MBIO 3812 Ex 1-5 & 6-1 Spread Plates & Viable Counts

MBIO 3812 Ex 1-5 & 6-1 Spread Plates &...

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Plate 0.1 ml samples Plate 0.1 ml samples TNTC TNTC TNTC Not enough Optimal MBIO 3812 Ex 1-5 Spread Plate Method of Isolation Ex 6-1 Standard Plate Count (Viable Counts) A standard plate count allows you to estimate how many viable/living bacterial cells are in a broth culture. Knowing the microbial density of a culture or sample is particularly important when examining food/water/environmental samples or in certain types of experiments that require specific bacterial concentrations. To determine the number of bacteria in a sample requires mastering 2 techniques: (1) preparing dilutions and (2) making spread plates for colony isolation and subsequent counting. Dilutions: The first thing needed to perform standard plate counts is the dilution of the bacterial culture you wish to count. Since a turbid bacterial culture can contain approximately 1,000,000,000 (10 9 ) colony forming units per ml (CFU/ml) it must be diluted before it can be counted. Why is the number of bacteria in a culture given in CFU/ml rather than bacteria/ml? Consider that one bacterium on the surface of an agar plate it is impossible to see let alone count; however, if that bacterium is allowed to replicate over time there eventually will be a large enough concentration of bacteria to form a visible colony that can be counted. Therefore only colonies of bacteria can be enumerated since they are visible to the naked eye rather than individual bacteria that are not. Spread Plates for Colony Isolation:
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MBIO 3812 Ex 1-5 & 6-1 Spread Plates &...

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