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If a bacterial species with a minimum doubling time of 20 minutes under ideal conditions is introduced into a nutrient-poor environment, what is the most likely initial impact on its growth curve?
If a bacterial species with a minimum doubling time of 20 minutes under ideal conditions is introduced into a nutrient-poor environment, what is the most likely initial impact on its growth curve?
- The death phase will immediately commence as the lack of nutrients prevents any initial replication.
- The exponential phase will be prolonged as the bacteria efficiently scavenge for scarce nutrients.
- The stationary phase will be reached more rapidly due to the accelerated depletion of the already limited nutrients.
- The lag phase will be extended as the bacteria require more time to synthesize necessary enzymes and adapt to the limited resources. (correct)
A researcher observes that a bacterial colony on an agar plate exhibits a unique iridescent sheen and a strong, fruity odor. This information is most useful for what purpose?
A researcher observes that a bacterial colony on an agar plate exhibits a unique iridescent sheen and a strong, fruity odor. This information is most useful for what purpose?
- Determining the exact genetic sequence of the bacteria.
- Estimating the bacteria's growth rate under different temperature conditions.
- Narrowing down the possible identity of the bacteria to a specific group or species. (correct)
- Predicting the bacteria's resistance to various antibiotics.
Why might a bacterial population enter the stationary phase despite the continued presence of some nutrients in its environment?
Why might a bacterial population enter the stationary phase despite the continued presence of some nutrients in its environment?
- The accumulation of toxic waste products inhibits further growth. (correct)
- Nutrients have been exhausted; toxic waste does not affect bacterial growth.
- The surviving bacteria undergo a mass sporulation event to conserve resources.
- Enzymatic activity decreases until the environment is replenished by the growth of a new colony.
A bacterial culture is transferred from an optimal growth temperature to a temperature significantly above the maximum tolerance for that species. What is the most likely immediate effect on the bacteria's cellular processes?
A bacterial culture is transferred from an optimal growth temperature to a temperature significantly above the maximum tolerance for that species. What is the most likely immediate effect on the bacteria's cellular processes?
In anaerobic respiration, which of the following compounds serves as an alternative final electron acceptor instead of oxygen?
In anaerobic respiration, which of the following compounds serves as an alternative final electron acceptor instead of oxygen?
A microbiology student is examining a culture of E. coli under various stress conditions. Which observation would most strongly suggest that the bacteria are undergoing fermentation rather than anaerobic respiration?
A microbiology student is examining a culture of E. coli under various stress conditions. Which observation would most strongly suggest that the bacteria are undergoing fermentation rather than anaerobic respiration?
A scientist is studying a newly discovered extremophile bacterium in a lab setting. What adjustment to typical lab procedures would be most crucial to ensure the bacterium's survival and growth?
A scientist is studying a newly discovered extremophile bacterium in a lab setting. What adjustment to typical lab procedures would be most crucial to ensure the bacterium's survival and growth?
A researcher is investigating a bacterial population that exhibits an unusually long lag phase in a new environment. Which hypothesis is the most plausible explanation for this extended lag phase?
A researcher is investigating a bacterial population that exhibits an unusually long lag phase in a new environment. Which hypothesis is the most plausible explanation for this extended lag phase?
A virologist is studying a newly discovered virus. After analyzing its structure and replication process, they conclude that it lacks ribosomes and cannot produce its own ATP. Based on this information, which of the following statements is most accurate?
A virologist is studying a newly discovered virus. After analyzing its structure and replication process, they conclude that it lacks ribosomes and cannot produce its own ATP. Based on this information, which of the following statements is most accurate?
A scientist is comparing bacterial growth rates in two different media: one rich in nutrients and one with minimal nutrients. Which of the following growth parameters would most likely be affected in the minimal nutrient medium compared to the nutrient-rich medium?
A scientist is comparing bacterial growth rates in two different media: one rich in nutrients and one with minimal nutrients. Which of the following growth parameters would most likely be affected in the minimal nutrient medium compared to the nutrient-rich medium?
Flashcards
Binary Fission
Binary Fission
Asexual reproduction in bacteria where one cell divides into two identical daughter cells.
Lag Phase
Lag Phase
Initial period where bacteria adapt to new conditions, synthesizing necessary molecules for growth but showing little to no population increase.
