Micro Lab exam #1
Which part of the microscope condenses the light and focuses it on the specimen?
What is the term used to state that microbes are found everywhere?
Which of the following is an incorrect way to aseptically transfer cultures?
A. Sterilize loop end until red hot in the bottom of the flame
B. Heat tube rim and stopper before inserting loop
C. Place stopper/lid on the table while transferring bacteria***
D. Let loop cool before touching cultures
Typically growth media is sterilized in an __________ which utilizes steam under pressure.
Name two out of the four differences between simple and negative stains.
Simple – basic, positive, stains cells, heat-fixed
Negative – negative, acidic, stains slide, not heat-fixed
True or False: Bacteria and fungi exist as resident flora and outnumber human cells by 10:1
Which safety guideline is not correct?
A. Wash your hands before and after your experiment
B. Be careful of lose clothing, long hair, and dangling jewelry
C. Do not use butane lighters to ignite the Bunsen burners
D. Throw broken glass into the trash can***
True or False: It is okay to mouth pipette substances and smell cultures
__________ means that the image should stay in focus when you change lenses
True or False: A danger of using heat to fix a specimen is that cells may become damaged or their cellular structures may become distorted.
Why is colony number more important than colony size?
Colony number gives you more of an indication of the number of species/organisms you started out with, while colony size just tells you that the colony is growing
What is the term that describes structural stains that detect specific physical and chemical characteristics of a cell?
What are two differences between a gram positive and a gram negative cell?
Gram+ = Stains purple, peptidoglycan, thick cell walls, no lipopolysaccharide layer, teichoic acids
Gram- = Stains red, no peptidoglycan, thin cell walls, lipopolysaccharide layer, teichoic acids
What is the additional cell wall component in Mycobacterium and Norcardia?
A. Mycolic Acid**
C. Anionic Cells
D. Lipopolysaccharide Layer
A less common structure that can be detected through staining is the bacterial __________.
True or False: Bacteria are complex single-celled organisms; therefore, many species do not share a common cell morphology and/or arrangement.
True or False: Determining the gram reaction for bacteria isolated from clinical specimens is vital in prescribing the appropriate antibiotic
What is the main cell wall component in gram positive bacteria?
What does a capsule help a bacteria do?
A. Escape from phagocytic cells
B. Resist dessication
C. Aids them in attachment
D. All of the above**
__________ can even be used in some cases to distinguish between pathogenic and nonpathogenic strains of a particular bacterial species.
What is the term for the following bacterial orientation: Chains of Cells?
Antimicrobial chemical are typically classified as either __________ or disinfectants.
What is the difference between disinfectants and antiseptics?
Disinfectants are for use on inanimate objects, while antiseptics are safe for use on living tissue
True or False: Antimicrobial chemicals are capable of eliminating all microbes.
What is the test most widely used for determining the sensitivity of microbes to antimicrobial drugs?
What is the term for the area with no bacterial growth?
A. Zone of diffusion
B. Zone of inhibition**
C. Zone of misery
D. Zone of selection
The _________ of the zone of inhibition indicates the level of effectiveness for a given compound against the organism.
True or False: The efficacy of a compound may vary depending on the characteristics of the microbe it is being tested against.
Term used when a drug causes little to no damage to the host cells and tissues.
A chemical that is produced by microbes that limits the growth of other microbes
What is the medical use for the toxin produced by Clostridium botulinum?
True or False: Water has great potential to serve as a vehicle for the transmission of pathogens.
Milk contains __________, fats, and sugars in addition to many __________ and minerals necessary for microbial growth.
Coliforms are gram __________ bacteria commonly found in the intestines of vertebrates.
A common method for detecting and enumerating coliforms in water
A. EMB Agar
B. Most Probable Number**
C. Disk Diffusion Test
What is the term for the process that removes both potential spoilage organisms and pathogens?
What are the four test involved in a IMViC test?
Indole production, Methyl-red test, Voges-Proskauer test, citrate utilization
True or False: Standard methods of pasteurization are to completely sterilize milk
Colonies are referred to instead as a __________ that allows for the more likely possibility of a colony originating from a small clump of cells.
Colony Forming Unit (CFU)
What is an example of an acidic dye?
Acid-fast staining is useful for identifying the causative agent of _______.
The working distance is the distance between ________.
The slide and the objective lenses
Agents that inhibit the growth of bacterial cells are referred to as:
Which of the following structures can prevent bacteria from phagocytic cells?
Mycobacterial will be stained with _____ color in the acid-fast staining?
