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## How do you calculate viable cell count?

To calculate viability:

1. Add together the live and dead cell count to obtain a total cell count.
2. Divide the live cell count by the total cell count to calculate the percentage viability.

What are the methods used for counting viable bacterial cells?

The two most widely used methods for determining bacterial numbers are the standard, or viable, plate count method and spectrophotometric (turbidimetric) analysis. Although the two methods are somewhat similar in the results they yield, there are distinct differences.

### Which of the following method is used for viable count of a culture?

To determine the viable count of culture, we must use a technique that allows viable cells to multiply, such as the plate-count method or membrane-filter method. 4. The number of bacteria per ml depends on the dilution of the sample.

Which method is used during the viable plate count procedure?

Viable Count In this method, serial dilutions of a sample containing viable microorganisms are plated onto a suitable growth medium. The suspension is either spread onto the surface of agar plates (spread plate method), or is mixed with molten agar, poured into plates, and allowed to solidify (pour plate method).

#### How do you calculate the number of bacteria?

How to calculate the number of bacteria in a population

1. Example.
2. The mean division time for bacteria population A is 20 minutes.
3. In order to answer this, you can split the calculations into two sections.
4. If the bacteria grow for six hours, each bacterium will divide 3 times per hour × 6 hours = 18 times.

What is considered a countable plate for the viable plate count assay?

The countable plate has between 30 and 300 colonies. More than 300 colonies would be difficult to count, and less than 30 colonies is too small a sample size to present an accurate representation of the original sample.

## What is the standard plate count method used for?

The most commonly used microbiological count method is the standard plate count (SPC) agar method. This method is used by the dairy industry for estimating the microbial populations in most types of dairy products and samples and for determining quality and sources of contamination at successive stages of processing.

What is a viable plate count?

The viable plate count, or simply plate count, is a count of viable or live cells. It is based on the principle that viable cells replicate and give rise to visible colonies when incubated under suitable conditions for the specimen.

### What is the purpose of a serial dilution in a viable plate assay?

Dilution is the process of making a solution weaker or less concentrated. In microbiology, serial dilutions (log dilutions) are used to decrease a bacterial concentration to a required concentration for a specific test method, or to a concentration which is easier to count when plated to an agar plate.

What is the principle of serial dilution?

Serial dilution is a common technique used in many immunologic procedures. A small amount of serum or solute can be serially diluted by transferring aliquots to diluent. One of the most common series doubles the dilution factor with each transfer (1:2, 1:4, 1:8 …).

#### How do you calculate serial dilution factor?

In serial dilutions, you multiply the dilution factors for each step. The dilution factor or the dilution is the initial volume divided by the final volume. For example, if you add a 1 mL sample to 9 mL of diluent to get 10 mL of solution, DF=ViVf = 1mL10mL=110 .

How do you calculate the amount of water needed to dilute a solution?

To make a fixed amount of a dilute solution from a stock solution, you can use the formula: C1V1 = C2V2 where: V1 = Volume of stock solution needed to make the new solution. C1 = Concentration of stock solution.

## What is the ratio 10 to 1?

For example, a 10:1 ratio means you mix 10 parts water to 1 part chemical. The amount of each liquid changes depending on the ratio used, and the size of the container.

What is a 1 to 4 dilution?

A 1:4 dilution ratio means that a simple dilution contains one part concentrated solution or solute and four parts of the solvent, which is usually water.

### How do you do a 1 to 2 dilution?

For example, a 1:2 serial dilution is made using a 1 mL volume of serum. This expression indicates that 1 mL of serum is added to 1 mL of H20 and then mixed. This initial dilution is 1:2. Then, 1 mL of this dilution is added to 1 mL of H20 further diluting the sample.

How do dilution factors work?

The dilution factor may also be expressed as the ratio of the volume of the final diluted solution to the initial volume removed from the stock solution. For example, if 100 mL of a stock solution is diluted with solvent/diluent to a total, final volume of 1000 mL, the resulting dilution factor is 10.

#### How do you write a dilution ratio?

A dilution ratio is usually written as [amount of carrier]:[amount of product]. So in the case of 25:1, this means [25 parts of a carrier]:[1 part of the product]. Parts = the measuring unit. For example: liter, milliliters, kilogram etc.

What does a dilution factor of 1 mean?

Dilution factor is a notation often used in commercial assays. There is often confusion between dilution ratio (1:n meaning 1 part solute to n parts solvent) and dilution factor (1:n+1) where the second number (n+1) represents the total volume of solute + solvent.

## What is dilution factor in bod?

Dilution is needed to prevent the depletion of entire oxygen present in in BOD bottle in less than incubation period of 5 days. For a valid BOD test APHA manual specifies some min DO of 1 mg/L to be present in the bottle after end of 5 days and DO consumed should be at least 2mg/L during incubation.

What is BOD formula?

Biochemical Oxygen Demand ???, ??/? = ?1 − ?2 ? When the dilution water is seeded ?????/?, = ?1 − ?2 − ?1 − ?2 ? ? Where: D1: Dissolved oxygen of diluted sample immediately after preparation, mg/L D2: Dissolved oxygen of diluted sample immediately after 5day incubation at 20⁰C, mg/L B1: Dissolved oxygen of seed control …

### How do you calculate the dilution factor of a BOD test?

1. BOD and COD number in wastewater are more homogenous than faecal sludge waste. Its values tend to vary from one place to another .
2. Data. BOD5(mg/l)
3. Data. BOD/COD Ratio.
4. Dilution factors will be determined: (
5. Ratio. BOD/COD.
6. DO0 (mg/L) △DO O2 Five Days Consumption (mg/L) 7.9.
7. 105. 148.
8. 137. 127.

What does 50X dilution mean?

A dilution is a technique used to make a solute (for example EDVOTEK’s 50X TAE) less concentrated by adding a solvent (distilled water). In other words, to get the workable concentration of 1X, you will dilute the initial stock (50X) 50 times!

2021-05-14