Lecture 7 - Growth PART 1 Flashcards
Bacteria will go in nature and in the lab.
In nature, what two forms do bacteria exist?
- Planktonic: individual, free-floating bacterial cells.
- Biofilm: polymer-encased communities of one or more bacterial species, which are attached to a surface.
what type of bacteria comprises 70% of human infections?
Biofilm
how do biofilm end up stroking surfaces?
with the help of capsule and pili
what benefits do bacteria receive when biofilm grows?
-There is a sharing of nutrients between bacteria.
-There is protection from harm (desiccation, antibiotics, immune system).
-There is an easier exchange of genetic material.
what harmful effects does biofilm have on us, humans? what is an example?
-They are harder to clean and treat for us.
Example: Pseudomonas aeruginosa in lungs of cystic fibrosis patients.
So it is good for bacteria but bad for us.
Biofilm has Quorum sensing - what is that?
It is a chemical language through which bacteria talk to each other
in what bacteria was quorum sensing discovered?
in Vibrio fischeri (short curved rod)
when does the quorum sensing produce light?
it produces light only at high cell density.
at high cell density, the concentration of a particular signal called ____ reaches a threshold, that turns on the genes responsible for group-specific behaviors like light or toxin production.
autoinducer
what does autoinducer do?
it turns on the genes that are responsible for group-specific behaviors like light or toxin production.
at low cell density, what happens with the bacterial quorum sensing?
nothing happens
quorum sensing allows bacteria to act in unison to do what?
to perform big tasks that are useful for the community
what does V. fischeri produce in the light organs of Hawaiian bobtail squid? how does this help the squid?
it produces light which minimizes the squid’s shadow and allows it to hunt stealthily
quorum sensing can be used to design ____ that attack ____?
can be used to design antimicrobials/antibiotics to attack the autoinducer.
in the lab, microbial growth is often in pure cultures, which are what?
they are cultures with only one species of bacteria
what are the two types of culture (growth) mediums?
-Nutrient broth (NB): liquid.
Turbidity = cloudiness.
-Nutrient agar (NA): solid.
Isolated colonies: a colony is a distinct mass of cells arising from a single cell by multiple rounds of cell division.
have all known bacteria been cultured in the lab?
NO, 99% of bacteria haven’t been cultured in the lab.
what is the great plate count anomaly?
it is the number of cells observed under the microscope are greater than the number of colonies on a plate.
this means that we aren’t able to grow 99% of bacteria in the culture.
what % of bacteria is unculturable?
99%
do we know the identity of bacteria though? how?
we do know the identity through DNA studies; we can find their DNA but don’t know how to grow them
how do we measure the growth of bacteria?
by the number of them
what is binary fission?
it is when the bacterial cell splits into two.
1. the cell gets longer and the DNA replicates.
2. the DNA is moved into each future daughter cell and the cross wall forms.
3. the cell divides into two cells
4. the cells separate
5. two daughter cells form
does binary fission of bacteria have mitosis or meiosis?
NO
bacteria has exponential growth, what is that?
it is the rapid and exponent growth of the bacteria
what is the generation (doubling) time of the bacteria? what is an example?
it is the time it takes for 1 cell to divide into 2 daughter cells.
example: E. coli on a salad at room temperature goes from 10 cells to 40,000 cells in 4 hours.
how do we grow bacteria?
in a closed (batch) system. this is when we use either broth or agar where we do not replenish the nutrients OR remove wastes.
what are the 4 phases of microbial growth and what do they consist of?
- Lag: this is before the actual division of bacterial cells, it is just prepping for the next steps.
- Log/exponential phase: this is when there is an exponential increase in cell number; this is the MAX growth rate.
- Stationary: this is when there is no increase in cell number. when the growth rate = the death rate. the dead cells lyse and provide food for the growing cells.
- Death: this is when there is a decrease in cell number; eventually all bacteria will die.
what does the X and Y axis of the growth curve chart consist of? what type of growth is recorded?
X-axis: time per hour, day, month, or year.
