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Scanning Objective lens


low power objective


dry high-power objective


oil-immersion objective


Uses elctrons as a radiation source

electron microscope

uses visible light

brightfield microscope

Electron and brightfield microscope use

electromagnet condenser lens

fluorescent microscope uses

ultra violet light and stained bacteria

steps to preperation of specimens

smear on microorganisms on slide, fixing, flood with stain, washing, drying, microscope observation


positive ion stain
Dyes used in microbiology are salts in which the colored ion is reffered as


basic- positive charge chromophore
acidic- negative charge chromophore

negative stains

aka acidic stain
stains the background, bacteria do not stain with electronegative stain, because both bacteria and dye are electronegative resulting in ionic repulsion.. Advantage is NO FIXING

Gram negative bacteria


Gram positive bacteria

purple after adding counterstain

Steps to gram staining

crystal violet, iodine, alcohol, safaranin

counter stain in gram stain

basic dye


prevent crystal violet from leaving the cell (iodine) intensifies stain

Gram stain primary stain

crystal violet

Gram stain mordant

iodine ( intensifies the stain) prevents crystal violet from leaving the cell

gram stain decolorizing agent

ethyl alcohol disrupts the lipids coat

gram stain counterstain

safranin ( positive)



Gram positive and negative bacteria may appear if

Bacteria stain poorly or not at all, or older cultures of gram positive bacteria give inconsistent results

crystal violet-iodine can be removed from gram negative bacteria with alcohol because

alcohol is decolorizing agent


Acid fast stain is used to differentiate what bacteria

mycolic acid

prevents the entrance of most stains into acid-fast positive cells


primary stain for acid fast stain

Test tubes

recycle and autoclaved before washing and disposing

Chemically defined medium

Medium whose exact chemical composition is known

Complex Media

Most chemoheterotrophic bacteria are grown... Media for which the exact chemical composition varies slightly from batch to batch.


Organic carbon, energy, in the form of meat extracts and partially digested proteins.

Nutrient broth

commonly used liquid complex medium.

Nutrient agar

When agar is added it becomes a solid medium


marine red algae with unique properties that make it useful in culture media. Few microbes degrade agar so it remains solid during microbial growth. Liquifies 100 degrees C and remains liquid state until cooled 40 degrees C.

Test tube

sterilized after preperation in autoclave using steam under pressure.

Auto clave

121degrees C for 15 pounds of pressure for 15 minutes.

Simple stains

Determines the morphology, size and arrangement


Kills microorganisms to observe, and attaches the organism to the slide while preserving structures w/ minimal distortion

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