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Published on: March 21, 2012
Norepinephrine as a growth stimulating factor in bacteria--mechanistic studies
K S Kinney1, C E Austin, D S Morton
1Department of Microbiology and Immunology, Morehouse School of Medicine, Atlanta, GA 30310, USA.
Life Sciences
|December 28, 2000
Summary
Catecholamines like norepinephrine enhance bacterial growth by acting as siderophores, improving iron uptake. Specific conditions, like culturing E. coli at 37°C with norepinephrine, yield a potent growth-enhancing factor in culture supernatants.
Area of Science:
- Microbiology
- Bacterial Physiology
- Biochemistry
Background:
- Catecholamines (norepinephrine, epinephrine, dopamine) are known to stimulate the growth of Gram-negative bacteria.
- The catechol structure in catecholamines suggests potential siderophore activity, aiding iron uptake in nutrient-limited environments.
Purpose of the Study:
- To investigate if catecholamines enhance bacterial growth by improving iron uptake.
- To determine if catecholamines are internalized by bacteria or adsorbed externally.
- To analyze bacterial culture supernatants for growth-enhancing substances, termed "autoinducers of growth".
Main Methods:
- Quantification of iron content in different bacterial growth media.
- Tracking the uptake of radiolabeled 3H-norepinephrine in bacteria.
- High-Performance Liquid Chromatography (HPLC) analysis of culture supernatants.
- Assessing the growth-promoting capacity of supernatants on naive bacterial cultures.
Main Results:
- Iron concentrations in fast-growth and slow-growth media were similar and generally unchanged in supernatants from norepinephrine-supplemented cultures.
- HPLC analysis revealed time-dependent changes in norepinephrine content in Escherichia coli supernatants cultured at 37°C, but not at 21°C.
- Supernatants from E. coli cultured with norepinephrine at 37°C significantly enhanced the growth of three bacterial species, more so than other tested conditions.
Conclusions:
- Catecholamines may not enhance bacterial growth solely by altering iron availability in the media.
- A potent growth-enhancing factor, potentially an "autoinducer of growth," is produced by bacteria (e.g., E. coli) in the presence of norepinephrine, particularly under specific temperature conditions (37°C).
- This factor is released into the culture supernatant and can stimulate the growth of other bacteria.
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