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Evidence for different pyoverdine-mediated iron uptake systems among Pseudomonas aeruginosa strains
P Cornelis1, D Hohnadel, J M Meyer
1Institut de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique, Strasbourg, France.
Abstract:
Fourteen strains of Pseudomonas aeruginosa (P. aeruginosa ATCC 15692, P. aeruginosa ATCC 27853, and 12 clinical isolates) were checked for the production of pyoverdine and for pyoverdine-mediated iron uptake. Under iron restriction, two isolates produced undetectable amounts of pyoverdine, but all the other strains produced a compound with physicochemical properties identical or close to those of the pyoverdine of P. aeruginosa ATCC 15692 (strain PAO1). The pyoverdines were purified and tested for their growth-promoting activity and for their ability to facilitate 59Fe uptake in homologous experiments involving each pyoverdine and its producing strain, as well as in heterologous systems involving all the other strains. The results of both types of experiments suggested the existence of three specificity groups. This was confirmed by analysis of the amino acid composition of the pyoverdines, which differed for each group. A partially purified polyclonal antiserum raised against a major 80-kilodalton (kDa) iron-regulated outer membrane protein (IROMP) of P. aeruginosa PAO1 recognized the 80-kDa IROMPs from P. aeruginosa PAO1 and the clinical isolates belonging to the same group, whereas the IROMPs from the strains belonging to the two other groups were not detected. A second antiserum raised against the P. aeruginosa ATCC 27853 80-kDa IROMP gave similar results by reacting specifically with the 80-kDa IROMP from the strains belonging to this group. Thus, together with the already known pyoverdine from P. aeruginosa PAO1, two new types of pyoverdines produced by strains belonging to this species were characterized.
Insights
This study identified two new types of pyoverdines in Pseudomonas aeruginosa strains, distinct from the known PAO1 pyoverdine. These findings reveal new variations in pyoverdine structure and function within this bacterial species.
Area of Science:
- Microbiology
- Bacterial Physiology
- Molecular Biology
Background:
- Pseudomonas aeruginosa utilizes pyoverdine, a siderophore, for iron acquisition.
- Pyoverdine structure and function can vary among bacterial strains.
- Understanding pyoverdine diversity is crucial for comprehending iron uptake mechanisms.
Purpose of the Study:
- To characterize pyoverdine production and iron uptake in various P. aeruginosa strains.
- To identify and differentiate novel pyoverdine types within the species.
- To investigate the relationship between pyoverdine types and iron-regulated outer membrane proteins (IROMPs).
Main Methods:
- Assay of pyoverdine production under iron-restricted conditions.
- Purification and testing of pyoverdines for growth promotion and 59Fe uptake.
- Analysis of pyoverdine amino acid composition.
- Immunological detection of 80-kDa iron-regulated outer membrane proteins (IROMPs) using specific antisera.
Main Results:
- Three distinct specificity groups were identified based on pyoverdine function and amino acid composition.
- Two new pyoverdine types, in addition to the known PAO1 pyoverdine, were characterized.
- Antisera against specific 80-kDa IROMPs confirmed strain groupings, correlating IROMP type with pyoverdine specificity.
Conclusions:
- Pseudomonas aeruginosa exhibits at least three distinct pyoverdine types.
- These pyoverdine types are associated with specific iron-regulated outer membrane proteins.
- The characterization of new pyoverdines expands our knowledge of iron metabolism in P. aeruginosa.