Bacteria are one of the simplest forms of life and they appeared on Earth long before other forms of life. It is
estimated that bacteria have been present for about 3.4 billion years and they are found almost everywhere on Earth.
Organisms
If we take all living organisms, we can split them into two major types.
Eukaryotes
Organisms
Eukaryotes,
Eukaryotes
Organisms
Prokaryotes
And prokaryotes
Genetic Material
This diagram illustrates some of the differences and similarities between eukaryotic
and prokaryotic cells.
Genetic Material
A eukaryotic cell has (click) a nucleus which is enclosed by a membrane.
Genetic Material
Whereas a prokaryotic cell (click) has its genetic material right in the cytoplasm, and it
is not enclosed by a membrane
Genetic Material
Eukaryotic cells contain mitochondria
Genetic Material
But we can see that the prokaryotic cell does not have any of these organelles in its
cytoplasm.
Genetic Material
Prokaryotic cells have a cell wall.
Genetic Material
Plants
But so do many eukaryotic cells, (click) such as plants.
Genetic Material
Plants
Some prokaryotic cells have a hard outer coating called a capsule.
Genetic Material
Plants
We see that both eukaryotes and prokaryotes have (click) ribosomes in their cells.
These are needed by both types of organisms to produce proteins.
Genetic Material
Plants
And we see that the cells of both eukaryotes and prokaryotes (click) have a cell
membrane. This is crucial for all cells, as it is needed to contain all of the cell’s parts.
Eukaryotes
Cells contain organelles such as:
• Mitochondria
• Golgi body
• Lysosomes
• Endoplasmic reticulum
• Chloroplasts (in plants)
The nucleus contains genetic material
and is surrounded by a membrane.
Organisms
Prokaryotes
So we can summarize what we looked at here, the cells in eukaryotes contain organelles such as mitochondria,
but they also have a golgi body, lysosomes, endoplasmic reticulum, and in the case of plants, chloroplasts.
Eukaryotes
Cells contain organelles such as:
• Mitochondria
• Golgi body
• Lysosomes
• Endoplasmic reticulum
• Chloroplasts (in plants)
The nucleus contains genetic material
and is surrounded by a membrane.
Organisms
Prokaryotes
In Eukaryotes, genetic material of a cell is in a nucleus which is surrounded by a nuclear
membrane.
Eukaryotes
Cells contain organelles such as:
• Mitochondria
• Golgi body
• Lysosomes
• Endoplasmic reticulum
• Chloroplasts (in plants)
The nucleus contains genetic material
and is surrounded by a membrane.
Organisms
Prokaryotes
Cells contain no mitochondria,
Golgi body, lysosomes, endoplasmic
reticulum, or chloroplasts
The nucleus contains genetic material
and is surrounded by a membrane.
The cells of Prokaryotes contain no mitochondria, golgi body, lysosomes, endoplasmic
reticulum, or chlroplasts. They are much more primitive than eukaryotes.
Eukaryotes
Cells contain organelles such as:
• Mitochondria
• Golgi body
• Lysosomes
• Endoplasmic reticulum
• Chloroplasts (in plants)
The nucleus contains genetic material
and is surrounded by a membrane.
Organisms
Prokaryotes
Cells contain no mitochondria,
Golgi body, lysosomes, endoplasmic
reticulum, or chloroplasts
The genetic material is in the
cytoplasm
The genetic material in a prokaryotic cell is simply floating around in the cytoplasm. It
is not contained in a nucleus.
Eukaryotes
Eukaryotes include all life forms except bacteria and some species of blue-green algae.
So animals and plants are all eukaryotes.
Eukaryotes
All life forms
except bacteria
and some
blue-green algae
Organisms
Bacteria
Prokaryotes
Blue-green algae
We’ll make a note here that Eukaryotes include all life forms except bacterial and some
species of blue-green algae.
Prokaryotes
Escherichia coli bacteria
Blue-green algae
Prokaryotes include bacteria and some species of blue-green algae.
