July 7, 2019  |  

Complete genome sequence of the heavy metal resistant bacterium Altererythrobacter atlanticus 26DY36(T), isolated from deep-sea sediment of the North Atlantic Mid-ocean ridge.

Altererythrobacter atlanticus 26DY36(T) (CGMCC 1.12411(T)=JCM 18865(T)) was isolated from the North Atlantic Mid-Ocean Ridge. The strain is resistant to heavy metals, such as Mn(2+) (200 mM), Co(2+) (2.0mM), Cu(2+) (1mM), Zn(2+) (1mM), Hg(2+) (0.1mM) and Cd(2+) (0.5mM). Here we describe the genome sequence and annotation, as well as the features of the organism. A. atlanticus 26DY36(T) harbors a chromosome (3,386,291 bp) and a circular plasmid (88,815 bp). The genome contains 3322 protein-coding genes (2483 with predicted functions), 47 tRNA genes and 6 rRNA genes. A. atlanticus 26DY36(T) encodes dozens of genes related to heavy metal resistance and has potential applications in the bioremediation of heavy metal-contaminated environments. Copyright © 2015 Elsevier B.V. All rights reserved.


July 7, 2019  |  

SMRT sequencing of the Campylobacter coli BfR-CA-9557 genome sequence reveals unique methylation motifs.

Campylobacter species are the most prevalent bacterial pathogen causing acute enteritis worldwide. In contrast to Campylobacter jejuni, about 5 % of Campylobacter coli strains exhibit susceptibility to restriction endonuclease digestion by DpnI cutting specifically 5′-G(m)ATC-3′ motifs. This indicates significant differences in DNA methylation between both microbial species. The goal of the study was to analyze the methylome of a C. coli strain susceptible to DpnI digestion, to identify its methylation motifs and restriction modification systems (RM-systems), and compare them to related organisms like C. jejuni and Helicobacter pylori. Using one SMRT cell and the PacBio RS sequencing technology followed by PacBio Modification and Motif Analysis the complete genome of the DpnI susceptible strain C. coli BfR-CA-9557 was sequenced to 500-fold coverage and assembled into a single contig of 1.7 Mbp. The genome contains a CJIE1-like element prophage and is phylogenetically closer to C. coli clade 1 isolates than clade 3. 45,881 6-methylated adenines (ca. 2.7 % of genome positions) that are predominantly arranged in eight different methylation motifs and 1,788 4-methylated cytosines (ca. 0.1 %) have been detected. Only two of these motifs correspond to known restriction modification motifs. Characteristic for this methylome was the very high fraction of methylation of motifs with mostly above 99 %.Only five dominant methylation motifs have been identified in C. jejuni, which have been associated with known RM-systems. C. coli BFR-CA-9557 shares one (RAATTY) of these, but four ORFs could be assigned to putative Type I RM-systems, seven ORFs to Type II RM-systems and three ORFs to Type IV RM-systems. In accordance with DpnI prescreening RM-system IIP, methylation of GATC motifs was detected in C. coli BfR-CA-9557. A homologous IIP RM-system has been described for H. pylori. The remaining methylation motifs are specific for C. coli BfR-CA-9557 and have been neither detected in C. jejuni nor in H. pylori. The results of this study give us new insights into epigenetics of Campylobacteraceae and provide the groundwork to resolve the function of RM-systems in C. coli.


July 7, 2019  |  

Isolation of Jeotgalibacillus malaysiensis sp. nov. from a sandy beach, and emended description of the genus Jeotgalibacillus.

A Gram-stain-positive, endospore-forming, rod-shaped bacterial strain, designated D5(T), was isolated from seawater collected from a sandy beach in a southern state of Malaysia and subjected to a polyphasic taxonomic study. Sequence analysis of the 16S rRNA gene demonstrated that this isolate belongs to the genus Jeotgalibacillus, with 99.87% similarity to Jeotgalibacillus alimentarius JCM 10872(T). DNA-DNA hybridization of strain D5(T) with J. alimentarius JCM 10872(T) demonstrated 26.3% relatedness. The peptidoglycan type was A1a linked directly to L-lysine as the diamino acid. The predominant quinones identified in strain D5(T) were menaquinones MK-7 and MK-8.The major fatty acids were iso-C15:0 and anteiso-C15:0. The G+C content of its DNA was 43.0 mol%. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and sulfoquinovosyl diacylglycerol, as well as two unknown phospholipids and three unknown lipids. The phenotypic, chemotaxonomic and genotypic data indicated that strain D5(T) represents a novel species of the genus Jeotgalibacillus, for which the name Jeotgalibacillus malaysiensis sp. nov. is proposed (type strain D5(T)?= DSM 28777(T) = KCTC33550(T)). An emended description of the genus Jeotgalibacillus is also provided.


