Growth & Nutrition Flashcards
What are macronutrients?
Elements required in large amounts to build macromolecules
What are the building blocks of proteins?
Amino acids
What are the building blocks of lipids?
Fatty acids and glycerol
What are the building blocks of carbohydrates?
Sugars
Are sugars polar or nonpolar and what does this mean for their solubility?
They are polar and soluble
What are the building blocks of nucleic acids?
Nucleotides
What do inorganic ions often function as?
Metabolic co-factors
What do enzymes involved in protein synthesis require?
K+
What do cytochromes (electron carriers) require?
Fe2+
What does Mg2+ help stabilize?
Membranes and nucleic acids
What does Ca2+ help stabilize?
Cell walls and heat
What are micronutrients?
Elements required in very small concentrations
What are growth factors?
Small organic molecules required for growth
What are the 3 classes of growth factors?
1) Amino acids
2) Purines and pyrimidines
3) Vitamins
What is the source of H and O?
No specific source, found in H2O and organic media components
What is the source of P?
Usually provided as phosphate salt (PO4 3-)
What is a limiting nutrient?
Growth will stop when this nutrient runs out
What is the source of inorganic N?
Salts (KNO3 or NH4Cl)
What must be done to inorganic nitrogen?
Must be reduced to NH3
What is the source of organic N?
Amino acids, which is a nitrogen rich organic molecule
What is nitrogen fixation?
N2 is reduced to 2NH3
What is NH3 used to make?
Amino acids
Which domains can do nitrogen fixation?
Bacteria and archaea
What is the source of inorganic S?
Salts (MgSO4)
What must be done to inorganic S?
Must be reduced to S2-
What is the source of organic S?
Amino acids (cysteine and methionine)
What kind of carbon do heterotrophs use?
Organic
What kind of carbon do autotrophs use?
Inorganic carbon (CO2)
What are 6 classes of culture media?
1) Defined medium
2) Minimal medium
3) Complex medium
4) Differential medium
5) Selective medium
6) Enriched medium
Describe defined medium
Exact chemical composition is known
What is minimal medium?
A defined medium that provides the minimum nutritional requirements for growth (no growth factors)
What does minimal medium allow the growth of?
Self-sufficient and “non-picky” microorganisms
Describe complex medium
- Exact chemical composition is not known
- Supply a variety of growth factors
What does differential medium allow for?
Different bacteria to be distinguished
What does selective medium contain?
Ingredients that inhibit the growth of unwanted microbes
What does enriched medium contain?
Special nutrients that encourage the growth of “picky” microorganisms
Define metabolism
The sum total of all of the chemical reactions that occur in a cell
Define catabolism
Energy-releasing metabolic reaction
Define anabolism
Energy-requiring metabolic reactions
What are chemorganotrophs?
Microorganisms that get energy from chemical reactions involving organic material
What are chemolithotrophs?
Microorganisms that get energy from inorganic chemical reactions
What are phototrophs?
Microorganisms that get energy from light
What is growth measured as?
An increase in the number of cells
What is binary fission?
Cell division following enlargement of a cell to twice its minimum size
What is generation time?
Time required for microbial cells to double in number
Is there ever mitosis in bacteria and archaea?
No
Do bacteria or eukarya have shorter generation times?
Bacteria
What is generation time dependent on?
Growth medium and incubation conditions
What is exponential growth?
Growth of a microbial population in which cell numbers double at a constant and specific time interval
What is the equation to determine final cell number using initial cell number and number of generations?
Nt = No * 2^n (Nt = final cell number; No = initial cell number; n = number of generations)
What must be plot to produce a linear graph of exponential growth?
The log scale
What is microorganism growth limited by?
Amount of nutrients and build-up of waste
Is exponential growth limited or unlimited?
Unlimited
What is growth rate?
The rate of increase in population number of biomass
What is growth rate expressed as for bacteria and archaea?
