Growth and Reproduction in Prokaryotes Flashcards
bacterial cells do not divide by meiosis and mitosis. Instead, most bacteria grow asexually by a process known as ___
binary fission
Describe the process of Binary fission
bacterium copies it chromosome
elongates, and splits off into two daughter bacteria with a genetic makeup identical to the parental bacterium
when dormant bacteria are transferred to a fresh medium with plenty of nutrients, they spend some time switching their metabolic machinery from a dormant state called
lag phase
can last from less than an hour to days, depending on the species of bacteria
lag phase
during the ___ phase, the bacteria are actively undergoing binary fission
log phase
the bacteria double their numbers every ___ ____
generation period
can range from 20 minutes to days, depending on the species
generation period
as long as there are plenty of nutrients and little waste buildup, the bacteria will continue growing ___
exponentially
it is convenient to represent the growth of the bacteria on a ___ graph, because the numbers of bacteria increase very rapidly with each subsequent generation
logarithmic graph
after the bacteria have grown for a while and they are starting to deplete the nutrients in the growth medium, some of the cells begin to die
stationary phase
phase where number of cells dying = new cells
stationary phase
after the bacteria have depleted most of their nutrients and their waste buildup is too great, the bacteria begins to deplete in larger numbers than are made
what phase
death phase
if a cell is to survive, it must switch its metabolism back to a ___ state
dormant
increase in cellular constituents
growth
§ Increase in cellular constituents
that may result in: (2)
increase in cell number
increase in cell size
If ____ ____ at the back of
your throat, a sore
throat.
Streptococcus pyogenes
Growth of
microorganisms in
refrigerator shortens/lengthns the
shelf life of the food
shortens
can produce beer, wine, cheese, yogurt, and other products
bacterial growth
most bacterial chromosomes are shaped __
circular
proceeds in both directions from the origin
DNA replication
after DNA replication, what happens to the cell?
elongation
formation of cross walls between daughter cells and cells separate
septation
types of bacterial division (4)
Binary Fission
Budding
Certain actinomycetes by conidiospores
Fragmentation
is a complex molecular machine responsible for DNA replication, ensuring that the genetic material is accurately duplicated before cell division
replisome
time required for the population to double in size
generation (doubling) time
§ varies depending on species of microorganism and
environmental conditions
generation (doubling) time
range is from 10 minutes for some bacteria to several days for
some eukaryotic microorganisms
generation (doubling) time
generation time is calculated during the ___ phase
log (growth)
what temperature can speed up generation time
room temp
what temp prolong doubling time
lower temperature
Microbial populations show a characteristic type of growth pattern called
exponential growth
convert to logarithmic number if arithmetic number is 1024
3.01
convert logarithmic number 6.02 to arithmetic
1047128.548
formula for the number of generation
= log no. of cells (end) - log no of cells (start) / 0.301 (constant)
constant number for number of generation
0.301
generation time is calculated using
= time lapse in minutes or (min/generation) / number of generations
if 100 cells growing for 5 hours produced 1,720,320 cells:
what is the number of generations
14.07
if 100 cells growing for 5 hours produced 1,720,320 cells:
what is the generation time
21.32 min/generation
final cell count formula
initial cell count*2^number of generations
pastry chef accidentally inoculated a cream pie with six S. aureus cells. If S. aureus has a generation time of 60 minutes, how many cells would be in the cream pie after 7 hours?
768 cells
Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is Clostridium killed by oxygen, whereas Streptococcus is not?
This happens because Clostridium and Streptococcus have distinct responses to oxygen due to their metabolic pathways and enzyme profiles. Clostridium is categorized as an obligate anaerobe, meaning it cannot live in the presence of oxygen as it lacks defensive enzymes such as catalase and superoxide dismutase resulting in oxidative damage and cell death. Contrastingly, Streptococcus is classified as a facultative anaerobe or microaerophile–it can thrive in both the presence and absence of oxygen. They contain partial enzymatic defenses against reactive oxygen species, allowing them to survive in low-oxygen environments. In terms of their metabolic processes, Clostridium relies on fermentation for energy while Streptococcus can switch between fermentation and aerobic respiration depending on oxygen availability, allowing for efficient ATP production
Flask A contains yeast cells in glucose–minimal salts broth incubated at 30°C with aeration. Flask B contains yeast cells in glucose–minimal salts broth incubated at 30°C in an anaerobic jar. The yeasts are facultative anaerobes.
Which culture produced more ATP?
