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Bacteria
Characteristics
Bacteria are smallest living organisms
Bacteria consist of a single cell
Bacteria are nearly 3.5 billion
years old. They are among the
earliest forms of life that appeared
on Earth.
Bacterial Cell
Bacterial cells are prokaryotic – they have
no nucleus or other membrane-bound organelles
Bacterial cells have a single chromosome – a circular
DNA molecule
Bacterial cells have a cell wall
Most bacteria reproduce by binary fission
Classification
Bacteria fall into a category of life called
the Prokaryotes. Prokaryotes' genetic
material, or DNA, is not enclosed in a
cellular compartment called the
nucleus.
Bacteria and archaea are the only
prokaryotes. All other life forms are
Eukaryotes, creatures whose cells have
nuclei.
What they look like?
There are thousands of species of bacteria,
but all of them are basically one of three
different shapes.
1. Cocci are
shaped like
little balls
2. Bacilli are
rod- or
stick-shaped
3. Spirilla are
helical or spiral
in shape
What they eat?
Autotrophs
photosynthetic bacteria can make their own food from
carbon dioxide using sunlight, just like plants.
chemosynthetic bacteria produce their own organic compounds
from inorganic substances such as iron or sulfur.
Heterotrophs
needs organic substances that have already been assembled by
autotrophs.
Where they live?
Bacteria live just about
everywhere: in the soil, water and
air; in animals, plants, rocks and
even in us!
Bacteria from boiling water
of hot springs in Yellowstone National Park
Bacteria on our teeth
Spores
Spore (or endospore) is a dormant cell. It has a tough shell that
insulates and protects the genes and basic cell parts.
Spores are resistant to heat and cannot be readily destroyed, even
by boiling.
In 2000, scientists revived bacteria that had lain in
suspended animation for 250 million years.
Role of bacteria
Negative:
Bacteria can cause illnesses:
Diarrhea
Lyme disease
Botulism
Leprosy
Wash up!
How can you protect yourself and others from
contamination by pathogenic bacteria?
Role of bacteria, cont.
Positive:
There are many important jobs bacteria do.
They are used to make medicine.
They break down oil from oil spills.
They make about half of the oxygen we
breath.
They are the foundation of the food chain
that feeds all life on earth
Our Friends
Bacteria do many good thins for us:
Escherichia coli:
one of many
kinds of microbes
that live in your
gut. Wanted for
helping you digest
your food every
day.
Pseudomonas
putida: one of
many microbes
wanted for cleaning
wastes from
sewage water at
water treatment
plants.
Lactobacillus
acidophilus: one of
the bacteria gang
wanted for turning milk
into yogurt.
Streptomyces:
soil bacteria
wanted for making
streptomycin, an
antibiotic used to
treat infections.
Questions
1. What kind of medication are antibiotics?
2. Why it is necessary to boil water before
drinking?
3. Why hospitals sterilize instruments in
autoclaves?
4. Escherichia coli is a normal resident of the
mammalian gut. What is its role?
5. Can bacteria sense and move?
6. What are the cell shapes of Lactobacillus,
Staphylococcus, Spirochaeta?
Answer 1
Antibiotics fight diseases that are
caused by bacteria.
Bacteria are constantly changing and
developing antibiotic-resistant strains.
We need new antibiotics that can fight
resistant strains of bacteria.
Answer 2
Drinking-water may be contaminated by a range of
microbes that may pose risks to health
1.8 million people die every year from diarrheal
diseases (including cholera); 90% are children under
5, mostly in developing countries.
High temperature kills the majority of
pathogenic bacteria
Answer 3
Boiling temperature is not enough to kill
bacteria spores.
An autoclave is designed to
produce temperatures and
pressures that will completely
sterilize objects.
Answer 4
E.coli :
enhances digestion
Impedes colonization of the gut by a variety
of pathogens
Can cause diarrhea (E.coli is the leading
cause of infant mortality for most of the
human population)
Answer 5
Bacteria sense light, detect the presence of oxygen and
other chemical compounds. Magnetotactic bacteria have a
chain of magnetite particles in their cytoplasm that serves
as a tiny compass.
Some bacteria move
about their
environment by means
of long, whip-like
structures called
flagella.
Answer 6
Lactobacillus
Staphylococcus
Spirochaeta
Interesting facts about
bacteria
Bacteria can live in temperatures above the
boiling point and in cold that would freeze
your blood. There's even a species of
bacteria—Deinococcus radiodurans—that can
withstand blasts of radiation 1,000 times
greater than would kill a human being.
They "eat" everything from sugar and starch
to sunlight, sulfur and iron.
Biggest Bacterium
The colossus among bacteria is a
single-celled giant that lives in the
ocean and is named Thiomargarita
namibiensis , which means "sulfur
pearl of Namibia." It was found in
the ocean floor off the coast of
Namibia in Africa. T. namibiensis’s
ball-shaped cells can grow to
almost 1 millimeter or 1/25th of an
inch in diameter. That’s about as
big as the period at the end of a
sentence.
Millions of them…
Your body is home to trillions of microbes. Run your
tongue over your teeth—you're licking thousands of
microbes that normally live on your teeth. Millions of
them live on your tongue, too. A large part of "you"
(that is, the mass of your body) is actually something
else: bacteria, viruses and fungi. Isn't that a weird
thought?
A single teaspoon of that soil contains over
1,000,000,000 bacteria,
Bacteria on Mars?
Some scientists even
believe there is the
possibility bacteria
may have once lived
on Mars. This
photograph shows
what some scientists
believe may be the
fossils of tiny
bacteria in a rock
that formed on Mars
about 4.5 billion
years ago.
Find more interesting facts
about bacteria