ABSTRACT
Yersinia pestis, the causative agent of plague, makes a siderophore termed yersiniabactin (Ybt), which it uses to obtain iron during growth at 37 degrees C. The genes required for the synthesis and utilization of Ybt are located within a large, unstable region of the Y. pestis chromosome called the pgm locus. Within the pgm locus, just upstream of a gene (ybtA) that regulates expression of the Ybt receptor and biosynthetic genes, is an operon consisting of 4 genes - ybtP, ybtQ, ybtX and ybtS. Transcription of the ybtPQXS operon is repressed by Fur and activated by YbtA. The product of ybtX is predicted to be an exceedingly hydrophobic cytoplasmic membrane protein that does not appear to contribute any vital function to Ybt biosynthesis or utilization in vitro. ybtP and ybtQ encode putative members of the traffic ATPase/ABC transporter family. YbtP and YbtQ are structurally unique among the subfamily of ABC transporters associated with iron transport, in that they both contain an amino-terminal membrane-spanning domain and a carboxy-terminal ATPase. Cells with mutations in ybtP or ybtQ still produced Ybt but were impaired in their ability to grow at 37 degrees C under iron-deficient conditions, indicating that YbtP and YbtQ are needed for iron uptake. In addition, a ybtP mutant showed reduced iron accumulation and was avirulent in mice by a subcutaneous route of infection that mimics flea transmission of bubonic plague.
Subject(s)
ATP-Binding Cassette Transporters/genetics , Bacterial Proteins/genetics , Gene Expression Regulation, Bacterial , Iron/metabolism , Phenols , Siderophores/genetics , Thiazoles , Yersinia pestis/metabolism , ATP-Binding Cassette Transporters/chemistry , ATP-Binding Cassette Transporters/metabolism , Amino Acid Sequence , Animals , Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Base Sequence , Chromosome Mapping , Genes, Bacterial , Mice , Molecular Sequence Data , Operon/genetics , Plague/microbiology , Promoter Regions, Genetic , Sequence Analysis, DNA , Siderophores/biosynthesis , Virulence , Yersinia pestis/genetics , Yersinia pestis/pathogenicity , beta-Galactosidase/metabolismABSTRACT
Neisseria gonorrhoeae infects a diverse array of niches in its human host, which expose the organism to dramatic variations in pH. We examined growth and lipooligosaccharide expression of two gonococcal strains in liquid and solid cultures under acidic, neutral, and alkaline conditions. Growth rates in broth were similar under the three conditions, and the pH remained fairly constant throughout the growth cycle. Altered lipooligosaccharide expression at the different pHs was noted in both plate- and broth-grown organisms.
