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Transient Microorganism

Pathogen picked up during brief contact with a contaminated reservoir

Resident Microorganism

generally non pathogens that are constantly present on skin

Aseptic Techinque

minimizes the chances of contamination

Working Distance

the distance between the specimen and the objective lens

Total Magnification

objective lens x ocular lens


1 of main functions of microscope, improving the clarity of the image

Brightfield Microscope

Microscope which allows light rays to pass directly from the light source through various other components of the microscope to the observers eye


remains in focus after objective lens is changed from low to high power


characteristic of microscope design that allows changing objective lenses without significant change in position of center of field of view.

Microscope Ocular


Microscope Arm

place you hold on to when carrying the microscope. Supports the body tube.

Microscope Stage

a small platform on a microscope where the specimen is mounted for examination

Microscope Base

located at the bottom of the microscope used for support

Microscope Condenser

gathers the light and passes it through the specimen

Microscope Light Source

to supply light to slide

Microscope Diaphragm

Regulates the amount of light on the specimen

Microscope Stage Clips

holds slide in place

Microscope Objectives

Individual lens attached to the revolving nose piece


a group of cells which a rises from a single cell


new cultures from isolated colonies

Steak Plate Method

common method for isolating bacteria from a mixed culture

Heat Fix

passing slide through flame, affix the bacteria to the slide

Simple Stain

only one dye used

Direct Stain

a stain of the bacteria itself

Negative Stain

stain the background, NEVER heat fix a negative stain


media used in culturing


test tubes containing solid medium that has been allowed to solidify at an angle and the surface of the agar is used for the maintenance of stock cultures of microorganisms, used fro long term bacteria storage 3mo or longer,

Pour Plates

isolation technique using a series of serial dilutions to separate CFUs, mixed with liquid agar which then solidifies

Direct Stain

a simple stain that stains the bacteria

Negative Stain

repelled from bacteria. Background in stained. Negative stains usually have a negative charge which is repelled by the negatively charged proteins on the surface of bacteria. Note: a negative stain does not mean a gram negative.

Methylene Blue

used in direct stain, green

Crystal Voilet

used in direct stain, purple


used in direct stain, red/pink

Congo Red

negative stain


negative stain

Differential Staining

Staining procedure which causes cells to stain differently based on properties of the cell wall

Gram Stain

has four steps. 1. Primary stain: crystalline violet that stains all bacteria purple 2. mordant: Gram's iodine sets the stain 3. decolorizer: ethanol washes out the stain from gram negative bacteria only 4. counterstain: safranin stains gram negative bacteria pink

Slime Layer

A thin protective structure loosely bound to the cell wall that protects the cell against drying, helps trap nutrients, and sometimes binds cells together


A sticky layer that surrounds the cell wall of some prokaryotes, protecting the cell surface and sometimes helping to glue the cell to surfaces.


A general term that includes slime layer and capsule


a thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions

Dormant State

Under harsh environmental conditions, such as loss of a nutritional requirement, bacteria can convert from a vegetative state to THIS or a spore. THIS allows the bacteria to exist in "suspended animation"


spore coat, Keratin like proteins

Acid Fast

used to stain small group of organisim that do not readily take up stain, the cell walls of these bacteria contains high concentrations of lipids, perventing uptake of dyes

Ways to prevent contamination

flame loop, inverted postition of plate, hand washing, work near bunsen burner, hold slant caps while removing sample, flame rim of slant...

Precautions used with microscope

make sure microscope is off before plug in, always start with lowest objective, carry with two hands, never use coarse adj for 40x or higher, clean lens after use of oil...

Best resolution

condenser should be as high, iris diaphragm should be open, immersion oil used at 100x

M. luteus

grows yellow in color

M. roseus

grows red in color

What is purpose of streak method?

"thin out" bacterial growth in successive sectors of a plate until individual colonies are obtained

What are the sources of contamination when transferring bacteria?

Not flaming loop, Not working near flame, touching loop to any contaminated surface while cooling

What is the purpose of heat fixing?

1. kills the bacteria 2. makes them adhere to the slide 3. coagulates their protein for better staining.

What is the primary function of the capsule?

Eliminates waste, prevents dehydration, less vulnerable to phagocytosis

What factors determine composition of a capsule?

Environment and the type of nutrients in which the bacterium is growing

What staining techniques are combined in the capsule stain?

direct staining and negative staining

Microorganism used in the capsule stain in lab?

Klebsiella Pneumoniae

Do you heat fix a capsule stain?

NO, because it is a negative stain

What is the genera of bacteria that have endospores?

Bacillus and Clostridium

Two methods used to stain endospores

Schaeffer-Fulton and Dorner Method

What genus of bacteria exhibit acid fast characteristics?

Mycobacterium tuberculosis, tuberculosis and Mycobacterium leprae, leprosy

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