Lab Exam 1 Flashcards
What does “ubiquitous” mean?
that they are found everywhere
What can microorganisms be isolated from?
- Soil
- Water
- Plants
- Animals
- Placed like the hot acid pools in Yellowstone
Are all microorganisms ubiquitous?
Not EVERY species is, but it applies to microorganisms as a group
What do you call microorganisms that do not reside on or in a specific plant or animal host and are not known to cause disease?
Free-living and nonpathogenic
Saprophytes play an important role in decomposition of the ecosystem. What is a Saprophyte?
A plant, fungus, or microorganism that lives on dead or decaying organic matter
What are the three types of relationships between microorganisms and their host?
Pathogenic, Mutualism, and Commensalism
Pathogenic relationship
Microorganism causes damage to the host
Mutualistic relationship
Both the host and the microbe benefit
Commensal relationship
Microbe benefits but no effect on host
What are opportunistic pathogens?
Pathogens that take advantage of a situation that is not normally available
-They 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 potential to cause infection resides
What is the composition of Blood Agar?
5% Sheep blood in a Tryptic Soy Agar (TSA) Base
What is the purpose of blood agar?
To differentiate bacteria based on their hemolytic characteristics
Three major types of hemolysis
Beta, Alpha, and Gamma
Beta hemolysis
Complete destruction; results in cleaning of the medium
- has a yellow halo around the microbes in the TSA plate
Alpha hemolysis
Partial destruction; results in greenish discoloration of the medium
Gamma hemolysis
No hemolysis
-has neither the beta or alpha characteristics and will likely appear like nothing happened
Germicides
Refers to substances or systems, both chemical and physical, that prevent the spread of pathogens
What are the three categories of germicides?
Decontamination, Disinfection, and Serilization
Decontamination
- Lowest level of control
- Defined as “reduction of pathogenic microorganisms to a level at high items are safe to handle without protective attire”
-involves the removal of all or most organic and inorganic matter
Disinfection
- next level of control
- kills most of targeted pathogens, but typically do not kill large numbers of spores
What are the two types of disinfectants?
Chemical sterilants and antiseptics
Examples of methods of disinfection
- typically liquid or gaseous chemical agents
- dry heat
- moist heat
- UV light
Sterilization
- highest level of pathogen control
- can kill all viable organisms, even spores
- achieved by chemicals, gases, incineration, dry heat, moist heat, ethylene oxide gas, ionizing radiation, low-temp plasma, or low-temp ozone
What is the most effective and most common method of sterilization? What is an example of it?
Steam Sterilization
Ex: Autoclave
What is the sterilizing temperature for autoclaving and how long should it be done for?
Between 121 and 127 degrees C for at least 15 at the optimum temperature
What is the only way to determine with certainty that sterilization has been achieved?
Biological indicators
What does aseptic transfer mean?
Transfer of living microbes from one place to another without contamination of the culture, the sterile medium, or the surroundings
What is a culture?
A medium that contains living microbes
What is a pure culture?
A culture that contains a single species
What is a mixed culture?
A culture that contains multiple species
What assumption should be made about cultures?
All cultures are assumed to be mixed prior to obtaining isolation
Broths
Used to grow microbes when fresh cultures or large number of cells are required
Agar Slants
Used to grow stock cultures that can be refrigerated after incubation and maintained for several weeks
What is Plated media used for?
Typically used for obtaining isolation of species, differential testing, and quantifying bacterial densities
methods of isolation
Spread plate, streak plate, and pour plate
Spread Plate Technique
Microbial sample is deposited on an agar plate and spread uniformly. After incubation, a portion of isolated colon can be transferred to a sterile medium to begin a pure culture.
-Can be used to quantify cell density of a broth culture
What are growth characteristics influenced by?
- nutrient availability
- temperature
- incubation time
Basic categories of colony morphology
Shape, margin, elevation, texture, color, and optical properties
What are agar slants used for?
Cultivation, maintenance, and storage of stock cultures
growth characteristics for organisms cultured on a slant
- Filiform
- dense and opaque with a smooth edge
- Friable
- Crusty
- Spreading Edge
- produced by motile organisms
- Pigmented or translucent/transparent
Growth patterns in broth
- Pellicle
- growth floats on top of the medium
- Sediment
-growth sinks to the bottom - Uniform fine turbidity
-Flocculent
-clumped growth
Who developed the concept of the pure culture in the 1850’s?
Louis Pasteur
What did Robert Koch develop a procedure for the the 1880’s?
Streaking for isolation
What is the purpose of streaking for isolation?
