L4.4 Nitrogen Cycles

Question 1

Makes up 78.1% of the Earth’s atmosphere

Answer 1

Nitrogen Gas

Question 2

three physiological groups under nitrogen cycle

Answer 2

Diazotrophs, Nitrifiers, and Denitrifiers

Question 3

Development of nitrogen was seen
with the discovery of________

Answer 3

Dynamite

Question 4

What does nitrogen do in plants?

Answer 4

Increase the production of crops by being a component of pesticides

Question 5

Nitrogen fixers genera

Answer 5

Mesorhizobium
Desulfovibrio
Azotobacter

Question 6

Characterize diazotrophs

Answer 6

• convert atmospheric nitrogen into ammonia

Question 7

gene that encodes the dinitrogenase reductase the component of nitrogenase that is used to measure diazotroph diversity

Answer 7

nifH

Question 7

Examples of symbiotic diazotrophs

Answer 7

microbes with mutual partnership with plants, animals, fungi

Rhizobia and legume plants

Question 7

Free-living Diazotrophs

Answer 7

• protect nitrogenase from oxygen

by
- growing in anoxic environment
-fixing N2 in low oxygen level
-has protective mechanism like those in cyanobacteria

Question 8

they thrive in oxygen depleted environment
give example

Answer 8

obligate anaerobes
desulfovibrio

Question 9

These bacteria can adapt to both aerobic and anaerobic conditions.

Answer 9

Facultative Aerobes
Klebsiella, fixes N2 when oxygen scarce

Question 10

They require low oxygen concentrations for Nº
fixation.

Answer 10

Microaerophiles

Question 10

Includes Cyanobacteria and some unicellular bacteria

Answer 10

• Obligate Aerobes
• Azotobacter- forms cysts to survive, uses nitrogenases w/ vanadium or iron replacing molybdenum

Question 11

Responsible for converting ammonia NH3 to nitrate through a two-step process

Answer 11

nitrifiers

Question 12

Differentiate
Nitrosomonas
Nitrobacter
Nitrospira

Answer 12

1. Ammonia oxiders
2. Nitrite oxidizers
3. perform both

Question 13

______ have internal membrane stacks. Enriched in mineral salt media with ammonia or nitrite as electron donors and bicarbonate as carbon source

Answer 13

Nitrifying bacteria

Question 14

Remove nitrogen through conversion of nitrate or nitrite to to nitric oxide, nitrous oxide, and nitrogen gas

Answer 14

Denitrifiers

Question 15

Describe denitrifiers and role in agriculture and environment

Answer 15

• facultative aerobes
• leads to fertilizer loss and N2O emission a GHG

Question 16

Describe denitrifiers

Answer 16

remove N by converting nitrate or nitrite to gas like nitric oxide, nitrous oxide, nitrogen gas

Question 17

example of denitrifiers

Answer 17

Paracoccus denitrificans