Chapter 2 Flashcards
How are microorganisms collected?
From environment: soil, water
From clinical specimens: blood, cerebrospinal fluid, sputum, urine, feces, diseases tissue
What are the five I’s of microbiology?
- Inoculation
- Incubation
- Isolation
- Inspection
- Identification
What is inoculation?
The implantation of microorganisms into or onto culture media
What is incubation?
Media containing inoculates are placed in temperature controlled chambers (20-40C)
What happens during incubation?
Microbes grow and multiply, producing visible growth in the media
What is isolation?
A cell separated from other cells on a nutrient surface, it will form a colony
What is a colony?
A macroscopic cluster of cells appearing on a solid medium arising from the multiplication of a single cell
What does isolation require?
- medium with a firm surface
- petri dish
- inoculating tools
Ex) streaking
What is inspection and identification?
Microbes can be identified thru
- microscopic appearance
- characterization of cellular metabolism
- genetic and immunological characteristics
What is a culture?
A propagation of microorganisms with various media
What is a medium?
A nutrient used to grow microorganisms outside their natural habitat
What are the physical states of media?
- liquid
- semisolid
- solid (can convert to liquid)
- solid (can’t convert to liquid)
Semisolid is to test for?
Motility
What are the different types of media?
Chemically defined(recipe)
Complex media (don’t know every ingredient)
Selective media
Differential media
What is chemically defined media?
- Media whose composition are precisely chemically defined
- contain organic and inorganic compounds
- molecular content specified by a specific formula(recipe)
What is complex media?
- contains at least 1 ingredient that is not chemically definable
- extracts of animals, plants, or yeast
- blood, serum, meat extracts, or infusions
What is selective media?
Contains one or more agents that inhibit the growth of a certain microbes but not others
-important when isolating a specific type of microorganism from samples containing dozens of species
What is differential media?
Allows multiple types of microorganisms to grow but are designed to display differences among those microorganisms
-it shows variations in colony size or color, media changes color, formation of gas bubbles or precipitates
What are methods for isolating bacteria?
- Streaking
- Dilution
- Spread plate
What does the objective lens do?
Closest to the specimen, forms the initial image called the real image
What does the ocular lens do?
Forms the second image called the virtual image that will be received by the eye and converted to the retinal and visual image
What is oil immersion lens?
- uses oil to capture light that would otherwise be lost to scatter
- liquid bends light onward towards lens
What does reducing scatter do?
Increases resolution
What is light field microscopy?
Light shining from under
What is dark field microscopy?
Light shining from side (makes background dark)
What is phase contrast microscopy?
See outside structures of the cell better and can move light source wherever
What is confocal microscopy?
Adding dyes and bacteria will light the bacteria up while the background is dark
What is electron microscopy?
Shows intense detail
Preparing specimens depends on what?
Condition of specimen, aims of the examiner, types of microscopy available
What mounts allow you to observe as near to the natural habitat state as possible?
- Wet mount
2. Hanging drop
What is a wet mount?
Consists of a drop or two of culture placed on a slide and overlaid with a cover slip
What is a hanging drop?
A drop of culture is placed in a concave slide, Vaseline adhesive or sealant, and cover slip are used to suspend the sample
What do short term mounts assess?
Size, shape, arrangement, color, and motility
What are permanent mounts?
Smear technique, stains
Who developed the smear technique?
Robert Koch
What is smear technique?
Spread a thin film made from a liquid suspension of cells on a slide, air dry, heat fix: heat gently to kill the specimen and attach to the slide
What dye has a positive charge?
Basic dyes
What dye has a negative charge?
Acidic dyes
Bacteria attract what dye?
Basic dyes even tho they attract negatively charged substances
Negative vs positive staining
Positive: dye sticks to the specimen and gives it color
Negative: does not stick to the specimen but settles distance from its outer boundary, forming a silhouette
Simple vs differential staining
Simple: only require a single dye, causes all the cells in the smear to appear more or less the same color regardless of type, reveals shape, size, and arrangement
Differential: uses 2 colored dyes; primary and counter stain, distinguish cell types or part, more complex and require additional chemical reagents to produce the desired reaction
What are the type of differential stains?
- Gram stain
- Acid fast stain
- Endospore stain
What is the most important differential stain?
Gram stain
Who developed the gram stain?
Hans Christian Gram
What does the gram stain consist of?
Crystal violet(primary stain),
iodine(the mordant),
alcohol rinse(decolorizer),
safranin(counterstain)
What is a practical aid in diagnosing infection and guiding drug treatment?
Gram stain
What is acid fast stain?
Differentiates acid fast bacteria (pink) from non acid fast bacteria (blue)
What stain detects Mycobacterium tuberculosis?
Acid fast stain
What is endospore stain?
Similar to acid fast stain in that a dye is forced by heat into resistant bodies called spores or endospores
What does endospore stain distinguish?
Spores and vegetative cells
What are the special stains?
Capsule staining and flagellar staining
What is capsule staining?
- used to observe the microbial capsule, an unstructured protective layer surrounding the cells of some bacteria and fungi
- neg. stained with India ink
What is flagellar staining?
- used to reveal tiny, slender, filaments used by bacteria for locomotion
- flagellar are enlarged by depositing a coating on the outside of the filament and then staining it
What are the types of electron microscopy?
- Scanning =surface ( low powered)
2. Transmission=internal
