Guide

Main Module | Energy from Mud? Thank a Microbe!
12
Background
backGrouNd
Some bacteria are also autotrophs but
use a process called chemosynthesis.
In chemosynthesis bacteria take in
materials such as carbon dioxide and
hydrogen sulde, or iron or ammonia
and process them to make organic
material.
Finally, many other bacteria and organisms (like us) are heterotrophs, meaning they
rely on external sources of organic matter from which they can get their energy. The
bacteria that make the MudWatt work are heterotrophs. They take in organic matter
that has been broken down to the right size and form by larger organisms, such as
worms and fungi.
To learn more about nutrient cycling in soils, see Sub-Module 3: Soil Ecology and Nutrient Cycling.
Howorganismsbreakdownfoodtoreleaseenergy(Metabolicprocesses)
All organisms need to metabolize, or break down their food so that the stored energy
can be converted into energy which can then
be used to grow, repair and reproduce. There
are several processes by which organisms are
able to process food for energy but we will
focus on cellular respiration.
Cellular respiration is the process by which
organic matter is oxidized (burned) and the
energy stored in the chemical bonds of the food is released. Cellular respiration
occurs in the mitochondria of cells.
The details cellular respiration are complex and are beyond the scope of this module,
but students should be aware that during respiration electrons are given off and are
then taken up by electron acceptors.
When oxygen is present the electrons are taken up by the oxygen, and the process is
referred to as aerobic respiration. When oxygen is not present, other materials such
as iron or sulfur can accept the electrons. This process is called anaerobic respiration.
For most organisms that occurs inside each cell but for a unique type of bacteria
the electrons are actually given off externally. These specialized bacteria are called
electrogenic bacteria. Electrogenic bacteria occur naturally in every type of soil,
ChemistryConnection!
In a chemical reaction Oxidation
occurs when there is a loss of
electrons and Reduction occurs
when there is a gain of electrons.