Iron acquisition functions expressed by the human pathogen Acinetobacter baumannii.
Daniel L Zimbler1, William F Penwell, Jennifer A Gaddy
1Department of Microbiology, Miami University, Oxford, OH 45056, USA.
Summary
Acinetobacter baumannii utilizes both siderophore and hemin for iron acquisition, but its capacity varies between strains. Unexpectedly, iron uptake relies on the SecA secretion system, a novel finding for bacterial iron acquisition.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Acinetobacter baumannii is a significant Gram-negative pathogen causing severe infections.
- This bacterium thrives under iron-limiting conditions, necessitating efficient iron acquisition systems.
- Previous studies highlighted the acinetobactin-mediated iron uptake system in A. baumannii.
Purpose of the Study:
- To investigate the iron acquisition mechanisms of Acinetobacter baumannii, focusing on siderophore and hemin utilization.
- To compare the iron uptake capabilities between different A. baumannii strains (19606 and 17978).
- To identify novel factors involved in bacterial iron acquisition.
Main Methods:
- Genomic analysis to identify iron acquisition gene clusters.
- PCR and Southern blot analysis to confirm gene presence.
- Transposome mutagenesis to generate mutants.
- Gene mapping, protein analysis, and complementation assays to characterize mutant phenotypes.
- Growth assays under iron-limiting conditions.
Main Results:
- Acinetobacter baumannii utilizes both acinetobactin (siderophore) and hemin for iron uptake.
- Strain 17978 possesses an additional iron acquisition gene cluster not found in strain 19606.
- Mutagenesis of strain 19606 revealed a requirement for a SecA secretion system component for both acinetobactin receptor (BauA) production and hemin utilization.
- Different A. baumannii isolates exhibit varying iron acquisition capacities.
Conclusions:
- Acinetobacter baumannii employs multiple iron acquisition strategies, including siderophore and hemin uptake.
- The SecA secretion system plays a critical, previously unrecognized role in A. baumannii iron acquisition.
- Inter-strain variability exists in the iron acquisition mechanisms of A. baumannii, impacting its adaptability and virulence.
Related Concept Videos
01:25Inhalation Anthrax
Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive, spore-forming bacterium. It primarily affects herbivorous animals but can be transmitted to humans through skin contact, ingestion, or inhalation of spores.Cutaneous anthrax, the most common form, typically results from direct contact with bacterial spores through skin abrasions and is generally less severe. Gastrointestinal anthrax results from eating undercooked or contaminated meat. It affects the mouth, throat, or...
01:28Gene Regulation in Microbial Communities: Quorum Sensing
Quorum sensing is a mechanism of bacterial communication that enables coordinated gene expression in response to changes in population density. This facilitates collective behaviors that enhance survival, resource acquisition, and ecological adaptation. This process relies on small signaling molecules called autoinducers that accumulate as bacterial populations grow. When a critical threshold concentration of autoinducers is reached, bacterial cells collectively modify gene expression,...
01:31Defense Against Bacterial Pathogens
The human immune system is a complex network of cells, tissues, and organs that work together to defend the body against bacterial infections. It consists of various immune cells, each playing a specific role in the defense mechanism.
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
01:23Antimicrobial Proteins
Antimicrobial proteins are important components of the immune system. They aid the body in combating pathogens by either killing them directly or hindering their replication processes. Four main types of antimicrobial substances are interferons, the complement system, iron-binding proteins, and antimicrobial proteins.
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
01:25Mechanism of Antibiotic Resistance in MRSA
Antibiotic resistance in bacteria arises when microorganisms evolve the ability to withstand drugs designed to kill them or inhibit their growth, rendering once-effective treatments useless. This phenomenon, driven by genetic change and selection under antibiotic exposure, poses a profound threat to modern medicine. Mechanisms include drug-inactivating enzymes (e.g., β-lactamases), efflux pumps that eject antibiotics, mutations altering antibiotic targets, decreased drug uptake, and acquisition...
01:20Determinants of Bacterial Pathogenicity and Virulence
Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...