Lab Final Review - Week #1 Flashcards
What is a pure culture?
A culture containing a single, unadulterated species of cells
What is culture medium?
It can be liquid, solid, or semisolid and it is made up of soluble low-molecular-weight substances derived from the enzymatic degradation of complex nutrients
What is agar?
A solidifying agent; it is an extract of seaweed and it is a complex carbohydrate composed mainly of galactose. It has no nutritional value, it solidifies at 40 C and liquefies at 100
What is the primary purpose of agar slants?
For maintaining pure cultures
What is the primary purpose of agar deep tubes?
To study the gaseous requirements of microorganisms
What is the primary purpose of agar plates?
They provide a large surface area for the isolation and study of microorganisms
Why are petri dishes incubated in an inverted position after incubation?
To prevent condensation, which forms on the cover during solidification, from dropping sown onto the surface of the hardened agar.
What is subculturing?
It is the transfer of microorganisms from stock cultures to various media for maintenance and study
What types of metals are wire loops and needles made from?
Inert metals such as nichrome and platinum
What is the estimated amount of normal (resident) flora on an adult?
one trillion bacteria
What are benefits and risks of residential flora?
It creates a symbiotic relationship with your skin which is vital to your health. Problems can occur however if the immune system is compromised or if the microorganisms gain entrance into the body
What is transient flora?
Microorganisms that are less permanent and can be removed with good hand washing techniques
Why is resident flora difficult to remove?
Because it can be found in the hair follicles which means it is covered by hair, oil, and dead skin cells
How can resident flora be removed?
Surgical scrubbing
Who is responsible for introducing surgical hand washing into the medical practice?
Hungarian physician Ignatz Semmelweis in the mid-nineteenth century
What is puerperal fever?
It is childbirth fever
Once flamed, how long do you wait before you insert the sterilized loop/needle into an inoculum?
10-20 seconds
Would you use a loop or a needle in a slant-to-broth transfer?
either, just ensure that you lightly shake it in order to dislodge the microorganisms into the broth
Would you use a loop or a needle in a broth-to-slant?
A loop, and you would zigzag it onto the slant
Would you use a loop or a needle in a slant-to-agar deep transfer? This transfer is also called what?
A needle; also called a stab inoculation
Why is isolation of pure cultures important?
It allows us to study their cultural, morphological, and biochemical properties
What are discrete colonies?
Individual, macroscopically visible masses of microbial growth on a solid medium; each representing the multiplication of a single organism
What are the 3 techniques commonly used for the isolation of discrete cultures?
- streak-plate
- spread-plate
- pour-plate
How does the pour-plate technique allow for the isolation of discrete cultures?
The mixed culture is serial diluted and the added to molten agar.
What are cultural characteristics?
Differences in the macroscopic appearance of the growth of microorganisms, these are used as a basis for separating microorganisms into taxonomic groups
How are cultural characteristics determined?
By culturing the organisms and observing their growth patterns.
What 5 cultural characteristics can be observed on a nutrient agar slant?
- abundance of growth
- pigmentation
- optical characteristics
- form
- consistency
What 5 cultural characteristcs can be observed on a nutrient agar plate?
- size
- pigmentation
- form
- margin
- elevation
What 4 cultural characteristics can be observed in a nutrient broth tube?
- uniform fine turbidity
- flocculent
- pellicle
- sediment
How are inoculating loops sterilized?
incineration
How many loopfuls of broth culture are used to inoculate a streak plate?
one
Identify two properties of agar that make it useful for cultivating microorganisms?
- solidifying agent
2. transparency
