Studied by 5 people
Looks like no one added any tags here yet for you.
Given a "recipe" for a specific culture medium, identify a complex or defined medium.
Complex media: composed of things like “yeast extracts” or “peptones/proteins extracts” or other unknown placeholders.
Ex: 5g peptone, 3g yeast extract, 5g NaCl, 15g agar.
Chemically defined media: has exact chemical compositions listed (ex: g, mL)
Ex: 10g glucose, 2g NH₄NO₃, 1g K₂HPO₄, 0.5g MgSO₄.
Which enzyme catalyzes the reaction: H202 + 2H* → 2H20?
Catalase
In a standard growth curve, what phase represents when the number of cells growing and dying are about equal.
Stationary phase
In a figure/graph, which line best depicts a psychotroph incubated at 0°C?
Psychotrophs are organisms that can tolerate cold temperatures so it would probably look like line B.
Psychrophiles are organisms that prefer cold temperatures so that would look more like A.
A media that has a pH indicator and high salt concentration can likely __________ the growth of most bacteria.
inhibit
Given a list, be able to distinguish which is NOT a direct measurement of microbial growth.
Direct forms:
Direct Microscopic Count
Plate Counts
Filtration
Most Probable Number Method
Pour Plates
Spread Plates
Indirect forms:
Turbidity
Metabolic Activity
Dry Weight.
If 100 colonies are on a 1:1000 dilution plate, how many bacteria/mL were in the original sample?
100,000 bacteria/mL were found in the original sample
# of bacteria = colonies x reciprocal of dilution = 100 × 1000 = 100,000
A sample of ocean water is tested for its bacterial content in a plate count assay. A one-milliliter sample of the water is diluted in a 1:10 dilution series. 0.1 milliliter of the second dilution tube is plated in a pour plate.
After incubation, the plate has 191 colonies, indicating that the original water sample contained
191,000 colonies/mL
The first 1 mL sample was already obtained from a 1:10 dilution. The 2nd dilution tube means it’s been diluted by 1:10 again. This means the 0.1 mL sample is a 1:100 dilution of the original.
If the 2nd dilution’s 0.1 mL sample contains 191 colonies, then a 1 mL sample would contain 1910 colonies. The 1st 1:10 dilution’s 1 mL sample would then contain 19100 colonies, and the original sample contained 191000.
# of bacteria = colonies x reciprocal of dilution = 1910 × 100 = 191000
