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In aqueous environments and their anoxic sediments, there is another carbon cycle taking place. In this case, the cycle is based on one-carbon compounds. In anoxic sediments, prokaryotes, mostly archaea, produce methane (CH 4 ). This methane moves into the zone above the sediment, which is richer in oxygen and supports bacteria called methane oxidizers that oxidize methane to carbon dioxide, which then returns to the atmosphere.

This illustration shows the role of bacteria in the carbon cycle. Bacteria break down organic carbon, which is released as carbon dioxide into the atmosphere.
Prokaryotes play a significant role in continuously moving carbon through the biosphere. (credit: modification of work by John M. Evans and Howard Perlman, USGS)

Prokaryotes and the nitrogen cycle

Nitrogen is a very important element for life because it is part of proteins and nucleic acids. It is a macronutrient, and in nature, it is recycled from organic compounds to ammonia, ammonium ions, nitrate, nitrite, and nitrogen gas by myriad processes, many of which are carried out only by prokaryotes. As illustrated in [link] , prokaryotes are key to the nitrogen cycle. The largest pool of nitrogen available in the terrestrial ecosystem is gaseous nitrogen from the air, but this nitrogen is not usable by plants, which are primary producers. Gaseous nitrogen is transformed, or “fixed” into more readily available forms such as ammonia through the process of nitrogen fixation    . Ammonia can be used by plants or converted to other forms.

Another source of ammonia is ammonification    , the process by which ammonia is released during the decomposition of nitrogen-containing organic compounds. Ammonia released to the atmosphere, however, represents only 15 percent of the total nitrogen released; the rest is as N 2 and N 2 O. Ammonia is catabolized anaerobically by some prokaryotes, yielding N 2 as the final product. Nitrification is the conversion of ammonium to nitrite and nitrate. Nitrification in soils is carried out by bacteria belonging to the genera Nitrosomas , Nitrobacter , and Nitrospira . The bacteria performs the reverse process, the reduction of nitrate from the soils to gaseous compounds such as N 2 O, NO, and N 2 , a process called denitrification    .

Art connection

This illustration shows the role of bacteria in the nitrogen cycle. Nitrogen-fixing bacteria in root nodules of legumes convert nitrogen gas, or N2, into organic nitrogen found in plants. Nitrogen-fixing soil bacteria produce ammonium ion, or NH4+. Decomposers, including bacteria and fungi, decompose organic matter, also releasing NH4+. Nitrification is the process by which nitrifying bacteria produce nitrites (NO2-) and nitrates (NO3-). Nitrates are assimilated by plants, then animals, then decomposers. Denitrifying bacteria convert nitrates to nitrogen gas, completing the cycle.
Prokaryotes play a key role in the nitrogen cycle. (credit: Environmental Protection Agency)

Which of the following statements about the nitrogen cycle is false?

  1. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil.
  2. Denitrifying bacteria convert nitrates (NO 3 - ) into nitrogen gas (N 2 ).
  3. Ammonification is the process by which ammonium ion (NH 4 + ) is released from decomposing organic compounds.
  4. Nitrification is the process by which nitrites (NO 2 - ) are converted to ammonium ion (NH 4 + ).

Section summary

Prokaryotes are the most metabolically diverse organisms; they flourish in many different environments with various carbon energy and carbon sources, variable temperature, pH, pressure, and water availability. Nutrients required in large amounts are called macronutrients, whereas those required in trace amounts are called micronutrients or trace elements. Macronutrients include C, H, O, N, P, S, K, Mg, Ca, and Na. In addition to these macronutrients, prokaryotes require various metallic elements for growth and enzyme function. Prokaryotes use different sources of energy to assemble macromolecules from smaller molecules. Phototrophs obtain their energy from sunlight, whereas chemotrophs obtain energy from chemical compounds.