Flask A produced more ATP than Flask B. This is because flask A uses aeration for aerobic respiration allowing yeast to fully oxidize glucose through glycolysis, the citric acid cycle, and oxidative phosphorylation. The theoretical maximum yield of ATP from aerobic respiration is 30 to 38 ATP molecules per glucose molecule. Flask B, on the other hand, utilizes an anaerobic environment, requiring yeast to rely only on fermentation for ATP production (the yield of ATP from fermentation is lower producing only 2 ATP molecules per glucose molecule).
Flask A contains yeast cells in glucose–minimal salts broth incubated at 30°C with aeration. Flask B contains yeast cells in glucose–minimal salts broth incubated at 30°C in an anaerobic jar. The yeasts are facultative anaerobes.
Which culture produced more alcohol?
Flask A (aerobic condition), yeast undergoes respiration which is more efficient for energy production but does not favor alcohol production. In flask B (anaerobic condition), yeast relies on fermentation to convert glucose into ethanol and carbon dioxide, which is less effective in terms of energy yield but produces a greater concentration of alcohol as a byproduct.
Flask A contains yeast cells in glucose–minimal salts broth incubated at 30°C with aeration. Flask B contains yeast cells in glucose–minimal salts broth incubated at 30°C in an anaerobic jar. The yeasts are facultative anaerobes.
Which culture had the shorter generation time
The culture with the shorter generation time is Flask A (Aerobic). This is because Aerobic conditions generally promote faster growth rates for facultative anaerobes due to the higher energy yield from aerobic respiration compared to fermentation, which occurs in anaerobic conditions.
Flask A contains yeast cells in glucose–minimal salts broth incubated at 30°C with aeration. Flask B contains yeast cells in glucose–minimal salts broth incubated at 30°C in an anaerobic jar. The yeasts are facultative anaerobes
Which culture had the greater cell mass
The culture with greater cell mass is Flask A (Aerobic). This is because the efficient energy production from aerobic respiration allows for more rapid cell division and biomass accumulation compared to the slower fermentation process in anaerobic conditions
Flask A contains yeast cells in glucose–minimal salts broth incubated at 30°C with aeration. Flask B contains yeast cells in glucose–minimal salts broth incubated at 30°C in an anaerobic jar. The yeasts are facultative anaerobes.
Which culture had the higher absorbance?
The culture with higher absorbance is Flask A (Aerobic). This is because in yeast cultures, absorbance at 600 nm (OD600) correlates with cell density; thus, the higher growth rate and biomass in aerobic conditions would result in a higher absorbance measurement compared to the anaerobic culture
As essential
nutrients are depleted or toxic products build up, growth ceases, and the
population enters the
stationary phase
longest time in the growth curve
stationary growth
soil bacteria would constantly be in ___ phase since the soil has a lot of nutrients
stationary
Cell synthesizing new components
what phase
lag phase
Cell synthesizing new components
for what reason (2)
replenish spent materials
adapt to new medium or conditions
some cases can be short or even absent
what phase
lag phase
lag phase can also depend on the ___ of the medium (is it selective or enrichment, or what temp is the medium in)
harshness
The general rule of thumb is that
microbes adapt to a shift to
improved conditions _______
rapidly than they do to a shift to
poorer conditions.
much more
Also called log phase or log
growth phase
exponential phase
Rate of growth and division is
constant and maximal
exponential phase
Population is most uniform in
terms of chemical and physical
properties during this phase
exponential phase
Bacteria from this stage would
be used for studies
exponential phase
Closed system population growth
ceases due to
§ Nutrient limitation
§ accumulation of a waste product.
§ Limited oxygen availability
§ Critical population density reached
§ Bacteria die off and liberate some
nutrients
stationary phase
§ no change in the number of viable
cells, active cells stop reproducing
or reproductive rate is balanced by
death rate
stationary phase
can last for a long period since microbes in microbes in nutrient-poor environments (like soils and many
aqueous environments) probably
spend most of their time in stationary
phase
stationary phase
Cell numbers begin to decline due to
§ DNA or protein damage or
§ perhaps exhaustion of energy reserves
§ Accumulation of toxic waste
what phase
death phase
Bacteria are dying off opposite to ___ growth phase
log
do bacteria die all at once?
no
two alternative hypothesis for death phase
cells are viable but not culturable (VBNC)
cells alive, but dormant, capable of new growth when conditions are right
fraction of the population genetically programmed to die
programmed cell death
can microbes regulate their internal temp?
