Microbial Nutrition Flashcards
How do viruses obtain nutrients?
Obtain ‘resources’
Why do microorganisms require food?
For synthesis of molecular constituents of the cell and as an energy supply
How do cynobacteria and algae obtain nutrients?
Photosynthesis
How do protozoa obtain nutrients?
Ingest solid food particles
How do bacteria and fungi obtain nutrients?
Receive nutrients in aqueous solution, digestion outside cell and secrete enzymes into the environment
What are the basic nutrients required for microorganisms?
Carbon, nitrogen, inorganic ions (phosphate, sulphate) essential metabolites and water
What are chemoheterotrophs?
Include bacteria, fungi, protozoa and all higher animals. They use complex organic materials for carbon and energy source
What are chemo autotrophs?
Include bacteria such as thiobacillus. They use carbon dioxide for their carbon source and use inorganic materials as energy source
What are photoheterotrophs?
Includes the purple non sulphur bacterium rhidospirillum and they use sunlight as energy source and complex organic materials as carbon source
What are photo autotrophs?
Includes all green plants, cynobacteria, and they use sunlight as energy source and fix carbon dioxide as carbon source
How do bacteria obtain energy from organic nutrients?
Respiration or fermentation
What are the three main points for respiration in microorganisms?
The substrate is oxidised by oxidising agents obtained from the environment. It gives up to 38 ATP per molecule of glucose and oxygen is used as the terminal electron acceptor in aerobic respiration
In anaerobic respiration what is the alternative terminal electron acceptor?
Carbon dioxide or inorganic ions such as sulphate and nitrate
What are the three main points for fermentation in microorganisms?
There is no overall net oxidation. The substrate is broken down by small steps and the net yield is 2 ATP per molecule of glucose
What are the three main steps in respiration?
- Through glycolysis a NADH molecule is released and the product of glycolysis pyruvic acid is used in the kreb cycle which is catalysed by the co enzyme acetyl.
- During the kreb cycle a carbon dioxide molecule, ATP and NADH are released.
- The NADH molecules are used for the electron transport chain and chemiosmosis. ATP is released and oxygen is used. Water is the final product.
Describe glycolysis and how it’s related to fermentation
2 NADH molecules are released and 2 ATP to make 2 pyruvic acid molecules. 2 NADH molecules are used to reduce the pyruvic acid to form fermentation end products like lactic acid
Name four ways of identifying bacteria
Gram stain
Catalase test
Oxidase test
O-F test
What are the comparisons of gram negative and gram positive cell walls?
Gram positive cells walls have peptidoglycan and plasma membrane. Gram negative cell walls have peptidoglycan, plasma membrane and an outer membrane
What are the 5 main steps in the gram stain procedure?
Heat fixation of the slide to ensure cells aren’t washed away.
Flood with crystal violet for 15 seconds
Flood with iodine for 15 seconds
Decolorisation by alternately flooding with alcohol and waster until no more colour is washed away.
Flood with saffronin for 15 seconds
If a bacteria is catalase positive what will be observed?
Bubbles of oxygen from hydrogen peroxide
What is the oxidase test looking for and what will happen if the test is positive?
Presence of cytochrome c oxidase and a positive result gives a blue colour
What does the O-F test look for and why is it useful?
Used to determine if gram negative bacteria metabolise carbohydrates oxidative lay or by fermentation.
It also differentiates between aerobes/ anaerobes and facultative anaerobes
What will be observed if the test is oxidative?
Green colour
What will be observed if test is fermentative?
Yellow colour
