Microbiology Day 10 - Microbiology Day 10 Cell Counting...

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Microbiology Day 10 Cell Counting Slide 1 Hemocytometer Slide 2 Growing? Is it growing? That would be at the log stage Overgrown = stationary phase where leads to degrading and stop cells How do we count cells? 1) Haemocytometer/Coulter counters 2) Serial dilutions and units is cells/mL No matter what you do, you get dilutions, and this is just dilutions with cells. Slide 3 Advantages: This is viable cells since they grow on plate. You won’t see cells. Also, plating does cause cell lysis, since osmotic pressure will make bacteria dry out and if you lyse. Each colony is one cell and clones of one cells Disadvantages: Assume we know what bacteria grows on (we have good medium). Problem with the technique is that it takes time, work (a lot of effort) and money (for medium). If you kept doing it for studies, it would be a lot of money, So you do absorbance curve along with serial dilutions the first time, so you can relate absorbance with serial dilution. Then, you do absorbance by itself after that and get number of cells from that relationship. If you get a relationship between culture and absorbance, it should give you a good means of relating the two. What if original culture is unknown? You have to do an estimate first in this case. As an example, we have an overnight culture of E. coli. We assume that it has 1 x 10^9 cells/mL. How does cell/mL differs from CFU. CFU = alive cells and cells/mL is all cells.
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