Microbial Growth - Chapter 3 Flashcards
How do eukaryotic cells replicate?
Through meiosis and mitosis
Binary Fission Steps
Replicate DNA, cell elongation, cell separation
Cell Elongation
Formation of division septum, where 2 cells separate
What is made at the septum?
Cell membrane, cell wall, capsule
Cell Separation
How mitochondria divide
FtsZ Ring
Protein that forms a ring, tells the cell where to build layers so that it can separate -> will get smaller and smaller, and eventually the 2 layers will separate themselves
Cytokinesis
Septum formation is faster and simpler to replicate bacteria compared to mitosis
What is fragmentation common in?
Bacteria that form filaments
Fragmentation
Break into 2 pieces which expand to a longer filament, not very common, not just limited to bacteria
Budding
How yeast divide, asymmetric division -> big and little cell form
Bacterial Counts Formula
Nn = N0 x 2n
Nn
Total bacteria after n replications
N0
Starting number of bacteria
2n
n is the number of replications, can calculate by doing the time passed divided by the doubling time
Doubling Time of E. coli
20 minutes
Doubling Time of M. tuberculosis
15-20 hours
Doubling Time of M. leprae
14 days
Bacteria Growth Curve
Lag phase, log phase, stationary phase, death phase
Lag Phase
Gearing up for replication as they have a good amount of nutrients, cell size increases, increased metabolism, and protein production
Lag Phase Line
Straight as the bacteria count doesn’t change
Log Phase
Exponential growth, actively dividing, most susceptible to antibiotics and disinfectants
Log Phase Line
Line going up
What can antibiotics target?
DNA, RNA, or protein synthesis
Stationary Phase
Run out of nutrients and oxygen, build-up of waste, rate of division is equal to the rate of death, bacteria go into survival mode
Survival Mode for Bacteria
Sporulation starts, slow growth, produces metabolites that are released
Stationary Phase Line
Straight line
Death Phase
Increase of toxic waste that’s killing them, no nutrients left, bacteria undergo lysis to make nutrients for other bacteria to survive, spores are released, persister cells
Persister Cells
Cells that refuse to die, tend to have antibiotic resistance
What tends to have antibiotics?
Plasmids
Direct Methods to Count Bacteria
Petroff-Hausser Chamber/Coulter Counter
Indirect Methods to Count Bacteria
Plate count (CFU), most probably number, optical density, measure dry weight, measure ATP (cell viability)
Direct Counting of Bacteria
Zoom in on one slide of the cell and count the cells in that square, can make a dilution to help count, not very common
CFU (Plate Count)
Colony-forming units, using a dilution to approximate the amount of bacteria
CFU Process
Have a stock solution and make serial dilutions, from each dilution plate a portion and spread it to find individual colonies (want 30-300), count colonies in the plate then plug into a formula to get the total bacteria
What does each colony start as?
1 bacteria
Is CFU accurate?
It may be inaccurate as there are a lot of steps and we have the bacteria grow in between our stock culture and counting
Optical Density
Uses a spectrophotometer to measure turbidity in bacteria
Turbidity
Cloudiness
Spectrophotometer
Measure turbidity in bacteria and will get a specific absorbance as the light bounces off of the bacteria
What blank is used in the spectrophotometer for optical density?
A TSB media as the same media needs to be used in the blank and the samples
Why is optical light density indirect?
It doesn’t give an actual amount of bacteria, but rather the cloudiness of the solution
How can bacteria grow?
Freely grow or attach to a surface to grow
Planktonic
Free-floating
Sessile
Attach to a surface
What growth do bacteria need to be to live in a community?
Need to be sessile
How do bacteria talk to each other?
Through quorum sensing
Quorum Sensing
Coordination of activities in response to environmental stimuli
What does quorum sensing occur between?
Microbes of the same or different species
Autoinducers
Small chemicals that the bacteria release that interact with cells
Gram-Positive Bacteria Autoinducers
Short peptide
Gram-Negative Bacteria Autoinducers
N-acetylated homoserine lactone
What needs to be done to make a community/biofilm?
The bacteria release autoinducers and must reach a threshold to make bacteria
What are the steps of biofilm formation?
-Reversible attachment of planktonic cells
-First colonizers become irreversibly attached
-Growth and cell division
-Production of EPS and formation of water channels
-Attachment of secondary colonizers and dispersion of microbes to new sites
When there are enough bacteria what do they secrete (2nd step)?
They secrete a matrix which holds them together
Extrapolymeric Substance
EPS, holds things together, semipermeable substance, and communities are normally antibiotic resistant
How do we get rid of the biofilm?
We have to disrupt the biofilm to get rid of it since it is antibiotic-resistant
Why is there attachment of secondary colonizers and dispersion of microbes to new sites?
The bacteria will run out of nutrients and room
Where do biofilms commonly form?
In water systems or on catheters
What is one of the only extreme places bacteria can’t grow in?
Volcanoes
What does thioglycolate medium do?