Y-axis: the logarithmic growth because of the exponential speed of growth.
what is a continuous system?
when the cells are in constant log/exponential phase.
how might you create a continuous system?
by taking out wastes and giving food for the bacteria to grow constantly
in agar, the cells on the outside are in the dead phase? ask prof
In a colony, cells in the middle are in the death phase and the ones on the periphery are in the exponential phase.
Penicillin attacks growing bacteria, so in which phase of the growth curve does penicillin work best?
during the log/exponential phase
what are the 4 environmental factors that can affect the growth of microbes?
they are physical (environmental) conditions.
1. temperature
2. pH
3. osmotic pressure (hyper vs. hypo)
4. oxygens
what are the chemical (nutrients) factors that can affect the growth of microbes?
- macronutrients (CHONPS; carbon, hydrogen, oxygen, nitrogen, phosphurus, sulfur).
- micronutrients: Fe, Zn, Me, Ni.
what are psychrophiles and psychrotrophs?
they are cold-loving bacteria.
(philes = loving; trophs = eating)
what are mesophiles?
they are bacteria that grow the fastest in optimum 37 degrees celsius.
can mesophiles grow in other temperatures?
yes they can still grow in other temperatures but just grow the fastest in optimum temp
all pathogens that create diseases in humans are what type of organism?
mesophiles
what are thermophiles?
heat-loving bacteria
what are hyperthermophiles?
superheat-loving
at minimum growth rate, what happens?
the membrane is gelling; the transport processes are so slow that growth cannot occur
on the way from minimum to optimum growth rate, what happens?
the enzymes and reactions occur at an increasingly rapid rate
what happens at optimum growth rate?
when the enzymes and reactions occur at the maximal possible rate
what happens at maximum growth rate?
protein denaturation: there is a collapse of the cytoplasmic membrane; thermal lysis occurs
how do bacteria survive in very hot environments?
through two things:
1. rigid thermostable proteins: tightly folded proteins to prevent denaturation.
2. rigid membranes: have tightly packing lipids
high temperatures are usually _____?
bactericidal = bacteria killing
low temperatures are usually ____?
bacteriostatic = bacterial growth stopped
what temperatures are considered the “danger zone”?
Between:
15 and 50 degrees celsius.
60 and 130 degrees Fahrenheit.
does the temperature in the fridge kill the bacteria?
no, but it stops its growth
are there significant growth of bacteria below freezing?
no
what is pH?
the concentration of H+
what is the pH of the cytoplasm of most bacteria?
7
what are neutrophiles?
pH of 6-8
what pH do most bacteria love?
most bacteria love neutral pH
what are acidophiles?
bacteria that live in a pH of less than 5.5
why do acidophiles live in that environment? what does it give them?
it gives them a competitive edge; it has more food and water to grow since not many other bacteria can live in that acidic of an environment
what are alkaliphiles?
bacteria that grow in a pH over 8.5
how do bacteria survive in low or high pH environments?
- Pumping protons in (which alkaliphiles do) or pumping protons out (which acidophiles do).
- Having membranes that are less permeable to protons.
- Having more buffers in the cytoplasm to maintain pH.
what is osmotic pressure?
water availability
what do bacteria undergo in hypertonic environments? what is it used for?
plasmolysis - it is used in food preservation
what does the term facultative refer to?
refers to when the bacteria can survive with or without that certain thing
what does the term obligate refer to?
when that bacteria NEEDS that certain thing and cannot live without it
what are facultative halophiles? what is another name for them?
there are salt-loving organisms that can survive with or without salt.
aka halotolerant
what NaCl percentage do facultative halophiles live under?
NaCl up to 10% or higher
what is an example of facultative halophiles?
S. epidermidis - it can grow on clean or sweaty skin (salty or non salty skin)
when there are more solutes outside of the cell than inside, where does water flow?
towards the outside of the cell
what are obligate halophiles?
these organisms NEED salt and cannot live without it.
what percentage of salt do obligate halophiles need to live under?
