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