Which test is effective in determining the effectiveness of antimicrobial drugs?
E. coli, which are commonly used indicators of water quality are Gram ____, and _______ bacteria.
Streptococcus refers to bacteria with which kind of morphology?
The total magnification when viewing the specimen under the high dry lens is _____.
Compound lifht microscopes constain a series of lenses that allow for magnification of a specimen up to _______.
Magnification is limited by the resolving_______.
Power of lenses
What does resolution indicate?
The clarity a microscope is able to achieve.
For most light microscopes, the limit of the resolution is ______.
What does immersion oil do?
Reduce refraction or bending of light and increase resolution
Light is passed through a condensor lens that _______.
Concentrates the light and focuses it on the specimen
What does the diaphragm do?
Regulates the amount of light passing through the condenser to the specimen.
What happens when the light passes through the objective lens?
It refracts, and creates a magnified image
The light is further magnified through the ______ known as the eyepiece.
What is working distance?
Distance between the specimen and the objective
What is the field of view?
The amount of the specimen you can visualize
As magnification increases the working distance, your field of view and the intensity of light all ______.
___________ may be required to the fine focus and the condenser in order to sharpen the image.
How do you determine the total magnification of a specimen?
Multiply the magnification of the objective lens by the magnification of the ocular lens.
The objective lenses on most lab-grade compound microscopes will have magnifications of _____,_______,and _______.
10X (low power), 40X (high dry), and 100X (oil immersion)
What are aseptic techniques?
Any technique employed to avoid contamination
What happens initially in order to prevent contaimination? How is this achieved?
All inoculating instruments (loops and needles) should be sterilized prior to use. Flaming the objects.
All growth media should be sterilized to ensure an ______.
What is an axenic culture?
Pure culture of organism of interest
Typically, growth media is sterilized in an _________.
What does an autoclave do?
Utilizes steam under pressure
Microbes play important roles in ___________________.
Agriculture, nutrient recycling, sewage processing, commercial food production, and industry, normal function of the human body.
Bacteria and fungi exist as _________, and outnumber human cells by 10:1.
Colonies can be described as ____, _______,_______,_______, and ______.
shape, margin, elevation, texture and pigment.
Edge of the colony
wet, shiny, opaque
Bacterial cells typically reproduce through _______, and asexual production.
___________ tend to be larger with different colors from top or bottom view and may be fuzzy due to spore forming structures.
The abililty to determine the causative agents of a specific infectious disease hinges on _______.
isolating the suspected culprit in a pure culture.
One of the most commonly used methods for generating a pure single species culture is ______.
streak plate method
What does the streak plate method assume?
Each cell in a mixed culture will give ruse to a single pure colony when grown on a semi-solid medium.
Bacteria can be distinguished based on what 2 things?
Cell morphology (shape) and arrangement
What are the three common bacterial shapes?
coccus (round), bacillus (rod), or spiral (spirillum, spirochete, or vibrio)
What is a pair of bacterial cells referred to as?
ex) diplococci and diplobacilli
In order to visualize the morphology and arrangements of tiny transparent bacterial cells, a thin _________is prepared and then ______.
__________Involves heat-fixing a bacterial sample to a microscope slide.
What does the addition of heat in a smear preparation do?
It kills the cells, causing them to adhere to the surface of the slide and so they are not dislodged during the staining process.
What is a danger of using heat to fix a specimen?
Cells may become damaged or their cellular structures may become distorted
Single color stains used to illustrate morphology and arrangement
Simple stains are what charge?
cationic, positively charged, and basic
These dyes are attracted to the negative nature of the bacterial cell and bind to the cell so that it takes on the color of the dye and becomes visible using microscopy
Basic dyes, that are positive and cationic (simple stains)
___________ employ acidic dyes that are anionic, negatively charged.
Negative stain techniques
These dyes are repelled by the negative nature of the bacterial cell and will bind to and stain the slide instead.
In ______ smears are not heat-fixed so the bacterial cell size and structural components are more accurate.
Negative stain techniques
Why may many species of bacterial cells share a common morphology and/or arrangement?
They are simplistic single-celled organisms
__________ Detect specific physical and chemical characteristics of a cell. Why may this be useful?
structural stains; removes some of the ambiguity of bacterial identification
Structural stains are also referred to as _________.
_______ is a form of glycocalyx; typically composed of extracellular layers of sticky _______.
Bacterial capsule; polysaccharides
What does the bacterial capsule help with?
