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Lab Midterm
Midterm Study Material
62
Microbiology
Undergraduate 3
02/16/2013

Additional Microbiology Flashcards

 


 

Cards

Term
Fomite
Definition
Any object, surface, or body part
Term
Reservoir
Definition
Any area where a microbe resides and serves as a potential source of infection
Term
Resolution
Definition

The ability to distinguish two adjacent points as separate objects based upon
resolving power.


Function of Three Things:

1. Numerical aperture
2. Wavelength of light

3. Design of condenser

Term
Numerical aperture (N A)
Definition
the measure of a lens’ ability to capture light coming from a
specimen and use it to make the image; increases with the use of oil and the higher objectives
Term
Limit of Resolution
Definition

 


D =                     Wavelength                         

(N A condenser) + (N A of objective lens)

Term
Phase Contrast vs. Brightfield Microscopy
Definition
- usually organelles and cells are transparent and difficult to differentiate without staining
- staining kills the cells so you don’t see living cell just artifacts
- phase-contrast allows one to view living transparent organisms using phase (wavelength
shifts) principles of light to produce dark objects in a bright background.
Term
Cyanobacteria
Definition
- blue-green organisms
- belong to Kingdom Monera
- prokaryotic type of nucleus
- Cyanobacteria: chlorophyll a
- phototrophic bacteria:bacteriochlorphyll
- Cellular structure is considerably different from the eukaryotic algae
Term
Protozoa
Definition
- unpigmented, motile organisms
- belongs to Kingdom Protista
- eukaryotic
- single-cell transparent organisms, with a cell membrane, and no cell wall
- in lab, paramecium are the most common to be seen
Term
Algae
Definition
- greenish or golden brown organisms
- belongs to Kingdom Protista and includes all the photosynthetic eukaryotic organisms
- no tissue differentiation
- distinct, visible nuclei and chloroplasts
- unicellular or colonial
Term
Purpose of Heat-fixing
Definition
1. To kill the bacteria
2. To fix them to the slide
3. To coagulate cytoplasmic proteins to make cells more visible
Term
Basic dyes
Definition
- have positive (+) charge
- ex. Methylene blue
- can penetrate the bacteria because of the attraction between charges
Term
Acidic dyes (negative stain)
Definition

- have negative (-) charge
- ex. Eosin, nigrosin (india ink), congo red
- can not penetrate the bacteria because the repulsion between the charges
- stains the background

-chromophores have negative charge

Term
Capsules
Definition

Function
1. Increases virulence in some organisms by protecting the cell from phagocytosis by
the immune system because antibodies are hidden
2. Prevents dehydration/desiccation due to the attraction of water by the layer
3. Attachment to host cells because of binding reactions between the host tissue and the glycocalyx


Organisms
1. Klebsiella pneumoniae => has a capsule and looks like a figure eight
2. Staphylococcus epidermidis => has no capsule

Term
Spore Staining: Schaeffer-Fulton Method
Definition
1. Make a smear of each bacteria: B. stearothermophilus, C. sporogenes,
and S. epidermidis (either on separate slides or 1-2 slides).
2. Setup a Bunsen burner on your ring stand with the ring clamp and wire gauze over it.
3. Fill the can (from your student drawer) with water from the tap until it is
about half-full. Place the can on top of the wire gauze on the ring
clamp.
4. Turn on the Bunsen burner to heat/boil the water. (Let steam start to
appear before putting the slide on the can.)
5. Place the slide with smear(s) on it on top of the can
6. Place a piece of paper towel on top of the smear on the slide and saturate
the paper with Malachite green.
7. Steam the smear over the boiling water for 5 minutes.
NOTE: If the Malachite green evaporates off, then add more - Keep
the paper wet. Use forceps to take the slide off the can when finished -
it will be hot!!
8. Allow the slide to cool, remove the paper, and rinse with water for 30 seconds.
9. Add Safranin to the slide for 1 minute.
10. Rinse off the Safranin with water.
11. Blot the slide between sheets of Bibulous paper.
12. Examine the slide under oil immersion.
Term
Acid-Fast stain
Definition

Differential staining technique that it used to detect the presence
of mycolic acid.

 

Mycobacterium

Term
Gram Stain
Definition
Components:
Crystal Violet - Primary stain - stains all the bacteria initially
Gram’s iodine - mordant - forms an insoluble compound upon interacting with crystal
violet
95% Ethanol - decolorizing agent - washes away the dye in Gram-negative bacteria and
does not touch the dye in Gram-positive bacteria
Safranin - counterstain - stains all the bacteria - Gram-negative bacteria appear red under
the microscope
Term
Amphitrichous
Definition
ex. Spirillum volutans
(flagella at both ends)
Term
Monotrichous
Definition
ex. Pseudomonas fluorescens
(a single flagella at one end)
Term
Brownian motion
Definition
organism vibrates due to molecules hitting the cell, i.e. H2O, etc.;
organism will remain in one place
Term
true motility
Definition
directional; independent movement over greater distances
Term
chemotaxis
Definition
movement towards chemical attractants (ex. food) and away from repellants
(ex. chemicals)
Term
Motility Test Medium contains TTC (2,3,5-triphenyl tetrazolium chloride)
Definition

