Transcript Microbes are the Foundation of Life

Microbes are the
Foundation of Life
What Is A Microbe?
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Microbe is a term for tiny
creatures that individually are
too small to be seen with the
unaided eye.
Microbes include bacteria,
archaea, fungi and protists
Archaea are bacteria-like
creatures
Protists include primitive
algae, amoebas, slime molds
and protozoa
They may live as individuals
or cluster together in
communities
Size of Micorbes
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So how small are microbes?
Well, let's say we could
enlarge an average virus, the
smallest of all microbes, to
the size of a baseball
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An average bacterium would
then be the size of the
pitcher's mound.
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And just one of the millions
of cells that make up your
body would be the size of
the ballpark!
Bacteria
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Bacteria consist of only
a single cell
They're an amazingly
complex and fascinating
group of creatures
They can live in
temperatures above the
boiling point and in cold
that would freeze your
blood
They "eat" everything
from sugar and starch
to sunlight, sulfur and
iron
Classification
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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
Eukaryotes, creatures
whose cells have nuclei
Early Origins
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Bacteria are among the earliest forms of life
that appeared on Earth billions of years ago
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Scientists think that they helped shape and
change the young planet's environment –
Oxygen
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Many believe that more complex cells
developed as once free-living bacteria took
up residence in other cells - Mitochondria
What They Look Like
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Some are rod- or
stick-shaped and called
bacilli
Others are shaped like
little balls and called
cocci
Others still are helical or
spiral in shape
Some bacterial cells
exist as individuals while
others cluster together
to form pairs, chains,
squares or other
groupings
Where They're Found
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Bacteria live on or in
just about every material
and environment on
Earth from soil to water
to air
Each square centimeter
of your skin averages
about 100,000 bacteria
A single teaspoon of
topsoil contains more
than a billion
(1,000,000,000)
bacteria
How They Move
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Some bacteria move
about their environment
by means of long,
whip-like structures
called flagella
Other bacteria secrete a
slime layer and ooze
over surfaces like slugs
Others are fairly
stationary
What They Eat
 Some
bacteria are photosynthetic
 Other bacteria absorb food from the
material they live on or in
 Some of these bacteria can live off
unusual "foods" such as iron or sulfur
 The microbes that live in your gut
absorb nutrients from the digested food
you've eat
Archaea
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archaea very much resemble
bacteria, so much so that they were
once thought to be a weird group of
bacteria. However, by studying archaeal
cells on a molecular level, scientists
have now come to think that these
"weird bacteria" actually are a separate
category of life altogether. In fact, in
some ways, archaea are more like you
than they are like bacteria!
Classification
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Archaeans are single-celled
creatures that join bacteria to make
up a category of life called the
Prokaryotes
However, while archaeans resemble
bacteria and have some genes that
are similar to bacterial genes, they
also contain other genes that are
more like what you'd find in
eukaryotes
Furthermore, they have some genes
that aren't like any found in anything
else
Early Origins
 Archaeans
are among the earliest forms
of life that appeared on Earth billions of
years ago
 Archaea and bacteria developed
separately from a common ancestor
nearly 4 billion years ago
 Millions of years later, the ancestors of
today's eukaryotes split off from the
archaea
Life at the Extreme
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Many archaeans thrive in
conditions that would kill other
creatures -extremophiles
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How do these extremophiles
do it? - They make a variety
of protective molecules and
enzymes
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Many live in more ordinary
temperatures and conditions
What They Eat
Archaeans dine on a variety of substances for
energy, including hydrogen gas, carbon
dioxide and sulfur
 One type of salt-loving archaean uses
sunlight to make energy, but not the way
plants do it
 This pigment, called bacteriorhodopsin,
reacts with light and enables the cell to make
ATP, an energy molecule
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Types of Archaea
Crenarchaeota, which are characterized by
their ability to tolerate extremes in
temperature and acidity
 Euryarchaeota, which include methaneproducers and salt-lovers
 Korarchaeota, a catch-all group for
archaeans about which very little is known
 Subtypes – Methanogens, Halophiles,
Thermophiles, Psychrophiles
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Fungi
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Fungi come in a
variety of shapes
and sizes and
different types. They
can range from
individual cells to
enormous chains of
cells that can stretch
for miles
Classification
 Fungi
are eukaryotic organisms—their
DNA is enclosed in a nucleus. Many of
them may look plant-like, but fungi do
not make their own food from sunlight
like plants do
What They Look Like
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Fungi include single-celled
creatures that exist individually—the
yeasts—and multicellular bunches,
such as molds or mushrooms
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Yeast cells look like little round or
oval blobs under a microscope.