Allows bacteria to escape from phagocytic cells, resist desiccation, and aids them in attachment. Help distinguish between pathogenic and nonpathogenic strains
How can Capsules be observed? What does it involve
Modified negative stain; Staining both the background and the cell while the capsule itself remains unstained.
Dormant structures that provide production for cells exposed to harsh environmental conditions
What do the "resting bodies"/bacterial endospore protect from?
excessive heat, cold, changes in pH, radiation, and various chemicals
____________ is steamed into bacterial endospores, and then the vegatative cells are counterstained with __________ which will replace the primary _______stain.
Endospores are typically characterized by shape as ___, ____,or _____ and common shapes are _____,_______,________.
terminal, subterminal, central; round, oval,or cylindrical
One of the most commonly used differential bacterial stains = ________.
Gram positive bacterial cells stain _____ and gram negative bacterial cells stain ___.
Characterisics of gram positive cell walls = _______.
thick, rigid, with many layers of the complex polysaccharide peptidoglycan with interwoven teichoic acids.
Characteristics of gram negative cell walls = ________.
Little or no peptidoglycan and lack teichoic acids, but possess an outer lipopolysaccharide membrane.
The thick layer of peptidoglycan are less susceptible to the organic solvent _______, than the ethanol soluble layers of the gram negative outer membrane.
What does it mean to be gram variable?
Gram positive cells that do not contain consistent amounts of teichoic acids in their cells walls and may give a gram negative reaction
Due to genetics or age of culture*
Bacteria of the mycobacterium and norcardia genera may have an additional cell wall component called __________.
This thick, waxy layer of lipids makes these bacteria resistant to water-based stains like those used in a gram stain
__________, which contains phenol, is used to penetrate through mycolic acid.
____utilizes heat to facilitate the penetration of carbolfuchsin into the cells.
_____Uses a stain with an increased concentration of both carbolfuchsin and phenol to eliminate the need for heat.
__________ are the causative agents of tuberculosis and leprosy.
___________is responsible for a tissue-destroying disease of the hands and feet in addition to polmonary disease.
Gram negative bacteria commonly found in the intestines of vertebrates.
__________are the most widely used to monitor water quality.
Coliform indicators are members of the ________ family.
Enterics are non-endospore forming, ________ that ferment _____ producing both acid and gas.
Enterics include members of the following genera:
Escherichia, Enterobacter, klebsiella, shigella, citrobacter, and many others.
Many dangerous pathogens in water are due to ____________.
__________ are indicative of intestinal pathogens.
One of the most commonly used fecal coliforms in assessing the potability of water.
A common method for detecting and enumerating coliforms in water involves a ______test.
Most Probable Number
_________Involves inoculating lactose broths with a water sample and monitoring the tubes for fermentation.
MPN: if acid and gas are observed, coliforms are present
Suspected coliforms are inoculated on a selective media like ______ and ____.
Levin's eosin methylene blue agar (EMB) or endo agar
They inhibit growth of gram + and differentiate between lactose fermenting or not.
_______ is a series of tests that can be used to differentiate between members of the Enteric family.
How do you incubate an inoculated agar plate and why?
You incubate it upside down so no air gets in and the bacteria will grow properly
Mention one reason why you would use the aseptic technique.
To keep things sterile and free from contamination
What is the purpose of heat-fixing a bacterial sample?
It kills the organisms without serious distortion, and they adhere better to the slide, taking up the dye more easily
Bacillus anthracis, the organism that causes anthrax is a ____ shaped bacterium.
The fact that milk makes an ideal growth medium for microbes increases the risk of both ______ and ______.
spoilage and the transmission of disease
Many dangerous pathogens in milk are due to _____.
_________Removes both the potential for spoilage organisms and pathogens.
Standard methods of pasteurization to not truly sterilize but....
Increase shelf life and reduce the ability to be used as a transmission for disease
________Involves dilutions of milkbeingplatedwith growth media.
standard plate count
Colonies are reffered to instead as a ________ that allows for the more likely possibility of a colony originating from a small clump of cells.
Antimicrobial chemicals are typically classified as either __________or________.
antiseptics or disinfectants
Antimicrobial chemicals meant for use on inanimate surfaces
Considered safe for use on living tissues
Reduce microbial numbers to an acceptable level
this test involves exposing bacterial inoculated agar to a filter disk impregnated with the chemical in question, incubating the plate, then looking for an effect on the bacterial growth pattern
Area with no microbial growth
zone of inhibition
__________are chemical compound that are used internally to interfere with the growth of microorganisms.
causing little or no damage to the host cells and tissues
A chemical that is produced by microorganisms that will inhibit the growth of other microbes