Lab Practical 2

Question 1

Which bacteria is responsible for the formation of characteristic nodules on the roots of leguminous plants and fixes atmospheric nitrogen in symbiosis with the host plant?

Answer 1

Rhizobium

Question 2

Which bacteria is free-living and nitrogen-fixing, and demonstrated nitrogen fixation by cyanobacteria?

Answer 2

Azotobacter

Question 3

Which type of media did we use to start the azotobacter lab? Where did the azotobacter come from?

Answer 3

Enrichment flask
Soil

Question 4

Which conditions select for the growth of azotobacter? Why?

Answer 4

Acid pH
Presence of sugar
Absence of added nitrogen
They fix nitrogen and are acid-tolerant.

Question 5

How did we observe the azotobacter during week 2?

Answer 5

Wet mount because it was in the broth

Question 6

What media did we use for azotobacter week 2?

Answer 6

Enrichment media

Question 7

How did we observe the azotobacter during week 3?

Answer 7

Wet mount

Question 8

What did we do with the azotobacter during week 3?

Answer 8

Streak plated to isolate individual colonies

Question 9

What did we do with the azotobacter during week 4?

Answer 9

Observed the streak plate and did 16s PCR isolation

Question 10

Physical characteristics of azotobacter

Answer 10

Gram negative
Rod shaped with curved ends
Coccoid
Motile or non-motile
Forms microcysts

Question 11

What did we do with azotobacter during week 5?

Answer 11

Ran the PCR in the gel and sequenced

Question 12

What did we do with azotobacter during week 6?

Answer 12

Performed BLAST on the sequenced genetic material to make sure it matched azotobacter

Question 13

Bacteria multiple by ____ ____ after reaching a certain size

Answer 13

Binary fission

Question 14

True or false: If you put the same bacteria in the same conditions, they will always double their population size at the same time

Answer 14

True

Question 15

____ time or ____ time can be constructed by making a growth curve

Answer 15

Doubling or generation

Question 16

To generate a growth curve, a ____ inoculum is introduced into a ___ volume of fresh
medium.

Answer 16

Small inoculum
Large volume

Question 17

Why does the lag phase occur in a growth curve?

Answer 17

The bacteria are adjusting to their new medium

Question 18

What are the conditions of the log or exponential growth phase? How long will they stay in this phase?

Answer 18

Growth rate is at a maximum
Doubling time is at a minimum
They will stay here until resources run out

Question 19

What is the stationary phase?

Answer 19

Bacteria growth rate decreases but overall population numbers still increase

Question 20

What are the two main ways to measure bacterial growth?

Answer 20

Plating: more straightforward but tedious and requires waiting overnight
Optical density: faster but can’t know what it’s doubling to and doesn’t account for dead cells

Question 21

Compare bacteriostatic and bactericidal/lytic antibiotics

Answer 21

Bacteriostatic: stop growth of bacteria but don’t kill them
Bactericidal: kill them
lytic: kill vis lysing

Question 22

What the three zones in the winogradsky column?

Answer 22

Anaerobic, microaerobic, aerobic

Question 23

The concept of ____ - observing bacteria that fix carbon dioxide for their carbon needs and obtain energy for cell growth by oxidizing inorganic ions - was first observed with a winogradsky column?

Answer 23

Chemoautotrophy

Question 24

What are the main components to start a winogradsky column?

Answer 24

Salts
A source of sulfate
Mud
Fermentable substrate (cellulose)
Water

Question 25

What is the color order of a winogradsky column from bottom to top?

Answer 25

Black Green Red/purple Red Light brown Water

Question 26

What are the two main types of winogradsky bacteria we studied?

Answer 26

Purple nonsulfur Sulfate reducing

Question 27

What is the distinguishing factor that places fungi in their own kingdom?

Answer 27

Chitin in their cell walls

Question 28

Why do fungi change their morphology?

Answer 28

To increase their surface area for better absorption of nutrients

Question 29

Reproduction of fungi is facilitated by ___

Answer 29

Spores

Question 30

(asexual) produced inside a sporangium from a zygospore

Answer 30

Sporangiospores

Question 31

(sexual) produced in sac- like structures. Ascus can be surrounded by a protective cover

Answer 31

Acospores

Question 32

(sexual) produced on the surface of a basidium. Mushrooms have a protective cover that hang basidia from the gills

Answer 32

Basidiospores

Question 33

One of the parameters to assess water quality is testing ____ ____ ____

Answer 33

Total coliform bacteria

Question 34

What are coliforms?

Answer 34

They are present in the digestive tracts of animals/water and fecal waste. They are also found in plant and soil materials. If coliform bacteria are present in your drinking water, they will likely be a gram-negative and lactose fermenting bacteria

Question 35

What is the selective media used to test for coliforms?

Answer 35

EMB

Question 36

Explain why EMB is both a differential and selective media

Answer 36

Selective: Methylene blue and are dyes in the agar that inhibit the growth of gram- positive bacteria Differential: Eosin responds to changes in pH, changing from colorless to black under acidic conditions

Question 37

___, ___, ___, and ___ are common colony morphologies

Answer 37

Circular, irregular, rhizoid, and filamentous

Question 38

Which media did we use for serial dilutions?

Answer 38

Top agar

Question 39

A bacterium’s fundamental niche is largely influenced by ___ ___. Bacteria generally grow ____ in the lab than in nature

Answer 39

External factors Worse

Question 40

What is the death phase of a growth curve?

Answer 40

It occurs when there aren't enough nutrients and metabolic wastes have built up

Question 41

Why is it good to study Vibrio natriegens?

Answer 41

They have the fastest growth rate of any known organism and they are non-pathogenic to humans

Question 42

Four reasons why optical density alone doesn't accurately represent bacterial growth

Answer 42

1. Dead bacteria still take up space 2. Not all cells begin reproducing at the same time 3. Smudges and air bubble can also impact optical density 4. There is a limited space in the container for growth

Question 43

Viable cells form colonies when plated on agar and is measured as a single ___ ___ ___

Answer 43

Colony forming unit (CFU)

Question 44

What is a plaque forming unit? What can we learn from it?

Answer 44

Measures the absence of bacteria due to phages

Question 45

Why do we use 16s rRNA for sequencing?

Answer 45

It is highly conserved in bacteria but also contains nine (9) variable regions that are unique to bacterial genera / species.

Question 46

Define epidemic

Answer 46

Sudden outbreaks of disease affecting a large number of people in a specific region or population caused by viruses, bacteria, and other organisms

Question 47

How does DNA move in gel electrophoresis?

Answer 47

Larger DNA moves slower Shorter DNA moves faster/further towards the + anode because DNA is negatively charged

Question 48

____ ____ is dense and keeps the DNA from diffusing away in the buffer.

Answer 48

Loading dye

Question 49

What does it mean to say "clean hands are not sterile hands?"

Answer 49

Clean hands still have some bacteria which is good for the skin microbiome

Question 50

What does the size of the zone of inhibition tell us?

Answer 50

The larger the zone, the more susceptible a bacteria is to an antibiotic

Question 51

What is special about Mueller-Hinton agar for Kirby Bauer disc diffusions?

Answer 51

MH agar is loose and contains starch, which absorbs bacterial toxins that may interfere with antibiotics

Question 52

What does RapidID help us test?

Answer 52

The pH change caused by the bacterium’s metabolic reactions to provide a color change in wells containing different substrates