Microbiology - Finished Flashcards
What is the definition of microbiology?
The study of organisms that are too small to be seen clearly without the use of a microscope
What are the 3 main shapes of bacteria?
Round (coccus)
Rod shaped (basillus)
Spiral (spirillium)
What colour do gram positive bacteria stain?
Purple
What colour do gram negative bacteria stain?
Red
What processes are involved in gram staining?
Application of crystal violet
Application of iodine
Alcohol wash
Application of saffarin
Why do the different bacteria stain differently?
The different staining properties are due to the differenve in the chemical composition of their cell walls. The Gram negative bacteria have a more complex wall structure
Which bacteria does penecillin act on?
Gram positive bacteria
Both bacteria have cell walls made of murein however gram negative bacteria have an additional outerlayer of lipopolysaccharide. Penicillin acts on the murein wall layer and makes it sstructurally weak.
What conditions are needed to grow bacteria?
- Water
- Nutrients (in medium)
organic form of carbon (usually glucose)
nitrogen
Growth factors e.g. vitamins/minerals - Particular pH/temperature
- Presence/absence of oxygen
What are obligate aerobes
Bacteria that can only survive in the presence of oxygen
What type of bacteria survives in both the presence and absence of oxygen (but grows better better with oxygen)?
Facultative anaerobes
What are obligate anaerobes?
Only survives in the absence of oxygen
What condition do pathogenic bacteria grow best?
anaerobic
What is aseptic technique?
Use of sterilized equiptment and methods that prevent contamination of culture or environment with unwanted organisms.
What is involved in aseptic technique?
- Sterilization
Autoclave equiptment to kill bacteria & endospores
Heat innocluating loops untill it glows red
Flame mouth of glass tubes and bottles - After Sterilization - Prevent contamination
Do NOT but culture bottle cap on to the bench
Use of sterile air supply - Working in a sterile cabinet/working near a bunsen burner for updraft - Heat labile plastics are iradicated
What is sterilization?
Removal or distruction of all living organisms and theri spores
What are the 2 methods of counting bacteria?
Total cell count = number of living + dead bacteria cells
Viable cell count = number of living bacterial cells
what do you do to find a viable cell count?
Take a 1cm3 sample from your source and place it in your petri dish using aseptic technique.
Incubate for a day at 25C
Count how many colonies have appeared. - ASSUME ONE CELL GIVES WAY TO ONE COLONY
What is one limitation of this method for finding a viable cell count?
Does not take clumping into account whic could cause an underestimation of the actual number of living bacteria present.
What happens if there are too many bacteria on the dish for you to count?
Dilute the sample. Dilutions are usually carried out in 10 fold (1cm into 9cm) or 100 fold (1cm into 99cm / 0.1cm into 9.9cm)
use around 3 dilutions for each sample, taking the next sample out of the tets tube before.
Number of bacteria per cm in original sample = no. of colonies x dilution factor
What is Industrial Fermentation?
anaerobic respiration in yeast
Large scale culturaling of bacterial and fungal cells in huge tanks known as industrial fermenters.
Why is it good to culture bacteria and fungus in large batches?
The cells can produce useful products such as alcohol, biogas, insulin & antibiotics
What is the first main principle of industrial fermentation?
A pure culture of the organism is needed for the formation of a pure product.
Maintain purity by:
- Sterilized vessel & growth medium
- Filters to prevent contamination
- Aseptic conditions & handling required
What is th secnd main principle of industrial fermentation?
Organism must be supplied with suitable conditons for growth (usually without comppetition) fr maximum efficiency.
To provide suitable growth conditions:
- Forced aeration - provide enough oxygen for maximum growth and mix culture
- Spargers improve aeration by dispersing are as bubbles through meduim
- Mixing devices such as impellers
- Temperature must be monitored - water jacket removes excess heat produced by respiration
- Temperature & pH monitors
What produces penecillin?
A species of fungus known as Penicillium Notatum
How is Penicillium Notatum grown?
Using a batch culture
What is Batch Culture?
In a batch Culture:
- All of the nutrients are added at the start of the culture process
- No microoganisms are added or removed during the incubation process
- The product is harvested at the end of the incubation process
What is continuous culture?
Where nutrients are added and cells harvested at a continuous rate.
How does the fungus produce penicillin?
Produced after the Growth(log) phase, when glucose is depleted. This reflects the need for the fungus (when the fungus is free living) to reduce competition when nutreit sources are depleted. It would normally release penicillin to kill off all of its competitors
How is the penicillin removed?
The fungal mycelium is removed by filtration of the culture fluid and the antibiotic is purified from the residual liquid.