It sucks the oxygen out of the bottom of the media
Obligate Aerobes
Require oxygen, growth on the top
Obligate Anaerobes
Dislike oxygen, growth on the bottom
Facultative Anaerobes
Prefers oxygen but can grow without it, the majority of growth on the top
Aerotolerant Anaerobes
Indifferent to oxygen, equal growth throughout
Microaerophiles
Like oxygen but not at the level of atmospheric oxygen, growth close to the top
Capnophiles
Like carbon dioxide, dislike oxygen
Where do capnophiles grow best?
Candle jars
Candle Jar
Candle consumes oxygen providing the preferred environment
Capnophiles Examples
Haemophilus sp. and Campylobacter jejuni
What does Haemophilus sp. cause?
Influenza-like disease
Where does Campylobacter jejuni live?
In the intestines
Acid
Low pH
Base
High pH
Neutral
Middle pH, ~7
Acidophile
Like acidic pH’s, 1-5.5
Neutrophile
Like neutral pH’s, 5.5-8.5
Alkaliphile
Like basic pH’s, 7.5-11.5
Acidic Environments
Vagina and stomach
Examples of acidophiles
Sulfolobus sp. and Lactobacillus sp.
Examples of neutrophiles
E. coli and Salmonella sp.
Examples of alkaliphiles
Vibrio cholera and Natronbacterium sp. (can survive the highest pH)
Is it easier for bacteria to survive low or high pHs?
Low pHs as it is easier to pump out hydrogen ions
Acidic - H or OH?
H
Basic - H or OH?
OH
pH effects on DNA
High pH breaks hydrogen bonds as the OH groups take the hydrogens
pH effects on lipids
High pH hydrolyzes (breaks down) lipids
pH effects on proteins
Slight changes in pH make a big difference (denature)
Changing ionization -> unfolding/misfolding -> degradation
What is proton motive force also known as?
Electron transport
High pH effects on proton motive force
At a high pH H binds to OH to form water instead of a gradient
Low pH effects on proton motive force
At a low pH you need energy to pump H out to the high H environment, against the gradient causing a gradient problem
Electron Transport
Pump H ions across the membrane and bring them back to make ATP
What changes do acidophiles make to adapt to a changing pH?
Proteins have negatively charged surfaces, hydrogen efflux pumps, change the lipid composition of the plasma membrane to withstand low pH (modify lipids)
What changes do alkaliphiles make to adapt to a changing pH?
Modified lipid and protein structures and modified proton motive force
How do acidophiles make the protein have negatively charged surfaces?
They bring in positively charged particles
Efflux Pump
Gets rid of hydrogen ions, takes energy
What are the changes in ions in alkaliphiles?
The molecules used for electron transport may be changed to keep the gradient such as Na instead of H to prevent the formation of water.
What temperature do psychrophiles like?
Cold temperatures around 10 degrees C
What temperature do mesophiles like?
Temperatures around 37 degrees C
What temperature do thermophiles like?
Temperatures around 65 degrees C
What temperature do hyperthermophiles like?
Temperatures around 95 degrees C
Psychrotolerant Temperatures
Can survive in the cold but prefer warmer temperatures, 3-35 degrees C
Optimal Temperature of Psychrophiles
15 degrees C, but can survive below 0 degrees C
At what temperature do psychrophiles die?
20 degrees C
Where do psychrophiles live?
Cold lakes and the ocean floor
Mesophiles Optimal Temperature
Moderate, around 20-40 degrees C
Mesophile Examples
E. coli, Salmonella sp., and Lactobacillus sp.
Where are thermophiles found?
Hot springs, geothermal soil, or compost
Thermophiles Examples
Thermus aquaticus and Geobacillus sp.
Where are thermophiles found?
Hydrothermal vents
Hyperthermophiles Examples
Pyrobolus sp. and Pyrodictium sp. (can survive the autoclave)
What are the effects of low temperatures on macromolecules?
Membranes slow down and lose fluidity, chemical reactions slow down, and diffusion slows down
What are the effects of high temperatures on macromolecules?
Membrane lipids speed up which disrupts metabolic processes, proteins and nucleic acids will denature
Psychrophiles Bonds
Decrease in secondary stabilizing bonds
Hyperthermophiles Bonds
Increase in G-T content in DNA and increased secondary bonds in proteins
Psychrophiles Flexibility
Proteins are highly hydrophobic due to increased flexibility
Hyperthermophiles Saturation
Increase saturated/polysaccharide lipids to limit membrane fluidity
Hyperthermophiles Amino Acid Usage
Alter amino acid usage to prevent protein denaturing
Isotonic
No net movement of water, equal solutes
Hypertonic
Higher concentration outside the cell, shrivel, water moves outside the cell
Hypotonic
Higher concentration inside the cell, burst/lyse, water moves inside
Halotolerant
High salt isn’t ideal, but it can grow
Nonhalophile
Don’t like salt, isotonic environment, like 0.5% concentrations of salt
Halophiles
Love salt, found in salt lakes and oceans, increased glycerol (prevents shrinking as water can’t move as well) and efflux pumps
Barophiles
Need high atmospheric pressure for growth, found at the bottom of the ocean
Photoautotrophs
Use light energy and CO2 is the primary carbon source
Photoheterotrophs
Use light energy, but can’t use Co2 as a sole carbon source, use organic moelcules as their main carbon source
