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Bacteria
Bacteria
“Wash your hands — you don’t want to get sick from bacteria!” How many times have
you heard a command like that? Bacteria are everywhere and some can make you
sick. But did you know that many types of bacteria are helpful? In fact, life on Earth
depends on them. Bacteria take elements like carbon and nitrogen out of the air and
turn them into compounds living things can use. They recycle nutrients from dead
plants and animals so they can be reused. There are even bacteria in your digestive
system (Figure 9.5)! In this section, you’ll learn about the structure and function of
bacterial cells.
What are bacteria?
Bacteria are the
only prokaryotes
Bacteria are organisms that consist of a single, prokaryotic cell.
Bacteria are the only prokaryotes (cells without a nucleus). All
other life forms on Earth are eukaryotes. Bacterial cells have a cell
membrane that is surrounded by a tough cell wall (Figure 9.6).
Where do
bacteria live?
Bacteria live on or in just about every material and environment
on Earth. They live in soil, water, and air. They are found in the
coldest regions of the Arctic and even in boiling waters near
undersea volcanoes. There are many bacteria in each
environment. A square centimeter of your skin has thousands of
bacteria. A teaspoon of soil contains more than a billion bacteria.
1 or 2 kingdoms
of bacteria?
Some scientists group all bacteria into the Kingdom Monera.
Others divide bacteria into two kingdoms, Archaebacteria and
Eubacteria. Archaebacteria are found in extreme environments
like volcanic vents in the ocean. They are thought to be the first
organisms on Earth. Eubacteria are found almost everywhere else
and have a different chemical makeup than archaebacteria. Both
types of bacteria are prokaryotic, single-celled organisms. As
future discoveries are made, these groups may change.
