Nutrition and Metabolism of Bacteria Flashcards
Why does ATP hydrolysis release energy?
- ATP is an unstable, high-energy molecule due to the presence on 2 phosphoanhydride bonds.
- Its hydrolysis is an exergenic reaction, releasing energy.
- Upon enzyme-catalysed hydrolysis, ATP dissociates into ADP and phosphate, releasing energy and allowing coupled thermodynamically unfavoured reactions to take place (free energy input required).
Why does ATP hydrolysis release energy?
- ATP is an unstable, high-energy molecule due to the presence on 2 phosphoanhydride bonds.
- Its hydrolysis is an exergenic reaction, releasing energy.
- Upon enzyme-catalysed hydrolysis, ATP dissociates into ADP and phosphate, releasing energy and allowing coupled thermodynamically unfavoured reactions to take place.
How is ATP formed from ADP?
Energy obtained from the oxidation of nutrients is used to convert ADP into ATP.
Bacteria can be classified based on their source of energy. What are the 4 sources of energy?
sunlight
chemical
radioactive
oxygen requirements
Bacteria can be classified based on oxygen requirements. There are obligate aerobes, obligate anaerobes, facultative anaerobes, aerotolerant anaerobes and microaerophiles. What does each term mean?
Obligate aerobes - require Oxygen for growth
Obligate anaerobes - Oxygen is toxic
Facultative anaerobes - can live without oxygen
Aerotolerant anaerobes - can tolerate oxygen
Microaerophiles - need some Oxygen
Bacteria can be classified based on oxygen requirements. There are obligate aerobes, obligate anaerobes, facultative anaerobes, aerotolerant anaerobes and microaerophiles. What does each term mean?
Obligate aerobes - require Oxygen for growth
Obligate anaerobes - Oxygen is toxic
Facultative anaerobes - can live without oxygen
Aerotolerant anaerobes - can live with oxygen
Microaerophiles - need some Oxygen
What is selective media?
Selective media - suppress growth of unwanted bacteria and promotes growth of target bacteria.
What is differential media?
Differential media - used to distinguish one bacteria from another - all bacteria grow but only certain bacteria can metabolise a dye and cause a colour change.
What did Robert Koch come up with?
Provided proof that microorganisms were the cause of infectious diseases.
Koch’s postulates show that certain microorganisms can be the cause of disease. Describe the 4 steps in Koch’s postulates process.
- Organism must be present in all cases of the disease (not in healthy individuals)
- Organism is isolated from infected animal and cultivated in pure culture away from healthy body.
- Cells from the pure culture, when inoculated into healthy animal, must give rise to characteristic symptoms of disease.
- Organism must then be re-isolated and grown and shown to be the same as the original organism.
What are the main environmental determinants of microbial growth?
Temperature, pH, oxygen, light, moisture, nutrient type and availability, environment.
Describe Psychrophiles.
Microbes which grow best at low temperatures.
Optimum = -10 to 20
Enzymes denatured at moderate temperatures.
Fluidity and flexibility of membranes are maintained by polyunsaturated fatty acids in lipid membranes.
Describe Mesophiles.
Microbes which grow at moderate temperatures.
Optimum = 20 to 45
Most common = are pathogens of mammals
Can survive at lower temperatures but will have slow rate of growth.
Describe Thermophiles.
Microbes which grow at very high temperatures.
Optimum = >45
Enzymes tolerate near boiling temperatures.
Enzymes used in industry for faster reaction.
Name 3 enzymes which can breakdown the toxic metabolites created when some microbes are exposed to oxygen.
Superoxide dismutase, catalase, and peroxidase
What is the optimal pH range for most bacteria?
pH 7.4 - 7.6
What is the optimal pH range for Enterobacteriaceae?
pH 4.3 - 9.5
What is the optimal pH range for moulds and yeasts?
pH 4 - 6
What are halophiles?
Microbes that require a salt rich environment for growth and survival.
What are osmophiles?
Organisms that can grow in very high solute conditions.
What happens when eubacteria is exposed to UV light?
UV light is lethal to eubacteria = non-photosynthetic bacteria - results in genetic mutation and cell death.
Certain bacteria produce pigments to protect themselves from strong sunlight/UV. What are these pigments called? How does it work?
Carotenoids.
They absorb sunlight and dissipate the energy thereby protecting themselves.
Metabolism fact.
Catabolic reactions provide the energy to drive the anabolic reactions which result in growth.
Many enzymes require cofactors in order to function. What are cofactors?
A cofactor is an inorganic non-protein chemical compound or metallic ion that is required for an enzyme’s activity as a catalyst, a substance that increases the rate of a chemical reaction.
Many co-factors are vitamins (nicotinic acid/niacin or vitamin B1 (thiamine) or B2 (riboflavin).
