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Project:OD600 Measurement: Difference between revisions
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[[File:Bacterial growth.png|thumb|right]] | |||
In the molecular biology of bacteria, it is often useful to obtain bacteria at the most productive stage of their population growth cycle. This stage is known as exponential phase, and more specifically the mid-exponential phase of growth is the most productive of that. This phase is also referred to as the "log phase", because plotting the log of the cell number against time produces a straight line. | In the molecular biology of bacteria, it is often useful to obtain bacteria at the most productive stage of their population growth cycle. This stage is known as exponential phase, and more specifically the mid-exponential phase of growth is the most productive of that. This phase is also referred to as the "log phase", because plotting the log of the cell number against time produces a straight line. | ||
OD600 is often used to estimate the current growth phase of a bacteria or other cells in suspension. It means the "optical density of the sample to light of 600nm". The measured OD600 of the sample relative to a plain reference sample, gives an estimate of the concentration of the cells in the liquid, which can be used to estimate the growth phase of the population. | OD600 is often used to estimate the current growth phase of a bacteria or other cells in suspension. It means the "optical density of the sample to light of 600nm". The measured OD600 of the sample relative to a plain reference sample, gives an estimate of the concentration of the cells in the liquid, which can be used to estimate the growth phase of the population. | ||
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The 2 samples are then placed in an incubator, and over time as the number of bacteria grow, this relative value will change according to the growth phase of the bacteria. | The 2 samples are then placed in an incubator, and over time as the number of bacteria grow, this relative value will change according to the growth phase of the bacteria. At the beginning the OD600 measures close to zero, because the bacterial population in is the early lag growth phase, and there are few bacteria in total. Reproduction accelerates, and the bacteria are at their most reproductive during the log or exponential phase, which usually corresponds to 0.5-0.6 OD600. Beyond these values, the bacterial population will stabilize and then decline. | ||
[[File:Growthcurve.jpeg|300px]] | [[File:Growthcurve.jpeg|300px]] | ||
600nm is in the visible wavelength an is approximately orange. These are some 605nm LEDs from ebay | 600nm is in the visible wavelength an is approximately orange. These are some 605nm LEDs from ebay. 600nm light is preferred to UV for example, because its much less phototoxic at those energies. It is also a wavelength at which organic materials readily absorb light. | ||
[[File:16227785328 baea849a33 c.jpg|400px]] | [[File:16227785328 baea849a33 c.jpg|400px|right]] | ||
[[File:27030-004-293E0372.jpg]] <br /> | [[File:27030-004-293E0372.jpg]] <br /> | ||
