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Metal uptake is vital for all living organisms. In metal scarce conditions a common bacterial strategy consists in the biosynthesis of metallophores, their export in the extracellular medium and the recovery of a metal-metallophore complex through dedicated membrane transporters. Staphylopine is a recently described metallophore distantly related to plant nicotianamine that contributes to the broad-spectrum metal uptake capabilities of Staphylococcus aureus. Here we characterize a four-gene operon (PA4837-PA4834) in Pseudomonas aeruginosa involved in the biosynthesis and trafficking of a staphylopine-like metallophore named pseudopaline. Pseudopaline differs from staphylopine with regard to the stereochemistry of its histidine moiety associated with an alpha ketoglutarate moiety instead of pyruvate. In vivo, the pseudopaline operon is regulated by zinc through the Zur repressor. The pseudopaline system is involved in nickel uptake in poor media, and, most importantly, in zinc uptake in metal scarce conditions mimicking a chelating environment, thus reconciling the regulation of the cnt operon by zinc with its function as the main zinc importer under these metal scarce conditions.

Staphylococcus aureus RN6390 presents a diauxic growth in milk, due to amino acid limitation. Inactivation of the oligopeptide permease Opp3 (dedicated to the nitrogen nutrition of the strain) not only affects the growth of the strain but also results in reduced expression levels of three major extracellular proteases.

The oligopeptide transport systems Opp belong to the nickel/peptide/opine PepT subfamily of ABC-transporters. The opportunist pathogen Staphylococcus aureus encodes four putative Opps and one orphean substrate binding protein Opp5A. Here, we report that the Opp2 permease complex (Opp2BCDF) and Opp5A are involved in nickel uptake and then renamed them NikBCDE and NikA respectively. S. aureus carries also a high-affinity nickel transporter NixA belonging to the NiCoT family of secondary transporters. The activity of these two nickel transporters determine that of urease, a multimeric nickel-dependent enzyme mainly involved in the neutralization of acidic environments. However, only the Nik system was responsible for the neutralization and deposit of pH-dependent crystals in human urine. Inactivation of the nik genes affected bacterial colonization of mouse urinary tract, as well as the 50% infective dose levels compared with the parental and nixA strains. Finally, complementation of the nik mutations restored bacterial colonization. Together, our results suggest a role for the Nik system in the urinary tract infection by S. aureus, probably due to the urease-mediated pH increase of the urine. [ABSTRACT FROM AUTHOR]

Oligopeptides internalized by oligopeptide permease (Opp) transporters play key roles in bacterial nutrition, signaling, and virulence. To date, two opp operons, opp-1 and opp-2, have been identified in Staphylococcus aureus. Systematic in silico analysis of 11 different S. aureus genomes revealed the existence of two new opp operons, opp-3 and opp-4, plus an opp-5A gene encoding a putative peptide-binding protein. With the exception of opp-4, the opp operons were present in all S. aureus strains. Within a single strain, the different opp operons displayed little sequence similarity and distinct genetic organization. Transcriptional studies showed that opp-1, opp-2, opp-3, and opp-4 operons were polycistronic and that opp-5A is monocistronic. We designed a minimal chemically defined medium for S. aureus RN6390 and showed that all opp genes were expressed but at different levels. Where tested, OppA protein production paralleled transcriptional profiles. opp-3, which encodes proteins most similar to known peptide transport proteins, displayed the highest expression level and was the only transporter to be regulated by specific amino acids, tyrosine and phenylalanine. Defined deletion mutants in one or several peptide permeases were constructed and tested for their capacity to grow in peptide-containing medium. Among the four putative Opp systems, Opp-3 was the only system able to provide oligopeptides for growth, ranging in length from 3 to 8 amino acids. Dipeptides were imported exclusively by DtpT, a proton-driven di- and tripeptide permease. These data provide a first complete inventory of the peptide transport systems opp and dtpT of S. aureus. Among them, the newly identified Opp-3 appears to be the main Opp system supplying the cell with peptides as nutritional sources. [ABSTRACT FROM AUTHOR]