized) were necropsied in California, USA. Stomach biopsies were collected and transected with equal portions frozen or placed in formalin and analyzed histologically and screened for Helicobacter spp. in gastric tissue. Helicobacter spp. were isolated from 9 sea otters (29%); 58% (18 of 31) animals were positive for helicobacter by PCR. The Helicobacter sp. was catalase- and oxidase-positive and urease-negative. By electron microscopy, the Helicobacter sp. had lateral and polar sheathed flagella and had a slightly curved rod morphology. 16S and 23S rRNA sequence analyses of all ‘H. enhydrae’ isolates had similar sequences, which clustered as a novel Helicobacter sp. closely related to H. mustelae (96-97%). The genome sequence of isolate MIT 01-6242 was assembled into a single ~1.6 Mb long contig with a 40.8% G+C content. The annotated genome contained 1699 protein-coding sequences and 43 RNAs, including 65 genes homologous to known Helicobacter spp. and Campylobacter spp. virulence factors. Histological changes in the gastric tissues extended from mild cystic degeneration of gastric glands to severe mucosal erosions and ulcers. Silver stains of infected tissues demonstrated slightly curved bacterial rods at the periphery of the gastric ulcers and on the epithelial surface of glands. The underlying mucosa and submucosa were infiltrated by low numbers of neutrophils, macrophages, and lymphocytes, with occasional lymphoid aggregates and well-defined lymphoid follicles. This is the second novel Helicobacter sp., which we have named ‘H. enhydrae’, isolated from inflamed stomachs of mustelids, the first being H. mustelae from a ferret.
Bacillus thuringiensis is a rod-shaped facultative anaerobic spore forming bacterium of the genus Bacillus . The defining feature of the species is the ability to produce parasporal crystal inclusion bodies, consisting of d-endotoxins, encoded by cry-genes. Here we present the complete annotated genome sequence of the nematicidal B. thuringiensis strain MYBT18246. The genome comprises one 5,867,749 bp chromosome and 11 plasmids which vary in size from 6330 bp to 150,790 bp. The chromosome contains 6092 protein-coding and 150 RNA genes, including 36 rRNA genes. The plasmids encode 997 proteins and 4 t-RNA’s. Analysis of the genome revealed a large number of mobile elements involved in genome plasticity including 11 plasmids and 16 chromosomal prophages. Three different nematicidal toxin genes were identified and classified according to the Cry toxin naming committee as cry13Aa2, cry13Ba1, and cry13Ab1. Strikingly, these genes are located on the chromosome in close proximity to three separate prophages. Moreover, four putative toxin genes of different toxin classes were identified on the plasmids p120510 (Vip-like toxin), p120416 (Cry-like toxin) and p109822 (two Bin-like toxins). A comparative genome analysis of B. thuringiensis MYBT18246 with three closely related B. thuringiensis strains enabled determination of the pan-genome of B. thuringiensis MYBT18246, revealing a large number of singletons, mostly represented by phage genes, morons and cryptic genes.
Prevotella intermedia, a major periodontal pathogen, is increasingly implicated in human respiratory tract and cystic fibrosis lung infections. Nevertheless, the specific mechanisms employed by this pathogen remain only partially characterized and poorly understood, largely due to its total lack of genetic accessibility. Here, using Single Molecule, Real-Time (SMRT) genome and methylome sequencing, bisulfite sequencing, in addition to cloning and restriction analysis, we define the specific genetic barriers to exogenous DNA present in two of the most widespread laboratory strains, P. intermedia ATCC 25611 and P. intermedia Strain 17. We identified and characterized multiple restriction-modification (R-M) systems, some of which are considerably divergent between the two strains. We propose that these R-M systems are the root cause of the P. intermedia transformation barrier. Additionally, we note the presence of conserved Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) systems in both strains, which could provide a further barrier to exogenous DNA uptake and incorporation. This work will provide a valuable resource during the development of a genetic system for P. intermedia, which will be required for fundamental investigation of this organism’s physiology, metabolism, and pathogenesis in human disease.
Stenotrophomonas sp. strain WZN-1, isolated from an e-waste recycling area in Tianjin, China, is capable of degrading polybrominated diphenyl ethers (PBDEs). The complete genome of strain WZN-1 consists of 4,512,703 bp. This genome information will provide important information about the biodegradation pathways and mechanisms of PBDEs. Copyright © 2017 Wu et al.
Streptomyces autolyticus CGMCC 0516 produces the anti-tumor benzoquinone ansamycins geldanamycin, autolytimycin, and reblastatin and the 16-membered macrodiolide elaiophylin. Here, we report the complete genome sequence of S. autolyticus CGMCC 0516, which consists of a 10,029,028bp linear chromosome and seven circular plasmids. Fifty-seven putative biosynthetic gene clusters for secondary metabolites were found. The geldanamycin, autolytimycin, and reblastatin biosynthetic gene clusters were located on the left arm (2.06-2.15Mb) of the chromosome, and the elaiophylin gene cluster was located on the right arm (9.45-9.53Mb). Twenty-one putative gene clusters with high or moderate similarity to important antibiotic biosynthetic gene clusters were found, including the antitumor agents echoside, bafilomycin, hygrocin, and toxoflavin; the antibacterial/antifungal agents nigericin, skyllamycin, kanamycin, naphthomycin, eco-02301, and bottromycin A2; the immunosuppressants meridamycin and brasilicardin A; the anti-inflammatory agent cyclooctatin; and the acute iron poisoning medication desferrioxamine B. The genome sequence reported here will enable us to study the biosynthetic mechanism of these important antibiotics and will facilitate the discovery of novel secondary metabolites with potential applications to human health. Copyright © 2017 Elsevier B.V. All rights reserved.
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