CH 7: Questions Flashcards
Which of the following can be used to isolate pure cultures of bacteria from mixtures: A. spread plates B. streak plates C. pour plates D. all of the above
all of the above
T/F: serial dilutions can be used to estimate the total number of bacterial cells in a solution, including living and dead cells
false
most bacterial and archaeal cells divide by
binary fission
t/f: all bacterial and archaeal cells are diploid
false
list the order of binary fission
cells elongates, replicates its chromosome, and separates the chromosome into the two parts of the cell , and a septum forms at midcells
the __ is a group of proteins needed for DNA synthesis that assembles at the origin of the replication
replisome
the process of forming a cross wall between wo daughter cells is known as
septation
the cell wall of bacteria constrains the __ __ that results from the osmolarity of the cytoplasmic contents
turgor pressure
the site at which replication of DNA starts in bacterial cells is known as the __ of ___
origin, replication
T/F: the purpose of penicillin binding proteins is to link phospholipids together in the cellular membrane
false
the actin- like protein that seems to be involved in determining cell shape is
MreB
during cytokinesis, critical step in septation is the assembly of the
z ring
the limitation on microbial growth rate at a high nutrient level is
the saturation of the transport proteins for nutrient uptake
the total number of viable microorganisms remains constant in stationary phase because
either there is a balance between cell division and cell death or there is a cessation of cell division even though the cells may remain metabolically active
cells may enter stationary phase because : A. the depletion of an essential nutrient b. a lack of available oxygen c. the accumulation of toxic waste products d. all of the choices
all of the choices
a culture in a closed vessel to which no additional medium is added and from which no waste products are removed is called a __ culture
batch
microorganisms are most nearly uniform in terms of chemical and physiological properties during what phase?
exponential
T/F: when a young, vigorously growing culture of bacteria is transferred to fresh medium of the same composition, the lag phase is usually short or absent
true
T/F: during the lag phase of microbial growth, the cells are metabolically inactive
false
The length of the lag phase of growth can vary depending on:
condition of microorganisms, the nature of the growth medium, and the temperature
T/F:when a young, vigorously growing culture of bacteria is transferred to fresh medium of DIFFERENT composition, the lag phase is usually short or absent
false; its longer
T/F:the growth rate of a given species of microorganism is dependent on the composition of the medium in which it is grown
true
microbial __ is an increase in cell constituents that may or may not be accompanied by an increase in cell number
growth
a cultural system with constant environmental conditions maintained through continual provision of nutrient and removal of wastes is called ___ culture system
continous
T/F: one of the major advantages of a continuous culture system is that the cells can be maintained in the exponential growth phase for extended periods of time
true
in a continuous culture system, the rate at which media is added and removed is called the ___ rate
dilution
organisms that are damaged by normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2-10% for growth are called
microaerophiles
when a microorganism is place in a(n) __ solution, water will enter the cell and cause it to burst unless something is done to prevent it
hypotonic
the membranes of psychrophilic bacteria have relatively high levels of ___ fatty acids, which allow them to remain semi-fluid at cold temps
unsaturated
organisms that are not drastically affected by increased pressure are called
barotoloerant
organisms that require increased pressure for optimum growth are called
barophilic
most microorganisms maintain their internal pH
near neutral (pH 7)
organisms that grow near deep-sea volcanic vents are likely to be
thermophilic
organisms that grow near deep - sea volcanic vents are likely to be
barophilic or barotolerant
organism that grow in the mud under relatively nonturbulent bodies of water are likely to be
anaerobes
T/F: obligate anaerobes are usually poisoned by molecular oxygen but may grow in aerobic habitats if associated with falcultative anerobes that use up all available oxygen
true
DNA of thermophiles is stabilized by binding of special nucleoid-associated proteins
true
membraines of some thermophilic archaea are stablized by ether linked phospholipids
true
organisms that can grow in habitats with low water activity by maintaining a high internal salt concentration are called __ organism
osmotolerant
organisms that require high levels of sodium chloride in order to grow are called __ organisms
halophilic
organisms that have their optimum growth pH btwn 0.0 and 5.5 are called
acidophiles
membranes of thermophilic bacteria are stabilized by phospholipids with fatty acids that :
tend to be more saturated
organism that have their optimum growth pH between 5.5 and 8.0 are called
neurophiles
organisms that have their optimum growth pH between 8.5 and 11.5 are called
alkaliphiles
organisms that growth best at pH levels above 10 are called
extreme alkaliphiles
many microbes that live in environments where there is high exposure to light use __ to provide protection from photoxidation by singlet oxygen
carotenoids
complex microbial communities that grow tightly adhered to surfaces are called
biofilms
quorum sensing in gram-positive bacteria generally involves the use of __ as the external signaling molecules
oligopeptides
T/F: a microbial environment containing high nutrient concentration is called an oligotrophic environment
false
a phenomenon in which bacteria monitor their own population density
quorum sensing
quorum sensing depends on the sensing of signal __ molecules
protein
quorum sensing plays an important role in formation of biofilms by what organism?
Pseudomonas aeruginosa
organisms that ignore oxygen and grow equally well in its presence or absence are called
aerotolerant
