Foundational Microbiology 2 Flashcards
is the ability of a lens to separate or distinguish between small objects that are close together
resolution
Consider the limits of theta
90 degrees
oil immersions change the refractive ___
index
air has a much ____ refractive index than glass. Glass has an equal refractive index to oil
less
With ____: you are maximizing the amount of light beams that end up reaching the objective lens (the light you can eventually see)
oil
We want to decrease d by:
- using smaller wavelengths
- increasing theta
- increase n (refractive index) by using an oil immersion
BUT STILL… at best, you can get 0.2 m of resolution
Dark-Field Microscopy
- Use peripheral beams
- The background is dark and specimens are light
Phase Contrast Microscopy
2 different populations of light
- The light that passes through the specimen
- Light that does not pass through the specimen
Able to see the structure of the cell but also structures within the cell
- Good for studying motility, detailed structures, organelles, complex structure
Differential Interference Contrast (DIC) Microscopy
Creates the illusion that the structures are 3D
Fluorescent Microscopes
Almost the reverse of what we’ve been talking about
The light source is from the side - high energy, short wavelengths
The solution: Confocal Scanning Laser Microscopy (CSLM)
Allows you to take a picture of a specific focal plane without getting any of the background information
Different vs light and electron
We use an electron gun instead of a light or lamp source
For light: when we want to manipulate the light - we use glass
For electrons: we use magnets to manipulate
BENDS THE BEAM
- Electrons - have a higher energy curve - more likely to pick things up
sphere
Coccus
rod
Bacillus
curve
Virbrio
Binary fission
- chromosome replication begins
- repication continues
- two copies go to opposite sides
- replication finishes
- two daughter cells results
the daughter regular chromosomes are stuck in opposite sides of the cell
Bacterial Reproduction
The new origins of replication move apart, towards opposite ends of the cell. A septum (wall) forms down the middle of the cell, partitioning it into two new cells, each with one of the two (now complete) bacterial chromosome copies. The cell pinches in two. We now have two new bacteria!
will break off and give rise to new filaments
spores
budding
- DNA is replicated
- one daughter DNA molecule is moved into bud
- young bud starts
- daughter cell buds off
strepto-
repeating segment
Tetrads
square of four cells
Sarcinae
8 cells in a cube
Staphlococci
random plane - just a grouping
Arrangement of bacteria: Cocci
is based on:
- Plane of cell division
- Do they stick together after division or not
arrangement of bacteria: bacilli
Only able to divide on their short axis
Palisade
stick together
V-shape
from snapping
two types of external structure (glycocalyx)
- capsule (packed together)
- slime layer Loosely packed
Slimy = they get stuck on teeth etc. and capsules are unrecognizable to the immune system (pneumonia-causing bacteria)
Peritrichous
flagella all over
Single Polar Flagellum
one on one side
Tuft of polar flagella
tuft of flagella on one side
How flagellated bacteria move: A biased random walk
Tumble: all flagellum are beating randomly - spin around in a random direction THEN
Run: all flagellum are operating at the same time in the same coordinated motion
If the run is the wrong direction, they will tumble again,
If the run is in the right direction, the run will be longer
chemotaxis and phototaxis
tumble THEN run - towards light or chemicals (scent)
Rod-like extensions - like grappling hooks
Fimbriae
Adhere to eachother and things in their environment
Disease-causing - affectability to adhere to host (especially if they lack the Slimy layer)
Pili
allow cells to connect and exchange nucleic acids with one another
If one has antibiotic resistance - it can be exchanged with another
Peptidoglycan
major structural polymer in most bacterial cell walls
Gram negative cell walls
Have an thin peptidoglycan cell wall (inner membrane) which is like the PM
Then a Outer membrane surrounding that
Harder to disrupt - medications usually target the cell wall however, there is an additional structure protecting it
Lipopolysacchardie in cell wall
Lipid A in this Lipopolysaccharide is very toxic and can cause shock and fevers in humans
Killing these molecules would therefore release this toxin - sometimes better just to deal with the general symptoms
Gram-positive
has no outer membrane, thicker cell walls
gram-positive cells remain ___
purple
gram-negative cells are _____
pink
Decolourizing agent
breaks down thin cell wall of gram negatives, causing stains to be washed away
what Gram positive bacteria have very waxy cell walls that reject
crystal violet
Mycobacterium and Nocardia
The Ziehl-Neelsen acid-fast staining technique was used instead
Acid-fast bacteria – pink/red
Non-acid-fast - blue
some bacteria can form endospores. This allows them to withstand ____
harsh conditions - go into hibernation