Prokaryotes play roles in the carbon and nitrogen cycles. Carbon is returned to the atmosphere by the respiration of animals and other chemoorganotrophic organisms. Consumers use organic compounds generated by producers and release carbon dioxide into the atmosphere. The most important contributor of carbon dioxide to the atmosphere is microbial decomposition of dead material. Nitrogen is recycled in nature from organic compounds to ammonia, ammonium ions, nitrite, nitrate, and nitrogen gas. Gaseous nitrogen is transformed into ammonia through nitrogen fixation. Ammonia is anaerobically catabolized by some prokaryotes, yielding N 2 as the final product. Nitrification is the conversion of ammonium into nitrite. Nitrification in soils is carried out by bacteria. Denitrification is also performed by bacteria and transforms nitrate from soils into gaseous nitrogen compounds, such as N 2 O, NO, and N 2 .

Art connections

[link] Which of the following statements about the nitrogen cycle is false?

  1. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil.
  2. Denitrifying bacteria convert nitrates (NO 3 - ) into nitrogen gas (N 2 ).
  3. Ammonification is the process by which ammonium ion (NH 4 + ) is released from decomposing organic compounds.
  4. Nitrification is the process by which nitrites (NO 2 - ) are converted to ammonium ion (NH 4 + ).

[link] D

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Questions & Answers

If Jane was in room(B) while her mother Stella was in room (Y). Jane was cooking fish, her mother came to smell the good scent, By what process did her mother came to smell the scent
Neimar Reply
Is it a serious question?
Ehsan Reply
what's the question
Joseph
how many days do a bean seed take to germinate
Nando
what is DNA
Yahaya Reply
genetic information
MG
Deoxyribonucliec acid (DNA) is the cell's hereditary material that contains instructions for growth, development and reproduction.
Joseph
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Are there differences between sex and gender?
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lol
Andrew
describe an experiment to show that plants require light for photosynthesis
Diyara Reply
What's an amoeba
Bigger Reply
An amoeba is a cell or an organism that has the ability to ulter it's shape.
Joseph
An amoeba has an irregular shape and it changes constantly,it's a unicellular organism belong to a group called protists it has a pseudopodia used for locomotion and ingestion...
Emmanuel
what is a zygote?
Darius Reply
zygote is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual.
MG
A zygote is an organism formed after fertilization
Neimar
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Paclina Reply
What is zygote
Van
what is zygote
Darius
Zygote is located inside the ovule, which is present in the ovary.
MG
zygote is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information necessary to form a new individual.
MG
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Van
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Aadan Reply
biology is the study of living n non living organism
Kelsia
what is procotist?
Kelsia
Biology is the branch of science that deals with the study of living and non living things
Neimar
Describe at least two major changes to the animal phylogenetic tree that have come about due to molecular or genetic findings.
Tamala Reply
what is herbarium sheet
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Which of the following is not a characteristics of all living organisms? A. Excretion B. Photosynthesis C. Reproduction D. Respiration
Abel
B.
Anastasiya
B photosynthesis
Survive
general equation for photosynthesis
Ojasope Reply
6CO2 + 6H2O + solar energy= C6H1206+ 6O2
Anastasiya
meaning of amino Acids
AJAYI Reply
An aminoacid is a base unit molecule for proteins. It s formed by a central Carbon, to which are attached: an amminic Group, a carbossilic Group, an H hydrogen, and an R group ( which varies for each different aminoacid). Glycin is the only aminoacid to have for an R group a simple H hydrogen.
Anastasiya
H NH2-C-COOH R this is the not ionized form but usually they are ionized, with NH+ and COO-
Anastasiya
The R group, the lateral Chain, is responsible for the characteristics of the aminoacid.
Anastasiya
* NH2+
Anastasiya
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a diagram of an adult mosquito
mubarak Reply
what are white blood cells
Mlungisi Reply
white blood cell is part of the immune system. that help fight the infection.
MG
what about tissue celss
Mlungisi
Cells with a similar function, form a tissue. For example the nervous tissue is composed by cells:neurons and glia cells. Muscle tissue, is composed by different cells.
Anastasiya
white blood cells are components of blood that help the body fight diseases
Neimar
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Calvin Reply
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Isala
on what?
Anastasiya
hie
Lish
Yes
ANDY
Please define mitosis for me
Juliet
mitosis is a process where a single cell divides into two identical daughter cells(cell division)
Sani
Kk
Juliet
yes
Sani
What about meiosis
Juliet
Meiosis is a process that produces gametes. From a single cell, 4 daughter cells (gametes) are formed.
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What is a tissue respiration
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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