TTC is:


- colorless and soluble when oxidized
- red when reduced
- makes it easy to see the results because the red color appears along the growth pattern

Term
Advantage / Disadvantage of Motility Test Media
Definition

Advantage of Motility Test Media:
- technique can be used to test for the motility of Pathogenic organisms


Disadvantages of Motility Test Media:
- requires incubation time
- if technique is not performed properly, non-motile organisms can appear motile

Term
A good solidifying agent
Definition
1. Is not utilized by the microorganisms
2. Doesn’t inhibit bacterial growth
3. Doesn’t liquefy at room temperature
Term
Nutrients
Definition
chemical compounds that can be broken down into or used to make monomers
Term
Synthetic (Defined) Media vs. Non-Synthetic (Complex Media)
Definition

Synthetic or defined media – exact composition is known; has been synthesized; chemical
compounds used are highly purified and defined

 

Non-synthetic or complex media – the exact composition is not known; utilizes compounds
that include all the nutrients but they are not defined

Term
Minimum requirements for Steam Sterilization
Definition
For 1 Liter of media: 15 minutes at 121.6oC or 250oF and 15psi
Term
Selective media
Definition

media that allows only certain organisms to grow


Selection is based on:

a. Absence of certain nutrients which prevent the growth of some but not all bacteria
b. Presence of a toxic or inhibitory substance like salt, acid, base, chemical (crystal
violet or methylene blue), and antibiotic

Term
Differential media
Definition
media that contain substances which change the appearance of one
species allowing for differentiation
ex. EMB – Eosin Methylene Blue
- both selective and differential
- methylene blue inhibits Gram (+) bacteria thereby selecting for Gram (-) bacteria
- eosin- an acidic dye which causes coliforms (bacteria found in the intestine) to turn a
metallic green color
Term
Minimal media
Definition
media that contains the basic requirements for the bacteria to grow
such as salts, a carbon source, and a nitrogen source
Term
Enriched media
Definition
media that contains all the basic requirements but has added amino
acids, vitamins, and minerals from such sources as peptone or yeast extract
Term
Methods of Sterilization
Definition
Autoclaving - Steam Sterilization; utilizes high temperature and pressure
UV Irradiation - utilizes UltraViolet light
Ethylene Oxide Gas - generally used for plastic surgical supplies and disposable medical supplies
that can not be autoclaved
Term
Streak plate – four streak techniques
Definition
a. Quadrant streak – we use a modified form of this method
b. Radiant streak
c. ‘T’ streak
d. Continuous streak
Term
Pour plate
Definition
use plates and agar tubes to isolate loopfuls of bacteria; requires less
skill and practice but a lot of media and supplies
Term
Phenyl Ethyl Alcohol (PEA) Agar
Definition
- selective media
- Selects for Gram positive bacteria
- inhibits the growth of Gram negative bacteria because the phenyl ethyl alcohol hinders their DNA synthesis
- used to grow Gram positive anaerobes if 5% Sheep blood is added
Term
Mannitol Salt Agar (MSA)
Definition

- selective and differential media

- contains mannitol, 7.5% NaCl, and the pH indicator Phenol red
- in general, organisms can not grow on this amount of salt. Thus, the media is selective for Staphylococcus species.
- Some species of Staph (pathogenic) have the ability to ferment mannitol.
- Acid is produced if mannitol fermentation occurs. Phenol Red can show the decrease in
pH. It is yellow when the pH is below 6.8, red at pH 7.4-8.4, and pink at above 8.4.
- If the organism is nonpathogenic, then it will grow well on MSA, but will not ferment
mannitol.
- If the organism does not grow well, then it is probably not Staph.

Term
MacConkey Agar
Definition

- selective and differential media

- select and differentiate members of Enterobacteriaceae

- contains lactose, bile salts, neutral red, and crystal violet
- Gram positive organisms are inhibited by the bile salts and crystal violet
- Some organisms have the ability to ferment lactose to acid
- Indicated by the neutral red which is red at pH below 6.8 and colorless at pH above 6.8.
- Red is indicative of lactose fermenters
- Colorless is indicative of non-lactose fermenters

Term
Eosin Methylene Blue (EMB)
Definition

- is a selective and differential media

- contains peptone, lactose, sucrose, eosin, and methylene blue
- The sugars provide fermentable substrates that promote the growth of fecal coliforms
- Methylene blue inhibits the growth of Gram positive bacteria
- Eosin is an acidic dye that differentiates on the basis of fermentation
- Green metallic sheen to deep purple is indicative of fecal coliforms.
- Pink is indicative of low acid production or slow fermenters.
- Colorless or same color as the media is indicative of nonfermenters.

