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Chapter 3

Microbiology

QuestionAnswer
How is the sample processed and profiled? (hint: the five I's) 1. Inoculation 2. Incubation 3. Isolation 4. Inspection 5. Identification
inoculation to introduce a tiny sample into a container of nutrient medium, which provides an environment in which they multiply or grow
incubation involves placing inoculated media in a temperature controlled environment for a specified time to enhance growth
isolation techniques based on the concept that if an individual bacterial cell is separated from other cells and provided adequate space on a nutrient surface, it will grow into a colony
inspection macroscopic observations of colonies and morphological observations using a microscope
identification biochemical tests to determine nutrient requirements, metabolism, presence of certain enzymes, and mechanism for deriving energy
what three properties classifies media? 1. physical state 2. chemical composition 3. purpose (functional type)
what are the four physical states of media? 1. liquid- broths, milks, and infusions 2. semisolid- clumpy liquid used to check for motility 3. solid- provide surfaces for growth of colonies
what are the two chemical states of media? 1. synthetic- chemically defined media; put together by following a formula 2. complex (non-synthetic)- partially digested meats with unknown exact composition
what are the four types of media? 1. enriched media 2. selective media 3. differential media 4. reducing media
enriched media media that meets special growth needs of certain bacteria
selective media media that inhibits growth of most bacteria, except for the desired type (game of elimination)
differential media media that allows several bacteria to grow, each with a unique indicator (colors, gas bubbles, precipitates, etc.)
reducing media media that contains chemicals that absorb oxygen to help anaerobic microbes grow
what are the two necessary aspects of microscopy? 1. magnification 2. resolution
magnification creating an enlarged view by way of two phases: 1. first, the objective lens forms a real image 2. then the ocular lens forms the virtual image
resolution the ability to reveal detail and see two close objects as distinctively separate objects; anything close than 0.2 micrometers cannot be resolved with the microscopes we use in lab
numerical aperture cone of light that enters the objective lens after passing through the specimen; numerical value is printed on the side of the lens
what is the purpose of immersion oil? the oil immersion lens is the highest power objective lens; the oil used prevents the loss of light due to refraction, effectively increasing the numerical aperture for that objective
refractive index the ability of a substance to bend light
bright-field microscopy the basic light microscope; the image is formed as light passes through the specimen
when is the appropriate time to use dark field and phase contrast microscopes? when staining is NOT appropriate in observing living organisms
fluorescence microscopy the use of fluorochromes (fluorescent dyes) to highlight organisms
electron microscopy consists of two types: 1. transmission microscopy 2. scanning microscopy
transmission electron microscopes transmission of electrons through thin slices of specimens coated with metals for contrast
what are the three questions that should be answered when preparing specimens for observation? 1. Are we observing living or prepared specimens? 2. What are we trying to do (observe, morphology, motility, or identify)? 3. What type of microscope is available?
scanning electron microscopes images of the surfaces of specimens coated with metal for contrast (electrons are deflected back and read by special detectors from which an image is formed)
smear thin film of material is spread over the slide surface; air-dried
fixing attach film to slide prior to staining either chemically or by heating
staining coloring the specimen with a dye; changes the refractive index of specimens so it will contrast with the background
simple stains stain that requires a single dye to highlight the entire organism (shows morphology)
differential stains stain that distinguishes between bacterial types (shows morphology)
special stains stains that show specific parts of the microbes (endospores, flagella, or capsules)
gram stains classifies bacteria into two groups: - gram positive (dyes purple) - gram negative (dyes red/pink)
what is the four step process of gram staining? 1. apply the primary stain (crystal violet) 2. add the mordant (iodine) 3. apply the decolorizing agent (alcohol/acetone) 4. apply the counterstain (safranin)
acid fast stains stains that bind to bacterial cells with waxy material in cell walls; these cells retain red dyes after an acid-alcohol wash and are used to identify bacteria in the genus group, Mycobacterium
Created by: 530113