Microbiology Lab Exam #1 Study Guide

The total magnification of the oil immersion objective is:

1000

Ocular/Eyepiece

Binocular microscopes have two. They magnify the image tenfold.

Body

It contains mirrors that bend the light into the ocular.

Nosepiece

Where the objectives are attached to.

Objectives

Contains lenses that magnify the image. A microscope has 4x, 10x, 40x and 100x

Arm

It supports the nosepiece, holds on/off toggle and focus adjustment knobs.

Stage/Mechanical stage

The black, flat platform on which your slide rests. Its the silver apparatus that actually holds the slide and moves the slide to position it on the stage.

Stage Adjustment knobs

These move the the mechanical stage

Light Intensity Control

This knob increases or decreases light output from the light source.

Substage condenser

It is made of at least two lenses that focus the light passing through the specimen and improve image sharpness.

Aperture diaphragm control

Controls the amount of light entering the substage condenser from the light source.

Field diaphragm lever

It opens and closes to increase and decrease light from the light source. It should remain open

Light source

The illuminator is a halogen bulb that produces light.

Base

It holds the illuminator and supports the rest of the microscope.

Fine focus adjustment knob

Brings the image into sharp focus. This knob raises and lowers the stage in very small increments.

Coarse focus adjustment knob

Moves the stage up and down by larger increments and allows you to bring the image into focus.

Resolution

The ability of a lens system to distinguish as separate entities objects that are very small and very close together. It is determined by the quality of the lens and the wavelength of light used.

Magnification

Make a small object appear larger.

Working distance

The distance between the tip of the objective and the stage

What is the purpose of oil immersion

to minimize light scattering. It allows for a clearer, sharper image and had better contrast

Aseptic technique

The method of handling microbes and materials in a way that minimizes contamination

Inoculation

The transfer of a microbe from medium to the next

Inoculum

The sample being transferred

Steps of aseptic technique

Place the back of the loop wire, where it meets the handle, just above the inner blue cone. Hold the wire in place until it becomes red hot the entire time. (do not place the loop or needle on the bench top) Allow the loop or needle to cool slightly before putting it into a culture. (do not wave the loop around to cool or blow on it) transfer the organisms. when transfer is finished, flame loop again to incinerate any bacteria remaining. Then store in test tube rack or storage area

When using a test tube, you first remove the cap using the ________

last two fingers

T/F After opening the test tube you flame it

True

T/F When removing an inoculum from a plate you remove the lid and place it on the lab bench

False

Identify a colony margin by name

Entire, Undulate, Lobate, Filamentous and Curled

T/F When inoculating a broth, the loop may not touch the sides of the tube

True

Ciguatera toxin is a naturally occurring toxin produced by the dinoflagellate:

Gambierdiscus toxicus

Cyanobacteria is classified as

in the past plants, protozoans and bacteria but now as bacteria

Cyanobacteria derived their energy from

oxygen-evolving photosynthesis

Cyanobacteria utilize

chlorophyll - the same pigment used by higher plants, to capture light energy

Cyanobacteria contain

accessory pigments called phycobilins

Heterocysts (thick walled cells) are responsible for ______ whereas akinetes are:

nitrogen fixation; reproductive structures, large usually about two to three times large than the average cell in a filamentous strand. It has a thicker wall and will have a grainy, mottled appearance.

What is anabaena. Know picture

genus of filamentous cyanobacteria.

Algae belong to the kingdom

Kingdom Plantae

The criss cross pattern on spirogyra are

Chloroplasts

Diatoms and dinoflagellates are commonly found in

Phytoplankton

The frustules of diatoms are composed of

silicon dioxide (the same element that makes up sand and glass)

T/F Euglena is photosynthetic

True

Which of the following describes protozoal movement

flagella, cilia, amoeboid, nonmotile

*What is methylcellulose used for

to slow down the movement of protozoans or making a culture less motile to observe the bacteria under the microscope

What magnification is seen on a steromicroscope

10x

What do you use a stereomicroscope for

low magnification observation of a sample

Candida albicans is a yeast in the phylum

ascomycota

Saccaromyces cerevisae is commonly known as

bakers yeast

Define dimorphism

organisms that can exist in two forms, either molds or yeast

These anchoring hyphae are called

rhizoids

Zygomycota asexually produce spores at the tips of the reproductive hyphae called

sporangiophores

Conidiophores are

ascomycetes reproduce asexually by producing haploid conidiosphores at the ends of reproductive hyphae

Brownian movement

it is typically caused when water molecules collide with cells and make them move. They get bounced around like a pinball. The cells oscillate and appear to shake in place (they don't move very far in any particular direction). This is not real motility.

Run and tumble motility

movement in bacteria with single and multiple flagella

Example of diplococci

spherical cells that are observed in packets of two

Example of streptococci

when cells form long chains

Example of Staphylococci

Grapelike clusters of cocci

Example of Streptobacilli

a chain of rod shaped cells

Example of spirilli

bacterial cells that have a curved shape

Simple staining techniques utilize a single stain and reveal the _________ and the __________ of cells in culture

morphology or shape and arrangement

The dyes used in negative staining have what kind of charge

negative

What is stained in negative staining

the stain is repelled by the charge of the cell and stains the background.

Examples of negative stains

nigrosin and eosin

How does a capsule stain differ from a negative stain

Capsule stain stains both cell and background. Negative stain stains only the background - which is also the best method to see cells

The capsule is created by a compact and firmly adhered

Glycolax

Capsules are useful for

they serve as energy and water reserves, a means to evade the host's immune system, and as an anchor or surface attachment

T/F The bacteria in capsule stain are heat fixed

False

Know the entire step by step process for Gram staining

--Crystal voilet --Gram's iodine --Alcohol --Safranin

Gram staining differentiates two major groups of bacteria by

Pseudomonas aeruginosa gram negative (Purple) Cell wall shows the thin layer of peptidogylcan. Staphylococcus aureus gram positive (pink) cell wall shows the thick layer of peptidogylcan.

Primary stain: Mordant

Gram's iodine

Primary stain: Decolorizer

Alcohol

Primary stain: Counterstain

Safranin (red dye)

Gram positive will appear _______

purple (staphylococcus aureus) Ex. S. aeru, S. epi, S. pyogenes, B. sub, B, meg

Gram negative will appear ________

pink (Psuedomonas aeruginosa) Ex. E. coli, P. vulg, Neisseria

The Ziehl-Neelson procedure is to:

facilitate staining of the cell by using a steaming water bath (acid fast staining)

Acid fast cells have ________ ______ in the cell walls making them resistant to

mycolic acid ; desiccation and disinfectants

Which of the following would test positive in Ziehl-Neelson technique

mycobacterium smegmatis

The primary stain in acid-fast staining is _____ _____ and the counterstain is _____ _____.

carbol fuchsin ; methylene blue

T/F The Ziehl-Neelson technique involves steaming/heat fixing

True

Clinically, acid fast staining is used for

visualize members of the genus mycobacterium particularly mycobacterium tuberculosis

Schaeffer-Fulton method is used to stain

Endospores (bacterial)

Vegetative cells appear _______ because they are stained by _______

red ; saffrain

The endospores appear _______ because they pick up the primary stain called ______ _______

green ; malachite green

Which of the following organisms will not test positive for endospores

bacillus

Which culture do you expect to see a greater quantity of endospores? Why?

24 hour incubation . ****

Know Lyme disease and its scientific name.

It is caused by borrelia