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Hub AI
Colony-forming unit AI simulator
(@Colony-forming unit_simulator)
Hub AI
Colony-forming unit AI simulator
(@Colony-forming unit_simulator)
Colony-forming unit
In microbiology, a colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable and able to multiply via binary fission under the controlled conditions. Determining colony-forming units requires culturing the microbes and counting only viable cells, in contrast with microscopic examination which counts all cells, living or dead. The visual appearance of a colony in a cell culture requires significant growth, and when counting colonies, it is uncertain if the colony arose from a single cell or a group of cells. Expressing results as colony-forming units reflects this uncertainty.
The purpose of plate counting is to estimate the number of cells present based on their ability to give rise to colonies under specific conditions of temperature, time, and nutrient medium. Theoretically, one viable cell can give rise to one colony through replication. However, solitary cells are the exception in nature, and in most cases the progenitor of a colony is a mass of cells deposited together. In addition, many bacteria grow in chains (e.g. Streptococcus) or clumps (e.g. Staphylococcus). Estimation of microbial numbers by CFU will, in most cases, undercount the number of living cells present in a sample for these reasons.
Typically, ten-fold serial dilutions of samples are plated to ensure that they will yield a countable number of colonies. Plating volumes generally range from 100 μL to 1 mL. The colonies on the plate are counted and then the CFU/g (or CFU/mL) of the original sample is calculated based on the volume plated and the dilution factor.
An advantage to this method is that different microbial species may give rise to colonies that are clearly different from each other, both microscopically and macroscopically. The colony morphology can be of great use in the identification of the microorganism present.
A prior understanding of the microscopic anatomy of the organism can give a better understanding of how the observed CFU/mL relates to the number of viable cells per milliliter. Alternatively it is possible to decrease the average number of cells per CFU in some cases by vortexing the sample before conducting the dilution. However, many microorganisms are delicate and would suffer a decrease in the proportion of cells that are viable when placed in a vortex.
Concentrations of colony-forming units can be expressed using logarithmic notation, where the value shown is the base 10 logarithm of the concentration. This allows the log reduction of a decontamination process to be computed as a simple subtraction.
Colony-forming units are used to quantify results in many microbiological plating and counting methods, including:
However, with the techniques that require the use of an agar plate, no fluid solution can be used because the purity of the specimen cannot be unidentified and it is not possible to count the cells one by one in the liquid.
Colony-forming unit
In microbiology, a colony-forming unit (CFU, cfu or Cfu) is a unit which estimates the number of microbial cells (bacteria, fungi, viruses etc.) in a sample that are viable and able to multiply via binary fission under the controlled conditions. Determining colony-forming units requires culturing the microbes and counting only viable cells, in contrast with microscopic examination which counts all cells, living or dead. The visual appearance of a colony in a cell culture requires significant growth, and when counting colonies, it is uncertain if the colony arose from a single cell or a group of cells. Expressing results as colony-forming units reflects this uncertainty.
The purpose of plate counting is to estimate the number of cells present based on their ability to give rise to colonies under specific conditions of temperature, time, and nutrient medium. Theoretically, one viable cell can give rise to one colony through replication. However, solitary cells are the exception in nature, and in most cases the progenitor of a colony is a mass of cells deposited together. In addition, many bacteria grow in chains (e.g. Streptococcus) or clumps (e.g. Staphylococcus). Estimation of microbial numbers by CFU will, in most cases, undercount the number of living cells present in a sample for these reasons.
Typically, ten-fold serial dilutions of samples are plated to ensure that they will yield a countable number of colonies. Plating volumes generally range from 100 μL to 1 mL. The colonies on the plate are counted and then the CFU/g (or CFU/mL) of the original sample is calculated based on the volume plated and the dilution factor.
An advantage to this method is that different microbial species may give rise to colonies that are clearly different from each other, both microscopically and macroscopically. The colony morphology can be of great use in the identification of the microorganism present.
A prior understanding of the microscopic anatomy of the organism can give a better understanding of how the observed CFU/mL relates to the number of viable cells per milliliter. Alternatively it is possible to decrease the average number of cells per CFU in some cases by vortexing the sample before conducting the dilution. However, many microorganisms are delicate and would suffer a decrease in the proportion of cells that are viable when placed in a vortex.
Concentrations of colony-forming units can be expressed using logarithmic notation, where the value shown is the base 10 logarithm of the concentration. This allows the log reduction of a decontamination process to be computed as a simple subtraction.
Colony-forming units are used to quantify results in many microbiological plating and counting methods, including:
However, with the techniques that require the use of an agar plate, no fluid solution can be used because the purity of the specimen cannot be unidentified and it is not possible to count the cells one by one in the liquid.