Exam 1 Flashcards
1
Q
Describe the ubiquity of microorganisms
A
- ## it means that they are found everywhere that other lifeforms exist, adapting successfully to other environments
2
Q
What are saprophytes?
A
- preform important role of decomposition in the ecosystem
3
Q
What are opportunistic pathogens?
A
- inhabit our bodies and are capable of producing a disease state if introduced into a suitable part of the body
- reservoir: any area where a microbe with the potential to cause infection resides
4
Q
Describe blood agar
A
- purpose: to differentiate bacteria based on their hemolytic characteristics
- composition: includes 5% sheep blood in a tryptic soy agar base
- theory: several species of G+ cocci produce endotoxins called hemolysins, which are able to destroy RBCs and hemoglobin. 3 major types
1. Beta: complete destruction; results in clearing of the medium
2. alpha: partial destruction; results in greenish discoloration of the medium
3. gamma: no hemolysis
5
Q
Describe germicides
A
- substances or systems that prevent the spread of pathogens (both physical and chemical)
- some are specific but most target a broad-spectrum
- 3 categories
1. decontamination
2. disinfection
3. sterilization
6
Q
Describe decontamination
A
- lowest level of control
- reduction of pathogenic microorganisms to a level at which items are safe to handle without protective attire
- physical cleaning with soap/detergents, removal of all/most inorganic/organic matter
7
Q
Describe disinfection
A
- next level of control from decontamination
- divided into 3 levels: low, medium, high based on effectiveness against specific control pathogens or their surrogates. All kill most of the targeted pathogens but typically do not kill large numbers of spore
- typically liquid, can be solid/aqueous
- other methods: dry heat, moist heat, ultraviolet light
- types: chemical sterilant (high level disinfectants that have the ability to kill all vegetative cell and some spores) and antiseptics (disinfectants used to reduce/eliminate pathogens on/in living tissue
8
Q
Describe sterilization
A
- highest level of pathogen control
- complete elimination of viable organisms including spores
- chemicals, gases, incineration, dry heat, moist heat, ethylene oxide gas, ionizing radiation, low-temperature plasma, low-temperature ozone
9
Q
Describe steam sterilization
A
- most effective and common method
- autoclave: most used device, uses superheated steam under pressure to kill heat-resistant organisms, Must reach optimum temperature for at least 15 min with color coded tapes
10
Q
Steam sterilization: describe biological indicators
A
- indicator vial: includes small ampule containing fermentation broth with pH indicator and strip of filter paper containing bacterial spores
- vial is autoclaved for 15 min, ampule is crushed to allow fermentation broth to come into contact with bacterial spores, and are then incubated for 48 hours
- are the only way with certainty to determine that sterilization has been achieved
11
Q
Micropipettes: blue and yellow tips
A
- blue: larger, used to P1000
- yellow: smaller, used for P200 and P20
12
Q
Micropipette ranges
A
- P1000: from .2 mL to 1 mL, 020 to 100
- P200: from 0.05 mL to 0.2 mL,
- P20: from 2uL to 20 uL, 020 to 200
13
Q
Describe the different medias
A
- broths: used to grow microbes when fresh cultures or large number of cells are required
- agar slants: grow stock cultures that can be refrigerated after incubation and maintained for several weeks
- plated media: used for obtaining isolation of species , differential testing, and quantifying bacterial densities
14
Q
What are the methods of isolation
A
- a bacterial sample is always assumed to be a mixed culture
- spread plate
- streak plate
- pour plate
15
Q
Describe the spread plate method
A
- diluted microbial sample is deposited on an agar plate and spread uniformly across the surface
- CFUs should be deposited far enough to grow into individual colonies
- used to quantify cell density of a broth culture
16
Q
What are growth characteristics influenced by?
A
- nutrient availability
- temperature
- incubation time
17
Q
What are the colony shapes?
A
- round
- irregular
- punctiform: tiny dots
18
Q
What are the colony cell margins?
A
- entire: smooth, no irregularities
- undulate: wavy
- lobate: lobed
- filamentous: unbranched strands
- rhizoid: branched like roots
19
Q
What are the colony cell elevations?
A
- flat
- raised
- convex
- pulvinate
- umbonate
20
Q
What are colony cell textures?
A
- moist
- mucoid
- butyrous
- dry
- shiny
- dull
- opaque: optical properties
- translucent: pigment production
21
Q
Describe the growth patterns on slants
A
- filiform: dense and opaque with a smooth edge, smooth texture with solid edge
- friable: crusty
- spreading edge: produced by motile organisms, goes outwards
- pigmented or translucent/transparent
22
Q
Describe the growth patterns in broth
A
- pellicle: growth floats on top of the medium, membrane on top
- sediment: growth sinks to the bottom
- uniform fine turbidity: evenly cloudy throughout
- flocculent: clumped growth, suspended chunks/pieces
- ring: growth at the top around the edge
23
Q
What is streaking for isolation?
