Alcamo's Ch 5
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Alcamo's Ch 5
Ch 5 cards
Organisms that live in extreme environments are known as ____.
Most bacterial organisms reproduce by an asexual process called ___ ___.
___ ___ at the midcell involves the synthesis of a partition or septum that separates the mother cell into 2 genetically identical daughter cells.
___ ___ is a process to maintain genetic constancy while increasing cell numbers.
The interval of time between successive binary fissions when a population doubles is known as what?
Generation times vary. For example it in about 30 mins for ___ ___ but 15hrs for ___ ___.
Why is knowing generation time useful?
In order to help determine at what point symptoms may appear
The time period fr when a pathogen enters the body to when symptoms first appear is known as ___ ___.
In preparation for fission, cells do what 3 things?
Grow in size
What does a bacterial growth curve illustrate?
Events occurring over time
What are the 4 distinct phases of the bacterial growth curve?
During the lag phase of the bacterial growth phase what happens?
Cells are adapting to their new environment and no cell divisions occur
The length of the lag phase is dependent upon what?
Metabolic activity in the cells
What phase of the bacterial growth curve is characterized by exponential growth and binary fission?
Why is it that disease symptoms develop during the log phase?
B/c the cells cause tissue damage during this phase
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
During the ____ phase population plateaus & reproductive and death rates equalize.
What are 2 factors that lead to cell death during the stationary phase?
Limitation of nutrients
Build up of waste material
What are 2 factors that contribute to the decline phase?
Limited nutrients in the external environment
Nutrient levels become exceedingly low
During the ____ phase cells death far exceeds cell reproduction.
What are 2 things that could keep bacteria alive during the decline phase?
Presence of a glycocalyx
Flagella enabling the cell to move about
____ are dormant structures that can endure times of nutrient stress.
Describe endospores. Gram status, genus.
Gram-positive Bacillus & Clostridium living in soil
When cells are said to be vegetative they are what?
Actively metabolizing and obtaining nutrients
When Bacillus & Clostridium experience limited carbon or nitrogen, reach critical mass & enter stationary phase what happens?
They begin sporulation
Sporulation begins when the bacterial ____ replicates & binary fission is characterized by ___ ___ ___.
Asymmetric cell division
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
What substances are contained in a perspire cell?
A unique organic substance that helps stabilize proteins & DNA in spores is called what?
What does an endospore represent in regards to a bacteria species?
A dormant stage in life
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
Botulism, gas gangrene & tetanus are diseases cause by different species of ____.
Where are Clostridium found?
Soil & human and animal intestines
What is one way to kill endospores?
High heat combined with high pressure
What are 3 grps of temp oriented microbes?
Microbes that have their optimal growth rates below 15⁰C but can still grow at 0⁰C - 20⁰C are called ___.
Psychrotrophs & psychrotolerant microorganisms, w/their higher minimal & maximal growth temps are commonly found where?
In spoiled refrigerated foods around 4⁰C
Which temp oriented organisms grow best at temps around 60⁰C?
Thermophiles are present in compost heaps & hot springs & an issue w/Pasteurization b/c . . . .
They can survive pasteurization temperatures
What 3 things make thermophiles stable at high temps?
Highly saturated fatty acids in cell membranes
Heat stabilizing proteins & enzymes
____ are archaeal species that grow optimally at temps exceeding 80⁰C.
Which bacterial species survive best in the middle temp range 10⁰C to 45⁰C?
Obligate aerobes must use ____ as the final e⁻ acceptor to make cellular energy.
Microaerophiles survive in environments where . . . . .
The concentration of oxygen is relatively low
Anaerobes are microbes that cannot or do not use ____ at all.
What effect does oxygen have on aerotolerant microbes?
They are insensitive to oxygen
Obligate anaerobes are ___ or ___ if oxygen is present.
Inhibited or killed
Clostridium that carry tetanus & gas gangrene multiply where and produce what?
In dead wound tissue
Toxins causing further damage
Microbes that are neither aerobic nor anaerobic & can grow in either the presence of or a reduced concentration of oxygen are termed ____ organisms.
A facultative aerobe prefers ____ conditions but can also grow ____.
A facultative anaerobe prefers ___-___ conditions but can also grow ____.
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
The cytoplasm of most organisms has a pH near ___.
Acid-tolerant bacteria are called ____ & are valuable in the ___ & ___ industries.
Food & Dairy
What is hydrostatic pressure?
Pressure exerted by water
____ live in high pressure areas.
Microbes, like E. coli, that are unable to grow in the presence of salt are known as ____.
Salt loving microorganisms are known as ___.
___ ___ represent a grp of archaea that tolerate salt concentration of 15% - 30%
Aggregates of molecules in a finely divided state dispersed in a solid medium is called ___.
What is a polysaccharide derived fr marine red algae & contains no essential nutrients used for growing colonies?
A chemically undefined medium that contains nutrients in which the exact components or their quantity is not exactly known is called what?
Why are complex mediums often used in teaching?
B/s we're not concerned about nutrients as long as the cultures grow
What is the name given to a medium where the precise chem composition & amt of all components are known?
When might a synthetic medium be utilized?
When we are trying to determine specific growth requirements
A ___ ___ contains ingredients to inhibit the growth of certain microbes while allowing the growth of others.
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.
If an organism is fastidious that organism has what?
Complex nutritional requirements
An enriched medium contains ___ ___.
If a bacteria is viable but non-culturable (VBNC) it is what?
This organism can not be grown in the lab
How can we ID VBNC organisms?
Direct microscopic exam
Amplification of diagnostic gene sequences
165 rRNA sequences
The process of transferring bacteria fr 1 tube or plate to another is known as what?
A pure culture is what?
Population consisting of only 1 species
What are direct methods for measuring microbial growth?
Direct microscopic count
Most probable number test
Std plate count procedure
Explain direct microscopic counting.
Using a specially designed counting chamber, count all cells
What is a downfall to direct microscopic counting?
It counts both live & dead cells
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
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
What is a colony-forming unit (CFUs)?
A figure used to estimate number of viable cells originally plated
What are 3 indirect methods of estimating cell numbers?
Measuring dry weight
Oxygen uptake in metabolism
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
If the carbon source in a growth medium is beef extract, the medium, the medium must be an example of a/an ___medium.