Microbial Growth (#4) Flashcards
often refers to an increase in the # of cells
growth
microbiologists usually study _______ growth rather than growth of individual cells
population
process of two cells arising from one
binary fission
microorganisms (like bacteria) use _____ ______ to “grow”/reproduce unlike eukarya who use ______
binary fission; mitosis
steps of binary fission (4):
1) cell elongation
2) genome is replicated and segregated
3) cell division
4) increase in cell #
step of binary fission: cellular constituents increase proportionally; gets bigger so each cell is equal in size
cell elongation
step of binary fission: septum is formed at midcell; purposely patching holes in cell wall + bits of peptidoglycan (in penicillin is there, amino acids CANT link)
cell division
one cell —> two cells = _____ ______
one generation
pinching in of cell membrane and wall
septum
extra pieces of DNA; not under replication of chromosome (not equally divided in binary fission)
plasmids
plasmids have _______ division unless they are incorporated permanently on the chromosomes
unequal
when the septum begins to grow, where do the chromosomes move to?
opposite ends of the cell (to the membrane)
some species separate completely, while others….
remain attached forming chains, doublets, or other cellular arrangments
if penicillin is present during binary fission, _____ _____ CANT link and cells aren’t able to patch holes in their cell wall properly
amino acids
time required for the population to double in number of cells
generation (doubling time)
generation time = ______ time
doubling time
generation time varies depending on what 2 things?
- the species
- environmental conditions
cell number doubles within a FIXED period of time; doesn’t last forever; maximal rate of division
exponential growth
generation (doubling) time is _______ growth
exponential
exponential growth shows a ______ line
straight
exponential growth tells you where the _______ cells are
healthiest
doubling time (best case scenarior) for E. coli =
20 minutes
calculating generation time: n =
number of generations for t
formula for n:
n = 3.3(logNt - logNo)
Nt =
final cell #
No =
initial cell #
how do you calculate generation time?
1) find n using equation
2) find g using t/n
g =
generation time
formula for g:
g = t/n
In aerobic respiration (for one molecule of glucose), how many ATPs can be made in the Kreb’s cycle (including the bridge step) via the oxidation of NADH?
24
there is a lot of _____ in generation time
diversity
as cells get LARGER, the generation time ______
increases (takes longer to double)
observed when microorganisms are cultivated in batch culture
growth curve (microbial growth cycle)
culture incubated in a CLOSED vessel with a single batch of medium; not continuously feeding them
batch culture
for the Growth Curve, you are looking at a ______ of cells in a batch culture, not a singular cell
population
how is the Growth Curve (microbial growth cycle) usually plotted?
logarithm of cell number vs. time
4 distinct phase of microbial Growth Curve:
- lag
- exponential (log)
- stationary
- death
T/F: the lag phase is always flat
False; might be a gradual incline
steepest slope on growth curve (maximal rate) =
exponential phase
phase can be exponential too but happens slower than exponential phase (less steep)
death phase
phase of growth curve: cells synthesizing new compounds to replenish spent materials and to adapt to new medium or other conditions (ex: use a new carbon source, produce new enzymes)
lag phase
lag phase varies in ______; in some cases, can be very short or even ABSENT
length
why might a lag phase be absent?
cells were already growing or are already used to the medium
exponential phase is also called the _____ phase
log phase
in the exponential phase, rate of growth is _____ and _______
constant and maximal
phase of growth curve: population is most uniform in terms of chemical and physical properties; most are same age
exponential phase
cells in which part of which phase are considered the healthiest?
mid-exponential
phase of growth curve: total number of viable cells remains CONSTANT
stationary phase
why is the total number of viable cells constant for stationary phase (2 reasons)?
- metabolically active cells STOP reproducing
- reproductive rate is balanced by death rate
possible reasons for stationary phase (4):
- nutrient limitation *
- limited oxygen availability
- toxic waste accumulation
- critical population density reached (no room)
critical population density limit is usually _____ cells
10^9 cells
important to note that the growth curve phases look at what the ______ of cells are doing — NOT all cells
majority
starvation responses (2):
1) morphological changes
2) persister cells
what morphological changes can cells do in response to starvation?
