Page 234 - (DK) Ocean - The Definitive Visual Guide

232 BACTERIA AND ARCHAEA

Bacteria and Archaea PEOPLE
CARL WOESE

THE SMALLEST ORGANISMS ON EARTH are the bacteria Born in New York Carl
DOMAINS Bacteria Woese (1928—2012) was the
and their relatives, the archaea. Bacteria occupy virtually
Archaea microbiologist who is responsible
all oceanic habitats, whereas many archaea are confined for the current division of living
KINGDOMS 13
organisms into three domains,
SPECIES Many millions to extreme environments, such as deep-sea vents. Bacteria Archaea, Bacteria, and Eucarya, on
and archaea play vital roles in the recycling of matter. Many the basis of his research into the
RNA (a chemical related to DNA,
are decomposers of dead organisms on the ocean floor. Others are remarkable in called ribonucleic acid) found in
being able to obtain their energy from minerals in the complete absence of light. ribosomes. Woese put forward his
new classification in 1976, but it
was not until the 1980s that his
Anatomy Habitats hypothesis was accepted.
Bacteria and archaea are single- Bacteria are found throughout the
celled organisms that are far smaller ocean environment, because nearly
than any other, even protists. Most all habitats provide them with the
have a cell wall, which, in bacteria, materials necessary to obtain
is made from a substance called energy. Most bacteria get energy
peptidoglycan. None has a nucleus by breaking down organic matter.
or any of the other cell structures Much of this matter accumulates
of more complex organisms on the ocean floor and provides
(eukaryotes). Some bacteria and excellent conditions for the
archaea can move by rotating decomposer bacteria. Bacteria
threads called flagella; others are also found in large numbers
have no means of propulsion. in the water column, feeding on
Scientists separated the Archaea suspended matter.
and Bacteria groups on the basis A few kinds of bacteria, such as
THRIVING IN THE RIGHT CONDITIONS
of chemical differences in their cell The bacterium Nitrosomonas forms colonies cyanobacteria, can photosynthesize
make-up. All living cells contain wherever there is enough ammonia and and so live nearer to the surface,
tiny granules (ribosomes), which oxygen in the water. in brightly lit waters. Some form
help to make proteins, but those in colonies and build huge structures,
archaea are differently shaped to those called stromatolites, near the shore.
in bacteria. The oily substances that make Many archaea and bacteria can
up their cell membranes are also different. live in extreme conditions, such as
Additionally, archaea have special molecules high temperatures, water with high
associated with their DNA that protect them acidity, or low oxygen levels. For
in the harsh environments in which they live. example, archaea and bacteria live
Scientists now think that their chemical around deep-sea vents, getting their
differences are sufficiently important to rank HEAT-LOVING ARCHAEA energy from chemical reactions of
Archaea as a distinct evolutionary branch of Most archaea can adapt methane and sulphide compounds
life. Initially considered to be primitive, the to extreme conditions. This ejected by the vents. Others survive LIVING ON THE SEA BED
heat-loving example, GRI,
Bacterial mats form on the sea bed where
archaea are now thought to be closer to the was ejected from the sea in the very high concentrations oxygen supply is low. This mat of Beggiatoa sp.
ancestors of eukaryotes than are the bacteria. floor in an undersea eruption. of salt on some sea shores. is at the mouth of the Mississippi, USA.

OCEAN LIFE HYPER-SALINE CONDITIONS

The hyper-saline water of Hamelin
Pool, west Australia, is one of only three
places where stromatolites are found.
The rocks are formed by the cyanobacteria
cementing sediment particles together.