microbes

MicrobesBy: Ita P. Rodríguez

3rd Grade Homeschool Biology

What is a MICROBE?

What makes a microbe? We suppose you need a microscope to

see them. That's about it.

There is a huge variety of creatures in this section.

They can work alone or in colonies.

They can help you or hurt you.

Most important fact is that they make up the largest number of living

organisms on the planet.

If you spend your life studying them, you would be a

microbiologist.

Some of them, like viruses, may not even be alive as we currently

define life.

Prokaryotes

Prokaryotes do not have an organized

nucleus. Their DNA is kind of floating around

the cell. It's clumped up, but not inside of a

nucleus.

Can You Exist Without a Nucleus?

You can't, but they can.

Most prokaryotes are bacteria and bacteria

can do amazing things.

They are found everywhere on the planet.

Some scientists even think that they may be

found on other planets (maybe even Mars).

Some places you can find bacteria every day

are in your intestines, a cup of natural yogurt,

or a bakery.

Prokaryotes

Prokaryotes are the simplest of simple

organisms. Here's the checklist.

Prokaryotes have no organized nucleus. The

DNA is clumped in an area but there is no

organized nucleus with a membrane.

Prokaryotes do not usually have any

organelles. They will probably have

ribosomes inside of their cells, but ribosomes

are not technically considered organelles.

No chloroplasts. No mitochondria. No nucleus.

Not much at all.

Bacterium

Prokaryotes

Prokaryotes are very small because they

don't have all of the normal cell machinery.

Mind you, compared to a bacteria they are big,

but next to an amoeba, tiny.

In this picture, an ameoba is going to eat a prokaryote.

Eukaryotes

Eukaryotes are what you think of when you think of a classic "cell" with a nucleus and organelles.

What makes a eukaryotic cell?

Eukaryotic cells have an organized nucleus with a nuclear envelope. They have a "brain" for the cell.

Eukaryotic cells usually have organelles. They might have mitochondria, maybe a chloroplast, or some endoplasmic reticulum.

Eukaryotes

Although limited in size by the physics of diffusion, eukaryotic cells

can get very large. There are even some extreme examples called

plasmodial slime molds that can be a meter wide.

Generally, eukaryotic cells are a couple hundred times the size of a

prokaryotic cell.

Eukaryotes

Eukaryotic cells have extra stuff going on and extra parts attached.

Since they have organelles and organized DNA they are able to create

parts.

One example is the flagellum (a tail-like structure to help it move). They

could also create cilia (little hairs that help scoot the cell through the

water).

Virus

Are Viruses Alive?

We're starting with the smallest of the small here. Some scientists argue that viruses are not even living things.

It's easier to give you a list of what they can't do as

opposed to what they can. What viruses can't do:

They can't reproduce on their own. They need to infect or invade a host cell. That host cell will do all the work to duplicate the virus.

They don't respond to anything. You can poke them or set up barriers, it doesn't matter. They either function or they are destroyed.

They don't really have any working parts. While there are some advanced viruses that seem fancy, viruses don't have any of the parts you would normally think of when you think of a cell. They have no nuclei, mitochondria, or ribosomes. Some viruses do not even have cytoplasm.

Virus

Every virus has a few basic parts.

The most important part is a small

piece of DNA or RNA (never both).

That strand of nucleic acid is

considered the core of the virus.

The second big part is a protein

coat to protect the nucleic acid.

That coat is called the capsid. The

capsid protects the core but also

helps the virus infect new cells.

Virus

Types of Viruses:

Helical virions: They are set up like a tube. The

protein coat winds up like a garden hose around

the core.

Polyhedral virions: This shape group includes the

classic virus shape that looks like a dodecahedron

(has 12 sides).

Complex virus: You may have seen this one in

books with the geometric head and long legs.

Viruses Makes Us Sick

Symptoms may include:

Fever

Runny nose

Coughing or sneezing

Headache

Nausea or vomiting

Diarrhea

Pain in the body

Internal bleeding

Blisters


Since viruses aren't alive, medicine won't

kill them. You can only treat the

symptoms. The best way is to prevent

an infection.

Preventing a viral infection:

Wash hands

Keeps hands away from mouth, nose,

and eyes

Avoid sharing personal items like a

toothbrush

Avoid sharing food and drinks with

other people


Viruses can affect any living organism.

Bacteria

They Are Alive!

Bacteria are the simplest of creatures

that are considered alive and they are

everywhere.

They are in the bread you eat, the soil

that plants grow in, and even inside of

you.

They are very simple cells that fall

under the heading prokaryotic.

Bacteria are small single cells whose

whole purpose in life is to replicate.

Bacteria

Types of Bacteria:

Spherical shaped: They are in the shape of little spheres or balls. They usually form chains of cells like a row of circles.

