With HiFi Sequencing from PacBio you get the benefits for short reads and traditional long reads in one easy-to-use technology. Watch this video to learn how HiFi sequencing is empowering…
In this SMRT Leiden 2020 Online Virtual Event presentation Pedro Oliveira of Mount Sinai shares his research on Clostridioides – a leading cause of nosocomial-acquired diarrhea and colitis across the…
Watch this short video to learn about highly accurate long-read sequencing and how HiFi reads can advance scientific discovery.
N6-methyladenosine (m6A) is a widespread RNA modification that influences nearly every aspect of the messenger RNA lifecycle. Our understanding of m6A has been facilitated by the development of global m6A mapping methods, which use antibodies to immunoprecipitate methylated RNA. However, these methods have several limitations, including high input RNA requirements and cross-reactivity to other RNA modifications. Here, we present DART-seq (deamination adjacent to RNA modification targets), an antibody-free method for detecting m6A sites. In DART-seq, the cytidine deaminase APOBEC1 is fused to the m6A-binding YTH domain. APOBEC1-YTH expression in cells induces C-to-U deamination at sites adjacent to m6A residues, which are detected using standard RNA-seq. DART-seq identifies thousands of m6A sites in cells from as little as 10?ng of total RNA and can detect m6A accumulation in cells over time. Additionally, we use long-read DART-seq to gain insights into m6A distribution along the length of individual transcripts.
A major barrier to both metabolic engineering and fundamental biological studies is the lack of genetic tools in most microorganisms. One example is Clostridium thermocellum ATCC 27405T, where genetic tools are not available to help validate decades of hypotheses. A significant barrier to DNA transformation is restriction-modification systems, which defend against foreign DNA methylated differently than the host. To determine the active restriction-modification systems in this strain, we performed complete methylome analysis via single-molecule, real-time sequencing to detect 6-methyladenine and 4-methylcytosine and the rarely used whole-genome bisulfite sequencing to detect 5-methylcytosine. Multiple active systems were identified, and corresponding DNA methyltransferases were expressed from the Escherichia coli chromosome to mimic the C. thermocellum methylome. Plasmid methylation was experimentally validated and successfully electroporated into C. thermocellum ATCC 27405. This combined approach enabled genetic modification of the C. thermocellum-type strain and acts as a blueprint for transformation of other non-model microorganisms.
Staphylococcus epidermidis is a significant opportunistic pathogen of humans. Molecular studies in this species have been hampered by the presence of restriction-modification (RM) systems that limit introduction of foreign DNA. Here we establish the complete genomes and methylomes for seven clinically significant, genetically diverse S. epidermidis isolates and perform the first systematic genomic analyses of the type I RM systems within both S. epidermidis and Staphylococcus aureus. Our analyses revealed marked differences in the gene arrangement, chromosomal location and movement of type I RM systems between the two species. Unlike S. aureus, S. epidermidis type I RM systems demonstrate extensive diversity even within a single genetic lineage. This is contrary to current assumptions and has important implications for approaching the genetic manipulation of S. epidermidis. Using Escherichia coli plasmid artificial modification (PAM) to express S. epidermidis hsdMS, we readily overcame restriction barriers in S. epidermidis, and achieved transformation efficiencies equivalent to those of modification deficient mutants. With these functional experiments we demonstrate how genomic data can be used to predict both the functionality of type I RM systems and the potential for a strain to be transformation proficient. We outline an efficient approach for the genetic manipulation of S. epidermidis from diverse genetic backgrounds, including those that have hitherto been intractable. Additionally, we identified S. epidermidis BPH0736, a naturally restriction defective, clinically significant, multidrug-resistant ST2 isolate as an ideal candidate for molecular studies.
Whole-genome sequencing (WGS) of Staphylococcus aureus is increasingly used as part of infection prevention practices, but most applications are focused on conserved core genomic regions due to limitations of short-read technologies. In this study we established a long-read technology-based WGS screening program of all first-episode MRSA blood infections at a major urban hospital. A survey of 132 MRSA genomes assembled from long reads revealed widespread gain/loss of accessory mobile genetic elements among established hospital- and community-associated lineages impacting >10% of each genome, and frequent megabase-scale inversions between endogenous prophages. We also characterized an outbreak of a CC5/ST105/USA100 clone among 3 adults and 18 infants in a neonatal intensive care unit (NICU) lasting 7 months. The pattern of changes among complete outbreak genomes provided full spatiotemporal resolution of its origins and progression, which was characterized by multiple sub-transmissions and likely precipitated by equipment sharing. Compared to other hospital strains, the outbreak strain carried distinct mutations and accessory genetic elements that impacted genes with roles in metabolism, resistance and persistence. This included a DNA-recognition domain recombination in the hsdS gene of a Type-I restriction-modification system that altered DNA methylation. RNA-Seq profiling showed that the (epi)genetic changes in the outbreak clone attenuated agr gene expression and upregulated genes involved in stress response and biofilm formation. Overall our findings demonstrate that long-read sequencing substantially improves our ability to characterize accessory genomic elements that impact MRSA virulence and persistence, and provides valuable information for infection control efforts.
