Activity and counting

15 important questions on Activity and counting

What major assumption is made when relating plate count results to total cell number?

That one cell forms one colony and that all the bacteria grow

How does a viable count differ from a total cell count?

A viable count refers to cells that are alive and able to grow and the total cell count observes all the cells present in the sample

How can turbidity measurements be used as a measure of cell numbers?

The amount of light scattered in a cell suspension is proportional to the number of cells present
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In liquid samples what method is used to count how many cells are present in the sample?

A counting chamber

What are disadvantages of the counting chamber?

Cells could be clumping together, moving or be on the square lines

What does it mean if a suspension is very turbid?

This means that there are more cells present

What is the lag phase of growth?

The period between inoculation and the onset of growth

What is the exponential phase of growth?

The period when the growing cell population doubles at regular intervals

What is the exponential growth phase influenced by?

The choice of media, growth conditions and the organism itself

What is the stationary phase of growth?

The phase with no net increase or decrease in cell number and thus a growth rate of zero

What happens to the metabolism in stationary phase of growth?

It shifts away from growth and the cell prepares for maintenance and survival

What is the death phase of growth?

In this phase the total number of cells decreases due to cell death

What is the monod equation?

The relationship between the specific growth rate (μ) and the concentration of a growth limiting nutrient (S)

What is the great plate count anomaly?

The observation that most of the microbes seen in the microscope cannot be grown under laboratory conditions

How can the rate of substrate utilization be measured?

With like colorimetry, gas chromatography, fluorimetry or  mass spectrometry

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