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
The pour plate method
- 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
Describe the bright-field microscopy
- 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
Describe light microscopy
- 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
Describe resolution
- 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
What are other types of microscopy?
- dark-field microscopy
- phase contrast microscopy
- fluorescence microscopy
30
Describe the ocular micrometer and stage micrometer
- 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
List the calibrations of each of the lenses
- 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
How are bacterial stains useful?
- determine cell size
- cell shape
- length, width, diameter
- cell morphology
- cellular arrangement
- other differentiating structures
33
List cell morphologies
- cocci: spheres
- bacilli: rods
- spirilla: spirals
- vibrio: slightly curved rods
- coccobacilli: short rods
- spirochetes: flexible spirals
34
What is pleomorphism?
- single species that exhibits a variety of cell shapes - slender, ellipsoidal, or ovoid rods - within a given sample
35
List bacterial cell arrangements
- pairs: diplo
- chains: strepto
- tetrads: micro
- cube: sarcina
- irregular cluster: staphylo
- palisade and angular: coryne
36
What are stains composed of?
- a solvent
- chromogen: colored molecule with 2 components
1. chromophore: color portion
2. charged portion
37
What are the 2 types of bacterial stains?
- simple stains
- differential stains
38
Describe simple stains
- 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
Describe differential stains
- 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
Describe negative stains
- 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
Describe gram stains
- 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
Describe the Acid Fast stains
- 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
Describe the endospore strain
- 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
Describe the flagella stain
- monotrichous: single flagella
- peritrichous: all around
- amphitrichous: at both ends
- lophotrichous: at one end
