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New iron acquisition system in Bacteroidetes.
Pablo Manfredi1, Frédéric Lauber2, Francesco Renzi2
1Biozentrum der Universität Basel, Basel, Switzerland.
Infection and Immunity
|November 5, 2014
Summary
Capnocytophaga canimorsus uses a unique iron capture system (ICS) derived from polysaccharide utilization loci (PUL) to grow in human serum. This novel ICS, found in other pathogens, likely contributes to virulence.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Capnocytophaga canimorsus, a bacterium found in dog mouths, can cause severe human infections.
- Bacteroidetes phylum bacteria utilize polysaccharide utilization loci (PUL) for nutrient acquisition.
- The function of PUL systems in iron acquisition has not been previously established.
Purpose of the Study:
- To investigate the mechanism by which C. canimorsus grows in human serum.
- To identify the genetic basis for serum growth and its potential role in virulence.
- To explore the evolutionary origin and broader distribution of this system.
Main Methods:
- Culturing C. canimorsus in heat-inactivated human serum.
- Genetic analysis of the polysaccharide utilization locus (PUL3) in strain Cc5.
- Investigating the role of PUL3 genes in iron acquisition from serotransferrin (STF).
- Genomic analysis of related bacterial species for the presence of similar gene clusters.
Main Results:
- C. canimorsus strains grow in heat-inactivated human serum, dependent on PUL3.
- PUL3 functions as an iron capture system (ICS), requiring all seven encoded proteins.
- The ICS likely captures iron directly from serotransferrin, independent of siderophores.
- Homologous ICS genes are present in various opportunistic pathogens, including Prevotella and Bacteroides species.
Conclusions:
- A novel iron capture system (ICS) has evolved in Bacteroidetes from a polysaccharide utilization system.
- This ICS is crucial for C. canimorsus growth in human serum and is likely a significant virulence factor.
- The presence of similar ICS in other pathogens suggests a conserved mechanism for iron acquisition in this phylum.
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