They're too tiny to see as individuals,
but you can see large clusters of
them as a white powdery coating on
fruits and leaves
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Molds are described as filament-like,
or filamentous, because they form
long filament-like, or thread-like,
strands of cells called hyphae
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They also form the fleshy body, or
mushroom, that some species grow
Where They're Found
 Fungi
usually grow best in environments
that are slightly acidic (a pH
measurement of 5 or so; a pH of 7 is
neutral). They can grow on substances
with very low moisture. Fungi live in the
soil and on your body, in your house
and on plants and animals, in
freshwater and seawater. A single
teaspoon of topsoil contains about
120,000 fungi
How They Spread
Fungi are basically
static
 But they can spread
either by forming
reproductive spores
that are carried on
wind and rain or by
growing and
extending their
hyphae
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What They Eat
 Fungi
absorb nutrients from living or
dead organic matter (plant or animal
stuff) that they grow on. They absorb
simple, easily dissolved nutrients, such
as sugars, through their cell walls. They
give off special digestive enzymes to
break down complex nutrients into
simpler forms that they can absorb
Friendly Fungi
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Some fungi are quite useful to us. We've
tapped several kinds to make antibiotics to
fight bacterial infections. These antibiotics
are based on natural compounds the fungi
produce to compete against bacteria for
nutrients and space. We use Saccharomyces
cerevisiae, aka baker's yeast, to make bread
rise and to brew beer. Fungi break down dead
plants and animals and keep the world tidier.
We're exploring ways to use natural fungal
enemies of insect pests to get rid of these
bugs
Fungal Enemies
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are some nasty fungi that cause
diseases in plants, animals and people.
One of the most famous is
Phytophthora infestans, which caused
the Great Potato Famine in Ireland in
the mid-1800s that resulted in a million
deaths. Fungi ruin about a quarter to
half of harvested fruits and vegetables
annually
Protists
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category of
Protists includes many
widely ranging
microbes, including
slime molds, protozoa
and primitive algae.
They are all eukaryotic
creatures, meaning
their DNA is enclosed
in a nucleus inside the
cell
Algae
Here we'll focus on the microscopic algae
 Algae are found in bodies of fresh and salt
water
 They can also grow on rocks and trees and in
soil when enough moisture is available
 Most algae are able to make energy from
sunlight, like plants do
 However, at some stages of their lives, some
algae get their nutrients from other living
things
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Dinoflagellates
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Pfiesteria belongs to a type
of algae called the
dinoflagellates
Some dinoflagellates make
their own energy from
sunlight, like plants
The Piesteria then feed on
the fish blood and fluids
This microbe has at least 24
different forms it cycles
through during its life
Pfiesteria produce toxic
substances
Diatoms
They have hard
shells made out of
silica, or glass
 Diatoms come in all
sorts of shapes—
some, like the one
pictured here, are
round and others are
oval. Some look like
leaves and others
like fat commas
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Protozoa
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The word protozoa means "little
animal.“
Protozoa mainly feed on
bacteria, but they also eat other
protozoa, and sometimes fungi
Some protozoa absorb food
through their cell membranes.
Others, like the amoebas <ahme-buhs>, surround food and
engulf it. Others have openings
called mouth pores into which
they sweep food.
All protozoa digest their food in
stomach-like compartments
called vacuoles
Protozoa range in size from
1/5,000 to 1/50 of an inch in
diameter
Ciliates
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They are generally the
largest protozoa. They
have hair-like
projections called cilia
and they eat the other
two types of protozoa
as well as bacteria. You
can just see the thin
cilia poking out around
the edges of the
protozoan in the image
to the right
Amoebae
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which can be
subdivided into the
testate amoebae,
which have a shelllike covering, and
the naked amoebae,
which don't have
this covering
Flagellates
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are generally the smallest of the
protozoa and have one or several long,
whip-like projections called flagella
poking out of their cells
Moving of protozoa
 Amoebas
ooze about by extending
parts of their cells as pseudopods or
"false feet."
 Many ciliates swim along by beating
their cilia in a rhythmic pattern, like so
many tiny oars
 Flagellates swim by waving their flagella,
using them much like a fish uses its tail
push itself through water
Protozoa & human
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The vast majority of protozoa do us no harm.
But, yes, there are a few that cause disease.
One type of amoeba can live in human
intestines. It feeds on red blood cells and
causes a disease known as dysentery . The
parasitic protozoan Cryptosporidium parvum
sickened around 400,000 people in
Milwaukee in 1993 when it got into the tap
water. Perhaps the best-known protozoal
menace is Plasmodium, the parasite that
causes malaria. This terrible disease leads to
about 800,000 deaths each year worldwide
Slime Molds
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They have very complex life
cycles involving multiple
forms and stages
During good times, they live
as independent, amoebalike cells, dining on fungi and
bacteria
Conditions become
uncomfortable—not enough
food available, the
temperature isn't right, etc.—
individual cells begin
gathering together to form a
single structure
Viruses
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Viruses are strange things
that straddle the fence
between living and nonliving
A virus is basically a tiny
bundle of genetic material—
either DNA or RNA—carried
in a shell called the viral coat,
or capsid, which is made up
of bits of protein called
capsomeres. Some viruses
have an additional layer
around this coat called an
envelope.
What They Look Like
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There are thousands of
different viruses that come in
a variety of shapes
Many are polyhedral, or
multi-sided
Other viruses are shaped like
spiky ovals or bricks with
rounded corners
Some are like skinny sticks
while others look like bits of
looped string
Some are more complex and
shaped like little lunar
landing pods
Single-Minded Mission
 Viruses
exist for one purpose only: to
reproduce
 To do that, they have to take over the
reproductive machinery of suitable host
cells.