Measurement Of Growth : [Cell Count]
Growth - Increase in Mass or Size with Time is Defined as "Growth".
Measurement Of Growth -
¹) Direct Microscopic Count / Total Cell Count :
In this method Petroff-Hauser Chamber is used where this method is simply a glass slide divided into tiny square wells of known as the 'Area & Depth'.
A drop of culture is placed on the silde and when a cover slip is applied each square well in the grid holds a known amount of Volume of liquid.
The number of cells is counted microscopy and the value is converted into cells per mili-liter using conversion factor which is based on the total number of the square wells counted and their volume.
A more sophisticated method is Electronic Cell Counting , The bacteria suspended in the saline solution are placed in a chamber with an electrode separated by a second chamber filled with the same saline solution and aslo provide with an electrode.
A microscopic pore separates the two chambers the bacterial suspension is pumped through the pore into the Second (II) chamber where ever a bacterium passes through the pore the electrical conductivity of the circuit decreases because the electrical conductivity of bacterial cell is less than that of saline solution.
This lead a result in a voltage pause i.e. 'Counted Electrically' The electronic counter has an advantage because they also measure size of bacterium beacuse of this reason the size of Pause is proportional to the size of Bacterium.
²) Total Viable Count :
Total Viable Count (TVC), gives a quantitative estimate of the concentration of microorganisms such as bacteria, yeast or mould spores in a sample. The count represents the number of colony forming units (cfu) per g (or per ml) of the sample.
The Total Viable Count in this method serially dilution of thr culture is spreaded on the surface of growth medium (Distributed using pour plate technique) and colonies are allowed to develop for counting.
Viable cell count will under estimate the numbers of live cells if the cells are clupmed , since each clump of cells will give rise to a Single Colony.
To calculate the cell concentration, take the average number of viable cells in the four sets of 16 squares and multiply by 10,000 to get the number of cells per milliliter. Then, multiply this by five to correct for the one in five dilution from the trypan blue addition.
Some bacteria plate with poor efficiency single cells give rise to colonies with low frequencies.
A TVC is achieved by plating serial tenfold dilutions of the sample until between 30 and 300 colonies can be counted on a single plate. The reported count is the number of colonies counted multiplied by the dilution used for the counted plate.
To quantify the number of cells in a culture, the cells can be simply plated on a petri dish with growth medium. If the cells are efficiently distributed on the plate, it can be generally assumed that each cell will give rise to a single colony or Colony Forming Unit (CFU).
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