Micro Lab Practical 1 Review
Cells that are round have the following morphology:
Cells that are rectangular in shape have the following morphology:
Long thing flexible cells shaped like a corkscrew, containing axial filaments, have the following morphology:
Two round cells that are physically stuck together have teh following arrangement:
several rectangular cells that form a chain have the following arrangement:
Cells shaped like a comma have the following morphology:
A simple staining employs the use of a ___ charged dye to stain cells that are ___ charged:
The purpose of a heat-fixation is to kill the organisms, they will adhere to the slide, and it will stimulate motility by activating flagella
Smears should never be heat-fixed while they are still wet because
creates living aerosols
Simple staining is not very useful for examining living organisms or for testing an organisms' motility.
When performing negative staining, it is important to heat fix the microbial smear prior to staining.
Cells that are wavy, large, and rigid, with external flagella, have the following morphology:
After performing a negative stain, for the most part, how will the cells look?
Four or more bacilli shaped cells that are arranged in a long chain:
Living cells have a net (negative OR positive) charge and will (attract OR repel) negatively charge stains.
Gram negative cells have a thick cell wall and are surrounded by an additional layer of lipid.
When Gram-negative cells lyce in KOH test, what cellular material causes the characteristic "stringing"?
In the Gram stain, the primary stain is:
If the iodine step is missed, Gram positive cells will appear ___ at the completion of the protocol:
Gram-positive cells are susceptible to Vancomycin while most Gram-negative cells are resistance.
Bacterial cells that are actively undergoing metabolic processes and binary fission are referred to as:
the two clinically significant genera that are capable of producing endospores:
Why is steam used during endospore staining?
Heat i necessary for driving stain into the spore coat
In the capsule stain, what stain serves as the negative stain?
In the capsule stain, what stain serves as the positive stain?
Four chemical elements essential for comprising 98% all living things:
Carbon (C), Hydrogen (H), Oxygen (O) and Nitrogen (N)
- Phosphorus (P) and Sulfur (S) are also necessary
What are the optimum temperatures at which all living organisms grow?
Body temperature 37*C
Room temperature 20-27*C
Refrigerator temperature 4-10*C
Freezer temperature -20*C
Note: Some microbes grow above or below these temperatures
Members of Microbial world
Living: bacteria, protozoa, fungi, algae, and parasitic worms
Nonliving: viruses, viroids, and prions
Media (singular: Medium)
the food that is used to culture microorganisms
Physical Factors that affect Growth of Microorganisms:
1. Temperature - there is an optimum temperature for all living organisms to grow
2. pH - reflects the relative acidity/alkalinity of a solution (0
[most acidic] to 14 [most alkaline]) all living organisms have an
- Human Blood has a pH of 7.2-7.4
3. Oxygen gas: only 50% of all microorganisms require oxygen
- In fact, even trace amounts of oxygen can be deadly to some microbes
4. Salt concentration: Controls the amount of water available to a cell (also the same with sugar)
Define: Solute concentration is the same outside & inside the cell
What happens: Stays the same
Why: Equilibrium already reached
Define: Solute concentration greater outside the cell than inside the cell
What happens: Crenates (shrinks)
Why: water rushes out of the cell
Define: Solute concentration less outside the cell than inside
What happens: Lysis (swells)
Why: water rushes into the cell
Types of media
1. Solid: Agar
2. Liquid: Broth
3. Semisolid: contains lower % of agar than solid media (bit runny)
an algal extract that acts as a solidifying ingredient when added to microbial media
- no nutritional substance
the media is mixed , heated to boiling, & sterilized into an autoclave. Once sterile, molten media is put into sterile Petri dishes or test tubes.
Why not use gelatin instead of agar?
Gelatinized media turns to a liquid at 37* (room temperature) and agar does not. Aldo some organisms produce enzymes that turn gelatin into a liquid.
Most bacteria divide by a process called...
- Binary - 2
- Fision - to split
the time it takes for a single cell to split into two new cells
When you start to see one little colony approximately how many cells need to be in the colony for you to be able to "see" it?
About 1 million
Descriptive terms for colonies grown on a solid surface
1. Whole colony shape
2.Margin (edge of the colony): Swarm - leaving an opaque pattern of waves across the medium (sometimes they do this)
3. Elevations: What the colony looks like from the side (how high off media
4. Size: measured in millimeter (mm) Punctiform- colonies of enormous size
5.Texture: wet, mucoid, erose (dry, crusty) granular, opaque (almost see through them), shiny, and dull
6. Pigment: may be within the colony or diffusing away from the colony
2 Round with scalloped margin,
3 Round with raised margin,
6 Irregular and spreding
2 L-Form (darker mass in middle)
3 Round with radiating margin
1. Smooth (entire)
2. Wavy (undulated)
4. Irregular (erose)
(5.) Umbonate ??
2. Ingrowing into medium
(4.) Umbonate ??
Film of growth clinging to the test tube at the liquid-air interface
A membrane or scum-like structure that floats on the top of the liquid media
Organisms may settle and grow, forming a layer at the bottom of the tube.
Visible chunks/flakes/broken particles supended throughout the broth medium
Uniform Fine Tubridity
Turbidity means "cloudy"
Why might an organism fail to grow?
bad culture, loop was too hot when trying to transfer, or the nutrients weren't right for the the organism
Why might two different organisms show exactly the same growth features even if they are not supposed to?
Why is it necessary to use a negative control?
It make it easier for a base-line comparison
What is meniscus?
When water beads or pools up on a surface
what growth patterns are similar or different among the organisms tested?
Bacillus subtilius - Pellicle (the only one that had it)
Everything had sediment
Is it possible for an organism to produce more than one growth pattern in the same tube?
A film of growth on teh surface:
Uniform fine turbidity
Growth adhering to the glass at the liquid/air interface:
Suspended flakes or particles:
A layer of growth at the bottom of the broth
#A is the Ocular
#B is the rotating nosepiece
# 3, 4, 5 are the objectives
#11 is the mechanical stage
#I is the stage adjustment knobs
#8 is the Substage light
#14 is the Base
#10 is the Arm
#G is the Coarse adjustment knob
#H is the Fine adjustment knob
#K is the power switch
- Connected to the condenser is the iris diaphragm lever which controls the light that filters through
The distance between the slide and the objective lens
Calculating total magnification:
Ocular 10X 10X 10X 10X
Objective (4X) (10X) (40X) (100X)
Total: 40X 100X 400X 1000X
The bending of light as it passes from one medium to the next
- The amount of available light decreases w/ magnification because the field of view becomes smaller and smaller
- At 1000X, there is not enough light available to see the specimen clearly w/o the use of immersion oil. Therefore, immersion oil must be used w/ the 100X objective
what happens to the field of view as the magnification increases?
What happens to the light when the iris diaphragm lever is moved to the left (increases or decreases)? Moved to the right (increases or decreases)?
What happens to the contrast when the iris diaphragm lever is moved the left (increases or decreases)? Moved to the right (increases or decreases)?
The Coarse adjustment knob may be used with all 4 objective lenses.
The fine adjustment knob may be used with all 4 objective lenses
What part of the microscope should be used to center the speciment in the field of view?
Stage adjustment knobs
What part of the microscope can be adjustment to increase or decrease the contrast?
iris diaphragm lever
Immersion oil helps to increase the refraction of light as it passes through the glass specimen slide
If the power of the ocular is 5X and the total magnification is 200X, what is the power f the objective? Justify your answer by showing your work.
200/5 = 40
If the power of the ovular is 10X and the power of the objective lens is 45X, what is the total magnification? Justify your answer by showing your work