期刊
MOLECULAR SYSTEMS BIOLOGY
卷 8, 期 -, 页码 -出版社
WILEY
DOI: 10.1038/msb.2012.46
关键词
active transport; futile cycle; integral feedback; metabolic coordination; microfluidics
资金
- NIH [R01-GM038361]
- Human Frontiers in Science Program [RGP0022]
- NSF [PHY-1058793]
- Direct For Mathematical & Physical Scien
- Division Of Physics [1058793] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [1308264] Funding Source: National Science Foundation
The efficient sequestration of nutrients is vital for the growth and survival of microorganisms. Some nutrients, such as CO2 and NH3, are readily diffusible across the cell membrane. The large membrane permeability of these nutrients obviates the need of transporters when the ambient level is high. When the ambient level is low, however, maintaining a high intracellular nutrient level against passive back diffusion is both challenging and costly. Here, we study the delicate management of ammonium (NH4+/NH3) sequestration by E. coli cells using microfluidic chemostats. We find that as the ambient ammonium concentration is reduced, E. coli cells first maximize their ability to assimilate the gaseous NH3 diffusing into the cytoplasm and then abruptly activate ammonium transport. The onset of transport varies under different growth conditions, but always occurring just as needed to maintain growth. Quantitative modeling of known interactions reveals an integral feedback mechanism by which this need-based uptake strategy is implemented. This novel strategy ensures that the expensive cost of upholding the internal ammonium concentration against back diffusion is kept at a minimum. Molecular Systems Biology 8: 616; published online 25 September 2012; doi:10.1038/msb.2012.46
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