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lecture_18v2 - Lecture18 GrowthRatecontrol,and Homeostasis...

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Lecture 18: Growth Rate control, and Homeostasis Reading: Chapters 2, and 15
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What can effect the growth rate of bacteria? Quality of nutrients (talk about this later) Carbon source Nitrogen source Etc. pH Salt conditions Temperature?
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Bacteria can live in a variety of pH ranges Neutrophiles Acidophile Alkaliphiles
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While bacteria can live in a broad pH range, Any one species has its limits! pH gradients effect the growth rate Neutrophiles Acidophile Alkaliphiles
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Homeostasis: pH pH out pH in Δ pH Neutrophiles 6 8 7.5 8 + Acidophiles 1 4 6.5 7 + Alkaliphiles 9 12 8.4 9 What are the implications for bacteria that live in alkaline environments???
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Osmotic Homeostasis An experiment from high school What happens to cells if they are placed in a hypo osmotic solution? What happens in a hyper osmotic solution?
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Osmotic Homeostasis Osmotic Homeostasis: How do cells keep turgor pressure: cells keep osmotic pressure higher inside then out. This is done by increasing the internal concentration of solutes called osmolytes Osmolytes or Compatible solutes : some are produced by the cell some are not and are accumulated via transport. Osmoprotectants : are osmolytes that are accumulated via transport, such as K+ or Betain (except for cyanobacteria) Others include: glutamine glutamate, proline and betaine as well as Treholase a disaccharide of glucose
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Therefore cells must regulate in the influx of solutes and production of osmoprotectants in response to changes in the environment.
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What about temperature
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How do you change the growth rate At kmax, change the nutrient composition Otherwise use a chemostat!
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The concept of μ μ is the number of doublings per hour; and is often referred to as the growth rate.
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