2 Growth and Cell Division Microbial Growth Defined:Mother or parent cell doubles in sizeDivides into two daughter cellsMicrobial growth is defined as the increase in the number of cells, which occurs by cell division
3 Cell DivisionBinary fission (equal cell division): A cell duplicates its components and divides into two cellsSeptum: A partition that grows between two daughter cells and they separate at this locationBudding (unequal cell division): A small, new cell develops from surface of exisiting cell and subsequently separates from parent cell
12 Phases of GrowthConsider a population of organisms introduced into a fresh, nutrient mediumSuch organisms display four major phases of growthThe lag phaseThe logarithmic phaseThe stationary phaseThe death phase
14 The Lag Phase Organisms do not increase significantly in number They are metabolically activeGrow in size, synthesize enzymes, and incorporate molecules from mediumProduce large quantities of energy in the form of ATP
15 The Log Phase Organisms have adapted to a growth medium Growth occurs at an exponential (log) rateThe organisms divide at their most rapid ratea regular, genetically determined interval (generation time)
16 Stationary Phase:Cell division decreases to a point that new cells are produced at same rate as old cell die.The number of live cells stays constant.Decline (Death) Phase:Condition in the medium become less and less supportive of cell divisionCell lose their ability to divide and thus dieNumber of live cells decreases at a logarithmic rate
17 Growth in Batch Culture Growth is generally used to refer to the acquisition(perolehan) of biomass leading to cell division, or reproductionA “batch culture” is a closed system in broth medium in which no additional nutrient is added after inoculation of the broth
18 Growth in Continuous Culture A “continuous culture” is an open system in which fresh media is continuously added to the culture at a constant rate, and old broth is removed at the same rate.This method is accomplished in a device called a chemostat.Typically, the concentration of cells will reach an equilibrium level that remains constant as long as the nutrient feed is maintained.