Molecular mechanism of plasmid elimination by the DdmDE defense system.

Seventh-pandemic strains contain two pathogenicity islands that encode the DNA defense modules DdmABC and DdmDE. In this study, we used cryogenic electron microscopy to determine the mechanistic basis for plasmid defense by DdmDE. The helicase-nuclease DdmD adopts an autoinhibited dimeric architecture.

Interactions between pili affect the outcome of bacterial competition driven by the type VI secretion system.

The bacterial type VI secretion system (T6SS) is a widespread, kin-discriminatory weapon capable of shaping microbial communities. Due to the system's dependency on contact, cellular interactions can lead to either competition or kin protection. Cell-to-cell contact is often accomplished via surface-exposed type IV pili (T4Ps).

Genome sequences of strains isolated in the DRC between 2009 and 2012.

has caused seven cholera pandemics in the past two centuries. The seventh and ongoing pandemic has been particularly severe on the African continent. Here, we report long read-based genome sequences of six strains isolated in the Democratic Republic of the Congo between 2009 and 2012.

DNA modifications impact natural transformation of Acinetobacter baumannii.

Acinetobacter baumannii is a dangerous nosocomial pathogen, especially due to its ability to rapidly acquire new genetic traits, including antibiotic resistance genes (ARG). In A. baumannii, natural competence for transformation, one of the primary modes of horizontal gene transfer (HGT), is thought to contribute to ARG acquisition and has therefore been intensively studied.

Sporadic type VI secretion in seventh pandemic .

is a pathogen that causes disease in millions of people every year by colonizing the small intestine and then secreting the potent cholera toxin. How the pathogen overcomes the colonization barrier created by the host's natural microbiota is, however, still not well understood. In this context, the type VI secretion system (T6SS) has gained considerable attention given its ability to mediate interbacterial killing.

Single nucleotide polymorphism determines constitutive versus inducible type VI secretion in Vibrio cholerae.

Vibrio cholerae is a well-studied human pathogen that is also a common inhabitant of marine habitats. In both environments, the bacterium is subject to interbacterial competition. A molecular nanomachine that is often involved in such competitive behavior is the type VI secretion system (T6SS).

Two defence systems eliminate plasmids from seventh pandemic Vibrio cholerae.

Horizontal gene transfer can trigger rapid shifts in bacterial evolution. Driven by a variety of mobile genetic elements-in particular bacteriophages and plasmids-the ability to share genes within and across species underpins the exceptional adaptability of bacteria. Nevertheless, invasive mobile genetic elements can also present grave risks to the host; bacteria have therefore evolved a vast array of defences against these elements.

The VarA-CsrA regulatory pathway influences cell shape in Vibrio cholerae.

Despite extensive studies on the curve-shaped bacterium Vibrio cholerae, the causative agent of the diarrheal disease cholera, its virulence-associated regulatory two-component signal transduction system VarS/VarA is not well understood. This pathway, which mainly signals through the downstream protein CsrA, is highly conserved among gamma-proteobacteria, indicating there is likely a broader function of this system beyond virulence regulation. In this study, we investigated the VarA-CsrA signaling pathway and discovered a previously unrecognized link to the shape of the bacterium.

Human commensal gut Proteobacteria withstand type VI secretion attacks through immunity protein-independent mechanisms.

While the major virulence factors for Vibrio cholerae, the cause of the devastating diarrheal disease cholera, have been extensively studied, the initial intestinal colonization of the bacterium is not well understood because non-human adult animals are refractory to its colonization. Recent studies suggest the involvement of an interbacterial killing device known as the type VI secretion system (T6SS). Here, we tested the T6SS-dependent interaction of V.

Pilus Production in Acinetobacter baumannii Is Growth Phase Dependent and Essential for Natural Transformation.

is a severe threat to human health as a frequently multidrug-resistant hospital-acquired pathogen. Part of the danger from this bacterium comes from its genome plasticity and ability to evolve quickly by taking up and recombining external DNA into its own genome in a process called natural competence for transformation. This mode of horizontal gene transfer is one of the major ways that bacteria can acquire new antimicrobial resistances and toxic traits.

Interbacterial competition and anti-predatory behaviour of environmental Vibrio cholerae strains.