A
- developed by Robert Koch
- purpose: to obtain isolated colonies, which can then be used to obtain a pure culture
24
Q
The quadrant streak method
A
- used with samples suspected of high cell density
- flame loop in between quadrants and do not take new inoculum in between quadrants
- rotate plate as you go and cool loop
25
Q
The pour plate method
A
- yields isolated colonies of bacteria and fungi. Original sample is diluted several times to reduce microbial population and to calculate original sample concentration
- then pour agar, after agar solidifies each cell will be fixed in place and form a colony
26
Q
Describe the bright-field microscopy
A
- produces an image made from light transmitted through a specimen
- specimen restricts light transmission and appears dark against a light background
- because most biological specimens are transparent, contrast is improved with the application of stains, which usually kills the cell
27
Q
Describe light microscopy
A
- begins with light from an internal or external light source
- light passes through the condenser, which concentrates the light, then through the specimen and the objective lens
- as light passes through the objective lens it is refracted, or bent, and produces a magnified “real” image
- the image is magnified again as it passes through the ocular lens to produce a “virtual image”
- total magnification = ocular x objective
- immersion oil only used in 100x objective
28
Q
Describe resolution
A
- the clarity of an image
- measurement of how far 2 points must be for the microscope to view them as separate
- resolution improves as limit of resolution decreases
- D = lambda / condenser x objective
- NA: numerical aperture which is ability to capture light coming from the specimen and use it to make an image, marked on the condenser and objective
29
Q
What are other types of microscopy?
A
- dark-field microscopy
- phase contrast microscopy
- fluorescence microscopy
30
Q
Describe the ocular micrometer and stage micrometer
A
- ocular: “ruler” installed in the microscope eyepiece, composed of uniform but unspecified graduations, must be calibrated before used to measure specimens
- stage: microscope slide containing a ruler with 100 um major divisions divided into 10 um increments. When magnified by the objective, the size of the graduations increases as magnification increases; the value of ocular micrometer division decreases as magnification increases
- calculation: divide the stage micrometer (count long lines) by the ocular micrometer and then multiple by 100 to get in um/ocular units
31
Q
List the calibrations of each of the lenses
A
- scanning: 4X objective, 40x total, 25
- low power: 10x obj, 100x total, 10
- high dry power: 40x obj, 400x total, 2.5
- oil immersion: 100x obj, 1000x total,1
32
Q
How are bacterial stains useful?
A
- determine cell size
- cell shape
- length, width, diameter
- cell morphology
- cellular arrangement
- other differentiating structures
33
Q
List cell morphologies
A
- cocci: spheres
- bacilli: rods
- spirilla: spirals
- vibrio: slightly curved rods
- coccobacilli: short rods
- spirochetes: flexible spirals
34
Q
What is pleomorphism?
A
- single species that exhibits a variety of cell shapes - slender, ellipsoidal, or ovoid rods - within a given sample
35
Q
List bacterial cell arrangements
A
- pairs: diplo
- chains: strepto
- tetrads: micro
- cube: sarcina
- irregular cluster: staphylo
- palisade and angular: coryne
36
Q
What are stains composed of?
A
- a solvent
- chromogen: colored molecule with 2 components
1. chromophore: color portion
2. charged portion
37
Q
What are the 2 types of bacterial stains?
A
- simple stains
- differential stains
38
Q
Describe simple stains
A
- smear is stained with a single dye that stains all cells the same color
- measure cell dimensions, morphology, and arrangements
- NOT for differentiation of cell types or structures
-purpose: stain heat-fixed cells with a colored dye to make them more visible under the microscope - theory: auxochrome picks up a H+ or loses a OH- and becomes positively charged. Attracted to the negative charges on the surface of most bacteria cells
- ex: methylene blue, crystal violet, safranin, carbolfuchsin
39
Q
Describe differential stains
A
- detect differences between organisms or between parts of the same organism
- used more frequently than simple stains because they provide additional information
- ex: acid fast stains, gram stains, capsule stains, endospore stains, flagella stains
40
Q
Describe negative stains
A
- a type of simple stain
- purpose: to determine morphology and cellular arrangement in bacteria that are too delicate to withstand heat-fixing
- theory: uses a dye in which the chromogen is acidic. it gives up H+ and becomes negatively charged, which repels with bacterial surface and remains unstained against a colored background
41
Q
Describe gram stains
A
- differentiates between G+ and G- cells
- G+: thick peptidoglycan wall and no outer membrane
- G-: thin cell wall of peptidoglycan and outer membrane
- coloration: G+ trap crystal violet-iodine complex due to teichoic acids. G- have higher lipid content. Alcohol step extracts lipids and makes cell wall porous, incapable of retaining primary stain
- decolorization: most critical step. overdecolorization leads to more red G+ cells and undercoloring leads to more purple G- cells
- preparation of emulsion and age of culture (no older than 24 hrs) also affect results
42
Q
Describe the Acid Fast stains
A
- based on the presence of mycolic acids in the cell wall of acid-fast + organisms
- mycolic acid: waxy substance that provides higher affinity for the primary stain and resistance to decolorization by the acid alcohol solution
- primary stain: carbolfuchsin
- Ziehl-Neelsen Acid-Fast Stain: acid fast cells stain reddish-purple and nonacid-fast cells stain methylene blue
- Kinyoun Acid- Fast Stain: acid fast cells stain reddish-purple, nonacid fast cells stain brilliant green
43
Q
Describe the endospore strain
A
- endospore: dormant form of the bacteria that allows it to survive poor environmental conditions. Resistant to heat, chemicals due to keratin covering
- spore location: central, terminal, subterminal
- spore shape: spherical or elliptical (oval)
- stain: differential stain used to detect presence/absence of spores
- method: steaming forces the primary stain, malachite green, into the spores. Then vegetative cells or spore mother cells are decolorized with water and stained with safranin
- results: spores appear green and vegetative cells and spore mother cells appear red
- known as the Schaeffer-Fulton Spore Stain
44
Q
Describe the flagella stain
A
- monotrichous: single flagella
- peritrichous: all around
- amphitrichous: at both ends
- lophotrichous: at one end
