Notes:
1)Number of
generation = Log number of cells(end) –
Log number of cells(beginning)
0.301
Generation time =
60 min X hours
Number of generations
2)
- Lag phase - Bacteria starts to adapt to a new environment. The number of bacteria incresed slowly.
- Log phase - Bacteria starts to replicate, enzymes are produced, metabolisms start to carry out and a lot of products found in Log phase. The number of bacteria increased sharply.
- Stationary phase - Depletion of nutrients causes bacteria to stop producing.
- Death phase - The number of bacteria start to reduce because nutrient is used up and finally bacteria will just died.
3) The direct measurement of microbial growth includes plate counts, filtration, direct microscopic count and multiple table MPN test.
- Plate count - First, perform serial dilutions of a sample. Then, inoculate petri plates from serial solutions. After inocubation, count colonies on plate.
- Filtration - Water is filtered on a filter which has holes smaller than bacteria.The filter is then placed on a dish of agar and bacteria grow on the top of the filter and count the bacteria
- Direct microscopic count - Number of bacteria = number of cells counted divide by volume of area counted.
- Multiple table MPN test
There will be three sets of five tubes. The first set received 10mL of inoculum, the second set received 1mL of inoculum, the third set received 0.1mL of inoculum. The results show that the number of postitive tubes in set 1 is 5, in set 2 is 3 and in set 3 is 1. The presence of negative tubes is due to insufficient of microbes to grow in every tubes in the sets.
The number of positive tubes recorded in each set is 5-3-1. Compare the number of positive tubes with MPN table to look for the confidence limit and count for the number of bacteria.
4) The indirect measurement of mirobial growth includes turbidity. Turbidity is a measure of how much of bacteria suspended in medium decreases the passage of light through the water. The higher the number of bacteria in the medium, the lower the percent of light transmitted.
5) Sterilization is the complete removal or destruction of all viable microorganisms. Usually used in inanimate objects. ( not alive）
6) Disinfection is the removal of vegetative pathogens but not bacterial endospores. Usually used only on inanimate objects. The chemical agent is called disinfectants.
7) Sanitization is the reduction of the microbial population to a safe level as determined by public health standards.
8) Antisepsis is the removal of pathogens from living tissue. The chemical agent is called antiseptics.
8) Commercial sterilization is to kill C. botulinum endospores.
10) Degerming is the removal of microbes from a limited area. Sanitization is the lower microbial counts on eating utensils.
11) Antimicrobial agents include chemotherapy, -cidal agents and -static agents. Chemotherapy is the method to kill or inhibit the growth of microorganisms within host tissue using chemical agents. -cide is the suffix that indicating agents that kill the microbes. -static is the suffix that indicating agents that inhibits the growth of microbes. e.g Biocide/Germicide and fungicides kill microbes while bacteriostasis inhibits the growth of bacteria but not killing.
12) Microorganisms are not killed instantly and their population death usually occurs exponentially.
13) Effectiveness of antimicrobial treatment depends on number of microbes, duration of exposure, microbial characteristics, concentration or intensity of an microbial agents, population composition, temperature and local environment.
13) Microbial control agents may alternate the membrane permeability, causes damage of proteins and nucleic acids.
Activity: Bacterial growth exercise and play might microbe
My own Explorace:
1) Bacteriostatic is used to inhibit the growth of bacteria but bacteria will being killed if too much of bacteriostatic is applied on the bacteria.
2) LD50 is the dose of antimicrobial agents that able to kill 50% of bacteria/microbes.
3) The colonies in a petri dish will reported as TNTC if over 300 colonies per dish.
Reflection:
At first, I really don't understand why the inoculum have to be diluted before culture it. The purpose of dilution of the sample is to get single colony. If the inoculum is not diluted, we will get full of colony in the petri dish and make the counting very difficult. I think counting bacteria colonies is quite interesting. I like to work with the calculation. I will feel very satisfied if I able to count the bacteria colonies correctly.
Activity: Bacterial growth exercise and play might microbe
My own Explorace:
1) Bacteriostatic is used to inhibit the growth of bacteria but bacteria will being killed if too much of bacteriostatic is applied on the bacteria.
2) LD50 is the dose of antimicrobial agents that able to kill 50% of bacteria/microbes.
3) The colonies in a petri dish will reported as TNTC if over 300 colonies per dish.
Reflection:
At first, I really don't understand why the inoculum have to be diluted before culture it. The purpose of dilution of the sample is to get single colony. If the inoculum is not diluted, we will get full of colony in the petri dish and make the counting very difficult. I think counting bacteria colonies is quite interesting. I like to work with the calculation. I will feel very satisfied if I able to count the bacteria colonies correctly.
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