July 7, 2019  |  

The functions of DNA methylation by CcrM in Caulobacter crescentus: a global approach.

DNA methylation is involved in a diversity of processes in bacteria, including maintenance of genome integrity and regulation of gene expression. Here, using Caulobacter crescentus as a model, we exploit genome-wide experimental methods to uncover the functions of CcrM, a DNA methyltransferase conserved in most Alphaproteobacteria. Using single molecule sequencing, we provide evidence that most CcrM target motifs (GANTC) switch from a fully methylated to a hemi-methylated state when they are replicated, and back to a fully methylated state at the onset of cell division. We show that DNA methylation by CcrM is not required for the control of the initiation of chromosome replication or for DNA mismatch repair. By contrast, our transcriptome analysis shows that >10% of the genes are misexpressed in cells lacking or constitutively over-expressing CcrM. Strikingly, GANTC methylation is needed for the efficient transcription of dozens of genes that are essential for cell cycle progression, in particular for DNA metabolism and cell division. Many of them are controlled by promoters methylated by CcrM and co-regulated by other global cell cycle regulators, demonstrating an extensive cross talk between DNA methylation and the complex regulatory network that controls the cell cycle of C. crescentus and, presumably, of many other Alphaproteobacteria.


July 7, 2019  |  

Expansion of the genetic toolkit for metabolic engineering of Clostridium pasteurianum: chromosomal gene disruption of the endogenous CpaAI restriction enzyme.

Clostridium pasteurianum is one of the most promising biofuel producers within the genus Clostridium owing to its unique metabolic ability to ferment glycerol into butanol. Although an efficient means is available for introducing foreign DNA to C. pasteurianum, major genetic tools, such as gene knockout, knockdown, or genome editing, are lacking, preventing metabolic engineering of C. pasteurianum.Here we present a methodology for performing chromosomal gene disruption in C. pasteurianum using the programmable lactococcus Ll.ltrB group II intron. Gene disruption was initially found to be impeded by inefficient electrotransformation of Escherichia coli-C. pasteurianum shuttle vectors, presumably due to host restriction. By assessing the ability of various vector deletion derivatives to electrotransform C. pasteurianum and probing the microorganism’s methylome using next-generation sequence data, we identified a new C. pasteurianum Type I restriction-methylation system, CpaAII, with a predicted recognition sequence of 5′-AAGNNNNNCTCC-3′ (N?=?A, C, G, or T). Following rescue of high-level electrotransformation via mutation of the sole CpaAII site within the shuttle vectors, we retargeted the intron to the cpaAIR gene encoding the CpaAI Type II restriction endonuclease (recognition site of 5′-CGCG-3′). Intron insertion was potentially hindered by low retrohoming efficiency, yet this limitation could be overcome by a procedure for enrichment of the intron insertion. The resulting ?cpaAIR mutant strain was efficiently electrotransformed with M.FnuDII-unmethylated plasmid DNA.The markerless and plasmidless ?cpaAIR mutant strain of C. pasteurianum developed in this study can serve as a general host strain for future genetic and metabolic manipulation. Further, the associated gene disruption protocol should not only serve as a guide for chromosomal gene inactivation studies involving mobile group II introns, but also prove invaluable for applying metabolic engineering strategies to C. pasteurianum.


July 7, 2019  |  

Genomes of diverse isolates of the marine cyanobacterium Prochlorococcus.

The marine cyanobacterium Prochlorococcus is the numerically dominant photosynthetic organism in the oligotrophic oceans, and a model system in marine microbial ecology. Here we report 27 new whole genome sequences (2 complete and closed; 25 of draft quality) of cultured isolates, representing five major phylogenetic clades of Prochlorococcus. The sequenced strains were isolated from diverse regions of the oceans, facilitating studies of the drivers of microbial diversity-both in the lab and in the field. To improve the utility of these genomes for comparative genomics, we also define pre-computed clusters of orthologous groups of proteins (COGs), indicating how genes are distributed among these and other publicly available Prochlorococcus genomes. These data represent a significant expansion of Prochlorococcus reference genomes that are useful for numerous applications in microbial ecology, evolution and oceanography.


July 7, 2019  |  

Genome sequence of the Leisingera aquimarina type strain (DSM 24565(T)), a member of the marine Roseobacter clade rich in extrachromosomal elements.

