2. What are the differences between deep freezer storage and cryo-storage methods? Deep freezing storage and cryo-storage, methods are some of the methods frequently used to preserve microorganisms for a long term storage. Both methods use extremely low temperature to ensure the biological material remains genetically stable and metabolically inert. However both methods differ slightly from each other. Cryo-storage, also known as cryopreservation, uses liquid nitrogen to freeze the microorganisms culture. On the other hand, deep freezer storage, requires only a standard laboratory freezer. Cryopreservation involves freezing in liquid nitrogen at -196°C or in the gas phase above the liquid nitrogen at -150°C. As for deep freeze storage method,
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It often used as a cryoprotectant. Glycerol can defend against cold temperatures by depressing the freezing point of the bacteria cells, enhancing supercooling. With bacteria, adding glycerol to final concentration of 15% will help protect from damage of freezing and thawing. When the freezing point of bacterial cells lowered by the use of glycerol, its prevent the formation of ice crystal which can cause intracellular injuries. Generally, the colder the storage temperature, the longer the culture will retain viable cells. The increase in salt concentration, can damage the bacterial cell by dehydration when the bacteria stored in freezer. When the water in the freezer converted to ice, solutes accumulate in the residual free water and cause high concentration of solutes that can denature biomolecules in the cell. Ice can also rupture membranes, though this problem is more often associated with cells lacking walls, such as cultured animal cells. Glycerol provide better protection to the preserved bacteria which are exposed to room temperature for extended …show more content…
A set of serial dilutions is made from water sample collected, a sample of each is placed into a liquefied agar medium, and the medium poured into a petri dish. Dilutions are designed in order to make the calculation of the number of cells/ml in the original sample easier. The most common dilutions are 1/10, 1/100, and 1/1000. After incubation, agar plates with 30-300 colonies are counted. Greater than 300 colonies on the agar plate and less than 30 leads to a high degree of error. This range is chosen because it is high enough to have statistical accuracy, yet low enough to avoid nutrient competition among the developing colonies. For this method, one colony is assumed to be produced by one cell only. Thus colonies produced can reflect how many bacteria are present in the
It often used as a cryoprotectant. Glycerol can defend against cold temperatures by depressing the freezing point of the bacteria cells, enhancing supercooling. With bacteria, adding glycerol to final concentration of 15% will help protect from damage of freezing and thawing. When the freezing point of bacterial cells lowered by the use of glycerol, its prevent the formation of ice crystal which can cause intracellular injuries. Generally, the colder the storage temperature, the longer the culture will retain viable cells. The increase in salt concentration, can damage the bacterial cell by dehydration when the bacteria stored in freezer. When the water in the freezer converted to ice, solutes accumulate in the residual free water and cause high concentration of solutes that can denature biomolecules in the cell. Ice can also rupture membranes, though this problem is more often associated with cells lacking walls, such as cultured animal cells. Glycerol provide better protection to the preserved bacteria which are exposed to room temperature for extended …show more content…
A set of serial dilutions is made from water sample collected, a sample of each is placed into a liquefied agar medium, and the medium poured into a petri dish. Dilutions are designed in order to make the calculation of the number of cells/ml in the original sample easier. The most common dilutions are 1/10, 1/100, and 1/1000. After incubation, agar plates with 30-300 colonies are counted. Greater than 300 colonies on the agar plate and less than 30 leads to a high degree of error. This range is chosen because it is high enough to have statistical accuracy, yet low enough to avoid nutrient competition among the developing colonies. For this method, one colony is assumed to be produced by one cell only. Thus colonies produced can reflect how many bacteria are present in the