EXERCISE 7

Question 1

What is a complex mixture of organic matter?

Answer 1

SOIL

Question 2

4 components of soil

Answer 2

mineral particles, water, air, and organic matter

Question 3

What microbial populations do soil contain? (4)

Answer 3

fungi
bacteria
algae
protozoa

Question 4

What level of soil has the highest number of microorganisms

Answer 4

topsoil

Question 5

What is the narrow soil region surrounding the plant roots?

Answer 5

Rhizosphere

Question 6

Microbial counts decrease with…?

Answer 6

Soil Depth

Question 7

Why does the top soil later have the highest microbial count? (3)

Answer 7

availability of ORGANIC MATTER, OXYGEN, and other NUTRIENT SOURCES

Question 8

Particularly where in the TOP SOIL REGION is there high microbial activity

Answer 8

Rhizosphere

Question 9

What type of bacteria can be found in the RHIZOSPHERE

Answer 9

nitrogen-fixing bacteria

Question 10

6 factors that affect population of microorganism

Answer 10

1. physical structure
2. nutrient composition
3. temperature
4. water potential
5. availability of oxygen
6. pH level

Question 11

2 types of enrichment on soil microorganisms

Answer 11

1. urea
2. starch

Question 12

TYPE OF ENRICHMENT ON SOIL MICROORGANISM

nitrogenous organic compound

Answer 12

urea

Question 13

TYPE OF ENRICHMENT ON SOIL MICROORGANISM

used as solid nitrogenous fertilizer

Answer 13

urea

Question 14

TYPE OF ENRICHMENT ON SOIL MICROORGANISM

polysaccharide

Answer 14

starch

Question 15

A soil rich in the ff will promote what kind of microorganism? And why?

1. urea
2. starch

Answer 15

1. bacteria — has UREASE which breaks down urea
2. molds — has AMYLASE which breaks down amylose in starch

Question 16

5 importance of microorganisms in the soil

Answer 16

1. weathering of rocks and soil formation
2. decomposition of complex organic materials
3. geo-chemical cycling of nitrogen, sulfur, carbon, and phosphorus
4. reservoir of pathogenic microorganisms
5. reservoir of microorganisms with unique metabolic pathways and enzyms

Question 17

What is the conversion of atmospheric N2 into AMMONIA by some species of bacteria?

Answer 17

Nitrogen Fixation

Question 18

What type of bacteria is involved in nitrogen fixation?

Answer 18

free-living and symbiotic bacteria

Question 19

TYPE OF NITROGEN-FIXING BACTERIA

ability to fix nitrogen without association with other microorganisms

Answer 19

free-living

Question 20

TYPE OF NITROGEN-FIXING BACTERIA

capable of fixing nitrogen with the aid of a symbiont

Answer 20

symbiotic

Question 21

A symbiont can be (2)

Answer 21

1. plant (legumes)
2. organism (termites or protozoa)

Question 22

BACTERIA UNDER:

1. Free-living (6)
2. Symbiotic (3)

Answer 22

FL
1. Cyanobacteria
2. Anabaena
3. Nostoc
4. Azotobacter
5. Beijerinckia
6. Clostridium

SB
1. Rhizobium
2. Frankia
3. Azospirillum

Question 23

Where can SYMBIOTIC nitrogen fixing bacteria be found?

Answer 23

root nodules

Question 24

What color are root nodules and why?

Answer 24

red-brown due to LEGHEMOGLOBIN

Question 25

What is leghemoglobin?

Answer 25

oxygen-binding protein and iron-containing protein

Question 26

2 functions of leghemoglobin

Answer 26

1. binds oxygen and supplies to the bacteria 2. protects oxygen-sensitive nitrogenase

Question 27

Can plants use N to convert to Ammonium?

Answer 27

No Thats why in symbiosissila w symbiotic bacteria

Question 28

TYPES OF GRAM NEGATIVE BACTERIA in 1. Free-living (1) 2. Symbiotic (1)

Answer 28

1. Azotobacter 2. Rhizobium

Question 29

2 Ways You Can Fix atmospheric nitrogen

Answer 29

1. physically 2. biologically

Question 30

Valid colony counts for: 1. Bacteria 2. Molds

Answer 30

1. B: 25-250 2. M: 10-150

Question 31

Can there be 3 consecutive dilutions with valid ranges for bacteria and molds?

Answer 31

No