Number of doublings per hour
How can growth rate (k) be calculated?
k = (log Nt - log No) / (0.301 delta t)
How is generation time (g) calculated?
g = 1 / k
What is batch culture?
A closed-system microbial culture of fixed volume
What 4 phases are present in a typical growth curve for the population of cells grown in a closed system?
1) Lag phase
2) Logarithmic / exponential phase
3) Stationary phase
4) Death phase
What occurs in the lag phase?
- Growth = death
- Nutrient-rich and low waste
What occurs in the logarithmic / exponential phase?
Growth > death
What occurs in the stationary phase?
- Growth = death
- Nutrient poor and high waste
What occurs in the death phase?
Death > growth
What is a continuous culture?
An open-system microbial culture of fixed volume (add nutrients and take away waste at same rate)
What is a chemostat?
Most common type of continuous culture device
What is dilution rate?
The rate at which fresh medium is pumped in and spent medium is pumped out
What does concentration of a limiting nutrient control?
Population size and growth rate
Describe the Petroff-Hausser counting chamber
Each square corresponds to a calibrated volume
What are 3 limitations of microscopic counts?
1) Cannot distinguish between living and dead cells without special stains
2) Small cells can be overlooked
3) Motile cells need to be immobilized
What does a cytometer use to enumerate cells in a liquid sample?
Laser beams, flourescent dyes, and electronics
What is a viable cell count?
A measurement of only living cells capable of growing to form a population
What are the two main ways to perform plate counts?
1) Spread-plate method
2) Pour-plate method
What is needed to obtain a plate count?
- Preparation and manipulations (dilution tubes, agar plates)
- Incubation time
What is the downside to selective culture media?
It only targets particular species
Is there a medium that will grow every microbe?
Nope
What is the great plate anomaly?
Direct microscopic counts of natural samples reveal far more organisms than those recoverable on plates
How is turbidity measured?
A spectrophotometer
What is turbidity measured in?
Optical density
What happens to absorbance and light transmission as the number of particles increases?
Absorbance increases and light transmission to the photocell decreases
Does absorbance distinguish live and dead cells?
Nope
What are 3 conditions to make turbidity measurements accurate?
1) Cells must be evenly distributed throughout the medium
2) Cuvette must not have scratches
3) Culture may need to be diluted
Define cardinal temperatures
The minimum, optimum, and maximum temperatures at which an organism can grow
What occurs at the minimum temperature that an organism can grow?
- Membrane gelling
- Transport processes so slow that growth cannot occur
What occurs at the optimum temperature for an organisms growth?
Enzymatic reaction occurring at maximal possible rate
What occurs at the maximum temperature that an organism can grow?
- Protein denaturation
- Collapse of the cytoplasmic membrane
- Thermal lysis
What is a psychrophile?
Low growth temperature optimum
What is a mesophile?
Midrange growth temperature optimum
What is a thermophile?
High growth temperature optimum
What is a hyperthermophile?
Very high growth temperature optimum
What are 2 examples of mesophiles?
1) Warm blooded animals
2) Organisms in terrestrial and aquatic environments
What must psychrophiles have to prevent their membrane from gelling?
An outer shell
What are psychrotolerant organisms?
Organisms that can grow at 0 C, but have optima of 20 C - 40 C
What are 3 molecular adaptations that support psychrophily?
1) Enzymes that function optimally in the cold
2) Modified cytoplasmic membrane
3) High unsaturated fatty acid content (don’t freeze as fast as saturated fatty acids)
What life forms exist above 65 C?
Only prokaryotic
Is there phototrophy above 70 C?
No
Where are thermophiles typically found?
Terrestrial hot springs
Where are hyperthermophiles found?
Boiling hot springs and seafloor hydrothermal vents
What are 2 molecular adaptations to support thermophily?
1) Thermal stability for enzymes and proteins
2) Cytoplasmic membrane modifications to ensure heat stability
What does bacteria have to support thermophily?
