Chimeric systems composed of swapped Tra subunits between distantly-related F plasmids reveal striking plasticity among type IV secretion machines.

Bacterial type IV secretion systems (T4SSs) are a versatile family of macromolecular translocators, collectively able to recruit diverse DNA and protein substrates and deliver them to a wide range of cell types. Presently, there is little understanding of how T4SSs recognize substrate repertoires and form productive contacts with specific target cells. Although T4SSs are composed of a number of conserved subunits and adopt certain conserved structural features, they also display considerable compositional and structural diversity.

Chimeric systems composed of swapped Tra subunits between distantly-related F plasmids reveal striking plasticity among type IV secretion machines.

Bacterial type IV secretion systems (T4SSs) are a versatile family of macromolecular translocators, collectively able to recruit diverse DNA and protein substrates and deliver them to a wide range of cell types. Presently, there is little understanding of how T4SSs recognize substrate repertoires and form productive contacts with specific target cells. Although T4SSs are composed of a number of conserved subunits and adopt certain conserved structural features, they also display considerable compositional and structural diversity.

Contributions of F-specific subunits to the F plasmid-encoded type IV secretion system and F pilus.

F plasmids circulate widely among the Enterobacteriaceae through encoded type IV secretion systems (T4SS s). Assembly of T4SS s and associated F pili requires 10 VirB/VirD4-like Tra subunits and eight or more F-specific subunits. Recently, we presented evidence using in situ cryoelectron tomography (cryoET) that T4SS s undergo structural transitions when activated for pilus production, and that assembled pili are deposited onto alternative basal platforms at the cell surface.

Structure of a type IV secretion system core complex encoded by multi-drug resistance F plasmids.

Bacterial type IV secretion systems (T4SSs) are largely responsible for the proliferation of multi-drug resistance. We solved the structure of the outer-membrane core complex (OMCC) of a T4SS encoded by a conjugative F plasmid at <3.0 Å resolution by cryoelectron microscopy.

Visualization of the pKM101-Encoded Type IV Secretion System Reveals a Highly Symmetric ATPase Energy Center.

Bacterial conjugation systems are members of the type IV secretion system (T4SS) superfamily. T4SSs can be classified as "minimized" or "expanded" based on whether they are composed of a core set of signature subunits or additional system-specific components. Prototypical minimized systems mediating Agrobacterium tumefaciens transfer DNA (T-DNA) and pKM101 and R388 plasmid transfer are built from subunits generically named VirB1 to VirB11 and VirD4.

Type IV secretion systems: Advances in structure, function, and activation.

Bacterial type IV secretion systems (T4SSs) are a functionally diverse translocation superfamily. They consist mainly of two large subfamilies: (i) conjugation systems that mediate interbacterial DNA transfer and (ii) effector translocators that deliver effector macromolecules into prokaryotic or eukaryotic cells. A few other T4SSs export DNA or proteins to the milieu, or import exogenous DNA.

ssRNA phage penetration triggers detachment of the F-pilus.

Although the F-specific ssRNA phage MS2 has long had paradigm status, little is known about penetration of the genomic RNA (gRNA) into the cell. The phage initially binds to the F-pilus using its maturation protein (Mat), and then the Mat-bound gRNA is released from the viral capsid and somehow crosses the bacterial envelope into the cytoplasm. To address the mechanics of this process, we fluorescently labeled the ssRNA phage MS2 to track F-pilus dynamics during infection.

Induction of expression by cell-wall targeting antibiotics in .

is one of the major bacteria of the human oral cavity that is associated with dental caries. The pathogenicity of this bacterium is attributed to its ability to rapidly respond and adapt to the ever-changing conditions of the oral cavity. The major player in this adaptive response is ClpP, an intracellular protease involved in degradation of misfolded proteins during stress responses.

Structural bases for F plasmid conjugation and F pilus biogenesis in .