Vibrio cholerae isolates responsible for cholera pandemics represent only a small portion of the diverse strains belonging to this species. Indeed, most V. cholerae are encountered in aquatic environments.

Comparison of chitin-induced natural transformation in pandemic Vibrio cholerae O1 El Tor strains.

The human pathogen Vibrio cholerae serves as a model organism for many important processes ranging from pathogenesis to natural transformation, which has been extensively studied in this bacterium. Previous work has deciphered important regulatory circuits involved in natural competence induction as well as mechanistic details related to its DNA acquisition and uptake potential. However, since competence was first reported for V.

A Vibriophage Takes Antirepression to the Next Level.

Since its isolation by Esther Lederberg, phage lambda and its repressor protein CI have contributed substantially to the advancement of molecular biology. In this issue of Cell Host & Microbe, Silpe et al. (2020) characterize the antirepressor Qtip of Vibrio phage VP882, which through CI sequestration triggers a lytic switch.

The type IV pilus protein PilU functions as a PilT-dependent retraction ATPase.

Type IV pili are dynamic cell surface appendages found throughout the bacteria. The ability of these structures to undergo repetitive cycles of extension and retraction underpins their crucial roles in adhesion, motility and natural competence for transformation. In the best-studied systems a dedicated retraction ATPase PilT powers pilus retraction.

Neighbor predation linked to natural competence fosters the transfer of large genomic regions in .

Natural competence for transformation is a primary mode of horizontal gene transfer. Competent bacteria are able to absorb free DNA from their surroundings and exchange this DNA against pieces of their own genome when sufficiently homologous. However, the prevalence of non-degraded DNA with sufficient coding capacity is not well understood.

Mechanisms of DNA Uptake by Naturally Competent Bacteria.

Transformation is a widespread mechanism of horizontal gene transfer in bacteria. DNA uptake to the periplasmic compartment requires a DNA-uptake pilus and the DNA-binding protein ComEA. In the gram-negative bacteria, DNA is first pulled toward the outer membrane by retraction of the pilus and then taken up by binding to periplasmic ComEA, acting as a Brownian ratchet to prevent backward diffusion.

Selection of Vibrio crassostreae relies on a plasmid expressing a type 6 secretion system cytotoxic for host immune cells.

Pacific oyster mortality syndrome affects juveniles of Crassostrea gigas oysters and threatens the sustainability of commercial and natural stocks of this species. Vibrio crassostreae (V. crassostreae) has been repeatedly isolated from diseased animals, and the majority of the strains have been demonstrated to be virulent for oysters.

DNA-uptake pili of Vibrio cholerae are required for chitin colonization and capable of kin recognition via sequence-specific self-interaction.

How bacteria colonize surfaces and how they distinguish the individuals around them are fundamental biological questions. Type IV pili are a widespread and multipurpose class of cell surface polymers. Here we directly visualize the DNA-uptake pilus of Vibrio cholerae, which is produced specifically during growth on its natural habitat-chitinous surfaces.

Ecological implications of gene regulation by TfoX and TfoY among diverse Vibrio species.

Bacteria of the genus Vibrio are common members of aquatic environments where they compete with other prokaryotes and defend themselves against grazing predators. A macromolecular protein complex called the type VI secretion system (T6SS) is used for both purposes. Previous research showed that the sole T6SS of the human pathogen V.

Long-Read-Based Genome Sequences of Pandemic and Environmental Vibrio cholerae Strains.

The bacterium Vibrio cholerae exhibits two distinct lifestyles, one as an aquatic bacterium and the other as the etiological agent of the pandemic human disease cholera. Here, we report closed genome sequences of two seventh pandemic V. cholerae O1 El Tor strains, A1552 and N16961, and the environmental strain Sa5Y.

Molecular insights into Vibrio cholerae's intra-amoebal host-pathogen interactions.

Vibrio cholerae, which causes the diarrheal disease cholera, is a species of bacteria commonly found in aquatic habitats. Within such environments, the bacterium must defend itself against predatory protozoan grazers. Amoebae are prominent grazers, with Acanthamoeba castellanii being one of the best-studied aquatic amoebae.