- endospore formation
- decrease in size
- production of starvation proteins
morphological change (starvation response): do this IF they can; triggered by nutrient limitation mostly
endospore formation
morphological change (starvation response): get skinnier; may see inclusion disappear
decrease in size
what 3 functions do starvation proteins do?
- increase cross-linking in cell wall
- protects DNA (Dps protein)
- prevent protein damage / being denatured (chaperone protein)
types of starvation proteins (2):
- Dps protein
- chaperone protein
type of starvation protein: protects DNA
Dps protein
type of starvation protein: prevent protein damage/being denatured
chaperone protein
production of starvation proteins may continue into the _____ phase
death
type of starvation response: long-term survival being starved; have increased virulence; sticky, shriveled up, unhealthy cells; almost like a dormant state bc they slow down but are STILL metabolically active
persister cells
persister cells are the “_____ and _____ cells”
mean and nasty cells
persister cells’ ________ aids in their virulence
stickiness
persister cells are not as strong as _______ but they do persist
endospores
phase of growth curve: total number of viable cells decreasing
death phase
what is occurring during death phase (2)?
- removal of critical nutrients below a threshold level
- metabolic end-product reaches toxic level
you might get a slight increase in the cells in the death phase due to _____ ______
persister cells
how do you know if cells are for sure dead (2)?
- irreversible loss of ability to REPRODUCE
- cells may lyse
2 types of measurements of cell numbers:
- direct
- indirect
type of measurement of cell #: total cell counts; count the number of cells that are observed in the medium
direct
type of measurement of cell #: gives you a rough estimate of cell numbers; must perform other experiments to get an actual number
indirect
methods of DIRECT cell counts (5):
- counting chamber
- electronic counter
- viable cell counts
- plating techniques
- membrane filter
method of direct cell count: grid put on microscope
counting chamber
method of direct cell count: put bacteria through a tiny tube with electric current; counts a cell every time current is blocked
electronic ocunter
method of direct cell count: count the number of CFU’s (colony-forming unit)
viable cell counts
method of direct cell count: counting colonies
plating techniques
types of indirect cell counts (2):
- dry weight
- turbidity
the Petroff-Hausser Counting Chamber is like a ________ where you count WBCs
hemocytometer
problem with Petroff-Hausser Counting Chamber:
unless you’re using a specialized staining kit, you can’t tell the difference between dead and live bacteria (if they don’t lyse, you could be counting dead cells)
T/F: with plating methods/techniques, you cannot count dead cells; it’s a VIABLE cell count
true
plating method steps (3):
1) plate dilutions of population on suitable solid medium
2) count # of colonies
3) calculate # of cells in original population
population sizes in plating methods are expressed as _____ per _____
CFU/mL
countable plate = ______ - ______ colonies
30 - 300
to calculate the number of cells in the original population, you count the # of colonies on a countable plate and then multiply by what?
reciprocal of the dilution
with the Spread-plate method, colonies are found where?
on the surface
with the Pour-plate method, colonies are found where?
on surface + subsurface (below)
type of direct cell count: used for water testing; make dilute water samples into concentrated samples of bacteria
membrane filter
turbidity is also known as:
optical density
type of indirect cell count: use a spectrophotometer
turbidity
problems with plating methods (2):
- counting/plating erros
- culture medium might not be perfect for bacteria and give inaccurate results of counts
in turbidity, more cells = more absorbed (________) light = less transmitted (________) light detected
scattered; unscattered
to relate a direct cell count to a turbidity value, what first must be established?
a standard curve
turbidity: more cells = ______ absorbance
higher
color of light where bacteria absorb the most light; what we used on spectrophotometer
green light
wavelength range of green light:
540-600 nm
problems with using turbidity (2):
- doesn’t give an actual # of cells (have to do other experiments like viable cell count + a standard curve)
- dead bodies ALSO absorb light; could you a potential overestimate
since dead bodies also absorb light, you could potentially get an ________ of cell count for turbidity
OVERESTIMATE
what 4 environmental factors affect microbial growth?
