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Classifying Living Things: The Domain Bacteria
What features distinguish bacteria from
other life forms?
Representing potentially the largest group
of organisms on this planet, the domain Bacteria is composed
of a remarkably diverse group.
From deadly diseases to “helper” bacteria in our bodies,
bacteria inhabit almost every ecological niche known. Colonizing
spaces in other organisms, in the deep-sea, and even in toxic
waste sites,
bacteria are single-celled organisms known for their striking
diversity.
Even though these prokaryotic organisms lack a
nucleus and organelles, they are able to exploit a wide range
of substances for food sources.
Bacteria do have a cell wall, which includes the compound peptidoglycan,
also found in fungal cell walls. There are two common shapes
among bacterial cells: rods and spheres.
Unlike animals, bacteria
do not ingest their food. Many bacteria are like fungi in
that they secrete digestive chemicals into
the local environment to break down complex molecules, which
they then absorb.
Some bacteria are like plants and are able to make their
own food through photosynthesis. In fact, most of the photosynthesis
on Earth occurs
in the open ocean and is carried out by a group of bacteria
called cyanobacteria, or blue-green algae. However, many
bacteria
use reactions
completely different from plants to make their own food from
an array of chemicals. And, there are bacteria that are able
to switch between
making their own food and absorbing food from an external
source.
How are bacteria important to people?
Bacteria
are important to humans in many ways. Did you know that bacterial
cells outnumber human cells in our bodies?
Many times they
are portrayed as germs and agents of disease but there
are also many beneficial and practical applications of
bacteria in our everyday lives.
Some bacteria serve to ward off infection in our bodies
as
well as to facilitate digestion. Wine, cheese, and yogurt
are produced with
bacterial cultures. Furthermore, certain bacteria produce
important compounds used in industrial and pharmaceutical
industries.
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