443 Lecture 15 Growth (1)

Direct physical measurement of dry weight wet weight

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Unformatted text preview: says Requires a fixed standard to relate chemical acFvity to cell mass and/or cell numbers Turbidity •  Spectrophotometer –  OpFcal density or OD –  Usually 600 nm λ •  Limited sensiFvity –  107 ­ 109 cells / ml –  Reads dead and live cells same Method Applica,on Comments Turbidity measurement EsFmaFons of large numbers of cells in clear liquid media and broths Fast and nondestrucFve, but cannot detect cell densiFes less than 107 cells per ml Measurement of Growth •  1. Direct physical measurement of dry weight, wet weight, volume of cells a\er centrifugaFon, or counts of the number of cells. •  2. Direct chemical measurement of some chemical component of the cells, such as total N, total protein, or total DNA content. •  3. Indirect measurement of chemical ac,vity such as the rate of O2 producFon or consumpFon, CO2 producFon or consumpFon, etc. •  4. Turbidity measurements to determine the amount of light scaSered by a suspension of cells. Ways to grow cells •  Batch •  ConFnuous –  “Bleed and Feed” –  Chemostat •  Synchronous Ln (number of cells) Batch Culture Growth staFonary death lag log (exponenFal) Time ConFnuous Culture ExponenFal growth Media in / g = culture volume /2 Synchronous culture •  Newly divided cells smaller •  Useful for studying cell cycle •  Ephemeral –  g not exact Cell Cycle A 2A Chromosome replicaFon Cell division 1 2 Time from Division to iniFaFon of DNA synthesis DNA synthesis Time from compleFon of DNA synthesis to Division CoordinaFon of Cell AcFviFes •  Rate of Cell Division not equal to the rate of chromosome...
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This document was uploaded on 11/11/2013.

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