Chapter 2 Flashcards
exam 1
most common bacterial shapes
coccus
bacillus
coccobacillus
vibrio
spirillum
spirochete
strepto..
bacteria are arranged in chains
staphylo
refers to a cluster or grape-like arrangement of bacteria.
sarcinae
bacteria arranged in groups of 8
tetrad
group of four bacteria that are arranged in a square shape.
wavelength
distance between two consecutive troughs of a wave
frequency
number of wave peaks that pass a point in one second.
high frequency
shorter wavelength
low frequency
longer wavelength
relationship between wavelength and resolution
shorter wavelengths provide greater resolution
resolution
the ability to see two objects as discrete objects
at the smallest distance
what are the conditions needed to resolve an object from its surroundings
contrast between the object and its surroundings
wavelength smaller than the object
detector with sufficient resolution for the given wavelength
what are the 4 ways light interacts with an object
absorption
reflection
refraction
scattering
absorption
photon energy absorbed by material
reflection
light bounces off the object in the same angle as the incident angle
refraction
bending of a light wave when light enters a different medium
scattering
the process in which light bounces off particles or objects in many different directions, rather than being absorbed or transmitted.
focal point
refers to the specific spot where light rays converge after passing through a lens.
In a microscope, the focal point is where the image of the object you’re observing comes into sharp focus.
compound light microscopy
uses visible light to illuminate the sample
visible light has a large wavelength which leads to lower resolution
bright field
dark field
phase contrast
fluorescence
bright field microscope
-the large wavelength can only increase the resolution by 1000x
-see the object against a bright background
- observing stained or naturally pigmented specimens.
aberrations
distortions or imperfections in the image produced by the microscope. These distortions occur when light does not focus properly due to imperfections in the lens system.
dark field microscope
Uses a special condenser to direct light at an angle, making the specimen appear bright against a dark background.
Good for observing live, unstained specimens like bacteria.
how is magnification calculated
ocular lens x objective lens
ocular - 10x
objective - 10x 40x 100x
oil immersion
in microscopes to increase the resolution and clarity of the image, especially at very high magnifications (like 100x).
Oil has a similar refractive index to glass, which helps light pass through the specimen more effectively. Oil helps focus more light onto the specimen, making the image clearer and sharper.
phase contrast microscope
Enhances contrast in transparent specimens by changing the phase of the light waves
microscope uses special optics to alter the speed or timing of the light waves as they pass through the specimen.
Fluorescence microscope
uses special dyes and UV light to make parts of the sample glow, making it easier to study tiny or transparent things in detail
electron microscopy
type of microscope that uses electron beams (instead of light) to view very small objects, like viruses, bacteria, or cell structures. It can magnify objects much more than regular light microscopes
Transmission Electron Microscopy
electron beams penetrate a thin section of tissue (HIGH RESOLUTION)
2D image
Scanning Electron Microscopy
electrons bounce off the surface of the sample
3D image
high resolution but less than TEM
Do compound light or electron microscopes have a higher resolution
electron microscopes
Specimen preparation for light microscopy
wet mount
smear
heat fixation
wet mount
drop of liquid placed on slide - match refractive index
smear
dried preparation of bacterial cells on a glass slide
heat fixation
smear is fixed (attached) to slide by heat or would be washed away during staining
Staining
Staining is coloring the microbes with a dye that creates a contract between the bacteria and the background or emphasizes certain microbial structures
positive stain (basic stain)
positively charged and attract to the negatively charged parts of the bacteria that allow the stain to bind to the bacteria
BACTERIA BECOMES STAINED
negative stain (acidic stain)
negatively charged
don’t interact well with bacterial structures so the background becomes stained to create a contrast with the specimen
simple stains
use a single dye
do not distinguish organisms and structures
differential staining
use two or more dyes that react differently allowing various kinds or parts of bacteria to be distinguished
gram staining
Hans Christian Gram
distinguish between gram-positive and gram-negative bacteria
gram (+) - purple
gram (-) - pink
steps of the gram stain
- smear specimen and heat fix
- Add crystal violet stain
- add iodine which binds crystal violet to stain
- wash with ethanol to decolorize
- add safranin to counterstain
gram-positive remains purple due to thick peptidoglycan
gram-negative remains pink
gram negative cells
single layer of peptidoglycan
has outer membrain containing LPS/endotoxin
gram positive cells
multiple layers of peptidoglycan
no outer membrane so has no LPS/endotoxin
Ziehl Nelson Stain - Acid fast stain
Gram-positive bacteria can be further differentiated into acid-fast and non acid-fast
Acid-fast have a thick waxy mycolic acid layer
Steps of the Ziehl-nelson acid fast stain
- Add primary stain carbolfuchsin
- both types will be red - heat up the smear to allow carbolfuchsin to properly adhere to the waxy mycolic acid layer
- wash with an acid-alcohol wash
acid-fast - red non acid fast - colorless - add counterstain methylene blue
acid fast - red non acid fast - blue
Schaeffer Fulton Method
identify bacterial species that produce spores
primary stain - malachite green (stains spores)
safranin (stains other parts of the cell)
parts of the microscope
light source
condensor
specimen
medium
objective lens
ocular lens