Two extremely halophilic archaea, namely, Natrinema versiforme BOL5-4 and Natrinema pallidum BOL6-1, were isolated from a Bolivian salt mine and their genomes sequenced using single-molecule real-time sequencing. The GC-rich genomes of BOL5-4 and BOL6-1 were 4.6 and 3.8 Mbp, respectively, with large chromosomes and multiple megaplasmids. Genome annotation was incorporated into HaloWeb and methylation patterns incorporated into REBASE.Copyright © 2019 DasSarma et al.
Here, we report the complete genome sequence and full methylome analysis of a newly isolated, aerobic, thermophilic, Gram-positive actinomycete, a strain of Thermoactinomyces vulgaris designated strain 2H.Copyright © 2019 Mankai et al.
The chromosomal methylation statuses of the highly virulent Vibrio vulnificus strain CMCP6 grown in human serum and in seawater are compared here. Growth in seawater resulted in ~4 times as much methylation as that in human serum, primarily N4-methylcytosines.Copyright © 2019 Conrad and Harwood.
The genomes of two extremely halophilic Archaea species, Haloarcula marismortui and Haloferax mediterranei, were sequenced using single-molecule real-time sequencing. The ~4-Mbp genomes are GC rich with multiple large plasmids and two 4-methyl-cytosine patterns. Methyl transferases were incorporated into the Restriction Enzymes Database (REBASE), and gene annotation was incorporated into the Haloarchaeal Genomes Database (HaloWeb).Copyright © 2019 DasSarma et al.
The bacteriophage exclusion (BREX) system is a novel prokaryotic defense system against bacteriophages. To our knowledge, no study has systematically characterized the function of the BREX system in lactic acid bacteria. Lactobacillus casei Zhang is a probiotic bacterium originating from koumiss. By using single-molecule real-time sequencing, we previously identified N6-methyladenine (m6A) signatures in the genome of L. casei Zhang and a putative methyltransferase (MTase), namely, pglX This work further analyzed the genomic locus near the pglX gene and identified it as a component of the BREX system. To decipher the biological role of pglX, an L. casei Zhang pglX mutant (?pglX) was constructed. Interestingly, m6A methylation of the 5′-ACRCAG-3′ motif was eliminated in the ?pglX mutant. The wild-type and mutant strains exhibited no significant difference in morphology or growth performance in de Man-Rogosa-Sharpe (MRS) medium. A significantly higher plasmid acquisition capacity was observed for the ?pglX mutant than for the wild type if the transformed plasmids contained pglX recognition sites (i.e., 5′-ACRCAG-3′). In contrast, no significant difference was observed in plasmid transformation efficiency between the two strains when plasmids lacking pglX recognition sites were tested. Moreover, the ?pglX mutant had a lower capacity to retain the plasmids than the wild type, suggesting a decrease in genetic stability. Since the Rebase database predicted that the L. casei PglX protein was bifunctional, as both an MTase and a restriction endonuclease, the PglX protein was heterologously expressed and purified but failed to show restriction endonuclease activity. Taken together, the results show that the L. casei Zhang pglX gene is a functional adenine MTase that belongs to the BREX system.IMPORTANCELactobacillus casei Zhang is a probiotic that confers beneficial effects on the host, and it is thus increasingly used in the dairy industry. The possession of an effective bacterial immune system that can defend against invasion of phages and exogenous DNA is a desirable feature for industrial bacterial strains. The bacteriophage exclusion (BREX) system is a recently described phage resistance system in prokaryotes. This work confirmed the function of the BREX system in L. casei and that the methyltransferase (pglX) is an indispensable part of the system. Overall, our study characterizes a BREX system component gene in lactic acid bacteria. Copyright © 2019 American Society for Microbiology.
Halorubrum sp. strain BOL3-1 was isolated from Salar de Uyuni, Bolivia, and sequenced using single-molecule real-time sequencing. Its 3.7-Mbp genome was analyzed for gene content and methylation patterns and incorporated into the Haloarchaeal Genomes Database (http://halo.umbc.edu). The polyextremophilic character and high-elevation environment make the microbe of interest for astrobiology. Copyright © 2019 DasSarma et al.
Deinococcus wulumuqiensis 479 (formerly known as Deinococcus radiodurans 479) is the original source strain for the restriction enzyme DrdI. Its complete sequence and full methylome were determined using Pacific Biosciences single-molecule real-time (SMRT) sequencing. Copyright © 2019 Fomenkov et al.
A physical genome map of Pseudomonas aeruginosa PAO1 had been constructed in the late 1980s by combinatorial SpeI/DpnI long-range restriction mapping. Whereas SpeI was known to cleave within the infrequent 5′-ACTAGT hexanucleotide, the rare recognition site 5′-Gm6ATC for the methylation-sensitive 4-cutter DpnI in the PAO1 genome remained elusive. Resequencing the PAO1 genome with the methylation-sensitive Single Molecule Real-Time (SMRT) sequencing technology identified DpnI to cleave the PAO1 genome at 15 palindromic GAC(N)6Gm6ATC(N)6GTC recognition sites with the central Gm6ATC palindrome to be methylated on both strands by the clone PAO1-specific type I HsdM superfamily methyltransferase M.PaePAOI (PA2735). © FEMS 2019.
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