Chemosynthesis
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
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Printed: August 25, 2015
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Chemosynthesis
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Chemosynthesis
• Define chemosynthesis.
• Describe organisms that use chemosynthesis.
Is it possible to live in temperatures over 175°F?
It is if you’re a Pompeii worm. The Pompeii worm, the most heat-tolerant animal on Earth, lives in the deep ocean
at super-heated hydrothermal vents. Covering this deep-sea worm’s back is a fleece of bacteria. These microbes
contain all the genes necessary for life in extreme environments.
Chemosynthesis
Why do bacteria that live deep below the ocean’s surface rely on chemical compounds instead of sunlight for energy
to make food?
Most autotrophs make food by photosynthesis, but this isn’t the only way that autotrophs produce food. Some
bacteria make food by another process, which uses chemical energy instead of light energy. This process is called
chemosynthesis. In chemosynthesis, one or more carbon molecules (usually carbon dioxide or methane, CH4 )
and nutrients is converted into organic matter, using the oxidation of inorganic molecules (such as hydrogen gas,
hydrogen sulfide (H2 S) or ammonia (NH3 )) or methane as a source of energy, rather than sunlight. In hydrogen
sulfide chemosynthesis, in the presence of carbon dioxide and oxygen, carbohydrates (CH2 O) can be produced:
CO2 + O2 + 4H2 S → CH2 O + 4S + 3H2 O
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Many organisms that use chemosynthesis are extremophiles, living in harsh conditions, such as in the absence of
sunlight and a wide range of water temperatures, some approaching the boiling point. Some chemosynthetic bacteria
live around deep-ocean vents known as “black smokers.” Compounds such as hydrogen sulfide, which flow out of
the vents from Earth’s interior, are used by the bacteria for energy to make food. Consumers that depend on these
bacteria to produce food for them include giant tubeworms, like those pictured in Figure 1.1. These organisms are
known as chemoautotrophs. Many chemosynthetic microorganisms are consumed by other organisms in the ocean,
and symbiotic associations between these organisms and respiring heterotrophs are quite common.
FIGURE 1.1
Tubeworms deep in the Galapagos Rift
get their energy from chemosynthetic
bacteria.
Tubeworms have no mouth,
eyes or stomach. Their survival depends
on a symbiotic relationship with the billions of bacteria that live inside them.
These bacteria convert the chemicals that
shoot out of the hydrothermal vents into
food for the worm.
Summary
• Chemosynthesis is a process in which some organisms use chemical energy instead of light energy to produce
"food."
Explore More
Use this resource to answer the questions that follow.
• Chemosynthesis at http://www.pmel.noaa.gov/eoi/nemo/explorer/concepts/chemosynthesis.html .
1.
2.
3.
4.
What is chemosynthesis?
What are hydrothermal vents?
Why do hydrothermal vent regions have high biomass?
What type of organisms are found in a hydrothermal vent region?
Review
1. What is chemosynthesis?
2. Why do bacteria that live deep below the ocean’s surface rely on chemical compounds instead of sunlight for
energy to make food?
3. Describe the habitats of extremophiles?
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Chapter 1. Chemosynthesis
References
1. Courtesy of the NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011. These tubeworms get
their energy from chemosynthesis . CC BY 2.0
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