NaCl of at least 9%.
They can live in saturated salt (32%)
what is an example of obligate halophiles?
Halobacterium salinarium
how do bacteria prevent plasmolysis in high-salt environments?
they accumulate solutes in the cytoplasm so that they are isotonic with the salty environments around them.
the salt in the environment = the salt in the cytoplasm
what are obligate aerobes? what is an example?
bacteria that need O2 to grow.
example: Pseudomonas
what are obligate anaerobes? what is an example?
bacteria that die in the presence of O2.
example: Clostridium
how do obligate anaerobes grow without O2?
they grow via an anaerobic chamber/jar
what are facultative anaerobes? what is an example?
bacteria that prefer O2 but can survive without it. example: E. coli
what are microaerophiles? what is an example?
these bacteria need a little bit of O2.
example: Helicobacter
what are aerotolerant anaerobes? what is an example?
anaerobes that can tolerate the presence of O2.
example: Streptococcus pyogenes
how do bacteria deal with the toxic byproducts of O2 metabolism (like H2O2)?
O2 often makes toxic byproducts. We deal with these toxins by our enzymes like catalase and superoxide dismutase to detoxify the toxins.
In which phase of the bacterial growth curve does the number of dividing bacteria equal the number of dying bacteria?
1. Lag phase
2. Log phase
3. Stationary phase
4. Death phase
5. Exponential phase
- Stationary Phase
The lag phase of the bacterial growth curve is marked by:
1. A decrease in cell mass
2. Dormant, metabolically inactive cells
3. Vigorously dividing cells
4. Metabolically active cells
5. A decrease in enzyme activity
- Metabolically active cells
Microorganisms that die in the presence of O2 are referred to as:
1. Facultative anaerobes
2. Obligate anaerobes
3. Microaerophiles
4. Aerotolerant anaerobes
5. Obligate aerobes
- Obligate anaerobes
In figure 1, which line represents the exponential growth phase of a mesophile with an optimum temperature of 350C incubated at 400C? (Hint: Distinguish optimum temperature vs. temperature range.)
1. a
2. b
3. c
- b
(not the fastest, but still grows)
Case study:
Of the following, what would be the LEAST important thing for the investigator to determine when studying the outbreak?
1. A description of the symptoms, including symptoms that are NOT present
2. If anyone else had been ill before or had gotten ill around the same time
3. A detailed food history over the last 72 hours
4. Contact information for the caller (phone numbers, address, etc.)
5. Where the caller suspects he got sick
- Where the caller suspects he got sick.
Explanation:
Regardless of the source of digestive illness (whether it be food, water, or another person), complainants will often associate their illness with the last food or meal they consumed.
While knowing about the restaurant as part of food history is good, one should not assume anything at this point.
The investigator should keep an open mind and solicit information about the following: 1) Foods and beverages that may have been eaten at least 72 hours ago–since incubation periods of certain diseases can be 3 days or more 2) If anyone else had been ill before or had gotten ill around the same time–find out which foods and beverages that affected individuals had in common 3) A description of the symptoms, including symptoms NOT present e.g. fever–since this may help narrow down the list of possible diseases 4) Contact information is important in order to follow-up on the case, especially if the situation turns into an outbreak
As the investigator, what would you advise the student to do?
1. Stay home and not go to school.
2. See a doctor.
3. Eat a bland diet until the symptoms stop.
4. Its okay to go to school if he feels better.
- See a doctor.
Explanation:
A public health investigator is not a doctor and should not be giving medical advice, especially over the phone. This could lead to great liability if the case takes a turn for the worse. The other answers may be things that a doctor will advise the student to do.
Do you think these cases of gastroenteritis represent an outbreak at the college?
1. Yes they do.
2. No, they do not.
3. They represent a student’s attempt to get out of his Microbiology test
- Yes they do.
Explanation:
YES. An outbreak is defined as the occurrence of more cases of a disease than expected for a particular place and time. Of course, the student’s thinking may still be to get out of the Microbiology test!
