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Lab Quiz 1 Review

Lab Ex.'s 1,2,6,8,9

QuestionAnswer
Simple Microscopes Consisted of biconvex lenses and were essentially magnifying glasses.
Compound Microscope AKA Bright-field compound microscope (Most commonly used microscope in Microbiology) Has two lenses between the eye and the object. Magnifies the object, uses visible light as a source of illumination and shows dark objects in a bright field.
What are the basic components of the compound microscope? Base, stage to hold the slide, an arm for carrying, a body tube, ocular lens(eyepiece.
How to calculate the total magnification of an object? Magnification of objective lens x magnification of ocular lens
Resolution or resolving power Refers to the ability of the lenses to reveal fine detail or two points distinctly separated.
Immersion oil Used with immersion lens on compound microscopes to reduce light loss between the slide and lens.
Why is is desirable that microscope objectives be parfocal? When object is in focus with one of the lens it will continue to stay in focus with the other lenses.
Which objective is closest to the slide when it is in focus? The high-dry lens (40x-45x)
Which controls on the microscope affect the amount of light reaching the ocular lens? Condenser, diaphragm, illuminator, and light intensity knob.
Phase-Contrast Microscope Brings direct and reflected or diffracted light rays together(in phase) to form an image of the specimen on the ocular lens.
Brownian Movement NOT true motility but rather the particles and microorganisms are all vibrating at the same time and maintaining there positions.
True motility A microorganism moves from one area or position to another.
What is the advantage of the hanging-drop procedure over the wet mount procedure? Minimizes the amount of movement, used mostly for large protists especially Protozoans so there not moving all over.
Why are microorganisms hard to see in wet preparations? There is very little contrast for translucent organisms.
Prokaryotic organisms Have NO nucleus or organelles.
Eukaryotic organisms Have a nucleus and organelles.
Why isn't the oil immersion lens use in the hanging-drop procedure? Hanging-drop procedure uses a thicker slide and may crack if oil immersion lens was used.
Negative stain technique Does not stain the bacteria but stains the background. Bacteria will appear clear against a stained background.
Coccobacilli short, oval bacilli or spiral bacteria which are difficult to stain, negative staining helps to view bacteria.
Why is size more accurate in a negative stain than in a direct stain? NO heat fixing or strong chemicals are used with negative staining so the bacteria are less distorted.
What is the purpose of heat-fixing the smear? To make the bacteria sticky so it will stick to the slide.
In heat fixing, what would happen if too much heat were applied? It would burn and or kill the bacteria.
What microscope technique gives a field of view similar in appearance to that seen in a negative stain? The Darkfield microscopy technique.
Darkfield Microscopy Shows a light silhouette of an organism against a dark background. Most useful for detecting the presence of extremely small organisms.
Acid-Fast stain A differential stain as well as diagnostic procedure. Can be used to diagnose tuberculosis and leprosy.
Pathogenic Disease causing.
Mycolic acid Cell walls of acid-fast organisms contain this wax-like lipid, which renders the cell wall impermeable to most stains.
What is the decolorizing agent in the Gram stain? Ethanol (alcohol).
What is the decolorizing agent in the acid-fast staining? Acid-alcohol.
What diseases are diagnosed using the acid-fast procedure? Tuberculosis (TB), and Leprosy.
Clinical specimens suspected of containing Myobacterium are digested with sodium hydroxide(NaOH) for 30 minutes prior to staining. Why is this technique used? Why isn't this technique used for staining other bacteria? Technique kills everything except the bacteria( removes debris and contaminating bacteria). Technique not used in other techniques because it would destroy the bacteria.
The acid-fast stain is used to detect Cryptosporidium protozoa in fecal samples. Which of the following would you expect to be a major component of their cell walls? Lipids (fats)
In 1882, after experimenting with the staining Myobacteruim, Paul Ehrlich wrote that only alkaline disinfectants would be effective against Myobacterium. How did he reach his conclusion without testing the disinfectants? The Myobacterium was resistant to acid.
Structural stains Can be used to identify and study the structure of the bacteria.
Endospores Also known as "resting bodies" because they do not metabolize, resistant to heating, various chemicals, and harsh environmental conditions. Forms with in a cell, cell disintegrates and endospores can remain dormant for long periods of time , but return.
Capsule Most composed of polysaccharides, which are water soluble and uncharged. Simple stains will not adhere to a capsule due to non-ionic nature, bacteria and background will stain leaving capsule unstained.
Virulence Disease causing ability. Capsule play an important role Ex. Bacteria Streptococcus pneumoniae has a capsule , the body's white blood cells cannot perform phagocytosis on on bacteria resulting in disease occurring.
Flagella Most common means of motility, there thin proteinaceous structures that originate in the cytoplasm and project out from the cell wall.
Types of Flagella Peritrichous (all around bacterium) and Polar (at one or both ends of the cell).
Of what morphology are most bacteria possessing flagella? Rods, Spiral
Which morphology usually does not have flagella? Cocci
How might a capsule contribute to pathogenicity? Capsule attachment inhibits white blood cell phagocytosis.
How might flagella contribute to pathogenicity? Allow certain bacteria to be motile.
Of what advantage to Clostridium is an endospore? The bacteria can with stand many things such as; resistant to heating, certain chemicals and harsh environments allowing it to survive and infect.
Created by: KJones040607
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