Site-Directed and Random Mutagenesis in Porphyromonas gingivalis: Construction of Fimbriae-Related-Gene Mutant.

Porphyromonas gingivalis, an etiological agent of chronic periodontitis, is an asaccharolytic anaerobic gram-negative coccobacillus. Genetic approaches greatly facilitate research on organisms at the molecular level. Although with some challenges, the use of genetic techniques (such as constructing knockout mutants) in P.

Structural basis of the binding affinity of chemoreceptors Mlp24p and Mlp37p for various amino acids.

Environmental sensing is crucial for bacterial survival and pathogenicity. Bacteria sense environmental chemicals using chemoreceptor proteins, such as Methyl-accepting Chemotaxis Proteins (MCPs). Vibrio cholerae, the etiological agent of cholera, has at least 44 chemoreceptor proteins homologous to MCP-Like Proteins (MLPs).

Calcium Ions Modulate Amino Acid Sensing of the Chemoreceptor Mlp24 of .

Bacteria sense environmental chemicals using chemosensor proteins, most of which are present in the cytoplasmic membrane. Canonical chemoreceptors bind their specific ligands in their periplasmic domain, and the ligand binding creates a molecular stimulus that is transmitted into the cytoplasm, leading to various cellular responses, such as chemotaxis and specific gene expression. , the causative agent of cholera, contains about 44 putative sensor proteins, which are homologous to methyl-accepting chemotaxis proteins involved in chemotaxis.

Dimerization site 2 of the bacterial DNA-binding protein H-NS is required for gene silencing and stiffened nucleoprotein filament formation.

The bacterial nucleoid-associated protein H-NS is a DNA-binding protein, playing a major role in gene regulation. To regulate transcription, H-NS silences genes, including horizontally acquired foreign genes. H-NS is 137 residues long and consists of two discrete and independent structural domains: an N-terminal oligomerization domain and a C-terminal DNA-binding domain, joined by a flexible linker.

Chemotactic Behaviors of Vibrio cholerae Cells.

Vibrio cholerae, the causative agent of cholera, swims in aqueous environments with a single polar flagellum. In a spatial gradient of a chemical, the bacterium can migrate in "favorable" directions, a property that is termed chemotaxis. The chemotaxis of V.

Identification of a Vibrio cholerae chemoreceptor that senses taurine and amino acids as attractants.

Vibrio cholerae, the etiological agent of cholera, was found to be attracted by taurine (2-aminoethanesulfonic acid), a major constituent of human bile. Mlp37, the closest homolog of the previously identified amino acid chemoreceptor Mlp24, was found to mediate taxis to taurine as well as L-serine, L-alanine, L-arginine, and other amino acids. Methylation of Mlp37 was enhanced upon the addition of taurine and amino acids.

Hypoxia-induced localization of chemotaxis-related signaling proteins in Vibrio cholerae.

Vibrio cholerae has three sets of chemotaxis-related signaling proteins, of which only System II has been shown to be involved in chemotaxis. Here, we examined localization of green fluorescent protein (GFP)-fused components of System I. The histidine kinase (CheA1) and the adaptor (CheW0) of System I localized to polar and lateral membrane regions with standing incubation (microaerobic conditions), but their localization was lost after shaking (aerobic conditions).

Mutational analysis of the P1 phosphorylation domain in Escherichia coli CheA, the signaling kinase for chemotaxis.

The histidine autokinase CheA functions as the central processing unit in the Escherichia coli chemotaxis signaling machinery. CheA receives autophosphorylation control inputs from chemoreceptors and in turn regulates the flux of signaling phosphates to the CheY and CheB response regulator proteins. Phospho-CheY changes the direction of flagellar rotation; phospho-CheB covalently modifies receptor molecules during sensory adaptation.

Mlp24 (McpX) of Vibrio cholerae implicated in pathogenicity functions as a chemoreceptor for multiple amino acids.