Lipids rich in saturated fatty acids
What does archaea have to support thermophily?
Lipid monolayer
Are enzymes of thermophiles or mesophiles more stable?
Thermophiles
What might be the closest descendants of ancient microbes?
Hyperthermophiles
What is common to many hyperthermophiles?
Oxidation of H2
How does pH affect microbial growth?
Interactions between R groups of amino acids
What are neutrophiles?
Organisms that grow best at pH 6 - 8
What are acidophiles?
Organisms that grow best at pH
What are alkaliphiles?
Organisms that grow best at pH > 9
Give 3 reasons why microbial culture media contain buffers.
1) Each organism has an optimal growth pH
2) Some bacteria produce acids, which decreases pH
3) Some bacteria grow on amino acids, releasing ammonia, which increases pH
What is water activity?
Water availability
-The amount of water that is interacting with ions and polar compounds in solution
What is water activity expressed in?
A ratio of vapor pressure of air in equilibrium with a substance/solution to the vapor pressure of pure water
Between a cytoplasm and the surrounding environment, which typically has a higher [solute] and why?
Cytoplasm because it is small and has a lot of solute per unit volume
In what direction does water normally move with respect to a cell and its environment and what does this create?
- Into the cell
- Creates turgor pressure
What are halophiles?
Organisms that grow best at reduced water potential
What do halophiles have a specific requirement for?
NaCl
Give an example of a halophile
Many marine microbes
What are extreme halophiles?
Organisms that require high levels (15 - 30%) of NaCl for growth
Give an example of extreme halophiles
Microbes from Great Salt lake or the Dead Sea
Define halotolerant
Can tolerate some reduction in water activity of environment, but generally got best at lower solute concentrations
Give an example of a halotolerant organism
Staphylococcus aureus
What level of NaCl is best for staphylococcus aureus to grow in?
Low
What are osmophiles?
Organisms that can grow with high sugar as solute
What are xerophiles?
Organisms that can grow in very dry environments
What are the 2 rarest categories of organisms?
Osmophiles and xerophiles
How do organisms combat low water activity in their surrounding environment?
Increase internal [solute] by
- Pumping inorganic ions into cell
- Synthesizing or concentrating organic solutes
What are compatible solutes?
Compounds used by cell to counteract low water activity in surrounding environment
Define obligate aerobes
Require oxygen to live
Define strict anaerobes
Do not require oxygen and may even be killed by it
Define facultative aerobes
Can live with or without oxygen; use oxygen when it is available
Define aerotolerant anaerobes
Can tolerate oxygen and grow in its presence but cannot use it
Define microaerophiles
Can use oxygen only when it is present at levels reduced from that in air
What can be used to distinguish differences in oxygen use/tolerance?
Thioglycolate broth
Describe the thioglycolate broth of an obligate aerobe
Grows only in the oxic zone at the top of the tube
Describe the thioglycolate broth of a strict anaerobe
Grows only in the anoxic zone at the bottom of the tube
- Will have majority of growth as far down tube as possible
Describe the thioglycolate broth of a facultative aerobe
Grows throughout the tube
- More growth in oxic zone, steady growth in anoxic zone
Describe the thioglycolate broth of a microaerophile
Grows in a narrow band between the oxic zone
- Can’t grow too close to the top because it is killed by atmospheric O2 levels
Describe the thioglycolate broth of an aerotolerant anaerobe
Grows continuous throughout entire tube
What are reducing agents?
Chemicals that may be added to culture media to reduce oxygen
What are examples of reducing agents?
Thioglycate, cysteine, H2S, and other sulfur containing compounds
What is needed to grow anaerobic microbes?
Removal of air and replacement with an inert gas (nitrogen or argon)
What are 3 examples of toxic forms of oxygen that can be formed in a cell?
1) Superoxide anion (O2-)
2) Hydrogen peroxide (H2O2)
3) Hydroxyl radical (OH●)
How is superoxide anion formed?
