Chapter 3 Flashcards
What are the five I’s of microorganism growth?
Inoculation, incubation, isolation, inspection, identification
What is culture (verb)?
Propogation of microorganisms with various media
What is a culture (noun)?
A growth of microorganisms in or on a nutrient medium
What is a medium?
A nutrient-containing environment in which microbes can multiply
What is inoculation?
Introduction of microbes into or upon media for culture
What does sterile mean?
Free of all life forms, including spores and viruses
What temperatures are typically used for incubation in lab?
20 to 45 degrees C
In addition to temperature, what else can incubators control?
Atmospheric gases
What are the signs of microbial growth in liquid medium?
Cloudiness, sediment, scum, color
What are the signs of microbial growth on solid medium?
Visible masses of piled-up cells (colonies)
What three properties are used to classify media?
Physical state, chemical composition, and functional type
What are the possible physical states of media?
Liquid, semisolid, liquefiable solid, non-liquefiable solid
What are the possible chemical compositions of media?
Chemically defined/synthetic and complex
What are the possible functional types of media?
General purpose, enriched, selective, differential, anaerobic growth, specimen transport, assay, enumeration
What are liquid media?
Water-based solutions that do not solidify at temperatures above freezing and flow freely
What are semisolid media?
Media with enough gelatin/agar to thicken but not produce a firm surface; exhibit clot-like consistency at room temperature
What are solid media?
Media with a firm surface upon which cells can form discrete colonies
What is agar?
Complex polysaccharide isolated from red alga; it is solid at room temp, liquifies at 100 degress C, and resolidifies at 42 degrees C
What is defined media?
Media whose exact chemical compositions are known and defined by an exact formula
What is a complex media?
Media containing at least one component that is not chemically definable
What are general purpose media?
Media that grow as broad a spectrum of microbes as possible
What are enriched media?
Media that contain complex organic substances that fastidious bacteria require for growth
What are growth factors?
Specific vitamins or amino acids
What are selective media?
Media that contain one or more agents that inhibit the growth of certain microbes and encourage others to grow
What are differential media?
Media that allow multiple types of microorganisms to grow, but display visible differences between colonies
What are hemolysins?
Enzymes that lyse red blood cells to release iron-rich hemoglobin
What is beta-hemolysis?
The complete lysis of red blood cells
What is alpha-hemolysis?
The incomplete lysis of red blood cells
What is gamma-hemolysis?
No hemolysis
What are reducing media?
Media that grow anaerobic bacteria by limiting available oxygen
What are carbohydrate fermentation media?
Media that contain sugars that can be fermented and a pH indicator to show this reaction
What are transport media?
Media that maintain and preserve specimens
What are assay media?
Media used to test the effectiveness of antimicrobial drugs and assess the effects of disinfectants, antiseptics, cosmetics, and preservatives on microbe growth
What are enumeration media?
Media used to count the number of organisms in milk, water, food, soil, etc.
What is a colony?
A discrete mound of cells formed on solid nutrient surface
What are the requirements of isolation?
Inoculation of a small number of cells into a large volume/expansive area of media, a relatively firm surface, a petri dish, and inoculating tools
What is the streak plate method?
A small droplet of culture is spread across the surface of a medium in a pattern that gradually thins out the sample
What is the pour plate method?
Sample is diluted serially into cooled, but still liquid agar tubes that are then poured into sterile petri dishes and allowed to solidify
What is the spread plate method?
A small volume of sample is pipetted onto the surface of the plate and spread around evenly
What is a pure culture?
A container of medium that contains only a single known species
What does anexic mean?
Free of other living things except for the one being studied
What is a subculture?
A second-level culture from a well-isolated colony
What is a mixed culture?
A container that holds two or more identified, easily differentiated species
What is a contaminated culture?
A culture that was once pure or mixed but now contains contaminants
What methods are used to determine microbial profiles?
Phenotypic testing, genotypic testing, immunologic testing, macroscopic analysis, microscopic analysis
What fundamental characteristics can be determined through biochemical tests?
Nutrient requirements, products of growth, enzyme presence, energy deriving mechanisms
What is refraction?
Bending or change in the angle of the light ray as it passes through a medium
When is refraction greater?
When there is a greater difference in refraction between the two substances
What three things were added to original microscopes to form the compound microscopes used today?
Second magnifying lens, lamp for specimen illumination, condenser for focusing light
What are the three properties of an effective microscope?
Magnification, resolution, contrast
Which microscope lens forms the virtual image?
Ocular lens
Which microscope lens forms the real image?
Objective lens
How is magnifying power calculated?
By multiplying the power of the ocular lens by the power of the objective lens
What is resolution?
The capacity of an optical system to distinguish or separate two adjacent objects or points from one another
What determines resolving power?
A combination of characteristics of the objective lens and the wavelength of light used to illuminate the sample
Why is oil able to increase numerical aperture and resolution?
Because it prevents the scattering of light rays
What is refractive index?
The degree of contrast between a magnified image and its surroundings
What are the four types of light mciroscopes?
Bright-field, dark-field, phase-contrast, and interference
What are the two variations on light microscopes?
Fluorescence microscope and confocal microscope
What three things are specimen preparation dependent upon?
Specimen condition, aims of the observer, and type of microscopy
Why are wet mounts and hanging drop mounts beneficial?
They provide a true assessment of size, shape, arrangement, color, and motility of cells
What is a wet mount?
A drop or two of culture placed on a slide overlaid with a coverslip
What are the disadvantages of a wet mount?
Can damage larger cells, susceptible to drying, can contaminate handler’s fingers
What is a hanging drop mount?
Concave slide with vaseline adhesive and a coverslip
What is the smear technique?
Spread a thin film made from a liquid suspension of cells on a slide and allow it to air dry
What are the important functions of heat fixing?
Kills cells, secures specimen to slide, preserves cellular components in a natural state with minimal distortion
Why are smears stained?
To provide contrast and make cell features stand out
How do basic, cationic dyes work?
They are positively charged and are attracted to the acidic, negatively charged components of cell walls
How do acidic, anionic dyes work?
They are negatively charged and are repelled by the acidic, negatively charged components of cell walls
What is a positive stain?
A positively charged stain that is attracted to negatively charged cell walls and gives cells color
What is a negative stain?
A negatively charged stain that is repelled by negatively charged cell walls and gives the background color
What are simple stains?
Stains that require a single dye and a simple procedure
What are differential stains?
Stains that use two differently colored stains to clearly contrast cell types/parts
What are the different types of differential stains?
Gram stain, acid-fast stain, endospore stain, capsule stain
What color do gram-positive bacteria stain?
Purple/blue
What color do gram-negative bacteria stain?
Pink/red
What color do acid-fast bacteria stain?
Pink
What color do nonacid-fast bacteria stain?
Blue
What is endospore stain used for?
To distinguish endospores from vegetative cells
What are special stains?
Stains that pinpoint a particular characteristic
What is a capsule?
An unstructured protective layer surrounding the cells of some bacteria and fungi
How can the capsule be visualized?
Through negative staining or with the use of special positive stains
What are flagella?
Tiny, slender filaments used by bacteria for movement
How does flagellar staining work?
A coating is deposited on the outside of the flagella filament and then stained