Rod shaped: This shape group (like the E. coli living in your intestine) are a bunch of bacteria that look like hot dogs. They can make chains like a set of linked sausages.

Spiral: These twist a little. Think about balloon animals for these shapes. It's like a balloon animal in the shape of a corkscrew.

Bacteria

What do good bacterias do?

Some help plants absorb nitrogen from the soil.

Some bacteria even live inside the stomachs of

cows to help them break down cellulose.

Bacteria

What do bad bacteria do?

Some cause diseases.

Symptoms are the same as viral infections:

Fever

Runny nose

Coughing or sneezing

Headache

Nausea or vomiting

Diarrhea

Pain in the body

Internal bleeding

Blisters. Since bacteria are alive, you can kill them with medicine called antibiotics.

Protozoa

Protists

Protozoa are also known as

protists. These are the bad boys of

the microbe world (bad meaning

"advanced").

Protists are eukaryotes with special

structures that may be the base

organisms of multicellular

organisms.

Protozoa

Slime Molds

Slime molds are not molds like a fungus. They are actually

independent organisms. There are two big kinds of slime molds.

Cellular slime molds are actually thousands of individual cells that team

up and work together. They specialize for a short time and some do the

eating, some work on reproduction, and some build special structures.

Acellular slime molds might also be called plasmodial slime molds. They

can be huge, a couple of feet across, but they are still only one cell. They

are able to grow so large because the one cell is multinucleated. They

ooze across the ground of forests digesting everything they can. When it

comes time to reproduce, they release all sorts of spores (like a fungus).

CellularAcellular

Protozoa

Amoebas

Amoebas are small-single celled organisms that ooze from place to

place.

They reach out with one part of the cell, a structure called a

pseudopod (it's like a foot).

They don't really have a shape because they are constantly on the

move, hunting down food and eating by a process called

phagocytosis.

They wrap themselves around the food and absorb it into their body for

digestion.

Protozoa

Protists with Tails

The next protists are called flagellates because they move with a

specialized tail called a flagellum.

They live in water and the water inside of dirt.

The flagella whip around like a not-so-coordinated fish tail. When it

whips, the protist scoots along though the water.

They do not do well in dry areas. They need that liquid environment to

move.

Protozoa

Protists with Hairs

Cilia are short little hairs. The classic example of a ciliate protist is a

Paramecium.

They are the very complex protists that have little hairs all over their body.

The hairs flap and push the organism through the water.

They can even hunt down food and attack them with a structure called a

trichocyst. Instead of surrounding their prey like an amoeba, they take in

the food through an oral groove (a protist version of a mouth).

They even have a way of getting rid of the food through an anal pore.

They might not seem like much to you, but the structures are very

advanced for a single-celled creature. They were the first creatures to

have them.

Protozoa

Parasitic Protists

Last, we'll talk about the parasites of the protist world. Not all protists

go about their life eating little bits of food in a pond.

Some, called sporozoans, are nasty little parasites.

These protists, like all parasites, cannot live on their own, and they harm

the host organism over time.

A disease called malaria is caused by one example of a sporozoan

protist.

Fungi

Fungus Among Us

There are no such things as molds. All molds are actually fungi.

We always heard about mold in the shower or mold on the bread. Mold

is actually a type of fungus. It has a shape called a zygote to be exact.

While yeasts are single celled fungi, molds are multicellular fungi.

Bread takes one kind of fungus (yeast) to make it rise. If you leave the

bread out, another type of fungus comes in (bread mold) to break it

down. It's not amazing, but it's true!

Fungi

Mushrooms

So what is a mushroom or a puffball? Bunches of strands living

underground are called hyphae (pronounced hi-fah).

Those strands are the basic fungus in action, decomposing leaves, or

rotting bark on the ground.

When it's time to reproduce, they develop a stalk and cap. The

mushroom that you see popping out of the ground.

On the bottom of that cap are a set of gills that have little clubs with fungus

spores.

Fungi

Zygotes

These have hyphae-like mushrooms but they reproduce in a different

way.

When it's time to make more fungi, they create a stalk and release

something called zygospores (thus the name zygote).

When your bread gets old and green or black, you are seeing a type of

zygote fungus in action. If you wait long enough, you will see the stalks

develop and the zygotes released.

Fungi

Single Cells

Sac Fungi are single celled fungi.

Yeast is used to make several types of food for humans. We need

yeast to make breads.

We also use them to make alcohol. It's a whole process called

fermentation. Sugars are broken down in an environment without

oxygen. It's called anaerobic fermentation. And voila, alcohol.

Even though they are single celled, you may find them in colonies. They

reproduce very quickly and hang out together. It takes a lot of them

(because they are so small) to get a lot of work done.

Lichen

Lichens are special organisms.