The chemotaxis of Vibrio cholerae, the causative agent of cholera, has been implicated in pathogenicity. The bacterium has more than 40 genes for methyl-accepting chemotaxis protein (MCP)-like proteins (MLPs). In this study, we found that glycine and at least 18 L-amino acids, including serine, arginine, asparagine, and proline, serve as attractants to the classical biotype strain O395N1.

Thermosensing function of the Escherichia coli redox sensor Aer.

Escherichia coli chemoreceptors can sense changes in temperature for thermotaxis. Here we found that the aerotaxis transducer Aer, a homolog of chemoreceptors lacking a periplasmic domain, mediates thermoresponses. We propose that thermosensing by the chemoreceptors is a general attribute of their highly conserved cytoplasmic domain (or their less conserved transmembrane domain).

Host adhesive activities and virulence of novel fimbrial proteins of Porphyromonas gingivalis.

The fimbriae of Porphyromonas gingivalis mediate critical roles in host colonization and evasion of innate defenses and comprise polymerized fimbrilin (FimA) associated with quantitatively minor accessory proteins (FimCDE) of unknown function. We now show that P. gingivalis fimbriae lacking FimCDE fail to interact with the CXC-chemokine receptor 4 (CXCR4), and bacteria expressing FimCDE-deficient fimbriae cannot exploit CXCR4 in vivo for promoting their persistence, as the wild-type organism does.

Subversion of innate immunity by periodontopathic bacteria via exploitation of complement receptor-3.

The capacity of certain pathogens to exploit innate immune receptors enables them to undermine immune clearance and persist in their host, often causing disease. Here we review subversive interactions of Porphyromonas gingivalis, a major periodontal pathogen, with the complement receptor-3 (CR3; CD11b/CD18) in monocytes/macrophages. Through its cell surface fimbriae, P.

Fimbrial proteins of porphyromonas gingivalis mediate in vivo virulence and exploit TLR2 and complement receptor 3 to persist in macrophages.

Porphyromonas gingivalis is an oral/systemic pathogen implicated in chronic conditions, although the mechanism(s) whereby it resists immune defenses and persists in the host is poorly understood. The virulence of this pathogen partially depends upon expression of fimbriae comprising polymerized fimbrillin (FimA) associated with quantitatively minor proteins (FimCDE). In this study, we show that isogenic mutants lacking FimCDE are dramatically less persistent and virulent in a mouse periodontitis model and express shorter fimbriae than the wild type.

Involvement of minor components associated with the FimA fimbriae of Porphyromonas gingivalis in adhesive functions.

The FimA fimbriae of Porphyromonas gingivalis, the causative agent of periodontitis, have been implicated in various aspects of pathogenicity, such as colonization, adhesion and aggregation. In this study, the four open reading frames (ORF1, ORF2, ORF3 and ORF4) downstream of the fimbrilin gene (fimA) in strain ATCC 33277 were examined. ORF2, ORF3 and ORF4 were demonstrated to encode minor components of the fimbriae and were therefore renamed fimC, fimD and fimE, respectively.

Differential interactions of fimbriae and lipopolysaccharide from Porphyromonas gingivalis with the Toll-like receptor 2-centred pattern recognition apparatus.

The lipopolysaccharide (LPS) and fimbriae of Porphyromonas gingivalis play important roles in periodontal inflammation and pathogenesis. We investigated fimbriae and LPS from several P. gingivalis strains in terms of relative dependence on Toll-like receptor (TLR) signalling partners or accessory pattern-recognition molecules mediating ligand transfer to TLRs, and determined induced assembly of receptor complexes in lipid rafts.

A novel type of two-component regulatory system affecting gingipains in Porphyromonas gingivalis.

We surveyed the Porphyromonas gingivalis W83 genome database for homologues of FimS, the first two-component sensor histidine kinase, which could possibly control virulence factors. Including fimS, we found six putative sensor kinase genes in the genome. The gene encoding one of the homologues was cloned from a P.