no
temperature with minimum growth
minimum temperature
growth rate will spike into exponential growth with what temp
optimum temp
growth rate will slow down with what temp (after optimum temp)
maximum temp
major environmental factor controlling microbial growth
temperature
are the minimum, optimum, and maximum temperatures at which each organism grows
cardinal temprature
optimum is 15C
and max is below 20 C
what microbes
psychropiles
opt. 20C to 40C
what microbes
psychrotolerant
0 oC to 35 oC
which microbes
psychrotrophs
which is more tolerant of chaging temperatures
psychrotrophs
psychrotolerant
psychrotrophs
- optima in the 20 oC
to 45 oC range
mesophiles
s have optima from
45 oC to 80 oC
thermophiles
optima,
above 80 C
extreme thermophiles
which microbes has the optimum temp at room temp
mesophile
core temp of body
37 degrees
surface temp of the body
35 degrees
which have midrange temperature optima, are found in warmblooded animals and in terrestrial and aquatic environments in temperate and
tropical latitudes
mesophiles
have evolved to grow optimally under very
hot or very cold conditions
extremophiles
Organisms with cold temperature optima are called
psychrophiles
most extreme representatives inhabit permanently cold environments.
psychrophiles
have evolved biomolecules that function best at cold
temperatures but that can be unusually sensitive to warm temperatures
psychrophiles
Organisms that grow at 0ºC but have optima of 20ºC to 40ºC are called
psychrotolerant
Organisms with growth temperature optima between 45ºC and 80ºC are called
thermophiles
optima greater than 80°C
hyperthermophiles
These organisms inhabit hot environments up to and including boiling hot
springs, as well as undersea hydrothermal vents that can have temperatures in
excess of 100ºC.
hyperthermophiles
Thermophiles and hyperthermophiles produce heat-stable macromolecules,
such as
taq polymerase
which is used to automate the repetitive steps in the
polymerase chain reaction (PCR) technique.
Taq polymerase
temperature where membrane is gelling; transport processes so slow that growth cannot occur
minimum temp
temperature where enzymatic reactions are occuring at maximal possible rate
optimum
what temperature where protein denaturation occurs; collapse of the cytoplasmic membrane; thermal lysis occurs
maximum temp
refers to the process where a liquid or sol forms a gel-like structure when it comes into contact with a membrane
membrane gelling
blood pH becomes ___ when you are sick
acidic
§ In water, the hydrogen ion concentration will range from 1 x 10-
14 M (a pH of 14) to 1 M (a pH of 0).
hydrogen ion concentration (pH)
Microbes are found at almost any conceivable pH, with most
common bacteria growing at or near
neutral pH (7)
ome organisms have evolved to grow best at low or high pH, but most
organisms grow best between pH
6 and 8
. The internal pH of a cell must
stay relatively close to ___ even though the external pH is highly
acidic or basic
neutral
Organisms that grow best at low pH are called
acidophiles
those that
grow best at high pH are called a
alkaliphiles
-pH optima 1-5.4
acidophiles
pH optima 5.5-7.9
Neutrophiles
pH optima between 0-2
extreme acidophiles
pH optima between 11-14
extreme alkalophiles
causes lactic acid formations
Lactobacillus acidophilus
The normal pH of blood is between
7.35 to 7.45
what processes can make water unavailable
high salt intake
freezing
evaporation
is a measurement of how
much free water is available
water availability
Pure water has a water activity of ___%
100
water activity decreases when ___ are added to the solution
solutes
(lower osmotic concentration)
hypotonic solution
what happens when the outside has a hypotonic solution
water enters the cell
occur when cell swells and burst (hypotonic solution)
plasmoptysis
higher osmotic concentration
hypertonic
water leaves the cell; membrane shrinks from the cell wall
what concentration
hypertionic
cells shrinking from membrane
crenation
he process by which a cell’s protoplasm bursts through its cell wall, releasing colloidal and liquid substances
plasmoptysis
the process by which cells lose water and shrink
plasmolysis
which happens when cell has an hypertonic solution outside
plasmolysis
which happens when cell has an hypotonic solution inside
plasmoptysis
aw stands for
water activity
bacteria are less tolerant of ___ water activity
less
an extremophile that thrives in high salt concentrations.
halophile
15-30% NaCl concentration
extreme halophiles
6-15% NaCl
moderate halophiles
1-6% NaCl
mild halophiles
– endures NaCl; organisms can tolerate some
reduction in the water activity of their environment but
generally grow best in the absence of the added solute.
halotolerant
– lives in high sugar
osmophiles
– microbes in dry environments
xerophiles
have evolved to grow best
at reduced water potentia
halophiles
require high levels of salts for growth
extreme halophiles
Water activity becomes limiting to an organism when the dissolved
solute concentration in its environment increases/decreases
increases
to counteract low water activity, organisms produce or accumulate
intracellular compatible solutes
Many microbes and most eukaryotes need
___ for growth as it is the terminal
electron acceptor.
