Motility, Aseptic Technique, and Isolation
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How can bacterial motility be determined?
Observe whether bacteria move away from the point of growth in a motility test medium
What is bacterial motility?
The ability of bacteria to move on their own
What structure is most commonly used for bacterial movement?
Flagella
What are flagellar arrangements?
The number and location of flagella on a bacterial cell
What is monotrichous?
One flagellum at one end of the cell
What is lophotrichous?
A cluster of flagella at one end of the cell
What is amphitrichous?
Flagella at both ends of the cell
What is peritrichous?
Flagella all around the cell
What is aseptic technique?
Procedures used to prevent contamination
Why is aseptic technique important?
It keeps cultures pure and prevents contamination
What is an isolated colony?
A colony that grew from a single bacterial cell or group of identical cells
What is a pure culture?
A culture containing only one species of microorganism
How are isolated colonies produced?
By spreading cells apart on agar so individual colonies can grow
What is the goal of isolation techniques?
To obtain a pure culture
What is a motility medium used for?
To determine whether bacteria can move
How does a non-motile bacterium appear in a motility test?
Growth stays along the stab line
How does a motile bacterium appear in a motility test?
Growth spreads away from the stab line
What does the O antigen represent in E. Coli O157
The LPS polysaccharide antigen
What does the H antigen represent in E. Coli O157:H7
The flagellar antigen
What does O157 mean?
A specific O antigen type
What does H7 mean?
A specific H antigen type
What does atrichous mean?
No flagella
What does monotrichous mean?
One flagellum at one end
What does lophotrichous mean?
A tuft of flagella at one en
What does amphitrichous mean?
Flagella at both ends
What does peritrichous mean?
Flagella all around the cell
Which flagellar arrangement is common in many enteric bacteria?
Peritrichous
Why are peritrichous bacteria often good swimmers?
They have many flagella that help with movement
What is the transfer of microbes?
Moving microorganisms from one culture to another.
Why is aseptic technique important during transfers?
To prevent contamination
What is the key idea of aseptic technique?
Prevent unwanted microbes from entering cultures or wounds
What is contamination?
The presence of unwanted microorganisms
What can happen if aseptic technique is not followed?
Contamination and infection.
What is an infection?
Growth of microorganisms in body tissues
What is a pure culture?
A culture that contains one type of microorganism
What is a mixed culture?
A culture that contains more than one type of microorganism
What is a contaminated culture?
A culture containing an unwanted microorganism.
What is the goal of microbial transfer techniques?
To transfer only the desired microorganism.
How long should culture containers remain open during transfers?
Only briefly
What should be used when transferring microbes?
Sterile tools and proper aseptic technique.
What can contamination do to experimental results?
Make the results inaccurate
What is a major benefit of aseptic technique?
It helps maintain pure cultures and prevents infection
What is isolation in microbiology?
Separating microorganisms so individual colonies can grow
What is the streak plate method?
A technique used to obtain isolated colonies on an agar plate
Why is the streak plate method performed?
To obtain a pure culture
What tool is commonly used in the streak plate method?
An inoculating loop.
What happens to bacteria as streaking continues across the plate?
They become more diluted
What is an isolated colony?
A colony that grows separately from other colonies
What can be obtained from an isolated colony?
A pure culture
What is dilution over distance?
Reducing bacterial concentration by streaking farther across the agar surface
Which scientist is associated with dilution over distance?
Koch
What is dilution over volume?
Reducing concentration by adding more liquid
Which scientist is associated with dilution over volume?
Pasteur
What are the three parts of a prokaryotic flagellum?
Filament, hook, and basal body
What protein makes up a flagellum?
Flagellin
What is the function of the basal body?
It anchors the flagellum to the cell.
What is an O antigen?
The polysaccharide portion of LPS
What is an H antigen?
A flagellar protein antigen
What is Brownian motion?
Random jittery movement caused by molecular collisions
Is Brownian motion true motility?
No.
What is taxis?
movement in response to an environmental signal
What is positive taxis
Movement toward a higher concentration of a signal
What is negative taxis
Movement away from a higher concentration of a signal
What is chemotaxis?
Movement in response to chemicals
What is photoaxis?
movement in response to light
What three things are required for good aseptic technique?
Organization, concentration, and quiet
Why are microbes transferred to a new media?
They need fresh nutrients and must be moved away from wastes?
Why else are microbes transferred?
For storage and metabolic testing
Why is streaking on solid media better than growing in liquid cultures for obtaining pure cultures?
It produces isolated colonies that can be used to obtain pure cultures
Why are pure cultures important?
They allow the study of one microorganism without interference from others.
How can gram-negative and gram-positive bacteria be separated from a mixed culture?
By isolating colonies with a streak plate and then performing a gram stain
What colony characteristic describes the overall shape?
Form
What colony characteristic describes the edge of a colony?
Margin
What colony characteristic describes the height of a colony?
Elevation
What are the main colony characterstics?
size, form, margin, elevation, color, and surface appearance
What does circular describe?
Colony form
What does entire describe?
What does convex describe?
What does convex describe?
Colony elevation
What is a coccus?
A spherical bacterium
What is a bacilus?
A rod-shaped bacterium
What is a spirillum or spirochete?
a spiral-shaped bacterium
What are diplococci?
Cocci arranged in pairs.
What are streptococci?
Cocci arranged in chains.
What are staphylococci?
Cocci arranged in clusters