- temperature
- pH
- water availability (osmolarity)
- oxygen
can microbes regulate their internal temperature?
no
microbes exhibit distinct ______ ________ temperatures
cardinal growth
3 cardinal growth temperatures:
- minimum
- maximum
- optimum
cardinal growth temp: membrane is so cold that it is gelling; transport processes are SLOW; if you go below this temp, growth STOPS
minimum temp
cardinal growth temp: protein/enzyme start to denature; growth rate DROPS; collapse of the cytoplasmic membrane; lots of cell lyse; above this temp, growth stops
maximum temp
cardinal growth temp: best temp for growth; enzymatic reactions occurring at maximal possible rate
optimum temp
temperature classes of microbes (4):
- psychrophile
- mesophile
- thermophile
- hyperthermophile
optimum temp for psychrophile =
4 degrees C (temperature of your fridge!!)
RANGE of cardinal temperatures for most bacteria:
25 - 40 degrees
hyperthermophiles have a ______ range (especially compared to mesophiles)
narrower
what temperature class are MOST bacteria?
mesophiles
optimum temperature (range) for psychorophiles:
< 15°C
optimum temperature (range) for psychrotolerant microbes:
20-40°C (AND able to grow at 0°C**)
optimum temperature (range) for mesophiles:
20-40°C (includes room temp (20°C) and body temp (30°C))
optimum temperature (range) for thermophiles:
45-80°C
optimum temperature (range) for hyperthermophiles:
> 80°C
which temperature class includes room temp (20°C) + body temp (30°C) in its optimum temperature range?
mesophiles
temperature class of microbes: grow in really cold temperatures; found in the depth of the ocean
psychrophiles
temperature class of microbes: mesophiles but can tolerate growing at 0°C
psychrotolerant
temperature class of microbes: most microbes
mesophiles
temperature class of microbes: found in warm water and hot springs
thermophiles
temperature class of microbes: grow in BOILING hot springs and volcanic vents; a lot of the time are ARCHEONS
hyperthermophiles
which two temperature classes can grow in your fridge (4 degrees C)?
psychrophiles and psychrotolerant
T/F: optimum temp ranges of microbes can match
True (look at psychrotolerant and mesophiles – they overlap)
anything that can survive above 65°C is a ________
prokaryote
average temp of ocean =
5°C
which temp classes can live in the ocean?
psychrophiles and psychrotolerant
adaptation for COLD environments (2):
- more flexible enzymes
- modified cytoplasmic membranes
how are cytoplasmic membranes modified in COLD environments to become more flexible for growth?
have high UNSATURATED fatty acid content
adaptations for HOT environments (2):
- thermally stable enzymes
- modified cytoplasmic membranes
how are cytoplasmic membranes modified in HOT environments to become more flexible for growth?
have high SATURATED fatty acid content (more stability so they’re not falling apart)
thermally stable enzymes have _____ bonds so they’re not denatured so easily in heat
ionic bonds
thermally stable enzyme; used in PCR; comes from a thermophylic bacteria
Taq polymerase
pH classes of microbes (3):
- acidophiles
- neutrophiles
- alkaliphiles
optimum pH range for acidophiles:
0 - 5.5
optimum pH range for neutrophiles:
5.5 - 8
optimum pH range for alkaliphiles:
> or equal to 8
most microbes are which pH class?
