Prevalence of phase variable epigenetic invertons among host-associated bacteria.

Type I restriction-modification (R-M) systems consist of a DNA endonuclease (HsdR, HsdM and HsdS subunits) and methyltransferase (HsdM and HsdS subunits). The hsdS sequences flanked by inverted repeats (referred to as epigenetic invertons) in certain Type I R-M systems undergo invertase-catalyzed inversions. Previous studies in Streptococcus pneumoniae have shown that hsdS inversions within clonal populations produce subpopulations with profound differences in the methylome, cellular physiology and virulence.

Lineage-specific evolution and gene flow in Listeria monocytogenes are independent of bacteriophages.

Listeria monocytogenes is a foodborne pathogen causing systemic infection with high mortality. To allow efficient tracking of outbreaks a clear definition of the genomic signature of a cluster of related isolates is required, but lineage-specific characteristics call for a more detailed understanding of evolution. In our work, we used core genome MLST (cgMLST) to identify new outbreaks combined to core genome SNP analysis to characterize the population structure and gene flow between lineages.

Genomic Stability of Composite SCC ACME and COMER-Like Genetic Elements in Correlates With Rate of Excision.

The epidemiological success of methicillin-resistant USA300 has been associated with the presence of two mobile elements, the arginine catabolic mobile element (ACME) and the copper and mercury resistance (COMER) element. These two mobile elements are associated with resistance to copper, which has been related to host fitness and survival within macrophages. Several studies found that ACME is more prevalent, and exhibits greater diversity, in while COMER has not been identified in or any other staphylococcal species.

Integrase-Controlled Excision of Metal-Resistance Genomic Islands in .

Genomic islands (GIs) are discrete gene clusters encoding for a variety of functions including antibiotic and heavy metal resistance, some of which are tightly associated to lineages of the core genome phylogenetic tree. We have investigated the functions of two distinct integrase genes in the mobilization of two metal resistant GIs, G08 and G62, of . Real-time PCR demonstrated integrase-dependent GI excision, utilizing isopropyl β-d-1-thiogalactopyranoside IPTG-inducible integrase genes in plasmid-based mini-GIs in .

Draft Whole-Genome Sequences of Periodontal Pathobionts , , and Contain Phase-Variable Restriction-Modification Systems.

Periodontal disease comprises mild to severe inflammatory host responses to oral bacteria that can cause destruction of the tooth-supporting tissue. We report genome sequences for 18 clinical isolates of , , and , Gram-negative obligate anaerobes that play a role in the periodontal disease process.

Phase-variable methylation and epigenetic regulation by type I restriction-modification systems.

Epigenetic modifications in bacteria, such as DNA methylation, have been shown to affect gene regulation, thereby generating cells that are isogenic but with distinctly different phenotypes. Restriction-modification (RM) systems contain prototypic methylases that are responsible for much of bacterial DNA methylation. This review focuses on a distinctive group of type I RM loci that , through phase variation, can modify their methylation target specificity and can thereby switch bacteria between alternative patterns of DNA methylation.