To obtain isolated colonies that can then be used to obtain a pure culture
Bright-field microscopy
Produces an image made from light transmitted through a specimen
total magnification = magnification of ______ _____ x magnification of ________ _____
Ocular lens; objective lens
Resolution
The clarity of an image
Ocular micrometer
Composed of uniform but unspecified graduations and must be calibrated before used to measure specimens
Stage micrometer
A microscope slide containing a ruler with 100 micrometers
How many micrometers is 0.01mm?
10
How are bacterial stains useful?
They are used to determine:
- Cell size
- Cell morphology
- cellular arrangement
- other bacterial structures or differentiating features
What is an important first step in identifying bacterial species?
Determining Cell Morphology
Types of cell morphologies:
- spheres
-cocci - rods
- bacilli
- spirals
- spirilla
What is pleomorphism?
A single species that exhibits a variety of cell shapes- slender, ellipsoidal, or ovoid rods - within a given sample
Pairs of cells have the prefix:
“Diplo”
Chains of cells have the prefix:
“Strepto”
Tetrads arrangement name example with cocci shape
Micrococcus
Cube “sarcina” cell arrangement name example with cocci shape
Sarcina
What is the prefix for an irregular cluster?
‘Staphylo”
Name example for a palisade and angular cell arrangement and a bacilli shape
Corynebacterium
what do stains contain?
A solvent and the chromogen (colored molecule)
What do chromogens consist of?
The Chromophore (portion of the chromogen that gives it color) and the Auxochrome ( changed portion of the chromogen)
What is the purpose of a negative stain?
To determine morphology and cellular arrangement in bacteria that are too delicate to withstand heat-fixing
Theory behind a Negative Stain
- uses a dye solution in which the chromogen is acidic
- acidic chromogen gives up a H+ and becomes negatively changed
- negative charge on bacterial surface repels the negatively charged chromogen
- cell remains untainted against a colored background
What is a Simple Stain?
Smear is stained with a single dye that stains the cells all the same color
-differentiation of cell types or structures is NOT the objective!
Differential stains
Detect differences between organisms or between parts of the same organism
-used more frequently than simple stains because they provide additional information
What is part of the group of stains are sometimes referred to as structural stains?
- Acid-fast stains
- Gram stain
- Capsule stain
- Endospore stain
- Flagella stain
What is the purpose of simple stains?
Stain heat-fixed cells with a colored dye to make them more visible under a microscope
Simple stain theory
- Auxochrome picks up a H+ or loses an OH- and becomes positively charged
- Attracted to the negative charges on the surface of most bacterial cells
what are examples of simple stains?
- Methylene Blue
-Crystal Violet - Safranin
- Carbolfuchsin
Differential stains are used to differentiate between _________ and _________ cells
Gram positive and Gram negative
Gram-Positive
Bacteria have a very thick cell wall made of peptidoglycan and NO outer membrane
Gram-negative (pink)
Bacteria have a thin cell wall made of peptidoglycan and have an outer membrane
Why do gram positive stains resist coloration?
It is because of the thicker peptidoglycan layers and greater cross-linking due to teichoic acids. It traps the crystal violet-iodine complex and resists decoloration
What is the most critical and most likely step that is the source of inconsistency? Why?
Decolonization because you could cause over-decolorization and under-decolorization
What are the three techniques that are executed poorly for variable results?
- Decolorization is done wrong
- Improper preparation of the emulsion
- Age of the culture
- best cultures are no older than 24 hours because they can lose their ability to retain the crystal violet-iodine complex
What is an Acid Fast Stain based on?
The presence of mycolic acids in the cell wall of acid-fast positive organisms
Mycolic acid
A waxy substance that provides a higher affinity for the primary stain and resistance to decoloration by an acid alcohol solution
what is an important differential stain used to identify bacteria in the genus Mycobacterium?
Acid-fast stain
Acid-Fast Positive final color is _____ while Acid-Fast Negative final color is _______
Pink; green
Endospore
-Dormant form of the bacterium that allows it to survive poor environmental conditions
-Resistant to heat and chemicals because of tough outer covering made of keratin
Spore Location meanings
- Central
- middle of the cell
- Terminal
- end of cell
- Subterminal
- between end and middle
Endospore Stain
Differential stain used to detect presence or absence of spores in bacterial cells
which two genera produce spores?
bacillus and Clostridium
If a spore producer is present, it will have a ______ spore against the red-stained mother cell
Malachite Green
Categories of flagellation
-Monotrichous (single flagellum)
-Peritrichous (flagella all around)
- Amphitrichous (flagella on both ends)
- Lophotrichous (flagella on one end)
