EXERCISE 7 Flashcards
What is a complex mixture of organic matter?
SOIL
4 components of soil
mineral particles, water, air, and organic matter
What microbial populations do soil contain? (4)
fungi
bacteria
algae
protozoa
What level of soil has the highest number of microorganisms
topsoil
What is the narrow soil region surrounding the plant roots?
Rhizosphere
Microbial counts decrease with…?
Soil Depth
Why does the top soil later have the highest microbial count? (3)
availability of ORGANIC MATTER, OXYGEN, and other NUTRIENT SOURCES
Particularly where in the TOP SOIL REGION is there high microbial activity
Rhizosphere
What type of bacteria can be found in the RHIZOSPHERE
nitrogen-fixing bacteria
6 factors that affect population of microorganism
- physical structure
- nutrient composition
- temperature
- water potential
- availability of oxygen
- pH level
2 types of enrichment on soil microorganisms
- urea
- starch
TYPE OF ENRICHMENT ON SOIL MICROORGANISM
nitrogenous organic compound
urea
TYPE OF ENRICHMENT ON SOIL MICROORGANISM
used as solid nitrogenous fertilizer
urea
TYPE OF ENRICHMENT ON SOIL MICROORGANISM
polysaccharide
starch
A soil rich in the ff will promote what kind of microorganism? And why?
- urea
- starch
- bacteria — has UREASE which breaks down urea
- molds — has AMYLASE which breaks down amylose in starch
5 importance of microorganisms in the soil
- weathering of rocks and soil formation
- decomposition of complex organic materials
- geo-chemical cycling of nitrogen, sulfur, carbon, and phosphorus
- reservoir of pathogenic microorganisms
- reservoir of microorganisms with unique metabolic pathways and enzyms
What is the conversion of atmospheric N2 into AMMONIA by some species of bacteria?
Nitrogen Fixation
What type of bacteria is involved in nitrogen fixation?
free-living and symbiotic bacteria
TYPE OF NITROGEN-FIXING BACTERIA
ability to fix nitrogen without association with other microorganisms
free-living
TYPE OF NITROGEN-FIXING BACTERIA
capable of fixing nitrogen with the aid of a symbiont
symbiotic
A symbiont can be (2)
- plant (legumes)
- organism (termites or protozoa)
BACTERIA UNDER:
- Free-living (6)
- Symbiotic (3)
FL
1. Cyanobacteria
2. Anabaena
3. Nostoc
4. Azotobacter
5. Beijerinckia
6. Clostridium
SB
1. Rhizobium
2. Frankia
3. Azospirillum
Where can SYMBIOTIC nitrogen fixing bacteria be found?
root nodules
What color are root nodules and why?
red-brown due to LEGHEMOGLOBIN
What is leghemoglobin?
oxygen-binding protein and iron-containing protein
2 functions of leghemoglobin
- binds oxygen and supplies to the bacteria
- protects oxygen-sensitive nitrogenase
Can plants use N to convert to Ammonium?
No
Thats why in symbiosissila w symbiotic bacteria
TYPES OF GRAM NEGATIVE BACTERIA in
- Free-living (1)
- Symbiotic (1)
- Azotobacter
- Rhizobium
2 Ways You Can Fix atmospheric nitrogen
- physically
- biologically
Valid colony counts for:
- Bacteria
- Molds
- B: 25-250
- M: 10-150
Can there be 3 consecutive dilutions with valid ranges for bacteria and molds?
No
