MICRO - Week 1 Flashcards
Thiomargarita magnifica
Significance:
Size:
Fact:
Thiomargarita magnifica
Significance: Is the largest known bacaterium
Size: up to 2 cm in length
Fact: has chromosomes in membrane-bound organelles
> 500 000 genome copies per cell
What defines prokaryotes?
Bacteria and Archaea = Prokaryotes
- DNA in cytoplasm
- Lack membrane-enclosed organelles
- Single-celled
What defines Eukaryotes?
- Eukarya
- DNA surrounded by a nuclear membrane
- Membrane-bound organelles (ER, Golgi …)
- Single celled or multicellular
What region of a prokaryotic cell contains DNA?
The Nucleoid is a region of the cytoplasm that contains DNA
What is one key way that a bacterium structure differs from a eukaryote?
Cell wall
What are some structural features of a prokaryotic cells?
- Capsule (in many)
- Cell wall (in all)
- Ribosomes
- Plasma membrane
- Nucleoid
- Flagellum (some)
- Inclusion bodies (All)
- DNA
Archaea vs Bacteria
Similarities vs Differences
Similarities:
- structure
- metabolism
Differences:
- cell wall components
- types of lipids in the membrane
- transcriptional and translational components
What are some specifications of binomial nomenclature?
- written Genus then species
- name is italicized
- capitalize the first letter
What is the key molecule is the bacterial cell wall?
peptidoglycan
Define: Strain
Strain: descendants of a single pure microbial culture
- have genetic differences
Define: Bacterial species
Bacterial species: a group of strains with similar properties
Can strains be different
- Strains can have genetic differences
Ex. E.coli can be safe, or it can cause foodborne illness
How can you identify prokaryotes?
- Morphology or composition
- Metabolism
- Ecology (where they’re found)
- Nucleotide sequences (16S rRNA, whole genomes)
What is the average size of a prokaryote?
1 um diameter
What is needed for light microscopy?
staining
Can you see prokaryotes macroscopically?
no, average prok is 1 um, human eye can see 0.1 mm
Staining
Simple vs Differential
Simple: size, shape, arrangement
Differential: differentiates based in type of cell wall (gram staining), other structures (capsules, flagella)
Why are there gram differences in gram staining
gram differentiation is due to the permeability differences in cell walls
Describe the process of gram straining?
- Crystal Violet - sticks to all cells
- Iodide - enhances the binding of the dye
- Alcohol - de-stains some of the cells
- Safranin - stains the de-stained cells
Results:
Gram positive = stained crystal violet
Gram negative = Stained by safranin
Provide examples of very large bacteria, and some benefits to being large?
Thiomargartia magnifica
- has long filaments up to 2cm
Thiomargartia namibiensis
- diameter: 100-750 um
- grows in linear chains
Large size may offer:
- more storage space
- less predation
Vey small bacteria
- name one
- diameter
- good/bad
Saccharibacteria
- 0.2 um in diameter
Parasitic
- live on other bacteria
- small genome, can’t make aa or vitamin
Common in oral cavity
- may protect against periodontal disease
Name and describe, provide example:
Morphology and Arrangements of bacteria
Cocci - spherical
- staphylococcus aureus
Bacilli - rods
- legionella pneumophila
Spirals
- campylobacter jejuni
Arrangements:
diplococci - two together
streptococci - chains
staphylococci - blobs
What impact does shape have on bacteria:
Shape impacts:
- motility
- pathogens
- ability to evade predators/immune system
What bacteria was used as an example for importance of shape…why?
Campylobacter jejuni
- has a helical shape that is important for motility
- demonstrated with a mutation that made it rod shaped - no longer infectious
Can bacteria change shape over time?
yes
What example of bacteria was given for changing shape?
uropathogenic E.coli
- lives inside the bladder
- can change from non-motile rods to mobile filament
What are bacteria that live in hot temperatures called?
Hyperthermophiles
Geogemma barossi - Significance
Example Hyperthermophile = geogrmma barosii
- grows at 120
- survives 10h in autoclaving
- unable to grow < 80
How to hyperthermophiles cope with the intense heat?
Membranes
- more viscous
- branched saturated fatty acids
Proteins
- more intermolecular interactions
What is bacteria called that lives in cold environments?
Psychrophiles: grow at low temperatures
Describe psychrophiles in terms of proteins and membrane?
Proteins
- makes cryoprotectants, antifreeze proteins (prevents ice from forming, protects membranes)
- proteins are more flexible (fewer H bond and ionic interactions)
Membranes
- have more unsaturated fatty acids
What is bacteria called that lives in acidic environments?
Acidophiles: grow at low pH
Picrophilus torridus - significance
Picrophilus torridus
- is an acidophile
- can grow at pH 0
How do acidophiles survive?
- they keep their cytoplasm near neutrality, use a proton pump to get H+ out of cell
- surface proteins are acid stable
What are bacteria that live at a high pH called?
Alkaliphiles: grow at high pH, basic conditions
Natronomonas pharaonis - Significance
Natronomonas pharaonis
- is an alkaliphile
- grows at pH 11
What strategies do alkaliphiles use?
- They keep their cytoplasm near neutral by increasing H+ uptake and retention
- They produce acidic metabolites
- Their extracellular enzymes work at high pH
How many microbes does the average adult have?
