Prokaryotic GrowthI. What is growth?A. Population growth:B. Cellular growth:C. What happens during growth?D. Generally cells make all their constituents until they havetwice as much and then they divide.II. How do prokaryotes grow?A. By a process called ____________ fission.B. The time required for a population of cells to double is:C. E. coli doubles every 20 min. Some take days to double.III. Population growth can be quantified because:A. Population growth is _____________________.• 1 cell >> 2 cells >> 4 cells >> 8 cells >> etc.• On a logarithmic scale cells # follows a_______________ line.IV. Population growth can be studied through growth curve analysis:A. One way to do this is by growing cells in a a closed system:which is called ______________ culture.This is done by:V. The growth phases in closed system:A. Lag Phase:B. Exponential phase:C. Stationary phase:D. Death phase:VI. Growth curve analysis is a classic approach to investigatingphysiological response of strains to a particular culturecondition:A. Example: determine temperature optimum of a new strain.VII. Here is how to quantify certain parameters of a growth curve:A. There is a direct relation between number of cellsinitially, and number of cells after a period of exponentialgrowth.• N=N02n• (N=final cell number, N0= initial cell number, n=number of generations or doublings)• Example: You start out with 50 cells, and you wantto end up with about 50,000.• How many doubling times should you allow?VIII.Calculating generation time g (doubling time):A. Calculation is only done in the exponential part of thegrowth curve.B. From the previous example, if it took 3 hours to growfrom 50 cells to 50,000 what would be the doubling timeor generation time?Enumerating Prokaryotic Growth• What are common ways that microbiologists measure growth? Total Cell Counts:• Use a microscope to obtain the cell counts• Calculate a cell density• Some problems with the method:• can’t count dilute samples• cells might be too small to count• cells might swim aroundViable Count:• If you are interested in only the living bacteria, viablecounts would be useful• Viable =• To determine the viable cell count:• Often called:• The bacterium that made a colony is referred to as:• If samples are to concentrated with bacteria what can youdo?• E. coli can get up to 3-5 x 109 cells/ml• 0.1 ml is usually used for spread plating.• That is 108 cells! That’s too much, will form a lawnof cells.• The solution is:Example:Indirect measurement of cell numbers using absorbance:1) Rapid method for estimating cell numbers.2) Bacterial suspensions look cloudy.3) Shine a light through and it scatters due to the turbidity ofthe culture.4) The spectrophotometer generates an optical densitynumber.5) 540, 600, 660 nm are typical wavelengths use for the ODmeasurements.SpectrophotometerOD measurement vs.microbial growthA. When you monitor growth vs. time:B. The data can be used to:C. Good value to compare physiological characteristics of twostrains.Pluses and minuses of various enumeration methods.Indirect countsViable countsDirect