Leisingera aquimarina Vandecandelaere et al. 2008 is a member of the genomically well characterized Roseobacter clade within the family Rhodobacteraceae. Representatives of the marine Roseobacter clade are metabolically versatile and involved in carbon fixation and biogeochemical processes. They form a physiologically heterogeneous group, found predominantly in coastal or polar waters, especially in symbiosis with algae, in microbial mats, in sediments or associated with invertebrates. Here we describe the features of L. aquimarina DSM 24565(T) together with the permanent-draft genome sequence and annotation. The 5,344,253 bp long genome consists of one chromosome and an unusually high number of seven extrachromosomal elements and contains 5,129 protein-coding and 89 RNA genes. It was sequenced as part of the DOE Joint Genome Institute Community Sequencing Program 2010 and of the activities of the Transregional Collaborative Research Centre 51 funded by the German Research Foundation (DFG).


July 7, 2019  |  

Enhanced 5-methylcytosine detection in single-molecule, real-time sequencing via Tet1 oxidation.

DNA methylation serves as an important epigenetic mark in both eukaryotic and prokaryotic organisms. In eukaryotes, the most common epigenetic mark is 5-methylcytosine, whereas prokaryotes can have 6-methyladenine, 4-methylcytosine, or 5-methylcytosine. Single-molecule, real-time sequencing is capable of directly detecting all three types of modified bases. However, the kinetic signature of 5-methylcytosine is subtle, which presents a challenge for detection. We investigated whether conversion of 5-methylcytosine to 5-carboxylcytosine using the enzyme Tet1 would enhance the kinetic signature, thereby improving detection.We characterized the kinetic signatures of various cytosine modifications, demonstrating that 5-carboxylcytosine has a larger impact on the local polymerase rate than 5-methylcytosine. Using Tet1-mediated conversion, we show improved detection of 5-methylcytosine using in vitro methylated templates and apply the method to the characterization of 5-methylcytosine sites in the genomes of Escherichia coli MG1655 and Bacillus halodurans C-125.We have developed a method for the enhancement of directly detecting 5-methylcytosine during single-molecule, real-time sequencing. Using Tet1 to convert 5-methylcytosine to 5-carboxylcytosine improves the detection rate of this important epigenetic marker, thereby complementing the set of readily detectable microbial base modifications, and enhancing the ability to interrogate eukaryotic epigenetic markers.


July 7, 2019  |  

Genome sequence of Phaeobacter daeponensis type strain (DSM 23529(T)), a facultatively anaerobic bacterium isolated from marine sediment, and emendation of Phaeobacter daeponensis.

TF-218(T) is the type strain of the species Phaeobacter daeponensis Yoon et al. 2007, a facultatively anaerobic Phaeobacter species isolated from tidal flats. Here we describe the draft genome sequence and annotation of this bacterium together with previously unreported aspects of its phenotype. We analyzed the genome for genes involved in secondary metabolite production and its anaerobic lifestyle, which have also been described for its closest relative Phaeobacter caeruleus. The 4,642,596 bp long genome of strain TF-218(T) contains 4,310 protein-coding genes and 78 RNA genes including four rRNA operons and consists of five replicons: one chromosome and four extrachromosomal elements with sizes of 276 kb, 174 kb, 117 kb and 90 kb. Genome analysis showed that TF-218(T) possesses all of the genes for indigoidine biosynthesis, and on specific media the strain showed a blue pigmentation. We also found genes for dissimilatory nitrate reduction, gene-transfer agents, NRPS/ PKS genes and signaling systems homologous to the LuxR/I system.


July 7, 2019  |  

Genome sequence of Phaeobacter caeruleus type strain (DSM 24564(T)), a surface-associated member of the marine Roseobacter clade.

In 2009 Phaeobacter caeruleus was described as a novel species affiliated with the marine Roseobacter clade, which, in turn, belongs to the class Alphaproteobacteria. The genus Phaeobacter is well known for members that produce various secondary metabolites. Here we report of putative quorum sensing systems, based on the finding of six N-acyl-homoserine lactone synthetases, and show that the blue color of P. caeruleus is probably due to the production of the secondary metabolite indigoidine. Therefore, P. caeruleus might have inhibitory effects on other bacteria. In this study the genome of the type strain DSM 24564(T) was sequenced, annotated and characterized. The 5,344,419 bp long genome with its seven plasmids contains 5,227 protein-coding genes (3,904 with a predicted function) and 108 RNA genes.


July 7, 2019  |  

Implementation and data analysis of Tn-seq, whole genome resequencing, and single-molecule real time sequencing for bacterial genetics.