oxygen
§Others microbes can live without it and some
cannot even tolerate its presence.
oxygen
with this, oxygen requirement for microorganisms are divided into five
obligate aerobes
facultative anaerobes
microaerophiles
aerotolorant anaerobes
strict anaerobes
require oxygen to live
aerobes
s do not and may
even be killed by oxygen.
anaerobes
e organisms can live with or without oxygen.
facultative aerobes
s are aerobes that can use oxygen only when it is
present at levels reduced from that in air.
microaerophiles
use oxygen lower than 21 percent
mircoaerophiles
can tolerate oxygen and grow in its presence
even though they cannot use it
aerotolerant anaerobes
are able to use
oxygen in metabolic processes and generate more energy per
mole of energy source consumed.
strict aerobes and facultative anaerobes
do not use
oxygen in their metabolism and typically have a lower energy
yield and slower growth rates.
aerotolerant anaerobes
strict anaerobes
requires oxygen
obligate aerobe
oxygen not required, but growth is better with O2
facultative aerobe
oxygen required at levels but at levels lower than atmospheric
microaerophilic
oxygen not required, growth no better when O2 is present
aerotolerant anaerobe
oxygen is harmful or lethal
obligate anaerobe
A reducing agent
such as
___ can be
added to a medium
to test an organism’s
requirement for
oxygen
thiogylcolate
Several toxic forms
of oxygen can be
formed in the cell,
but enzymes are
present that can
neutralize most of
them
example of toxic oxygen
superoxide
O2 + e- becomes
O2- superoxide
superoxide with addition of e- and 2H becomes
hydrogen peroxide (H2O2)
H2O2 + e- + H+
hydroxy radical + water
are molecules thjat help protect your body from damage caused by harmful molecules called free radicals
antioxidant
enzymes that destroy toxic forms of oxygen (5)
catalase
peroxidase
superoxide dismutase
superoxide dismustase + catalase
superoxide reductase
convert two molecules of hydrogen peroxide to waste rand oxygen
catalase
an enzyme that catalyzes the oxidation of various substances using peroxides, particularly hydrogen peroxide
peroxidase
requirement for nutrition of microorganisms
macronutrients
micronutrients
trace elements
temperature
pH
osmotic pressure (Aw)
Oxygen
macronutrients needed by oxygen (5)
Carbon
Oxygen
Nitrogen
Hydrogen
Phosphorus
Main constituent of cellular material
carbon
list out the macronutrients based on % of dryweight (highest to lowest)
Carbon
Oxygen
Nitrogen
Hydrogen
Phosphorus
Constituent of cell material and cell
water; O2 is electron acceptor in
aerobic respiration
oxygen
Constituent of amino acids, nucleic
acids nucleotides, and
coenzymes
nitrogen
Constituent of organic compounds
and cell water. Also important in
energy generation as protons.
hydrogen
Constituent of nucleic acids,
nucleotides, phospholipids, LPS,
teichoic acids
phosphorus
micronutrients present (5)
sulfur
potassium
magnesium
calcium
iron
list the micronutrients from highest to lowest based on % of dryweight
Sulfur
Potassium
Magnesium
Calcium
Iron
Constituent of cysteine, methionine,
glutathione, several coenzymes
sulfur
Main cellular inorganic cation and
cofactor for certain enzymes
potassium
Inorganic cellular cation, cofactor
for certain enzymatic reactions
magnesium
Inorganic cellular cation, cofactor
for certain enzymes and a
component of endospores
calcium
Component of cytochromes and
other proteins and a cofactor for
some enzymatic reactions
iron
In amino acids,
proteins
Most bacteria
decompose proteins
Some bacteria use
NH4
+ or NO3
-
A few bacteria use N2
in nitrogen fixation
what element
nitrogen
In amino acids,
thiamine, biotin
Most bacteria
decompose proteins
Some bacteria use
SO4
2- or H2S
what element
sulfur
In DNA, RNA, ATP, and
membranes
PO4
3- is a source of
phosphorus
what element
phosphorus
trace element that play a role in metabolism (5)
Cobalt
Zinc
Molybdenum
Copper
Manganese
Nickel
Part of vitamin B12, which is used to carry
methyl groups
cobalt
Structural role in many enzymes including
DNA polymerase
Zinc
Certain reactions involving nitrogen
assimilation. Found in nitrate reductase and
nitrogenase
Molbydenum
Catalytic role in some enzymes that react
with oxygen for example cytochrome
oxidase.
copper
Required by a number of enzymes in
catalytic sites. Certain photosynthetic
enzymes use manganese to split water into
oxygen and protons.
