Lab Practical 2

Question 1

Winogradsky: what was added? what is the carbon source?

Answer 1

We added mineral salts and cellulose to a mud slurry. The cellulose is the carbon source

Question 2

Winogradsky: why did we cover the columns the first couple weeks? what happened when it was uncovered?

Answer 2

We covered the columns to allow bacteria to use fermentation, anaerobic cellulose degradation, and sulfate reduction via anaerobic respiration. When it was uncovered the photosynthetic/phototrophic bacteria started growing.

Question 3

Media: Natural

Answer 3

Material taken from the environment (already contains organisms)
Varies significantly from batch to batch
Lowest cost

Question 4

Media: Semi-synthetic (complex)

Answer 4

Uses powders prepared from digests of industrial products
Varies from batch to batch
Low cost

Question 5

Media: Synthetic

Answer 5

Uses known mix of reagent-grade chemicals
Very consistent
High cost

Question 6

Media: Selective

Answer 6

Only allows certain organisms to grow, the rest are killed

Question 7

Media: Enrichment

Answer 7

Multiple organisms can grow, but some have a growth advantage over others

Question 8

Media: Differential

Answer 8

Organisms will show differences in appearance (typically color) based on a metabolic capability

Question 9

Media: Rich

Answer 9

Has abundant nutrients, sometimes because blood or serum have been added
TSA and NA plates are examples of rich media
Will allow many types of culturable bacteria to grow

Question 10

Media: Minimal

Answer 10

Has the bare minimum needed for a species to survive

Question 11

Media: Liquid

Answer 11

In a flask

Question 12

Media: Solid

Answer 12

In a petri dish

Question 13

EMB plates

Answer 13

selective for gram negative bacteria and differential for lactose fermenters (turns them red/pink) - lactose fermenters are associated with fecal matter

Question 14

Fungi: Hyphae? Mycelium? Septa?

Answer 14

hyphae: hair like structures on fungi
mycelium: mass of hyphae
septa: cross wall in hyphae - porous and allow for pass transfer of proteins, ribosomes, etc.

Question 15

Fungi: Sporangiophore? Sporangium? Sporangiospore?

Answer 15

Sporangiophore: Haploid spore-bearing structure of rhizopus; Looks like a round bulb
Sporangium: Bulb-like structure that contains sporangiospores
Sporangiospore: Haploid spore of Rhizopus

Question 16

Fungi: Conidiophore? Conidium/Conidiospore?

Answer 16

Conidiophore: Asexual (haploid) spore-bearing structure of Aspergillus and Penicillium; Looks like a glove
Conidium/Conidiospore: Haploid spore of Aspergillus and Penicillium

Question 17

What allows fungi to cover large areas? Why do they?

Answer 17

Hyphal morphology allows for a fungus to cover a large area despite consisting of microscopic hair-like structures. This is because fungi are absorptive rather than digestive

Question 18

Fungi spend most of their life in diploid (2n) or haploid (n) state?

Answer 18

Haploid (n)

Question 19

Fungi: Perithecium

Answer 19

Ascus-bearing structures of Sordaria (looks like a flask)

Question 20

Fungi: Ascus

Answer 20

Spore-bearing structure of Sordaria (looks like a sac and contains 8 spores)

Question 21

Fungi: Sordaria/ What’d we do? What’d we see?

Answer 21

We mated black and tan strains of Sordaria. If we saw a 4:4 spore configuration = no recombination (in theory)
Sometimes recombinatory events can cancel each other out
If we saw a 2:2:2:2 or 2:4:2 spore configuration = recombination

Question 22

Fungi: What does the frequency of recombination tell us?

Answer 22

Recombination allows us to map where the gene is on the chromosome. The more recombination, the further it is from the centromere.

Question 23

Serial Dilution

Answer 23

Used to make a sample less concentrated; A small amount of stock (containing concentrated bacteria) is added to sterile broth (30-300 colonies in middle plate)

Question 24

Titer=

Answer 24

(# Colonies) / (Cumulative Dilution * Volume Plated)
volume plated= 0.1mL (100uL)

Question 25

Mutations: Auxotrophs

Answer 25

A mutant that requires an additional nutrient due to a loss of metabolic function
I.e. unable to synthesize histidine, so the organism needs histidine in media
Detectable by plating on Rich media and Minimal media
An auxotroph should only grow on Rich media

Question 26

Resistance

Answer 26

It is easiest for bacteria to adapt to a low-concentration of antibiotics
Low concentration to high concentration = probably colonies forming
Starting off with high concentration = probably few/no colonies forming

Question 27

Growth curve: How do you find the doubling time? How do you get an estimate of titer in absolute numbers?

Answer 27

To find the doubling time, see how long it takes for Optical Density (OD) measurement to double in the exponential (growth) phase.
OD readings give us relative numbers (i.e. the bacteria have doubled/tripled/etc. in number) but not absolute numbers (i.e. 107 cells/mL)
To get an estimate of our titer in absolute numbers, we would have perform a serial dilution and then make plates

Question 28

Antibiotics: Bacteriostatic? Bacteriolytic? Bactericidal?

Answer 28

Kills cells: bacteriolytic and bactericidal, Lyses cells: only bacteriolytic, Optical density: bacteriostatic and bactericidal levels off while bacteriolytic decreases, Plate growth: only on bacteriostatic

Question 29

Kirby-Bauer Antibiotic Sensitivity Test: Zone of Inhibition (halo) size (diameter in mm) depends on:

Answer 29

Sensitivity of the bacteria to the antibiotic- Larger halo = generally more sensitive, but other factors can have a large effect
Solubility of antibiotic in water- Less soluble = theoretically smaller halo, Plate agar is predominantly water
Growth rate of bacteria- Faster = theoretically smaller halo
Incubation temperature- Influences growth rate of bacteria

Question 30

Serology: Our experiment? Antibodies?

Answer 30

In our experiment, antibodies bind to antigens on the cell surface
Antigens are often proteins, polysaccharides, or glycoproteins; they have multiple variable domains (multivalence that allows for agglutination (clumping)); Antibodies have specificity – the shape of the variable domain must closely correspond to the shape of the antigen for binding to occur

Question 31

Enteric Unknown

Answer 31

Be familiar with the RapID test kit (see Lab 12 Page for explanation of similar test kit): figure out difference based on shape, margin, elevation, size, texture, appearance, pigmentation, optical property