Exponential (Log) Phase
Exponential (Log) Phase
Phase of rapid bacterial growth where the population doubles at a constant rate.
Stationary Phase
Stationary Phase
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Death Phase
Death Phase
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Anaerobic Respiration
Anaerobic Respiration
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Anaerobic Fermentation
Anaerobic Fermentation
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Bacterial Colony
Bacterial Colony
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Viruses
Viruses
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Study Notes
- Bacteria reproduce asexually through binary fission, leading to a logarithmic increase in numbers.
- Growth rates depend on the bacterial species and available nutrients.
- The doubling time, which is the time it takes for the bacterial population to double, varies from 10 minutes to several days, depending on the species.
Binary Fission Steps
- DNA Replication: The bacterium's circular DNA is copied, with each copy attaching to different parts of the cell membrane.
- Cell Elongation: The cell grows, and the DNA copies move to opposite ends.
- Septum Formation: A new cell wall forms in the middle, dividing the cell.
- Division: The cell divides into two identical daughter cells, each with a complete set of DNA.
Bacterial Growth Phases in Liquid Medium
- Lag Phase: Bacteria adapt to the growing conditions and synthesize necessary molecules for division.
- Exponential Phase: Bacterial growth occurs exponentially, with rapid division, also called the log phase.
- Stationary Phase: Growth slows and ceases, reaching a plateau where the rate of reproduction equals the rate of death.
- Death Phase: Bacterial death exceeds reproduction, typically due to nutrient scarcity.
- A single E. Coli in a complete liquid broth can give rise to more than 10 million cells in eight hours.
Bacterial Growth on Surfaces
- A single bacterium on a solid nutrient agar undergoes binary fission, forming a colony, each colony originating from a single cell.
- Colony morphology (color, shape, adherence, smell, texture) can aid in identification.
Factors Affecting Bacterial Growth
- Nutrient availability is critical; microbes require carbohydrates, fats, proteins, metals, and vitamins.
- Nutritional stress reduces or stalls growth, though some microbes have adaptable processes to resist it.
- Temperature impacts growth, with an optimal range between 40°F and 140°F.
- Pathogens thrive at human body temperature; high fever temperatures can sometimes kill them.
- Extremophiles are bacteria that resist high temperatures.
- Moisture, oxygen, and pH are all important factors affecting bacterial growth.
Detailed breakdown of bacterial growth phases
- Lag Phase: Bacteria adapt to the environment and synthesize necessary components for growth.
- The duration varies depending on the bacteria and its replication speed, with virtually no growth occurring.
- Exponential Phase (Log Phase): Rapid bacterial growth and division occur every few hours or days.
- Stationary Phase: The production of new bacteria matches the rate of bacterial death, no net bacterial growth occurs and a carrying capacity is reached.
- Carrying Capacity: The maximum population size the environment can sustain due to limited nutrients.
- Nutrients are depleted, and toxic waste products accumulate.
- Death Phase: More bacteria die than are produced, leading to a decline in population size.
- Some bacteria form spores to preserve themselves.
Are Viruses Alive ?
- Viruses contain genetic material (DNA or RNA) used for replication and evolution
- Viruses reproduce by hijacking host cells
- Viruses mutate and evolve over time, adapting to their environment and host defenses
- Viruses infect host cells, spread, and influence ecosystems
Viruses as Non-Living
- Viruses are acellular
- Viruses lack the ability to carry out metabolic processes on their own
- Viruses are inert outside a host
- Unlike living organisms, viruses do not respond to environmental stimuli in the way cells do
Viruses in between Living and Non-Living
- Viruses are "biological entities" or "life at the edge of life."
- Viruses blur traditional definitions of life
Anaerobic Respiration vs. Anaerobic Fermentation
- Anaerobic Respiration: Does not use oxygen as the final electron acceptor relying on inorganic molecules.
- Anaerobic Fermentation: Does not use oxygen relying on organic molecules as the final electron acceptors.
- Anaerobic Respiration: Produces more ATP than fermentation but less than aerobic respiration.
- Anaerobic Fermentation: Generates less ATP compared to anaerobic respiration.
- Common end products are lactic acid or ethanol and carbon dioxide.
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