manganese
Several different enzymes including some
involved in carbon monoxide metabolism,
urea metabolism and methanogenesis
Nickel
§ Some examples of growth factors include (3)
vitamins
amino acids
nucleic acid
are non-protein components of many enzymes
vitamins
Inorganic elements required in small amounts
§ Usually as enzyme cofactors
trace elements
nutritional classification of microbes based on energy
phototrophic
chemotrophic
nutritional classification of microbes based on carbon
autotrophs
heterotrophs
nutritional classification of microbes based on electron
organotrophs
lithotrophs
utilize
light as a source of
energy
photorophic
obtain
energy by the oxidation
of either inorganic or
organic compounds.
chemtrophs
obtain
their carbon from
carbon dioxide
autotrophs
rely on
pre-made organic
compounds for carbon.
heterotrophs
obtain
their electrons from
organic compounds
organotrophs
- obtain
electrons from inorganic
compounds
lithotrophs
nutritional type of cyanobacteria
Photoautothropic lithotrophs
most bacteria and some archea have this nutritional type
chemoheterotrophic organotrophs
check the drawing of sir wilson
+1
§ Parameters used as a measure of growth of a population of
bacteria. They include (3)
change in cell number
change in turbidity or light scattering
change in amount of cell component
three types of measurement of microbial growth
microscopic count
viable counting method
measurement of cell mass
three methods of microscopic counts
counting chambers
electronic counters - flow cytometry
on membrane filters
three methods of viable counting methods
spread and pour plate thechnique
membrane filter
turbidity for most probable number (MPN)
three methods of measurement of cell mass
dry weight analysis
measurement of cell components
turbidity
Easy, inexpensive, and
quick
§ Useful for counting both
eukaryotes and prokaryotes
§ Cannot distinguish living
from dead cells
direct count: counting chambers
§ Microbial suspension forced through small orifice with a
laser light beam
what method
direct count: flow cytometry
§ Movement of microbe through orifice impacts electric
current that flows through orifice
what method of direct count
flow cytometry
Instances of disruption of current are counted = result in
count of individual cells.
what direct count
flow cytometry
limitations of direct count
§ (1) Without special staining techniques dead cells cannot be
distinguished from live cells.
§ (2) Small cells are diffi- cult to see under the microscope, and some
cells are inevitably missed.
§ (3) Precision is difficult to achieve.
§ (4) A phase-contrast microscope is required if the sample is not
stained.
§ (5) Cell suspensions of low density (less than about 106
cells/milliliter) have few if any bacteria in the microscope field
unless a sample is first concentrated and resuspended in a small
volume.
§ (6) Motile cells must be immobilized before counting.
§ (7) Debris in the sample may be mistaken for microbial cells
VBNC stand sfor
viable but not culturable
diluted sample of bacteria is spread over solid agar surface or
mixed with agar and poured into Petri plate
spread plate
after incubation the numbers of organisms are determined by
counting the number of colonies multiplied by the dilution factor
§ results expressed as colony forming units (CFU)
spread and pour plate
can only be used when it has a specified amount of inoculum in the loop
spread and pour plate techniques
optimal number of CFU
30-300
bacteria from aquatic samples are
trapped on membranes
§ membrane placed on culture media
§ colonies grow on membrane
§ colony count determines # of bacteria in
sample
what technique
membrane filter technique
medium selective for gram-negative bacteria
endo agar
determined to yield the most probable number
(MPN)
turbidity
MPN means
most probable number
small test tube used in microbiology to detect the production of gas by microorganisms
durhan tumbe
can be highly unreliable when used to assess
total cell numbers of natural samples such as soil and water
plate counts
typically reveal
far more organisms than are recoverable on plates of any
given culture medium.
direct count
Direct microscopic counts of natural samples typically reveal
far more organisms than are recoverable on plates of any
given culture medium.
is called what phenomenon
great plate count anomaly
occurs because direct microscopic methods count dead cells
whereas viable methods do not, and different organisms in
even a very small sample may have vastly different
requirements for resources and conditions in laboratory
culture.
great plate count anomaly
measurement of cell mass can be done by (3)
dry weight
quantity of particular cell constituent
turbidometric measures
§ time consuming and not very sensitive
what measurement of cell mass
dry weight
what measurement of cell mass
e.g., protein, DNA, ATP, or chlorophyll
§ useful if amount of substance in each cell is constant
quantity of a particular cell constituent
what measurement of cell mass
quick, easy, and sensitive
turbidometric measures (light scattering)
are an indirect but very rapid and useful
method of measuring microbial growth
turbidity measurements
However, to relate
a direct cell count to a turbidity value, a ____ curve must first be
established
standard