Eukaryotes
All life forms
except bacteria
and some
blue-green algae
Organisms
Bacteria
Prokaryotes
Blue-green algae
We’ll make a note of that here. (click) Prokaryotes can be bacteria (click) or blue-green
algae
A Bacterium
Let’s take a closer look at a bacterium. This diagram represents one type of bacterium.
We’ll look at some of the important structures and organelles
A Bacterium
Capsule
Outer protective
coating
Bacteria are surrounded by an outer coating, called a capsule. This protects the bacterium. It is actually a
factor in disease because it protects bacteria from being attacked by our immune system.
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Right inside the capsule is the cell wall, shown in yellow in this diagram. This helps
keep the cell together and offers more protection.
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
The cell membrane is the next layer, shown in green on this diagram. The cell
membrane helps control what enters or leaves the bacterial cell.
Ribosomes
Manufacture proteins
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Like all other living cells, bacterial cells contain ribosomes. These are the organelles which manufacture proteins.
All the ribosomes in bacteria are free-floating in the cytoplasm. Bacterial cells do not have endoplasmic reticula.
Ribosomes
Manufacture proteins
Plasmid
Separate piece of DNA
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
This is called a plasmid. Plasmids are strands of DNA which are separate from the main bacterial DNA,
which is in the center. They provide a blueprint for the cell to produce certain types of proteins.
Ribosomes
Manufacture proteins
Plasmid
Separate piece of DNA
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Pilli
Hair-like
appendages
These are pilli. They are hair-like appendages found on the outside of many bacteria. Some viruses can attach to these
and infect bacterial cells. Some of these are also used to connect to other bacteria and exchange genetic material.
Ribosomes
Manufacture proteins
Plasmid
Separate piece of DNA
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Pilli
Hair-like
appendages
Cytoplasm
The cytoplasm is the gel-like liquid that fills the interior of a bacterial cell. Many
organelles float around in the cytoplasm.
Ribosomes
Manufacture proteins
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Plasmid
Separate piece of DNA
Pilli
Hair-like
appendages
Cytoplasm
Bacterial DNA
Called a nucleoid
This is the main piece of bacterial genetic material, or DNA. It is not contained in a membrane-bound nucleus, like
DNA is in eukaryotic cells. This DNA in a bacterium is often called a nucleoid because it is not a true nucleus.
Ribosomes
Manufacture proteins
Cell Membrane
Cell Wall
A Bacterium
Capsule
Outer protective
coating
Plasmid
Separate piece of DNA
Pilli
Hair-like
appendages
Cytoplasm
Flagellum
Bacterial DNA
Called a nucleoid
This tail-like appendage is called a flagellum. It whips back and forth and helps bacteria move
around. Some bacteria like this one, has one flagellum, while others have more than one.
Bacteria can be classified as having three main shapes.
Cocci
Spherical or
egg-shaped
bacteria
Cox-eye are spherical, or egg-shaped bacteria.
Bacilli
Rod-shaped
bacteria
Bacilli are rod-shaped bacteria
Spirilla
Spiral-shaped
bacteria
And spirilla are spiral-shaped bacteria
Many bacteria are beneficial to us. Let’s look at a few of them.
Lactobacillus
Acidophilus
is naturally
present in the
human digestive
system. It is
added to some
yogurts as a
probiotic, which
helps us digest
milk products.
Lactobacillus Acidophilus is naturally present in the human digestive system. It is
added to some yogurts as a probiotic, which helps us digest milk products.
Lactococcus
lactis is used in
making cheese
and buttermilk.
It helps turn a
sugar in milk
called lactose,
into lactic acid.
Lactococcus lactis is used in making cheese and buttermilk. It helps turn a sugar in
milk called lactose, into lactic acid.
Escherichia coli
is naturally present
in the large
intestine of
humans and other
warm-blooded
species. It
produces some B
vitamins and
vitamin K, needed
for blood clotting.