Bacterial conjugation systems are members of the large type IV secretion system (T4SS) superfamily. Conjugative transfer of F plasmids residing in the was first reported in the 1940s, yet the architecture of F plasmid-encoded transfer channel and its physical relationship with the F pilus remain unknown. We visualized F-encoded structures in the native bacterial cell envelope by in situ cryoelectron tomography (CryoET).

Molecular Architecture of the Helicobacter pylori Cag Type IV Secretion System.

colonizes about half of humans worldwide, and its presence in the gastric mucosa is associated with an increased risk of gastric adenocarcinoma, gastric lymphoma, and peptic ulcer disease. strains carrying the pathogenicity island (PAI) are associated with increased risk of disease progression. The PAI encodes the Cag type IV secretion system (Cag), which delivers the CagA oncoprotein and other effector molecules into human gastric epithelial cells.

Two pKM101-encoded proteins, the pilus-tip protein TraC and Pep, assemble on the Escherichia coli cell surface as adhesins required for efficient conjugative DNA transfer.

Mobile genetic elements (MGEs) encode type IV secretion systems (T4SSs) known as conjugation machines for their transmission between bacterial cells. Conjugation machines are composed of an envelope-spanning translocation channel, and those functioning in Gram-negative species additionally elaborate an extracellular pilus to initiate donor-recipient cell contacts. We report that pKM101, a self-transmissible MGE functioning in the Enterobacteriaceae, has evolved a second target cell attachment mechanism.

Role of CovR phosphorylation in gene transcription in Streptococcus mutans.

Streptococcus mutans, the primary aetiological agent of dental caries, is one of the major bacteria of the human oral cavity. The pathogenicity of this bacterium is attributed not only to the expression of virulence factors, but also to its ability to respond and adapt rapidly to the ever-changing conditions of the oral cavity. The two-component signal transduction system (TCS) CovR/S plays a crucial role in virulence and stress response in many streptococci.

Characterization of a topologically unique oxygenase from Sphingobium sp. PNB capable of catalyzing a broad spectrum of aromatics.

A Rieske non-heme iron ring-hydroxylating oxygenase (RHO) from Sphingobium sp. PNB involved in the initial oxidation of a wide range of low and high molecular weight polycyclic aromatic hydrocarbons (PAHs) was investigated. The RHO was shown to comprise of the gene products of distantly located ahdA1f-ahdA2f, ahdA3 and ahdA4 genes, which encoded the oxygenase α- and β-subunits, ferredoxin and reductase, respectively.

Functional characterization of diverse ring-hydroxylating oxygenases and induction of complex aromatic catabolic gene clusters in Sphingobium sp. PNB.

Sphingobium sp. PNB, like other sphingomonads, has multiple ring-hydroxylating oxygenase (RHO) genes. Three different fosmid clones have been sequenced to identify the putative genes responsible for the degradation of various aromatics in this bacterial strain.

meta-Cleavage of hydroxynaphthoic acids in the degradation of phenanthrene by Sphingobium sp. strain PNB.

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of priority organic pollutants that are toxic and/or carcinogenic. Phenanthrene, the simplest PAH among recognized priority pollutants, is commonly used as a model compound for the study of PAH biodegradation. Sphingobium sp.

Cloning and characterization of a p-cymene monooxygenase from Pseudomonas chlororaphis subsp. aureofaciens.

p-Cymene monooxygenase is the enzyme system that catalyzes the hydroxylation of p-cymene to 4-isopropylbenzyl alcohol (p-cumic alcohol), the initial step in the assimilation of p-cymene by Pseudomonas chlororaphis subsp. aureofaciens. Cloning and sequencing of single NADH-dependent cytochrome c reductase gene (cymA) present in P.

Degradation of phenanthrene via meta-cleavage of 2-hydroxy-1-naphthoic acid by Ochrobactrum sp. strain PWTJD.

The present study describes the assimilation of phenanthrene by an aerobic bacterium, Ochrobactrum sp. strain PWTJD, isolated from municipal waste-contaminated soil sample utilizing phenanthrene as a sole source of carbon and energy. The isolate was identified as Ochrobactrum sp.