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Acquisition of iron from host sources by mesophilic Aeromonas species
G Massad1, J E Arceneaux, B R Byers
1Department of Microbiology, University of Mississippi Medical Center, Jackson 39216.
Abstract:
The mesophilic Aeromonas species are opportunistic pathogens that produce either of the siderophores amonabactin or enterobactin. Acquisition of iron for growth from Fe-transferrin in serum was dependent on the siderophore amonabactin; 50 of 54 amonabactin-producing isolates grew in heat-inactivated serum, whereas none of 30 enterobactin-producing strains were able to grow. Most isolates (regardless of siderophore produced) used haem as a sole source of iron for growth; all of 33 isolates grew with either haematin or haemoglobin and 30 of these used haemoglobin when complexed to human haptoglobin. Mutants unable to synthesize a siderophore used iron from haem, suggesting that this capacity was unrelated to siderophore production. Some members of the mesophilic Aeromonas species have evolved both siderophore-dependent and -independent mechanisms for acquisition of iron from a host.
Insights
Mesophilic Aeromonas species use siderophores like amonabactin to acquire iron from transferrin. They also utilize heme-based iron sources, demonstrating versatile iron acquisition strategies for opportunistic infections.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Iron Metabolism
Background:
- Mesophilic Aeromonas species are opportunistic pathogens.
- Iron is essential for bacterial growth and virulence.
- Pathogens employ various strategies to acquire iron from host environments.
Purpose of the Study:
- To investigate the iron acquisition mechanisms of mesophilic Aeromonas species.
- To determine the role of siderophores (amonabactin, enterobactin) in iron uptake.
- To assess the utilization of host iron sources like transferrin and heme.
Main Methods:
- Culturing Aeromonas isolates under iron-limiting conditions.
- Testing growth in serum supplemented with Fe-transferrin.
- Evaluating iron acquisition from heme, hemin, and hemoglobin-haptoglobin complexes.
- Analyzing siderophore-deficient mutants.
Main Results:
- Amonabactin-producing Aeromonas efficiently acquired iron from Fe-transferrin in serum.
- Enterobactin-producing strains failed to grow in serum, indicating amonabactin's specific role.
- Most isolates, irrespective of siderophore production, utilized heme, hemin, and hemoglobin as iron sources.
- Siderophore-independent iron acquisition from heme was confirmed in mutants.
Conclusions:
- Mesophilic Aeromonas species possess both siderophore-dependent (amonabactin) and siderophore-independent (heme-based) iron acquisition mechanisms.
- Amonabactin is crucial for Aeromonas to scavenge iron from transferrin.
- These adaptable iron acquisition strategies contribute to the opportunistic pathogenicity of Aeromonas.