neutrophiles
most neutrophiles are found between ____ and ____ pH but prefer ____
3 - 9
prefer 7
cytoplasm is kept at a pH of ___
7
pH scale is a ____-fold change between each unit
10-fold
some microbes like extreme pH’s (like archeons) but they are _____
rare
pH of seawater =
8 (alkaline)
T/F: most microbes maintain an internal pH near neutrality
true
respones to pH (3):
- acid shock proteins
- use of sodium motive force (instead of PMF)
- some microbes buffer the pH of their habitat by producing acidic or basic waste products
type of response to pH: produced when exposed to acid in their environment; use protein to negate it; FIX enzymes beginning to denature from acid
acid shock proteins
pH range of microbes is usually between ____ units
2 units
bacteria that can survive in stomach acid; uses flagella to burrow into the stomach and cause ulcers; breaks down urease into ammonia and uses it as a buffer
Helicobacter pylori
amount of water available to organisms
water activity (aw)
water activity values range from ___ to ____
0 to 1
water associated with solutes is ______ to microorganisms (<1)
solutes
higher solute concentration = ______ water activity
LOWER
adaptation to HYPOtonic solution:
use mechanosenstive (MS) channels in membrane to allow solutes to leave
when cells uses mechanosensative (MS) channels, _____ water comes into the cell
LESS
release solutes (NOT water) to make environment more hypertonic so less water comes in
MS channels
adaptation to HYPERtonic solutions:
increase internal solute concentration with compatible solutes
when cells use compatible solutes, _____ water comes into the cell
MORE
cells hoard _____ _____ in hypertonic environments to balance the concentration gradient
compatible solutes
where cells wanna live; bring water INTO the cell; gives them turgid pressure
hypotonic environments
gram-______ can tolerate a lot lower water activity than gram-_____
POS
neg.
gram-______ can tolerate a lot lower water activity than gram-_____
POS
neg.
classes of NaCL (salt) microbes (4):
- nonhalophile
- halotolerant
- halophiles
- extreme halophiles
class of NaCl (salt) microbe: does NOT require NaCL; can grow if environment is <1% of NaCL
nonhalophile
halotolerant microbes include _____ ______ and _________ bacteria
staph aureus and gram-POS
class of NaCl (salt) microbe: doesnt love NaCL but can tolerate it
halotolerant
class of NaCl (salt) microbe: requires NaCL for growth; grow optimally at 1-15% NaCl
halophiles
class of NaCl (salt) microbe: require 15-30% NaCl
extreme halophiles
NaCl range for nonhalophile growth:
<1%
NaCl range for halophile growth:
1 - 15%
NaCl range for extreme halophile growth:
15 - 30%
example of extreme halophile; archeon that makes a pink pigment; contributes to pink color of the dead sea
Halobacterium salinarum
classes of oxygen microbes:
- aerobe
- obligate (strict) aerobe
- anaerobe
- obligate (strict) anaerobe
- microaerophile
- facultative aerobe/anaerobe
- aerotolerant anaerobe
class of oxygen microbe: grows in presence of atmospheric oxygen, which is 21% O2
aerobe
class of oxygen microbe: requires oxygen
obligate aerobe
class of oxygen microbe: grows in the absence of oxygen
anaerobe
class of oxygen microbe: usually KILLED in presence of oxygen
obligate (strict) anaerobe
class of oxygen microbe: requires 2-10% oxygen; lives down in water columns
microaerophile
atmospheric oxygen = _____% oxygen
21% oxygen
narrow range of % oxygen that microaerophiles require to grow
2-10% oxygen
class of oxygen microbe: does not require oxygen, but grows BETTER in its presence; if there is O2, it will use it for aerobic respiration
facultative aerobe/anaerobe
class of oxygen microbe: grows with or without oxygen; does not affect growth
aerotolerant anaerobe
type of metabolism obligate aerobes use:
aerobic respiration
type of metabolism facultative aerobes use:
aerobic or anaerobic respiration + fermentation
type of metabolism microaerophilic microbes use:
aerobic respiration
type of metabolism aerotolerant microbes use:
fermentation **
type of metabolism obligate anaerobes use:
fermentation or anaerobic respiration
oxic zone is found at the _____ of the tube and the anoxic zone is found at the _____ of the tube
top; bottom (majority of tube)
oxygen is easily reduced to ______ reactive oxygen species (ROS)
toxic
toxic reactive oxygen species (ROS) are ____ ______
free radicals
types of toxic reactive oxygen species (ROS - 3):
- O2⁻
- H2O2
- OH*
ROS =
reactive oxygen species
protective enzymes from ROS (3):
- superoxide dismutase
- catalase
- peroxidase
most dangerous ROS =
OH* (hydroxyl radical)
superoxide dismutase, catalase, and peroxidase transform ROS into _____
oxygen
the ocean has a an average pH of 8.3, an average salt concentration of 3%, and an average temperature of 5 degrees Celcius. If a bacterium lives in these conditions, it could be described as an:
