Kingdom Eubacteria and
Characteristics of Bacteria
Bacteria are by far the most abundant organisms on Earth.
As a group they are very diverse, but they all share certain
1. All bacteria are single-celled.
2. All bacteria are prokaryotes:
Their DNA is not surrounded by a membrane.
Cell organelles in bacteria are not surrounded by
3. The DNA of bacteria is made of a single chromosome.
4. All bacteria reproduce asexually by binary fission.
• As a group, bacteria are the smallest organisms.
• They are usually 1–10 microns
• A typical eukaryotic cell is about 10 times larger.
Structure of a Bacteria
• The structure is simple:
• Cell wall: provides support and protection for the
contents of the cell.
• Cell membrane controls the passage of materials into
and out of the cell.
• The cytoplasm contains ribosomes, responsible for the
formation of proteins
• The DNA is a single chromosome formed into a ring
• There is roughly 1/1000th the amount of DNA than in a
typical eukaryotic cell.
Projections Provide Locomotion
• Some bacteria have whip-like flagella (singular:
• They act like propellers moving in reverse, drawing the
• Some bacteria have cilia (also called pili), tiny hair-like
structures on the surface of the cell
• They beat to move the bacteria forward
• spherical cell is called a coccus (pural: cocci)
• a rod shaped cell is called a bacillus (plural: bacilli)
• a spiral-shaped cell is called a spirillum (plural: spirilli).
• monococci: cocci that live as separate cells
• Diplococci: cocci that live in pairs.
• Streptococci: cocci that live in linear chains
• Staphlococci: cocci that live in grapelike clusters
• Bacilli also exist as single cells, pairs (diplobacilli), or
• Spiralbacteria exist only as single cells.
• There is a large variety of nutritional patterns among
• All living things must carry out cellular respiration to
receive a supply of energy for life’s functions.
• Bacteria differ in whether or not they require oxygen.
• If cellular respiration involves oxygen to produce energy,
bacteria are termed aerobes.
• If oxygen is absolutely necessary for their survival, they
are called obligate aerobes.
• Those bacteria that can carry out cellular respiration in
an oxygen-free environment are termed anaerobes.
• If the presence of oxygen kills these organisms, they are
called obligate anaerobes.
• A third group of bacteria can survive with or without
oxygen and they are called facultative anaerobes.
• All bacteria reproduce asexually and divide
by the process of binary fission
• Bacteria can reproduce in 15 to 20 minutes as long as
there is sufficient food, warmth, and space.
• Under the right conditions, a single E.coli bacterium can
produce between 10 and 100 million bacteria in 12
Conjugation- sexual reproduction
• During conjugation, two bacterial cells connect to each other
by long protein bridges
• The plasmid (ring of extra DNA) of one cell is transferred to
the other cell.
• When the process is completed, the bacterium that received
the genetic material from the other cell now has a different
• Having an altered genetic makeup increases the chance that a
bacterium might possess a gene combination that enables the
organism to adapt to worsening conditions.
Bacteria and Disease
• Only a small percentage of prokaryotes are pathogenic,
or disease causing.
• Pathogenic bacteria produce deadly substances (toxins)
in the human body that cause disease symptoms.
The Two Kingdoms of Bacteria
• There are two kingdoms of bacteria:
– Archaebacteria in the domain Archea
– Eubacteria in the domain Bacteria
• Most archaebacteria live in extreme environments. These
are called extremophyles.
• Other Archaebacteria species are not extremophiles and
live in ordinary temperatures and salinities. Some even
live in your guts!
• Some extremophile species love the heat! They like to live in boiling
water, like the geysers of Yellowstone Park, and inside volcanoes.
• These are called "thermophiles" which means "loving heat", and it
would probably freeze to death at ordinary room temperature.
• Other extremophile Archaea live in very salty, called hypersaline,
environments. These salt-loving Archaea are called halophyles.
• Other achaea are known as methanogens.
• Methanogens are methane producers. Most of these bacteria use
carbon dioxide as their carbon source. They are found in soil,
swamps, and most animals digestive tracts
• Eubacteria are more common and more widespread than
• There are typically 40 million bacterial cells in a gram of
soil and a million bacterial cells in a millilitre of fresh
• There are approximately five nonillion (5×1030) bacteria
on Earth, forming much of the world's biomass.