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Organisms that live in extreme environments are known as ____.
Extremophiles
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Most bacterial organisms reproduce by an asexual process called ___ ___.
Binary Fission
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___ ___ at the midcell involves the synthesis of a partition or septum that separates the mother cell into 2 genetically identical daughter cells.
Cell fission
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___ ___ is a process to maintain genetic constancy while increasing cell numbers.
Asexual reproduction
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The interval of time between successive binary fissions when a population doubles is known as what?
Generation time
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Generation times vary. For example it in about 30 mins for ___ ___ but 15hrs for ___ ___.
- Staphylococcus aureus
- Mycobacterium Tuberculosis
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Why is knowing generation time useful?
In order to help determine at what point symptoms may appear
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The time period fr when a pathogen enters the body to when symptoms first appear is known as ___ ___.
Incubation period
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In preparation for fission, cells do what 3 things?
- Grow in size
- Store nutrients
- Synthesis nutrients
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What does a bacterial growth curve illustrate?
Events occurring over time
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What are the 4 distinct phases of the bacterial growth curve?
- Lag phase
- Log phase
- Stationary phase
- Decline phase
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During the lag phase of the bacterial growth phase what happens?
Cells are adapting to their new environment and no cell divisions occur
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The length of the lag phase is dependent upon what?
Metabolic activity in the cells
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What phase of the bacterial growth curve is characterized by exponential growth and binary fission?
Log phase
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Why is it that disease symptoms develop during the log phase?
B/c the cells cause tissue damage during this phase
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During what phase of the bacterial growth curve are bacteria most vulnerable to antibiotics and why?
The log phase b/c many antibiotics affect metabolizing cells
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During the ____ phase population plateaus & reproductive and death rates equalize.
Stationary
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What are 2 factors that lead to cell death during the stationary phase?
- Limitation of nutrients
- Build up of waste material
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What are 2 factors that contribute to the decline phase?
- Limited nutrients in the external environment
- Nutrient levels become exceedingly low
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During the ____ phase cells death far exceeds cell reproduction.
Decline phase
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What are 2 things that could keep bacteria alive during the decline phase?
- Presence of a glycocalyx
- Flagella enabling the cell to move about
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____ are dormant structures that can endure times of nutrient stress.
Endospores
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Describe endospores. Gram status, genus.
Gram-positive Bacillus & Clostridium living in soil
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When cells are said to be vegetative they are what?
Actively metabolizing and obtaining nutrients
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When Bacillus & Clostridium experience limited carbon or nitrogen, reach critical mass & enter stationary phase what happens?
They begin sporulation
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Sporulation begins when the bacterial ____ replicates & binary fission is characterized by ___ ___ ___.
- Chromosome
- Asymmetric cell division
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Explain what happens to a cell during sporulation.
The smaller cell (prespore) becomes mature endospore & mother cells commits itself to maturation of endospore then lyses
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What substances are contained in a perspire cell?
- Cytoplasm
- DNA
- Dipicolinic Acid
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A unique organic substance that helps stabilize proteins & DNA in spores is called what?
Diplicolinic Acid
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What does an endospore represent in regards to a bacteria species?
A dormant stage in life
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What happens to an endospore when it comes into a favorable environment for growth?
The protective layers break down & it germinates into a vegetative state
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Botulism, gas gangrene & tetanus are diseases cause by different species of ____.
Clostridium
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Where are Clostridium found?
Soil & human and animal intestines
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What is one way to kill endospores?
High heat combined with high pressure
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What are 3 grps of temp oriented microbes?
- Psychrophiles
- Mesophiles
- Thermophiles
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Microbes that have their optimal growth rates below 15⁰C but can still grow at 0⁰C - 20⁰C are called ___.
Psychrophiles
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Psychrotrophs & psychrotolerant microorganisms, w/their higher minimal & maximal growth temps are commonly found where?
In spoiled refrigerated foods around 4⁰C
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Which temp oriented organisms grow best at temps around 60⁰C?
Thermophiles
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Thermophiles are present in compost heaps & hot springs & an issue w/Pasteurization b/c . . . .
They can survive pasteurization temperatures
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What 3 things make thermophiles stable at high temps?
- Highly saturated fatty acids in cell membranes
- Heat stabilizing proteins & enzymes
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____ are archaeal species that grow optimally at temps exceeding 80⁰C.
