Richard J Siehnel

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Bacteria become highly tolerant to antibiotics when nutrients are limited. The inactivity of antibiotic targets caused by starvation-induced growth arrest is thought to be a key mechanism producing tolerance. Here we show that the antibiotic tolerance of nutrient-limited and biofilm Pseudomonas aeruginosa is mediated by active responses to starvation,(More)
Quorum-sensing (QS) systems allow organisms, such as the pathogen Pseudomonas aeruginosa, to link gene expression with their population density and the diffusion and flow characteristics of their environment. The leading hypotheses about QS systems' biological functions necessitate that QS-controlled gene expression be suppressed until a threshold culture(More)
In this review, we describe the outer membrane proteins of Pseudomonas aeruginosa and related strains from the Pseudomonas fluorescens rRNA homology group of the Pseudomonadaceae, with emphasis on the physiological function and biochemical characteristics of these proteins. The use of opr (for outer membrane protein) is proposed as the genetic designation(More)
The oprO gene of Pseudomonas aeruginosa codes for a polyphosphate-specific porin and terminates 458 bp upstream of the start codon for the phosphate-specific porin OprP. OprO was found to be expressed only under phosphate-starvation conditions in both wild-type and oprP::Tn501 mutant P. aeruginosa strains. However, unlike the rest of the genes of the Pho(More)
In this article we describe the application of structural biology methods to the discovery of novel potent inhibitors of methionine aminopeptidases. These enzymes are employed by the cells to cleave the N-terminal methionine from nascent peptides and proteins. As this is one of the critical steps in protein maturation, it is very likely that inhibitors of(More)
Allelic exchange is an efficient method of bacterial genome engineering. This protocol describes the use of this technique to make gene knockouts and knock-ins, as well as single-nucleotide insertions, deletions and substitutions, in Pseudomonas aeruginosa. Unlike other approaches to allelic exchange, this protocol does not require heterologous recombinases(More)
In pathogenic Gram-negative bacteria, interactions among membrane proteins are key mediators of host cell attachment, invasion, pathogenesis, and antibiotic resistance. Membrane protein interactions are highly dependent upon local properties and environment, warranting direct measurements on native protein complex structures as they exist in cells. Here we(More)
The oprP gene encoding the Pseudomonas aeruginosa phosphate-specific outer membrane porin protein OprP was sequenced. Comparison of the derived amino acid sequence with the known sequences of other bacterial porins demonstrated that OprP could be no better aligned to these porin sequences than it could to the periplasmic phosphate-binding protein PhoS of(More)
TnphoA mutagenesis of the cloned oprF gene was utilized to generate 16 classes of fusions encoding differing lengths of the amino terminus of OprF fused to either alkaline phosphatase or to peptide tags of 1 to 20 amino acids, depending on the orientation and reading frame into which TnphoA was inserted. Representatives of each of the 16 classes were(More)
This reports the synthesis and in vitro antimicrobial properties of a series of 2-thioether-linked quinolonyl-carbapenems. Although the title compounds exhibited broad spectrum activity, the MICs were generally higher than those observed for selected benchmark carbapenems, quinolonyl-penems, and quinolones. Enzyme assays suggested that the title compounds(More)