10^13
Define: Commensalism
Commensalism: one benefits, the other is not benefitted/harmed
In what ways do microbes living in the human body benefit us?
- Nutrient absorption
- Vitamin production
- Maintain immune system
- Colonization resistance
What is an intercellular habitat?
When bacteria lives within other cells
What is an example of a bacterium that live intercellularly
Listeria monocytogens
Define: Culturing
Culturing: The deliberate controlled growth or microbes
What are the types of media that bacteria can be cultured in
Liquid media - ex. broth
Solid media - ex. agar
What % of media can be cutured?
Approx. 1% of bacterial species can be cultured. Limited to what bacteria we can grow in the lab bc we don’t know what the cultures need to grow.
Define: Pure Cultures
Pure Cultures: contain only one strain
How can you isolate a pure culture?
- Have a liquid mixed media culture
- Put on solid media agar plate
- Take pure colony you want and put it in a liquid growth media
What is a colony derived from
Each colony is derived from a single cell
Define: synthetic growth media
Benefits
Synthetic: of known composition
- can use to study nutritional needs
- less batch to batch variability
Growth Media: Complex Media
Descibe
- contains complex products from other organisms that are hard to define in terms of composition
- can support many species
- useful for bacteria with unknown nutritional requirements
WTF is LB
LB = a common complex growth medium
contains:
- peptone
- yeast extract
- sodium chloride
Define: differential growth media
Give example
Differential growth media: distinguishes between different kinds of bacteria
- doesn’t favor or disfavor certain species
Ex. Blood agar
- used to detect hemolytic bacteria
- hemolysis is a defining feature of some pathogens
Define: selective media
Selective media: supports certain species, or inhibits certain species
Tell me about MacConkey agar
MacConkey agar
Selective for Gram-negatives
- bile salts, crystal violet inhibits Gram-positives
Differential
- bacterial the ferment lactose make acidic products that turn the pH indicator red
What disease is the leading cause of death?
Diarrheal
Define: Growth
Growth: increase in number of cells
What are the steps of binary fission? (Simple)
- Chromosome is replicated
- Cell elongates
- Septum forms, chromosomes partitioned
- Daughter cell forms
What is FtsZ
FtsZ is a tubulin like protein that forms the Z ring in the middle of the cell. It’s involved in binary fission
What is the divisisome?
Divisome: is a complex that forms at the Z ring during binary fission. The Z ring constricts invaginating the membrane, and the divisome makes septum (peptidoglycan)
Name 2 other bacterial reproductive strategies aside from binary fission?
- Budding (Listeria monocytogenes)
- Spore formation (strept0momyces)
Define: Generation time
What factors impact?
Generation time: time it takes a population to double
- condition dependent
- depends on species
Define: Batch culture
Batch culture: closed vessel, single batch of medium deliberate growth of bacteria (medium is inoculated with bacteria)
What are the 4 phases of growth in a batch culture
Lag Phase: metabolic activity is increasing, cells prepare to replication, and they adapt to the nutrients present in their environment
Log Phase: Exponential growth, grow as fast as possible
Stationary Phase: growth is off set by death
Death Phase: little nutrients and lost of waste, drives evolution bc only the strongest survive
What is the y axis on a growth graph?
The y-axis is the log of viable cell count
In the Log phase of cell division, cells divide as fast as possible according to:
- species/strain
- growth medium
- conditions
What are you counting in direct counting methods
Cells/mL
Plate Counting - Define
Plate counting: add sample to agar plate, then count the number of colonies
TF
1. Plate count only counts viable cells
2. Plate count counts individual cells
3. Plate counts give smaller counts than direct counts
TF
1. T - Plate count only counts viable cells
2. F - Plate count counts individual cells (Plate count counts colony forming units)
3. T - Plate counts give smaller counts than direct counts
Name some of the plate count anomalies
- plate counts give smaller counts than direct counts
- Living vs dead
- viable but not culturable
- many species can’t be grown in lab
If your sample is too dense to count what technique can you use?
Serial dilutions
Growth (G) vs Cell mass (M)
indicate which is measured:
1. Cell mass
2. Dry weight
3. # genomic copies
4. Metabolic activity
5. Turbidity
6. Spectrometer
- Cell mass (G)
- Dry weight (M)
- # genomic copies (G)
- Metabolic activity (G)
- Turbidity (M)
- Spectrometer (M)
How do cells cope with hypertonic conditions?
- plasmolysis conditions cause membrane damage
- dehydration slows growth
- some bacteria make compatible solutes, to draw water in
How do cells respond to hypotonic conditions
Mechanoselective channels: regulated by stretching of the cytoplasmic membrane
- when stretched the channel opens and solutes leave, this decreases the osmotic pressure
Name the classification of bacteria based on the pH:
pH< 5.5
pH 5.5-8
pH> 8.0
Acidophile = pH< 5.5
Neutrophiles = pH 5.5-8
Alkaliphiles = pH> 8.0
How do cells cope with pH changes?
They import or export protons
There are 5 classifications of bacteria based on the temperature they live in…name them from coldest to warmest?
Psychrophiles
Psychrotrophs
Mesophiles
Thermophiles
Hyperthermophiles
What is the name for bacteria that grows at the temperature of the fridge
psychrophiles
