bacteria cell division part 3 Flashcards
calculate pH
pH=-log{H+}
what pH do most microbes love
6-8
acidophiles vs alkaphiles
acid less than 7
alk more than 7
neutralophiles
love neutral pH
What helps acid and alkaphiles live in their environment
membrane adaptations
Minimum growth temperature
decreases membrane fluidity
decrease enzyme activity
maximum growth temperature
increase membrane fluidity
membrane collapses
proteins denature (enzymes)
see slide 18 picture
Requires O2 for growth
Obligate aerobe
O2 not required but grows better with it
Facultative anaerobe
requires low amounts of oxygen for growth
Microaerophile
Not killed by O2
Aerotolerant anaerobe (SOD but no catalse)
Killed by O2
Obligate anaerobe (strict), no enzymes SOD, catalase
where does growth occur in test tube
more oxygen needed towards the top
less needed towards bottom
Organisms that do not require oxygen for growth but grow better in its presence are called \_\_\_\_\_\_\_\_. A) facultative anaerobes B) microaerophiles C) aerotolerant D) anoxygenic
A) facultative anaerobes
Organisms that ignore oxygen and grow equally well in its presence or absence are called \_\_\_\_\_\_\_\_. A) facultative anaerobes B) microaerophiles C) aerotolerant D) anoxygenic
C)aerotolerant
Organisms that are damaged by the normal atmospheric levels of oxygen (20%) but require oxygen at levels of 2–10% for growth are called \_\_\_\_\_\_\_\_. A) facultative anaerobes B) microaerophiles C) aerotolerant D) anoxygenic
B) microaerophiles
Organisms that grow in mud under relatively nonturbulent bodies of water are likely to be \_\_\_\_\_\_\_\_. A) obligate aerobes B) thermophilic C) barophilic D) anaerobes
D) anaerobes
no oxygen under mud
obligate anaerobes are usually poisoned by molecular oxygen but may grow in aerobic habitats if associated with facultative anaerobes that use up all available oxygen.
true
Aerotolerant anaerobes ________.
A) synthesize superoxide dismutase, but not catalase
B) synthesize both superoxide dismutase and catalase
C) synthesize neither superoxide dismutase nor catalase
D) synthesize catalase but not superoxide dismutase
A) synthesize superoxide dismutase, but not catalase
Reactive oxygen species
Produced during aerobic respiration
Enzymes to destroy toxic reactive oxygen species
Have all, some or no enzymes
Which reactive oxygen species have all enzymes
Obligate aerobes, facultative anaerobes
have SOD, catalase
which reactive oxygen species Produced during aerobic respiration
Superoxide and hydroxyl radicals; H2O2
Damage cell components
which reactive oxygen species has some enzymes
Microaerophiles; aerotolerant anaerobes
which reactive oxygen species has no enzymes usually
Obligate (strict) anaerobes
Exception: some obligate anaerobes may have superoxide reductase
have sod might have catalase
Facultative anaerobes differ from aerotolerant anaerobes in that ________.
look at both
A) facultative anaerobes synthesize both superoxide dismutase and catalase for protection against reactive oxygen species (ROS), whereas aerotolerant anaerobes synthesize superoxide dismutase only, allowing survival in the presence of ROS, but they do not utilize O2 in their metabolic pathways
How to culture anaerobes
need to remove and exclude oxygen
How to remove or exclude oxygen
Special reducing agent (eliminate O2 in media)
Anaerobic chamber
Capnophiles
require high CO2 for growth
Exponential growth (log scale)
of cells doubles during fixed time
arithmetic plot
cell number vs time
linear
semilogarithmic plot (see slide 23)
cell number vs time
Exponential growth
N1=N0 x 2^N
exponents of exponential growth
N1= final cell #
No= initial cell #
2=cell doubles (constant #)
n= # generations
Microorganisms are at their most uniform in terms of chemical and physiological properties during \_\_\_\_\_\_\_\_ phase. A) lag B) exponential C) stationary D) decline
B) exponential
see slide 25
lag phase
repairing damage, cell making components
log (exponential) phase
actively growing cells
what affects log phase
temp, media, genetics
Stationary phase
no net increase or decrease in number of cells
nutrients used up and waste builds up
death phase
exponential decline
cells die constant rate
how do resistant cells arise
from long stationary phase
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
Which of the following are a reason(s) for the decline in cell numbers during the death phase? A) Depletion of nutrients B) Accumulation of toxic waste materials C) Depletion of O2 D) All of the choices are correct.
D) all choices
One hypothesis about the decline in cell numbers during death phase is that the cells aren’t all dying but instead remain alive but unable to grow when cultured, at least temporarily. These are known as ________.
A) viable but nonculturable cells
A microbiologist is studying the growth of a particular strain of bacteria to determine when it will transition from exponential growth to stationary phase and from stationary phase to death phase. Which of the following methods of measuring microbial growth would be best for this purpose?
viable plate count
The total number of viable microorganisms remains constant in stationary phase because ________.
C) 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 of ________.
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 are correct.
D) all choices are correct
Microorganisms are at their most uniform in terms of chemical and physiological properties during \_\_\_\_\_\_\_\_ phase. A) lag B) exponential C) stationary D) decline
B) exponential
Which of the following is a reason for the occurrence of a lag phase in a bacterial growth curve?
A) The cells may be old and depleted of ATP, essential cofactors, and ribosomes that must be synthesized before growth can begin.
B) The medium may be different from the previous growth medium so that the cells must synthesize new enzymes to use different nutrients.
C) The organisms may have been injured and require time to recover.
D) All of these are potential reasons.
D) All of these are potential reasons.
During the lag phase of microbial growth, the cells are metabolically inactive.
False, they are repairing and making parts
The length of the lag phase of growth can vary depending on \_\_\_\_\_\_\_\_. A) the condition of the microorganisms B) the nature of the growth medium C) the temperature D) All of the choices are correct.
D) all choices are correct