Hyperthermophiles
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Which bacterial species survive best in the middle temp range 10⁰C to 45⁰C?
Mesophiles
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Obligate aerobes must use ____ as the final e⁻ acceptor to make cellular energy.
Oxygen
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Microaerophiles survive in environments where . . . . .
The concentration of oxygen is relatively low
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Anaerobes are microbes that cannot or do not use ____ at all.
oxygen
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What effect does oxygen have on aerotolerant microbes?
They are insensitive to oxygen
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Obligate anaerobes are ___ or ___ if oxygen is present.
Inhibited or killed
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Clostridium that carry tetanus & gas gangrene multiply where and produce what?
- In dead wound tissue
- Toxins causing further damage
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Microbes that are neither aerobic nor anaerobic & can grow in either the presence of or a reduced concentration of oxygen are termed ____ organisms.
Facultative
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A facultative aerobe prefers ____ conditions but can also grow ____.
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A facultative anaerobe prefers ___-___ conditions but can also grow ____.
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Why do we use thioglycollate broth to test an organisms oxygen sensitivity?
B/c it binds to free oxygen so that only fresh oxygen entering at the top of the tube would be available
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The cytoplasm of most organisms has a pH near ___.
7.0
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Acid-tolerant bacteria are called ____ & are valuable in the ___ & ___ industries.
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What is hydrostatic pressure?
Pressure exerted by water
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____ live in high pressure areas.
Barophiles
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Microbes, like E. coli, that are unable to grow in the presence of salt are known as ____.
Nonhalophiles
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Salt loving microorganisms are known as ___.
Halophiles
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___ ___ represent a grp of archaea that tolerate salt concentration of 15% - 30%
Extreme halophiles
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Aggregates of molecules in a finely divided state dispersed in a solid medium is called ___.
Colloid
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What is a polysaccharide derived fr marine red algae & contains no essential nutrients used for growing colonies?
Agar
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A chemically undefined medium that contains nutrients in which the exact components or their quantity is not exactly known is called what?
Complex medium
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Why are complex mediums often used in teaching?
B/s we're not concerned about nutrients as long as the cultures grow
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What is the name given to a medium where the precise chem composition & amt of all components are known?
Synthetic medium
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When might a synthetic medium be utilized?
When we are trying to determine specific growth requirements
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A ___ ___ contains ingredients to inhibit the growth of certain microbes while allowing the growth of others.
Selective medium
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A ___ ___ is a basic growth medium w/addition of 1 or more compounds that allows one to differentiate between very similar species based on biochemical or physiological properties.
Differential medium
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If an organism is fastidious that organism has what?
Complex nutritional requirements
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An enriched medium contains ___ ___.
Special nutrients
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If a bacteria is viable but non-culturable (VBNC) it is what?
This organism can not be grown in the lab
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How can we ID VBNC organisms?
- Direct microscopic exam
- Amplification of diagnostic gene sequences
- 165 rRNA sequences
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The process of transferring bacteria fr 1 tube or plate to another is known as what?
Subculturing
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A pure culture is what?
Population consisting of only 1 species
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What are direct methods for measuring microbial growth?
- Direct microscopic count
- Most probable number test
- Std plate count procedure
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Explain direct microscopic counting.
Using a specially designed counting chamber, count all cells
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What is a downfall to direct microscopic counting?
It counts both live & dead cells
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Explain the most probable number test for counting cell growth.
Samples added to lactose broth tubes & presence or absence of gas formed in fermentation gives rough statistical estimation of cell number
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Explain std plate count procedure.
Samples of broth culture spread on agar plates using pour plate technique. Assume that each cell will divide numerous times to produce separate colonies. Count expressed in colony-forming units
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What is a colony-forming unit (CFUs)?
A figure used to estimate number of viable cells originally plated
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What are 3 indirect methods of estimating cell numbers?
- Measuring dry weight
- Oxygen uptake in metabolism
- Spectrophotometry
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Which of the following is NOT an event of sporulation (A. symmetrical cell division B. mother cell disintegration C. DNA replication D. Prespore engulfment by mother cell)?
A. Symmetrical cell division
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If the carbon source in a growth medium is beef extract, the medium, the medium must be an example of a/an ___medium.
Complex
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