Topic 6: Cultivating Microorganisms Flashcards
Anabolism
Energy-consuming process.
introduces compounds into macromolecules like DNA, RNA, lipids, and proteins
Catabolism
Releases energy by breaking down chemicals or by harnessing light
Macronutrients
Required by ALL cells to build macromolecules
- C, N, P, S, O
Micronutrients
Required by only some cells
- Fe, Cu, Na, Mg, Mn, and others
—- Fe is sometimes considered to be a macronutrient because it is essential to almost all organisms. It is often a population-limiting micronutrient
Assigning metabolic categories (naming)
- Energy Source
- Chemicals (chemotrophs)
- Light (phototrophs) - Electron Source
- Organic matter (organotrophs)
- Inorganic chemicals, like water (lithotrophs)
*only archaea and bacteria can be litho - Carbon source
- Fixed organic C-C bonds (heterotrophs)
- Gaseous inorganic CO2 (autotrophs)
Which of the following nutritional categories is unlikely to exist? In other words, which category would be energetically unfavourable?
Chemoorganoautotroph
Chemolithoheterotroph
Photolithoautotroph
Photolithoheterotroph
Chemoorganoautotroph
If a microorganism can oxidize organic carbon for energy and electrons (requires a lot of organic carbon), it can also assimilate that carbon source and would not need to use energy to fix inorganic carbon into biomass.
Oxygen Tolerance
Aerobic growth: Uses oxygen
- Obligate aerobes: Require O2
- Microaerophiles: Grow best in low levels of O2
Anaerobic growth: Occurs without oxygen
- Aerotolerant anaerobes: Are not harmed by O2, but don’t use it
- Obligate anaerobes: Cannot grow when O2 is present
- Facultative anaerobes: Can grow in the absence of O2, but grow better when it is present
Toxic Oxygen Species
Reactive oxygen species (ROS): responsible for harmful effects of oxygen
- Pigments, enzymes (e.g., superoxide dismutase, catalase, peroxidase), and antioxidants used for protection
pH Tolerance
- pH affects macromolecule structures and transmembrane electrochemical gradients
Each microbe has an optimal pH range:
- Acidophiles (low pH, 0-5.5)
- Neutrophiles (neutral pH, 5.5-8.5)
- Alkalophiles (high pH, 8.5-13.5)
Regardless of pH preference, intracellular pH stays relatively neutral, internal pH found as low as 4.6 or as high as 9.5
Moisture Content
- Different solute concentrations can result in influx or efflux of water. This can cause stress to the cell, causing it to either swell or shrink
- Water must also be available for biochemical reactions
- measure in terms of water activity (aw)
- interactions with solutes can decrease aw values
- pure water aw=1.0
- seawater aw= 0.98
- most bacteria require aw > 0.9
-Cytoplasm typically has a higher solute concentration than the external environment
– Water tends to move into the cell
– Positive water balance
- Water will flow out in a hypertonic environment.
Water loss is prevented by increasing internal solute concentration by pumping in inorganic ions from environment or synthesis/concentration of compatible solutes
Temperature
- Growth max, min, and optima are organism-specific. They can be modified by factors such as growth medium composition.
- can affect molecular structure, membrane fluidity and enzyme function
Psychrotolerant organisms
- Able to grow ~0°C
- Optimal growth between 20–40°C
- “mesophiles capable of low-temperature growth”
Psychrophiles
- Minimum <0°C, Optimum ~10–15°C, Maximum ~20°C
- Higher proportion of unsaturated fatty acids in the membrane phospholipids
Mesophiles
- Optimal growth between 10–55°C
- Most common
Thermophiles and Hyperthermophiles
- Hyperthermophiles: Optimal growth between 80–130°C
- Thermophiles: Optimal growth between 55–80°C
- Critical amino acid substitutions in key locations to produce heat-tolerant folds
- Increases in ionic bonds between acidic and basic residues to resist protein unfolding
- Certain solutes stabilize proteins
