Week 1

Question 1

What is the goal of aseptic technique?

Answer 1

ensure that only the desired organisms are present within a growth medium

Question 2

What is the simplest way to sterilize a wire loop?

Answer 2

incinerate any organisms already present by heating the wire.

Question 3

What is the fundamental concept for single colony isolation?

Answer 3

if individual cells of a microorganism can be immobilized on a solid growth medium, each cell will grow to form a visible pile of cells which is a colony.

Question 4

What is the principal of “one cell, one colony”?

Answer 4

That all of the cells present in an isolated colony arose from one progenitor cell, meaning that they all must be the same organism.

Question 5

What are the respective pipette sizes and colors?

Answer 5

1 mL pipette: blue
5 and 10 mL: green

Question 6

What is a cell colony?

Answer 6

When a single bacterial cell is deposited on a suitable solid medium and it continually replicates to form a visible mass (colony).

Question 7

What is a pure culture?

Answer 7

When each individual colony consists of a population of organisms descended from a single cell.

Question 8

What are protozoans?

Answer 8

eukaryotic microorganisms that are typically unicellular and range from 20 micrometers to 100 micrometers. They can be motile and nonmotile, and are either hetetorophic or photosynthetic, or both.

Question 9

What are yeasts?

Answer 9

non filamentous forms of fungi appearing as small, ovoid cells deem 4-10 micrometers. Typically non-motile and reproduce by budding.

Question 10

What are bacteria?

Answer 10

prokaryotic cells that are typically unicellular but can grow as aggregates or chains. They are 0.5-2 micrometers and usually appear as rods, cocci, or spirals.

Question 11

What is a hay infusion?

Answer 11

created by inoculating pond water with grains of barley or other grass clippings.

Question 12

What is a simple stain?

Answer 12

A stain used to increase contrast

Question 13

What is a differential stain?

Answer 13

Causes certain microorganisms to appear a different color.

Question 14

What is a specialized stain?

Answer 14

Used to identify the presence or location of specific sub cellular structures.

Question 15

What is the procedure a gram stain?

Answer 15

1. Cover the fixed smear with crystal violet. This will stain both g+ and g- purple.
2. Wash with iodine. This mordants with cv to form a complex that gets trapped in PG.
3. Wash with decolonized. This will loosen the complex and will wash out the stain from g- bacteria.
4. Counter stain with safranin. This will dye both g+ and g- pink, but bc g+ is already purple, only g- will show up as pink.

Question 16

What is nitrogen fixation and why is it critical?

Answer 16

The reduction of nitrogen gas to form ammonia, it is critical because reduced nitrogen is limiting in the natural environment.

Question 17

What are nitrogenases?

Answer 17

Nitrogenases catalyze nitrogen fixation and are extremely O2 sensitive, and are irreversibly inactivated by reacting with O2.

Question 18

What are some common features of azotobacteria?

Answer 18

contain PHB granules, obligate aerobic chemoheterotrophs that produce EPS slime when grown on nitrogen free soil, this layer serves as a diffusion barrier.

Question 19

What are common features of azotobacter bacteria?

Answer 19

Form metabolically inert cysts that are resistant to nutrient starvation and desiccation, predominantly found in soil, positive for urease which means they can use urea as a reduced nitrogen source.

Question 20

What are common features of azomonas bacteria?

Answer 20

Does not form cysts, found in freshwater environments, urease negative and can utilize ammonia as reduced nitrogen source.

Question 21

What is being done in the azotobacter experiment?

Answer 21

Inhibitng growth of all organisms that do not fix nitrogen aerobically by growing them in an environment with lack of reduced nitrogen and abundant O2.