MICR 302 Lecture Notes - Lecture 3: Lac Operon, Sigma Factor, Osmotic Shock
16 Mar 2018
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Document Summary
Bacteria cells grow exponentially until a density of population is reached causing the cells to enter a stationary phase in which growth is arrested (equal number growing/dying) In lab cultures this is ~10^9 cells/ml. Stationary phase occurs due to factors including nutrient limitation, oxygen limitation or waste toxicity (waste build up causes a change in ph) Plays a role in other cell stress pathways besides starvation. Activation: by starvation stress that either causes a short-term nutrient source switch (lac operon; diauxic growth) or a long-term stationary phase. Two examples involve the sigma s and the stringent response. Cellular resources depend on the quality of the environment, and the cell will use those resources to feed their growth/reproduction and maintenance/survival pathways. If the cell is under feast conditions" = reproduction levels are high and maintenance levels are low. If the cell is under famine conditions" = the cell uses resources to perform maintenance functions and not reproduction.
