RESULTS:
1 - 2 of 2 for "Lauren A. Hinkel"
The Pseudomonas aeruginosa sphBC genes are important for growth in the presence of sphingosine by promoting sphingosine metabolism
Sphingoid bases including sphingosine are important components of the antimicrobial barrier at epithelial surfaces where they can cause growth inhibition and killing of susceptible bacteria. Pseudomonas aeruginosa is a common opportunistic pathogen that is less susceptible to sphingosine than many Gram-negative bacteria. Here we determined that the deletion of the sphBCD operon reduced growth in the presence of sphingosine. Using deletion mutants complementation and growth assays in P. aeruginosa PAO1 we determined that the sphC and sphB genes encoding a periplasmic oxidase and periplasmic cytochrome c respectively were important for growth on sphingosine while sphD was dispensable under these conditions. Deletion of sphBCD in P. aeruginosa PA14 Pseudomonas protegens Pf-5 and Pseudomonas fluorescens Pf01 also showed reduced growth in the presence of sphingosine. The P. aeruginosa sphBC genes were also important for growth in the presence of two other sphingoid bases phytosphingosine and sphinganine. In WT P. aeruginosa sphingosine is metabolized to an unknown non-inhibitory product as sphingosine concentrations drop in the culture. However in the absence of sphBC sphingosine accumulates pointing to SphC and SphB as having a role in sphingosine metabolism. Finally the metabolism of sphingosine by WT P. aeruginosa protected susceptible cells from full growth inhibition by sphingosine pointing to a role for sphingosine metabolism as a public good. This work shows that the metabolism of sphingosine by P. aeruginosa presents a novel pathway by which bacteria can alter host-derived sphingolipids but it remains an open question whether SphB and SphC act directly on sphingosine.
Creatine utilization as a sole nitrogen source in Pseudomonas putida KT2440 is transcriptionally regulated by CahR
Glutamine amidotransferase-1 domain-containing AraC-family transcriptional regulators (GATRs) are present in the genomes of many bacteria including all Pseudomonas species. The involvement of several characterized GATRs in amine-containing compound metabolism has been determined but the full scope of GATR ligands and regulatory networks are still unknown. Here we characterize Pseudomonas putida ’s detection of the animal-derived amine compound creatine a compound particularly enriched in muscle and ciliated cells by a creatine-specific GATR PP_3665 here named CahR (Creatine amidohydrolase Regulator). cahR is necessary for transcription of the gene encoding creatinase (PP_3667/creA) in the presence of creatine and is critical for P. putida’s ability to utilize creatine as a sole source of nitrogen. The CahR/creatine regulon is small and an electrophoretic mobility shift assay demonstrates strong and specific CahR binding only at the creA promoter supporting the conclusion that much of the regulon is dependent on downstream metabolites. Phylogenetic analysis of creA orthologues associated with cahR orthologues highlights a strain distribution and organization supporting probable horizontal gene transfer particularly evident within the genus Acinetobacter . This study identifies and characterizes the GATR that transcriptionally controls P. putida ’s metabolism of creatine broadening the scope of known GATR ligands and suggesting GATR diversification during evolution of metabolism for aliphatic nitrogen compounds.