They are actually two types of

organisms in one. It's all about a

fungus and some algae. Lichen is

two organisms working together.

When you read about fungi we

talked about hyphae. Hyphae are

strands of the fungi that form a

mesh as they grow. In lichen are

actually cells of algae living between

those strands.

The two organisms work together. The fungus acts as a protector from the environment and loss of moisture. The algae go about their business of photosynthesis and creating food. The fungus uses the energy and the algae are protected and can survive.

Lichen

Lichens can live in places that many

organisms cannot.

Lichens can even live on the side of a

rock.

They don't need soil.

Slowly the fungus can break down the

minerals in the rock. The algae provide

energy. They are a self-sufficient team.

Scientists may call that team a

composite organism. They are both

able to be in places they could not go

alone. It's an advantage for their

survival.

Lichen

Are we killing off the lichens of the world?

In some places, yes. Indirectly we may be killing many species of

lichen in the same way that air and water pollution are killing off many

species of amphibians.

Lichens are very delicate organisms. Changes in the levels of poisons

and toxins hurt the relationship that the fungi and algae have. Always

remember, even if the fungi can survive the poisons, if you hurt the

algae, the whole organism will die. They are dependent on each other.

Good Microbes

Fixing nitrogen in soil: There are bacteria

that go through a process called fixing

nitrogen.

These bacteria, living in the roots of plants,

actually help them absorb nitrogen from the

surrounding soil. The nitrogen is very important

for the growth of the plant, and these little

bacteria give them an advantage for survival.

Helping cows eat grass: In the bacteria

section we already told you about a species

that lives in the digestive system in cows.

These bacteria help cows break down the

cellulose in plants. Similar bacteria live in all

sorts of grazing animals, helping them survive

off plant material.

Good Microbes

Antibiotics: Scientists have even discovered fungi that will help you battle

bacterial diseases. So you get sick, the doctor looks at you and says you have a bacterial

infection, maybe bronchitis. He prescribes an antibiotic to help you get better.

Antibiotics are drugs designed to destroy bacteria by weakening their cell walls. When the bacterial cell walls are weak, your immune cells can go in and destroy the bacteria.

Although there are many types now, one of the first antibiotics was called penicillin. It was developed from a fungus (a fungus named Penicillium found on an orange, to be exact).

Bad Microbes

Diseases: Many species of bacteria cause disease in humans, animals, and

even plants. Humans worry about bacteria that cause botulism (bacteria living in spaces

without oxygen, such as cans), tetanus and E. coli. You should know that there are also some good forms of E. Coli living in your intestines. They help break down food and live a simple life (and yes, they make it smell down there). There are also E. Coli that can be passed to you from undercooked meat. These bad bacteria can make you very sick and even kill you.

Bad Microbes

A Role in Natural Selection: We don't know of any

viruses that are good for the world.

They are an important piece of evolution and natural

selection. Weaker and older animals are more easily

infected. Those organisms are removed from the

population so that healthier animals can survive.

But the virus life cycle only hurts the organisms. Some

even destroy cells in order to reproduce.

And don't think you are the only one to get sick. Viruses

attack plants and even bacteria.

Man and Microbes

Scientists all over the world are experimenting with viruses, bacteria, and fungi for hundreds of reasons. Why mess around with these little creatures? They are the simplest of all organisms. They can also be the most deadly. That is reason enough to study them.

Microbes to make medicine

Scientists are working with microbes and the compounds they create to make new medicines to save our lives.

You might be vaccinated for pox or the flu. Scientists have studied those viruses to see how they act. Then they came up with

a way to teach your immune system to do battle. If you get sick at all, you will be able to fight off the infection.

Labs are also developing drugs that help you fight infections after you get the disease. We already spoke about antibiotics. Labs are creating new and stronger antibiotics every day.

Man and Microbes

Microbes in War

Although nobody likes to talk about it, humans have a

history of using disease and compounds created by

microbes in warfare.

Labs were built to create chemical compounds that

would kill people.

They also isolate diseases (viruses) that could be

released to infect entire populations of people.

Most of the world has chosen not to develop diseases

for use in war. They realized how dangerous and

uncontrollable these diseases are. Once they are out,

they might not be able to be stopped.

Man and Microbes

Cleaning the Environment

Scientists are also working with microbes to help the environment.

In reality, the environment did not need help; we're just trying to lower the

negative impact we have on the environment.

Good examples are the bacteria that have developed to break down oil in

the water. If a tanker leaked and oil began to get into the water, these

bacteria could be released to break down the oil. The resulting compounds

would not hurt the environment.

Scientists are also working with bacteria and fungi to help breakdown

garbage.

THE END

microbes

Science

organized nucleus

host cell

prokaryotic cell

classic cell

organized dna

normal cell machinery

eukaryoteseukaryotic

virusare viruses alive