Lecture 2.10 Notes

# Lecture 2.10 Notes - Notes lecture 8 BIOL401 Growth of...

This preview shows pages 1–3. Sign up to view the full content.

Notes, lecture 8, BIOL401 – 2/10/10 Growth of Bacterial Populations Length of time it takes for the formation of 2 cells from 1 generation time ( doubling time) Generation time can vary widely among different types of bacteria Dependent on growth conditions Exponential Growth: n N N 2 0 = where n = number of doublings N = number of bacteria after n doublings N 0 = starting number of bacteria ) log (log 3 . 3 301 . 0 log log 2 log log log 2 log log log 2 0 0 0 0 0 N N N N n n N N n N N N N n - = - = = - + = = Determination of growth parameters: Semilogarithmic graph of Cell# vs Time yields straight line during exponential growth (since cells double in a constant period of time) o Such graphs can be used to estimate doubling times (see Fig 6.7) Related Growth Parameters Generation Time ( a.k.a. - doubling time ): time required for cell population to double time/doubling also time needed for single cell to divide by binary fission g=t/n, also, g = 0.301/slope Division Rate: # of generations per unit time v = 1/g, where g = generation time Specific Growth Rate : k = 0.301 n/t, where n= # of doublings, and, t = time note that n/t = 1/g so k=0.301/g g = 0.301/ k Generation time is also equal to 0.301/slope as described below: For cells that are in the exponential phase of growth, we can plot the number of cells per ml vs time on a semilog graph and we observe a straight line.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
The slope of a straight line is defined as: X Y slope = By definition, when Δ X = g (generation, or, doubling time), Δ Y = 2 However, we only get a straight line when we plot the number of cells/ml vs time on semilog paper ( i.e. when we are actually plotting time vs the log of the # of cells per ml). Therefore the linear relationship holds, when Δ X = g, and, Δ Y = log 2 So, k g g X Y slope = = = = 301 . 0 2 log ( specific growth rate) Given g slope 301 . 0 = we can multiply both sides of the equation by slope g to obtain: slope g 301 . 0 = The Growth Cycle Batch culture – closed system lag phase – cells adjust to new conditions; length variable depending on history of culture and growth conditions exponential phase – cells in healthiest state, rate influenced by environmental conditions stationary phase – exponential growth limited in batch culture, growth limited by variety of factors including, depletion of essential nutrient(s) and accumulation of waste products
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 6

Lecture 2.10 Notes - Notes lecture 8 BIOL401 Growth of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online