Bacterial metabolism Flashcards
Define the terms “metabolism”, “catabolism” and “anabolism”
Metabolism
* is all chemical reactions occurring inside the cell for them to survive and reproduce
Catabolism
* is the breaking down of fuel sources for energy and basic building blocks for biosynthesis
Anabolism
* is the building of new organic molecules from smaller precursors
What do bacteria need energy for?
- Chemical work: anabolism
- Transport work: take up nutrients, eliminate wastes, maintain ion balance
- Mechanical work: cell moving around, moving materials into cell
CTM
What are the sources of energy for bacteria?
- Lipids
- Light
- Iron
- Oxygen
- Carbohydrates
- Proteins
- Water, vitamins, salts
- Inorganic and organic molecules molecules
What are the two types of media used to grow bacteria?
• Defined media: all components are known
- Complex media: containing unknown components
What are the physical properties of media used to grow bacteria?
• Liquid: useful for large-scale growth
• Solid: useful for isolation of particular microbes. A solid base helps isolate colonies, but if it’s in a liquid form, it will mix around with other colonies
* Most common form of solid media is agar. It is resistant to degradation
What are growth conditions needed for media?
TOP
• Temperature: Most grow at 37 D (mesiophiles), 0D (psychrophiles), 50D -115D (thermophiles)
- Oxygen: Some NEED O2 (strict aerobes), some may prefer 02 but can survive without it (facultative aerobes), some prefer NO O2, but can survive with it (facultative anaerobic), and some need NO o2 (strict anaerobes)
• pH: neutral (neutrophiles), can vary from 0 (acidophiles) to 11 (alkiphiles)
What are the four ways to quanitfy bacteria in a media?
- Cell counting under a microscope
- Serial dilution and plating
- Optical density of culture
- Quantitative PCR
Describe cell counting under a microscope
Achieved with a cover slip with grid lines. Helps to determine the volume of liquid within that slide, and multiply it with the total amount of bacteria in liquid.
Advantage: easy to do, simple maths, inexpensive, instant results.
Disadvantage: human error, tedious
Describe serial dilution and plating.
Keep diluted a bacterial solution with sterile liquid, and then plating each diluted solution. Then, count the amount grown on the plate, and multiply by dilution factor.
Advantage: easy. Disadvantage: Have to wait for bacterial samples to grow
Describe optical density.
- Optical density, is a measurement of a refractive medium’s ability to slow or delay the transmission of light
- The slower that light is able to travel through a given medium, the higher the optical density of the medium
- Light is absorbed by the molecules within the solution, meaning it will come out at a lower intensity than when it entered
Advantage: Quick, no work
Disadvantage: not very accurate, depends on calibration of device
Describe quantitative PCR.
- DNA is extracted from a bacterial colony
- The DNA is placed into the solution containing primers and fluorescent dyes, amongst other things
- The DNA is heated, and the double helix structure unwinds, separating into two strands
- The solution is cooled down and primers attach to their corresponding, exposed nucleotides
- TAQ polymerase will complete the rest of the strand sequence after the primers have attached
- Meanwhile, the fluorescent dye’s attach to the DNA strands
- This process is constantly repeated
- The sample will fluoresce, and the detector will pick up these signals and graph them
The more DNA in the sample initially, the fewer amount of cycles it will take for the sample to fluoresce.
The fewer DNA in the sample initially, the larger the amount of cycles it will take for the sample to fluoresce.
What are the 4 phases of a bacteria’s life?
- Lag
- Exponential
- Stationary phase
- Death phase
Describe the lag phase
Needs a new set of proteins/enzymes to adapt to new environment. Cells may be old, depleted of ATP, vitamins, ribosomes OR injured, require repair & recovery
Describe the exponential phase
Rate of growth is maximal and constant. Balanced growth; cell components are produced at a constant rate relative to each other
Describe the stationary phase
Due to nutrient limitation, oxygen limitation, waste build up. Number of cells remain constant; balance between growth and death or not dividing but remain viable.
Cells go into starvation mode: express proteins to help survival in stressful conditions eg. cell wall cross-linking, spore formation, protein & DNA protectants