Few discoveries have been more transformative to the biological sciences than the development of DNA sequencing technologies. The rapid advancement of sequencing and bioinformatics tools has revolutionized bacterial genetics, deepening our understanding of model and clinically relevant organisms. Although application of newer sequencing technologies to studies in bacterial genetics is increasing, the implementation of DNA sequencing technologies and development of the bioinformatics tools required for analyzing the large data sets generated remains a challenge for many. In this minireview, we have chosen to summarize three sequencing approaches that are particularly useful for bacterial genetics. We provide resources for scientists new to and interested in their application. Herein, we discuss the analysis of Tn-seq data to determine gene disruptions differentially represented in a mutant population, Illumina sequencing for identification of suppressor or other mutations, and we summarize single-molecule real time (SMRT) sequencing for de novo genome assembly and the use of the output data for detection of DNA base modifications. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


July 7, 2019  |  

Complete genome sequence of Lutibacter profundi LP1T isolated from an Arctic deep-sea hydrothermal vent system

Lutibacter profundi LP1T within the family Flavobacteriaceae was isolated from a biofilm growing on the surface of a black smoker chimney at the Loki’s Castle vent field, located on the Arctic Mid-Ocean Ridge. The complete genome of L. profundi LP1T is the first genome to be published within the genus Lutibacter. L. profundi LP1T consists of a single 2,966,978 bp circular chromosome with a GC content of 29.8%. The genome comprises 2,537 protein-coding genes, 40 tRNA species and 2 rRNA operons. The microaerophilic, organotrophic isolate contains genes for all central carbohydrate metabolic pathways. However, genes for the oxidative branch of the pentose-phosphate-pathway, the glyoxylate shunt of the tricarboxylic acid cycle and the ATP citrate lyase for reverse TCA are not present. L. profundi LP1T utilizes starch, sucrose and diverse proteinous carbon sources. In accordance, the genome harbours 130 proteases and 104 carbohydrate-active enzymes, indicating a specialization in degrading organic matter. Among a small arsenal of 24 glycosyl hydrolases, which offer the possibility to hydrolyse diverse poly- and oligosaccharides, a starch utilization cluster was identified. Furthermore, a variety of enzymes may be secreted via T9SS and contribute to the hydrolytic variety of the microorganism. Genes for gliding motility are present, which may enable the bacteria to move within the biofilm. A substantial number of genes encoding for extracellular polysaccharide synthesis pathways, curli fibres and attachment to surfaces could mediate adhesion in the biofilm and may contribute to the biofilm formation. In addition to aerobic respiration, the complete denitrification pathway and genes for sulphide oxidation e.g. sulphide:quinone reductase are present in the genome. sulphide:quinone reductase and denitrification may serve as detoxification systems allowing L. profundi LP1T to thrive in a sulphide and nitrate enriched environment. The information gained from the genome gives a greater insight in the functional role of L. profundi LP1T in the biofilm and its adaption strategy in an extreme environment.


July 7, 2019  |  

Identification of a Pseudomonas aeruginosa PAO1 DNA methyltransferase, its targets, and physiological roles.

DNA methylation is widespread among prokaryotes, and most DNA methylation reactions are catalyzed by adenine DNA methyltransferases, which are part of restriction-modification (R-M) systems. R-M systems are known for their role in the defense against foreign DNA; however, DNA methyltransferases also play functional roles in gene regulation. In this study, we used single-molecule real-time (SMRT) sequencing to uncover the genome-wide DNA methylation pattern in the opportunistic pathogen Pseudomonas aeruginosa PAO1. We identified a conserved sequence motif targeted by an adenine methyltransferase of a type I R-M system and quantified the presence of N(6)-methyladenine using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Changes in the PAO1 methylation status were dependent on growth conditions and affected P. aeruginosa pathogenicity in a Galleria mellonella infection model. Furthermore, we found that methylated motifs in promoter regions led to shifts in sense and antisense gene expression, emphasizing the role of enzymatic DNA methylation as an epigenetic control of phenotypic traits in P. aeruginosa Since the DNA methylation enzymes are not encoded in the core genome, our findings illustrate how the acquisition of accessory genes can shape the global P. aeruginosa transcriptome and thus may facilitate adaptation to new and challenging habitats.IMPORTANCE With the introduction of advanced technologies, epigenetic regulation by DNA methyltransferases in bacteria has become a subject of intense studies. Here we identified an adenosine DNA methyltransferase in the opportunistic pathogen Pseudomonas aeruginosa PAO1, which is responsible for DNA methylation of a conserved sequence motif. The methylation level of all target sequences throughout the PAO1 genome was approximated to be in the range of 65 to 85% and was dependent on growth conditions. Inactivation of the methyltransferase revealed an attenuated-virulence phenotype in the Galleria mellonella infection model. Furthermore, differential expression of more than 90 genes was detected, including the small regulatory RNA prrF1, which contributes to a global iron-sparing response via the repression of a set of gene targets. Our finding of a methylation-dependent repression of the antisense transcript of the prrF1 small regulatory RNA significantly expands our understanding of the regulatory mechanisms underlying active DNA methylation in bacteria. Copyright © 2017 Doberenz et al.


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