Term
Hektoen Enteric (HE) agar
Definition

- is a selective and differential media

- isolate Salmonella and Shigella species from other enterics

 

- contains peptone, lactose, sucrose, salicin, bile salts, sodium thiosulfate, ferric ammonium
citrate, bromthymol blue, and acid fuchsin
- The sugars (lactose, sucrose, and salicin) provide fermentable substrates that promote the growth
of fecal coliforms
- Sodium thiosulfate acts as a source of sulfur.
- Ferric ammonium citrate reacts with H2S produces by the reduction of sulfur to form a black
precipitate.
- Bile salts inhibit the growth of most Gram positive bacteria
- Bromthymol blue and acid fuchsin dyes act as color indicators to indicate the fermentation of
sugars and production of acids that lower the pH of the medium.
- Enterics that produce acid from fermentation will produce yellow to salmon-pink colonies.
- Bacteria that do not ferment any of the sugars will produce blue-green colonies.
- Bacteria that reduce sulfur to H2S form colonies containing a black precipitate

Term
Mycology is the study of
Definition
fungi
Term
Characteristics of Fungi
Definition
Eukaryotic
2. Non-motile
3. Non-photosynthetic
4. Lack tissue differentiation
5. Have cell walls of chitin or other polysaccharides; not of peptidoglycan
6. Reproduce through spores which are for reproductive purposes only and do
not give the fungi resistance to anything like the endospore does.
7. Saprophytic – decompose dead organic matter
8. Heterotrophs – produce exoenzymes that digest nutrients in the environment
then absorbs the products
Term
Molds
Definition
mycelium - mass of intermeshed hyphae; what is seen macroscopically
- hyphae - microscopic filaments that may (septate) or may not (nonseptate) have
walls
- can form either asexual or sexual spores or both
Term
Yeasts
Definition
have pseudohyphae which are multicellular structures produced through
budding
- spores - produced by budding which is an outpouching of a cell
- smaller in size than the parent cell
- may or may not stay attached to the parent cell
Term
Sabouraud’s Dextrose Agar (SDA)
Definition

- grows molds

- has a pH of 5.6 which inhibits
bacterial growth

Term
Slide-mold culture
Definition
method is used because wet mounts and simple transfer of
hyphae does not provide the structures necessary for identification due to
distortion or destruction of these structures during transfer. This also allows
conidiophores to grow on a single horizontal plane
Term
Plate Count - Direct Measurement
Definition
Dilute the organisms and count them on microscopic fields on a slide.
Term
Plate Count - Indirect Measurement
Definition

1. Quantitative Plating (Standard/ Viable Plate Count)


2. Turbidity measurement
(using a Spectrophotometer)

Term
Quantitative Plating (Serial Dilutions)
Definition
info on the viable organisms is obtained
- easy to perform but uses lots of glassware and media and takes time to get results
- can calculate the number of organisms in a bacterial culture
- must use aseptic technique when handling the pipettes
Term
Dilution Factor
Definition


(DF)= Vol added to the dilution blank
               Total volume in the tube

Term
Final Dilution Factor
Definition
= product of individual dilutions
Term
Original Cell Concentration
Definition


Original Cell Conc.=  number of colonies

                                (volume plated) (FDF)

Term
CFU
Definition
Colony Forming Units (or the number of viable cells that can make a colony)
Term
Turbidity Measurement
Definition
(uses a spectrophotometer)
-information on both living and dead cells is obtained
-easy to perform and uses less glassware and media
Term
Serological pipette
Definition

pipettes that have graduations down to the tip.


Two types of Serological Pipettes
A. TC (“to contain”) – these pipettes expel all the volume down to the tip, then the
last drop must be “blown out” using the pipette pump or syringe
B. TD (“to deliver”) – these pipettes expel all the volume down to the tip, but the
last drop should not be blown out

Term
Mohr pipette
Definition
pipettes that are not graduated down to the tip so fluid must only be
expelled to the last calibration line
Term
Viruses vs. Bacteria
Definition
- viruses are smaller, non-cellular, and intracellular parasites
- viruses can not be grown on normal media because they
require a host since they have their own DNA or RNA but
lack the cellular machinery needed to replicate
- viruses can infect all types of cells: prokaryotic and eukaryotic
Term
Phages
Definition
viruses that infect bacteria; also called bacteriophages
Phages that parasitize E. coli are referred to as coliphages.
Term
Lytic viruses
Definition
considered virulent; viruses enter the cell, take over the cell, replicate, then
lyse the cell for release
Term
Lysogenic viruses
Definition
considered temperate; viruses enter the cell, integrate into the DNA of the
host; cell replicates normally then eventually viruses replicate and lyse the cell to be released
Term
VIU
Definition

Virus Infection Units

Smallest unit causing an effect with a host

Term
1 plaque =
Definition
1 virus
Term
PFU
Definition

- Plaque Forming Units

- Efficiency of count from the assay is always less then with an electron microscope because efficiency of infection by viruses is not 100%

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