O2 + electron
How is hydrogen peroxide formed?
O2- + electron + 2 H+
How is hydroxyl radical formed?
H2O2 + electron + H+
What are 4 enzymes that neutralize toxic oxygen species?
1) Catalase
2) Peroxidase
3) Superoxide dismutase
4) Superoxide reductase
What happens if an obligate anaerobe doesn’t have enzymes to neutralize toxic oxygen species?
It can’t combat oxidative stress
What is the catalase reaction?
H2O2 + H2O2 –> 2 H2O + O2
What is the peroxidase reaction?
H2O2 + NADH + H+ –> 2 H2O + NAD+
What is the superoxide dismutase reaction?
O2- + O2- + 2H+ –> H2O2 + O2
What is the superoxide reductase reaction?
O2- + 2H+ + rubredoxin reduced –> H2O2 + rubredoxin oxidized
Define sterilization
The killing or removal of all viable organisms (including endospores) within a growth medium
Define inhibition
Effectively limiting microbial growth
- No killing
- Interferes with binary fission, and holds number of bacteria constant so immune system has an easier job
Define decontamination
Treatment of an object to make it safe to handle
Define disinfection
Directly targets the removal of all pathogens, not necessarily all microorganisms
What is decimal reduction time?
Time it takes for a 10 fold reduction in bacterial numbers
What is pasteurization?
The process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
- Does not kill all organisms
What is the typical pasteurization for milk?
Low-temperature / long-time
-63 C for 30 minutes
What is HTST conbination of pasteurization?
High-temperature / short-time
- 72 C for 15 seconds
What is purpose of pastuerizing milk?
Kill Coxiella burnetii, the causative agent of Q fever
What is an autoclave?
A sealed device that uses steam under pressure
In an autoclave, what actually kills the microbes?
The high temp, NOT the pressure
What is the typical temp/time minimum for an autoclave?
The point that takes the longest to hear must stay at 121 C for 15 minutes
What are 5 examples of radiation that can reduce microbial growth?
1) Microwaves
2) UV
3) X-rays
4) Gamma rays
5) Electrons
What does UV have that can cause damage, and what kind of damage can it cause to DNA?
Sufficient energy that can cause modifications and breaks in DNA
What is useful for in regards to surfaces?
Decontaminating surfaces
What is generated by electromagnetic radiation that produces ions and other reactive molecules?
- Electrons
- Hydroxyl radicals
- Hydride radicals
What are 3 sources of radiation?
1) Cathode ray tubes
2) X-rays
3) Radioactive nuclides
What is radiation used for in the food industry and medical field?
Sterilization
What can filtration be used as another option for?
Heat on sensitive liquids and gases
What can be used to accomplish membrane filtration?
Syringes, pumps, or vacuums
What is needed for filtration to be successful?
Pores must be small enough to prevent bacteria from passing through
Define bacteriostatic
Prevents cell growth as long as the antimicrobial agent is present
What are the 3 classifications of antimicrobial agents?
1) Bacteriostatic
2) Bacteriocidal
3) Bacteriolytic
Define bacteriocidal
Kill cells, but does not lyse them
Define bacteriolytic
Kills and lyses cells
What is the minimum inhibitory concentration?
The smallest amount of an agent needed to inhibit growth of a microorganism
What can cause minimum inhibitory concentration to vary?
Organism used, inoculum size, temperature, and pH
What is different between the minimum inhibitory concentration (MIC) and the minimum lethal concentration (MLC) and which is usually higher?
- MIC has no growth, but may still have living organisms
- MLC has no colonies
- MLC usually higher
What kind of media does disc diffusion assay use?
Solid
Describe a disc diffusion assay
- Antimicrobial agent is added to filter paper disc
- MIC is reached at some distance
What is a zone of inhibition?
Area of no growth around the disc in a disc diffusion assay
Where is disinfectant used?
Inanimate objects
Where is antiseptic used?
Tissue (ex: mouth wash)
