Murine Model for Measuring Effects of Humanized-Dosing of Antibiotics on the Gut Microbiome.

There is a current need for enhancing our insight in the effects of antimicrobial treatment on the composition of human microbiota. Also, the spontaneous restoration of the microbiota after antimicrobial treatment requires better understanding. This is best addressed in well-defined animal models.

Extensive Gene Amplification as a Mechanism for Piperacillin-Tazobactam Resistance in Escherichia coli.

Although the TEM-1 β-lactamase (Bla) hydrolyzes penicillins and narrow-spectrum cephalosporins, organisms expressing this enzyme are typically susceptible to β-lactam/β-lactamase inhibitor combinations such as piperacillin-tazobactam (TZP). However, our previous work led to the discovery of 28 clinical isolates of resistant to TZP that contained only One of these isolates, 907355, was investigated further in this study. 907355 exhibited significantly higher β-lactamase activity and Bla protein levels when grown in the presence of subinhibitory concentrations of TZP.

Carbon source and cell density-dependent regulation of type III secretion system gene expression in Pseudomonas syringae pathovar tomato DC3000.

Pseudomonas syringae utilizes a type III secretion system (T3SS) encoded by the hrp/hrc genes to translocate virulence proteins called effectors into plant cells. To ensure that the T3SS functions at appropriate times during infection, hrp/hrc and effector gene expression is modulated by environmental conditions and a complex network of transcription factors. The sigma factor HrpL activates hrp/hrc and effector genes, while σ(54) and enhancer binding proteins HrpR and HrpS regulate hrpL.

Functional and computational analysis of amino acid patterns predictive of type III secretion system substrates in Pseudomonas syringae.

Bacterial type III secretion systems (T3SSs) deliver proteins called effectors into eukaryotic cells. Although N-terminal amino acid sequences are required for translocation, the mechanism of substrate recognition by the T3SS is unknown. Almost all actively deployed T3SS substrates in the plant pathogen Pseudomonas syringae pathovar tomato strain DC3000 possess characteristic patterns, including (i) greater than 10% serine within the first 50 amino acids, (ii) an aliphatic residue or proline at position 3 or 4, and (iii) a lack of acidic amino acids within the first 12 residues.

Translocation of NopP by Sinorhizobium fredii USDA257 into Vigna unguiculata root nodules.

Sinorhizobium fredii is a nitrogen-fixing legume symbiont that stimulates the formation of root nodules. S. fredii nodulation of roots is influenced by Nop proteins, which are secreted through a type III secretion system (T3SS).

Multiple approaches to a complete inventory of Pseudomonas syringae pv. tomato DC3000 type III secretion system effector proteins.

Pseudomonas syringae pv. tomato DC3000 is a pathogen of tomato and Arabidopsis that translocates virulence effector proteins into host cells via a type III secretion system (T3SS). Many effector-encoding hypersensitive response and pathogenicity (Hrp) outer protein (hop) genes have been identified previously in DC3000 using bioinformatic methods based on Hrp promoter sequences and characteristic N-terminal amino acid patterns that are associated with T3SS substrates.

Closing the circle on the discovery of genes encoding Hrp regulon members and type III secretion system effectors in the genomes of three model Pseudomonas syringae strains.

Pseudomonas syringae strains translocate large and distinct collections of effector proteins into plant cells via the type III secretion system (T3SS). Mutations in T3SS-encoding hrp genes are unable to elicit the hypersensitive response or pathogenesis in nonhost and host plants, respectively. Mutations in individual effectors lack strong phenotypes, which has impeded their discovery.

The Erwinia chrysanthemi EC16 hrp/hrc gene cluster encodes an active Hrp type III secretion system that is flanked by virulence genes functionally unrelated to the Hrp system.

Erwinia chrysanthemi is a host-promiscuous plant pathogen that possesses a type III secretion system (TTSS) similar to that of the host-specific pathogens E. amylovora and Pseudomonas syringae. The regions flanking the TTSS-encoding hrp/hrc gene clusters in the latter pathogens encode various TTSS-secreted proteins.

Pseudomonas syringae type III secretion system targeting signals and novel effectors studied with a Cya translocation reporter.

Pseudomonas syringae pv. tomato strain DC3000 is a pathogen of tomato and Arabidopsis: The hrp-hrc-encoded type III secretion system (TTSS), which injects bacterial effector proteins (primarily called Hop or Avr proteins) into plant cells, is required for pathogenicity. In addition to being regulated by the HrpL alternative sigma factor, most avr or hop genes encode proteins with N termini that have several characteristic features, including (i) a high percentage of Ser residues, (ii) an aliphatic amino acid (Ile, Leu, or Val) or Pro at the third or fourth position, and (iii) a lack of negatively charged amino acids within the first 12 residues.

The small nucleoid-binding proteins H-NS, HU, and Fis affect hilA expression in Salmonella enterica serovar Typhimurium.

hilA encodes an activator of Salmonella enterica serovar Typhimurium virulence genes and is transcriptionally modulated by environmental conditions. We show that H-NS represses hilA under low-osmolarity conditions. H-NS, HU, and Fis also appear to affect the derepression of hilA by HilD.

AraC/XylS family members, HilD and HilC, directly activate virulence gene expression independently of HilA in Salmonella typhimurium.

Salmonella typhimurium is a Gram-negative enteric pathogen that can infect intestinal epithelial cells and induce inflammation of the intestinal mucosa. These processes are mediated by a type III secretion system (TTSS), which is encoded on Salmonella pathogenicity island 1 (SPI1). Previous studies showed that four SPI1-encoded transcriptional regulators, HilD, HilC, HilA and InvF, act in an ordered fashion to co-ordinately activate expression of the SPI1 TTSS.

Detection and characterization of the S. typhimurium HilA protein.

Background: Virulence genes on Salmonella pathogenicity island 1 (SPI1) are coordinately regulated by HilA, a member of the OmpR/ToxR family of transcription factors. Although a great deal is known about the complex regulation of hilA gene expression, very little is known about the HilA protein.

Results: In order to detect and localize the HilA protein in S.

Genomewide identification of proteins secreted by the Hrp type III protein secretion system of Pseudomonas syringae pv. tomato DC3000.

The ability of Pseudomonas syringae pv. tomato DC3000 to be pathogenic on plants depends on the Hrp (hypersensitive response and pathogenicity) type III protein secretion system and the effector proteins it translocates into plant cells. Through iterative application of experimental and computational techniques, the DC3000 effector inventory has been substantially enlarged.