Es share eek ee ya coal eye is naturally present in the large intestine of humans and other warm-blooded
species. It produces some B vitamins and vitamin K, needed for blood clotting. There are many strains of E coli
bacteria. Most are harmless, but there are some strains that can cause disease.
Bacteria that are harmful and can cause disease are said to be pathogenic
Pathogenic means
“able to cause disease”
The word Pathogenic means “able to cause disease”
Helicobacter
pylori
Is found in the
stomach of
some people. In
some cases, it
can cause
stomach ulcers.
Helicobacter pylori Is found in the stomach of some people. In some cases, it can
cause stomach ulcers.
Escherichia
coli O157:H7
is a strain of
E. coli that can
cause severe
diarrhea and in
some cases, kidney
failure. It can be
contacted by eating
contaminated raw
vegetables or
uncooked meat.
Escherichia coli O157:H7 is a strain of E. coli that can cause severe diarrhea and in some cases, kidney failure.
It can be contacted by eating contaminated raw green-leaf vegetables or uncooked meat. Although
contamination is rare, it occasionally occurs, and leads to recalls of certain food products.
Salmonella
enterica
is contacted by
eating food from
infected cattle or
poultry. It can
sometimes be
found in raw eggs.
It can cause “food
poisoning”.
Salmonella N-tare-ica is contacted by eating food from infected cattle or poultry. It can
sometimes be found in raw eggs. It can cause a type of “food poisoning” called salmonella.
Clostridium
botulinum
causes botulism,
which is contacted
by eating
improperly
prepared homecanned foods that
are low in acid. It
can also occur from
infected wounds.
Clostridium bot chew lin um causes botulism, which is contacted by eating improperly prepared home-canned
foods that are low in acid. It can also occur from infected wounds. Botulism can be fatal if not treated very
quickly.
Borrelia
burgdorferi
is the main cause of
Lyme Disease. It is
contacted mainly
through tick bites. If
bitten by a tick, seek
medical attention
immediately. Untreated
Lyme disease is very
serious.
Borrelia burg door furry causes Lyme Disease. It is contacted mainly through tick bites. If bitten by a tick,
seek medical attention immediately. Untreated Lyme disease is very serious.
Scientists have identified thousands of species of
bacteria but it has been estimated that there are
millions of bacterial species on Earth.
The total mass of all the bacteria on Earth is greater
than the total mass of all plants and animals.
The number of bacterial cells in our body is about ten
times the number of our cells.
We’ve looked at only a few bacteria here, (click) Scientists have identified thousands of species of
bacteria but it has been estimated that there are millions of bacterial species on Earth.
Scientists have identified thousands of species of
bacteria but it has been estimated that there are
millions of bacterial species on Earth.
The total mass of all the bacteria on Earth is greater
than the total mass of all plants and animals.
The number of bacterial cells in our body is about ten
times the number of our cells.
In fact, it is thought that the total mass of all the bacteria on Earth is greater than the
total mass of all of the plants and animals.
Scientists have identified thousands of species of
bacteria but it has been estimated that there are
millions of bacterial species on Earth.
The total mass of all the bacteria on Earth is greater
than the total mass of all plants and animals.
The number of bacterial cells in our body is about ten
times the number of our cells.
It is interesting to note that the number of bacterial cells living in our body is about ten
times the number of our cells.
Acknowledgements for Images Used
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H. B. from Schweiz
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"Lactobacillus acidophilus (259 09) Lactobacillus acidophilus
(Döderlein bacillus)" by Doc. RNDr. Josef Reischig, CSc. - Author's
archive. Licensed under CC BY-SA 3.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Lactobacillus_acidophil
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"Lactococcus lactis" by Minyoung Choi from Cupertino, CA,
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"Clostridium botulinum 01" by Content Providers: CDC - This media
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"Average prokaryote cell- en" by Mariana Ruiz Villarreal, LadyofHats - Own
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