quiz 2- week 2/3 Flashcards
What temperature do psychrophiles grow best at, and why?
Psychrophiles grow best below 15°C. Their proteins are more flexible (fewer stabilizing bonds) and require less energy, and their cell membranes are more fluid due to a high proportion of unsaturated fatty acids.
What is the ideal temperature range for mesophiles?
Mesophiles grow best between 15°C and 45°C.
What adaptations do thermophiles have to survive in high temperatures (50-80°C)?
Thermophiles have enzymes with low amounts of glycine and more side chains, allowing for more stabilizing intramolecular bonds, which help maintain protein structure at high temperatures.
What is the definition of barophiles, and what are their adaptations?
Barophiles grow in high pressures (greater than 380 atms). They have adapted to have fluid membranes and internal structures that can withstand high pressures.
How do halophiles maintain isotonic intracellular concentrations in hypertonic environments?
Halophiles pump sodium out of the cell and use potassium instead of sodium whenever possible to maintain isotonic intracellular concentrations.
Describe the characteristics of acidophiles and alkaliphiles.
Acidophiles thrive in pH 5 or lower and have decreased proton permeability in their lipid composition. Alkaliphiles live in pH 9 or higher and maintain an intracellular pH of around 8, with acidic cell walls and peptidoglycan.
What reactive oxygen species (ROS) can oxygen produce, and how do bacteria neutralize them?
Oxygen can produce superoxide radicals (ROS), which damage DNA, RNA, proteins, and lipids. Bacteria neutralize ROS with enzymes such as superoxide dismutase (SOD), catalase, and peroxidase.
What are the two types of heterotrophs, and how do they differ?
Heterotrophs break down carbon into energy. Organotrophs are a subset of heterotrophs that use organic molecules for energy.
How do photoheterotrophs differ from chemoheterotrophs?
Photoheterotrophs break down multi-carbon nutrients but require light as a secondary energy source, whereas chemoheterotrophs break down nutrients completely into CO2 and generate energy via cellular respiration.
What is the main energy source for chemoautotrophs?
Chemoautotrophs use chemical energy from the breakdown of chemical bonds (e.g., nitrogen, sulfur, or carbon monoxide oxidation) to make multi-carbon molecules from CO2.
What is the process of biofilm formation, and why are biofilms difficult to treat?
Biofilms form in nutrient-rich environments where bacteria produce an extracellular matrix to attach to surfaces and each other. Biofilms are hard to treat because they behave like a multi-cellular, multi-layered organism with specialized functions in their structure.
What is the role of superoxide dismutase, catalase, and peroxidase in bacteria?
These enzymes neutralize reactive oxygen species (ROS) like superoxide radicals, protecting bacteria from oxidative damage.
Describe the four phases of bacterial growth.
- Lag phase: Cells orient to the new environment.
- Log phase: Exponential growth occurs.
- Stationary phase: Growth rate equals death rate.
- Death phase: Cells die faster than they replicate.
What adaptations allow bacteria to survive in different pH environments?
Bacteria can secrete enzymes that alter the pH (e.g., H. pylori uses urease to produce ammonia and neutralize acids). They also change gene expression to adapt to different pH levels.
What are endospores, and which bacteria commonly produce them?
Endospores are heat-resistant, desiccation-resistant structures that do not require nutrients. Gram-positive rods like Clostridium and Bacillus produce endospores, which convert to vegetative cells in the right conditions.
