Questions and Answers
A chemoheterotroph obtains its energy from ______ and its carbon from ______ sources.
redox reactions; organic
Human pathogens are classified as?
mesophiles
Organisms that can grow with or without oxygen present are?
either facultative anaerobes or aerotolerant anaerobes
The ______ growth temperature is the temperature at which an organism exhibits the highest growth rate.
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Organisms that require sources of carbon and energy are called ______.
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Which of the following represent the majority of pathogenic bacteria?
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Obligate anaerobes have enzymes such as superoxide dismutase to protect them from the damaging effects of oxygen.
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A capnophile is a microorganism that thrives in conditions of high...
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Microbes in the ______ phase of the microbial growth curve are most susceptible to antimicrobial drugs.
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The ______ of a population is the time it takes for the cells to double in number.
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A cell that uses an organic carbon source and obtains energy from light would be called a...
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A ______ can measure changes in the turbidity of a bacterial culture.
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Crenation can result from a change in which of the following?
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The ______ radical is formed during the incomplete reduction of oxygen during electron transport in aerobes.
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A microbiologist inoculates a flask of broth with 1 mL of 100 bacterial cells/mL. The generation time of the species is 1 hour, and there is no lag phase. How long will it be before the culture contains more than 6,000 cells/mL?
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Thermoduric mesophiles are often responsible for spoilage of improperly canned foods.
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Which of the following does NOT use an inorganic source of carbon as its sole source?
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Which of the following is an indirect method for estimating the number of microbes in a sample?
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What results when a single bacterium reproduces?
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If you begin with six cells, how many cells would you have after three rounds of division?
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Which of the following is NOT a step in bacterial cell division?
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Which step of binary fission is the reason for genetically identical daughter cells?
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The generation time of bacterial cells is shortest during the ______ phase.
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A sample placed into fresh medium is initially in the ______ phase of microbial growth in most instances.
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At temperatures higher than the maximum growth temperature for an organism...
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When cells are metabolically active but not dividing, they are in the ______ phase.
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Which of the following organisms would be most likely to contaminate a jar of pickles?
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Study Notes
Microbial Metabolism and Growth
- Chemoheterotrophs obtain energy from redox reactions and carbon from organic sources.
- Human pathogens are classified as mesophiles, thriving at moderate temperatures.
- Organisms that can grow in the presence or absence of oxygen are either facultative anaerobes or aerotolerant anaerobes.
Growth Characteristics
- The optimum growth temperature is where an organism shows the highest growth rate.
- Generation time refers to the time required for a population to double in number.
- Microbes in the log phase are most susceptible to antimicrobial drugs.
Bacterial Cell Division
- A bacterium reproducing results in two genetically identical daughter cells.
- Inoculating a flask with 100 cells/mL and a generation time of 1 hour leads to more than 6,000 cells/mL after 6 hours without a lag phase.
- Maximum growth temperature damages proteins, breaks hydrogen bonds, and causes membranes to become too fluid.
Environmental Adaptations
- Capnophiles thrive in high carbon dioxide conditions.
- Crenation, or cell shrinkage, results from changes in osmotic pressure.
- Thermoduric mesophiles can spoil improperly canned foods.
Bacterial Growth Measurements
- Turbidity is an indirect method for estimating microbial counts.
- A spectrophotometer can measure changes in the turbidity of bacterial cultures.
Types of Bacteria
- Photoheterotrophs use organic carbon and obtain energy from light; they do not use inorganic carbon sources.
- Acidophiles, which thrive in acidic environments, are most likely to contaminate pickles.
Misconceptions about Bacterial Division
- Obligate anaerobes lack enzymes like superoxide dismutase, which protect from oxygen's effects.
- The disappearance of the nuclear envelope is not a step in bacterial cell division.
Phases of Microbial Growth
- Lag phase is when cells are metabolically active but not dividing, often seen after inoculation into fresh medium.
- Generation time is shortest in the log phase of growth, highlighting rapid division.
Binary Fission
- Genetic identity of daughter cells results from replication of the bacterial chromosome before division.
- After three rounds of division starting with six cells, the culture would grow to 48 cells.
Studying That Suits You
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Description
Test your knowledge on key concepts from Chapter 6 of your biology curriculum with these flashcards. Covering topics like chemoheterotrophs, human pathogens, and oxygen-related growth classifications, this quiz is a valuable study aid for understanding microbial growth and classification.
