Salmonella enterica serovar Montevideo has been linked to recent foodborne illness outbreaks resulting from contamination of products such as fruits, vegetables, seeds and spices. Studies have shown that Montevideo also is frequently associated with healthy cattle and can be isolated from ground beef, yet human salmonellosis outbreaks of Montevideo associated with ground beef contamination are rare. This disparity fuelled our interest in characterizing the genomic differences between Montevideo strains isolated from healthy cattle and beef products, and those isolated from human patients and outbreak sources. To that end, we sequenced 13 Montevideo strains to completion, producing high-quality genome assemblies of…
Methylation has a profound role in the regulation of numerous biological processes in bacteria including virulence. The study of methylation in bacteria has greatly advanced thanks to next-generation sequencing technologies. These technologies have expedited the process of uncovering unique features of many bacterial methylomes such as characterizing previously uncharacterized methyltransferases, cataloging genome-wide DNA methylations in bacteria, identifying the frequency of methylation at particular genomic loci, and revealing regulatory roles of methylation in the biology of various bacterial species. For instance, methylation has been cited as a potential source for the pathogenicity differences observed in C. jejuni strains with syntenic genomes…
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…
Staphylococcusepidermidisis the leading cause of infections on indwelling medical devices worldwide. Intrinsic antibiotic resistance and vigorous biofilm production have rendered these infections difficult to treat and, in some cases, require the removal of the offending medical prostheses. With the exception of two widely-passaged isolates RP62A and 1457, the pathogenesis of infections caused by clinicalS. epidermidisstrains is poorly understood due to the strong genetic barrier that precludes efficient transformation of foreign DNA into clinical isolates. The difficulty in transforming clinicalS. epidermidisisolates is primarily due to the type I and IV restriction modification systems which act as genetic barriers. Here, we showed…
Escherichia coli is the most well-studied bacterium and a common colonizer of the lower mammalian gastrointestinal tract. We report here the complete genome sequence of the original Escherichia coli isolate, strain NCTC86, which was described by Theodor Escherich, for whom the genus is named. Copyright © 2017 Khetrapal et al.
Thermosipho species inhabit various extreme environments such as marine hydrothermal vents, petroleum reservoirs and terrestrial hot springs. A 16S rRNA phylogeny of available Thermosipho spp. sequences suggested habitat specialists adapted to living in hydrothermal vents only, and habitat generalists inhabiting oil reservoirs, hydrothermal vents and hotsprings. Comparative genomics and recombination analysis of the genomes of 15 Thermosipho isolates separated them into three species with different habitat distributions, the widely distributed T. africanus and the more specialized, T. melanesiensis and T. affectus. The three Thermosipho species can also be differentiated on the basis of genome content. For instance the T. africanus…
Streptococcus thermophilus ACA-DC 2 is a newly sequenced strain isolated from traditional Greek yogurt. Among the 14 fully sequenced strains of S. thermophilus currently deposited in the NCBI database, the ACA-DC 2 strain has the smallest chromosome, containing 1,731,838 bp. The annotation of its genome revealed the presence of 1,850 genes, including 1,556 protein-coding genes, 70 RNA genes and 224 potential pseudogenes. A large number of pseudogenes were identified. This was also accompanied by the absence of pathogenic features suggesting evolution of strain ACA-DC 2 through genome decay processes, most probably due to adaptation to the milk ecosystem. Analysis revealed the…
We identify a new subgroup of Type I Restriction-Modification enzymes that modify cytosine in one DNA strand and adenine in the opposite strand for host protection. Recognition specificity has been determined for ten systems using SMRT sequencing and each recognizes a novel DNA sequence motif. Previously characterized Type I systems use two identical copies of a single methyltransferase (MTase) subunit, with one bound at each half site of the specificity (S) subunit to form the MTase. The new m4C-producing Type I systems we describe have two separate yet highly similar MTase subunits that form a heterodimeric M1M2S MTase. The MTase…
Clostridium species are both heroes and villains. Some cause serious human and animal diseases, those present in the gut microbiota generally contribute to health and wellbeing, while others represent useful industrial chassis for the production of chemicals and fuels. To understand, counter or exploit, there is a fundamental requirement for effective systems that may be used for directed or random genome modifications. We have formulated a simple roadmap whereby the necessary gene systems maybe developed and deployed. At its heart is the use of 'pseudo-suicide' vectors and the creation of a pyrE mutant (a uracil auxotroph), initially aided by ClosTron…
A rapidly growing bacterial host would be desirable for a range of routine applications in molecular biology and biotechnology. The bacterium Vibrio natriegens has the fastest growth rate of any known organism, with a reported doubling time of
DNA methylation, defined by the addition of a methyl group to adenine or cytosine bases in DNA catalyzed by DNA methyltransferases (MTases), is one of the most studied post-replicative DNA modification mechanism in bacteria (Roberts et al., 2003b). The three forms of nucleotide methylation identified to date are: N6-methyladenine(m6A), N4-methylcytosine (m4C), and 5-methylcytosine (m5C) (Gromova and Khoroshaev, 2003).
Engineering restriction enzymes with new sequence specificity has been an unaccomplished challenge, presumably because of the complexity of target recognition. Here we report detailed analyses of target recognition by Type ISP restriction-modification enzymes. We determined the structure of the Type ISP enzyme LlaGI bound to its target and compared it with the previously reported structure of a close homologue that binds to a distinct target, LlaBIII. The comparison revealed that, although the two enzymes use almost a similar set of structural elements for target recognition, the residues that read the bases vary. Change in specificity resulted not only from appropriate…
Single Molecule, Real-Time (SMRT) Sequencing directly detects DNA modifications by measuring variation in the polymerase kinetics of DNA base incorporation during sequencing. With high throughput, long reads, and the sensitivity to detect epigenetic modification without amplification or chemical conversions, the PacBio Systems offer scalable solutions for assessing DNA modifications in bacterial and eukaryotic genomes.
Restriction-modification (R-M) systems are often regarded as bacteria's innate immune systems, protecting cells from infection by mobile genetic elements (MGEs). Their diversification has been recently associated with the emergence of particularly virulent lineages. However, we have previously found more R-M systems in genomes carrying more MGEs. Furthermore, it has been suggested that R-M systems might favor genetic transfer by producing recombinogenic double-stranded DNA ends. To test whether R-M systems favor or disfavor genetic exchanges, we analyzed their frequency with respect to the inferred events of homologous recombination and horizontal gene transfer within 79 bacterial species. Genetic exchanges were more frequent…
Yoshihiko Suzuki, Graduate Student from University of Tokyo presents his poster (in Japanese) on characterizing a methylome of the human gut microbiome using SMRT Sequencing and metagenomic assembly