Microbial Nutrition and Growth Flashcards
What are macronutrients?
Elements required in large amounts to build macromolecules.
What are the 4 organic macromolecules made of?
Protein: CHON(+S) - polymers of amino acids
Lipids: CHO(+P) - fatty acids and glycerol
Carbohydrates: CHO(+N) - sugars
Nucleic acids: CHONP - nucleotides
What inorganic ions are included in the macronutrients? what do they do?
K+: enzymes required in protein synthesis
Fe2+: Cytochromes (e- carriers)
Mg2+: stabilize membranes and nucleic acids
Ca2+: stabilize cell wall and plays a role in heat stability of endospores
What are micronutrients? Give 6 examples.
Elements required in very small amounts (trace elements) and serve as cofactors for enzymes. (e.g. Mn, Zn, Co, Ni, Cu, Mo)
What are growth factors?
small organic molecules required for growth; must be added to medium to grow it in lab
What are three classes of growth factors?
- Amino acids: 20 needed for protein synthesis
- Purines and Pyrimidines: AGTCU
- Vitamins: small molecules used to make organic cofactors, non-protein components required by some enzymes
What bacteria require growth factors, and what bacteria doesn’t require growth factors.
No growth factor requirements: E. coli
Many growth factor requirements: Leuconostoc mesenteroides (requires all 20 amino acids, purines+pyrimidines, and 10 different vitamins)
Where is H and O typically found?
Found in H2O and organic media components.
Where is P found?
Provided as phosphate salt (PO4^3-) as it is acquired that way in the environment. In freshwater systems, it is often limiting.
What is limiting nutrient?
A nutrient that stops growth when it runs out, despite the other nutrients present
Where does inorganic, organic and atmospheric N come from?
inorganic N: provided as salts and must be reduced to amino groups to make amino acids
organic N: provided as N rich organic molecules (e.g. amino acids/short peptides) and does not need to be reduced
atmospheric N: N2 is reduced to 2NH3 due to nitrogen fixation and is used to make amino acids, though energetically expensive. (only done by some bacteria and archaea, never eukaryotes)
What does inorganic and organic S come from?
Inorganic S: provided as salts and must be reduced to the level of S2- to make amino acids (process known as assimilative sulfate reduction)
Organic S: pre-made amino acids, less energy to assimilate.
What is a heterotroph?
A group of organisms that use organic atoms (e.g. organic acids, alcohols, carbohydrates, amino acids) where one more C is reduced.
What is an autotroph?
Use of inorganic carbon (CO2) as their sole source of carbon. Requires energy to assimilate, typically obtained through photosynthesis.
What is metabolism?
The sum total of all the chemical reactions (anabolism, catabolism) that occur in a cell.
What is the difference between catabolic and anabolic reactions?
Catabolism: energy-releasing metabolic reactions (fermentation, respiration)
Anabolism: energy-requiring metabolic reactions (biosynthesis)
What is the difference between a phototroph and a chemotroph?
chemotroph: energy source is from chemical reactions either involving organic or inorganic material
phototroph: energy source is from light
What is the difference between a chemorganotroph and a chemolithotroph?
chemorganotroph: Energy from chemical reactions involving organic material
chemolithotrophs: energy from inorganic chemical reactions
What is the difference between a heterotroph and an autotroph?
Heterotroph: use organic carbon for building cell carbon and biomass
autotroph: use CO2 to synthesize cell carbon
What are the essential macro nutrients needed for media?
C HOPKNS CaFe Mg
Carbon
Hydrogen
Oxygen
Phosphorus
Potassium
Nitrogen
Sulfur
Calcium
Iron
Magnesium
What is a defined medium?
Culture media where exact chemical composition is known, useful for studying metabolism
What is a minimal medium
Culture medium that provides the minimum nutritional requirements for growth
What is a complex medium?
Exact chemical composition is not known, often made from meat or yeast extracts made of hydrolyzed proteins with undefined chemical composition to supply a variety of growth factors.
What is a differential medium?
contains specific ingredients that distinguish which species possess and which species lack a specific biochemical process (e.g. blood agar)
What is blood agar?
A complex, differential medium made of T-soy and 5% sheeps blood to allow the differentiation of hemolytic bacteria.
What are the three results of bacteria growth on blood agar?
alpha hemolysis: faintly yellow, incomplete destruction of blood cells
beta hemolysis: bright yellow, complete destruction of blood cells
gamma hemolysis: no colour, no destruction of blood cells
What is a selective medium?
Contains ingredients that inhibit the growth of unwanted microbes and allow specific microbes to grow (e.g. mannitol salt agar)
What is mannitol salt agar?
A selective medium that contains a very high salt so that only halotolerant bacteria will grow.
What is an enriched medium?
A medium supplemented with special nutrients to encourage the growth of fastidious bacteria (e.g. blood agar, chocolate agar)
