Question

1. Describe how you could use a turbidity measurement to tell how many colonies you would expect from plating a culture of a given OD.
2. Escherichia coli can grow at a higher temperature in a complex medium than in a defined medium. Why?
3. What is Taq polymerase and why is important?

Answer 1

The method is known as spectrometry.Spectometer is used to count the bacterial colonies by determining increase in cell mass which indicates the growth of the microorganisms bacterias are unicellular.

Increased turbidity in a culture is another index of bacterial growth and cell numbers ie the biomass.By using the spectrophotometer, the amount of transmitted light decreases as the cell population increases. The transmitted light is converted to electrical energy, and this is indicated on a galvanometer. The reading, called absorbance or optical density, indirectly reflects the number of bacteria. This method is faster than the standard plate count but is limited because sensitivity is restricted to bacterial suspensions of 107cells or greater. This procedure we can determine the colonies of bacteria.

Escherichia coli can grow at a very high temperature the cell growth increases with an increase in temperature.complex media usually contain complex materials of biological origin such as blood or milk or yeast extract or beef extract, the exact chemical composition of which is obviously undetermined.Complex media contain often protein hydrolysate which are are excellent natural sources of amino acids, peptides and proteins in growth media. It is the most important source for nitrogenous nutrients.This is why E coli are grown in complex medium at high temperature than defined medium.

Taq polymerase is an enzyme which is used to copy DNA.And It is isolated from a heat-loving bacterium that is found in hot springs, so the enzyme doesn't break down at the high temperatures necessary for copying DNA using a polymerase chain reaction.It plays a major role in pcr and for copying of DNA hence very important.