All flashcards
Flashcard 1: Which metabolic category uses chemical compounds for energy and organic molecules for carbon?
Answer: Chemoheterotroph. They derive energy from oxidizing organic compounds and use them as carbon sources, common in pathogens.
Flashcard 2: What is the definition of bacterial transduction as a mechanism of genetic exchange?
Answer: DNA transfer mediated by bacteriophages. Phages accidentally package host DNA during infection, transferring it to new bacterial cells.
Flashcard 3: What is the definition of bacterial conjugation including the key structure required?
Answer: Direct DNA transfer via cell-to-cell contact using a sex pilus. The pilus forms a bridge for plasmid DNA transfer from donor to recipient, promoting genetic diversity.
Flashcard 4: What is the primary purpose of bacterial endospore formation under harsh conditions?
Answer: Long-term survival via a highly resistant dormant state. Endospores withstand extreme conditions like heat and desiccation, allowing revival when favorable.
Flashcard 5: Calculate n if a culture increases from N0=103 to N=8×103 cells.
Answer: n=3 generations. The population increases eightfold, corresponding to 23 doublings via binary fission.
Flashcard 6: Identify the term for the maximum population size an environment can sustain for a species.
Answer: Carrying capacity. Resources like nutrients and space limit indefinite population growth in a given environment.
Flashcard 7: What is the key difference between batch culture and continuous culture (chemostat)?
Answer: Chemostat adds nutrients and removes waste to maintain steady state. This open system sustains exponential growth by controlling flow rates, unlike closed batch cultures.
Flashcard 8: Which method measures total cell number by light scattering but cannot distinguish live from dead cells?
Answer: Optical density (turbidity) measurement. Light absorbance correlates with cell density but includes both viable and non-viable cells.
Flashcard 9: Which method measures viable bacteria by counting colonies after dilution and plating?
Answer: Colony-forming unit (CFU) count. Each colony originates from a single viable cell, providing a count of culturable bacteria.
Flashcard 10: Which metabolic category uses light as an energy source and CO2 as the carbon source?
Answer: Photoautotroph. These organisms fix inorganic carbon using energy from photosynthesis, like cyanobacteria.
Flashcard 11: What is the definition of an obligate aerobe in terms of oxygen requirement?
Answer: Requires O2 for growth; uses aerobic respiration. Oxygen serves as the essential terminal electron acceptor in their electron transport chain.
Flashcard 12: What is the definition of an obligate anaerobe in terms of oxygen tolerance?
Answer: Cannot grow in O2; oxygen is toxic. They lack protective enzymes against reactive oxygen species, making aerobic environments lethal.
Flashcard 13: What is the definition of a facultative anaerobe regarding metabolism with or without O2?
Answer: Uses O2 when present; can ferment/anaerobically respire without it. They flexibly switch between aerobic respiration and anaerobic pathways for energy production.
Flashcard 14: Which oxygen-handling category grows best with low O2 levels (below atmospheric concentration)?
Answer: Microaerophile. They require oxygen for respiration but are damaged by atmospheric levels of O2.
Flashcard 15: Which enzyme converts superoxide radicals O2− into H2O2 and O2?
Answer: Superoxide dismutase. It neutralizes harmful superoxide ions generated during aerobic metabolism to prevent oxidative damage.
Flashcard 16: Which bacterial growth phase is characterized by little net growth while cells adjust to a new medium?
Answer: Lag phase. Cells synthesize enzymes and repair damage to prepare for division without significant population increase.
Flashcard 17: State the formula for bacterial population after n generations starting from N0 cells.
Answer: N=N0×2n. Binary fission doubles the cell count each generation, yielding exponential growth.
Flashcard 18: Which bacterial growth phase is characterized by a net decrease in viable cells over time?
Answer: Death (decline) phase. Continued resource depletion results in cell death exceeding division, leading to population decline.
Flashcard 19: Which bacterial growth phase has net zero growth because division rate equals death rate?
Answer: Stationary phase. Nutrient exhaustion and toxin buildup cause the rate of cell death to match the rate of division.
Flashcard 20: Calculate N if N0=500 cells and n=3 generations have occurred.
Answer: N=4000 cells. Each generation doubles the population, so three generations multiply the initial count by 23=8.
Flashcard 21: Which growth phase is defined by rapid, constant-rate cell division and maximal metabolism?
Answer: Log (exponential) phase. Abundant nutrients and space allow cells to divide at their maximum rate with high metabolic activity.
Flashcard 22: What is the definition of the bacterial generation time during exponential growth?
Answer: Time required for a population to double in number. This interval reflects the duration of one complete cycle of binary fission under optimal conditions during the log phase.
Flashcard 23: Identify n in terms of time t and generation time g for binary fission growth.
Answer: n=gt. The number of generations equals the total elapsed time divided by the time per generation.
Flashcard 24: Which enzyme detoxifies hydrogen peroxide by converting 2H2O2 to 2H2O+O2?
Answer: Catalase. It breaks down toxic hydrogen peroxide, a byproduct of superoxide dismutase activity, into harmless products.
Flashcard 25: What is the definition of bacterial transformation as a mechanism of genetic exchange?
Answer: Uptake of naked DNA from the environment. Competent cells incorporate exogenous DNA, enabling horizontal gene transfer and adaptation.