Download Bacteria

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Bacteria
Directions: Read and highlight answering each question as you go.
Do you ever wonder what the first Earth life form looked like? Or how about when that first life form showed up? In
order to answer these questions requires a look back many years ago, matter of fact billions of years ago.
Some of the oldest cells on Earth are single-cell organisms called bacteria (short for Eubacteria). Yes, those same
prokaryotic cells that we’ve been looking for in yogurt. Bacteria, the most common cell on
earth, happen to be the oldest cells on earth with fossils records showing up 3.5 billion years
ago (Earth is only 4.5 billion years).
1. What are prokaryotes? _______________________________________________
2. What is the most common prokaryotic cell (and the smallest cell)? ___________________
Fossil records indicate that mounds of bacteria once covered a very young Earth. Think of how much trouble we’ve been
having searching for bacteria in yogurt. Billions of years ago bacteria mounded up under water much like the bushes in
your front yard.
Bacteria, if you’ve forgotten, come in 2 different forms, eubacteria and archeabacteria. The archeabacteria are the
weirdoes we’ve talked about loving heat, salt, and even methane-making lives. Eubacteria are the most typical forms
that we interact with every day.
Growth and Development
Most bacteria fall into 3 shape categories: spheres, rods, and
spirals. There are several others, but these 3 are the most
common. The picture to the right shows the different shapes. As
for the growth part, bacteria do not grow like humans. There is no “baby” stage to “adult” stage. Bacteria are a one-size
fits all kind of like you being born as a full grown adult (we probably wouldn’t need car seats ).
3. What are the 3 shapes of bacteria? _________________________________________________________
Reproduction
Bacteria can multiply quickly - in fact, one cell can double within 20 to 30 minutes. Most cells in
your body take upwards of 24 hours to divide (some, like your liver, even longer). So the video
we saw in class was definitely sped up since they can’t reproduce in seconds.
When bacteria reproduce, they use a process called binary fission. With binary fission, the cell
copies its 1 and only chromosome and then pinches in half (remember humans have 46
chromosomes). Although the cell may look like its growing, it’s actually not. The size of a
bacteria cell pretty much remains the same throughout its life.
If binary fission sounds similar to mitosis, you are kind of right. Both processes deal with
copying chromosomes, moving chromosomes to each side of the cell (Anaphase), and pinching the cell into two daughter
cells (cytokinesis). Because cells that undergo binary fission do not have a nucleus (the chromosomes just float around in
the cytoplasm), the extra stages of dissolving the nucleus (metaphase) and reforming a nucleus (telophase) aren’t
needed. This makes binary fission a much simpler and faster way to reproduce.
4. Name two ways mitosis and binary fission are similar.
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5. Name two ways mitosis and binary fission are different.
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DelliGatti 2013 – Bacteria Reading.docx
Obtain and Use energy
Depending on the bacteria type, they obtain energy in 3 different ways.
Heterotrophs – These are like scavengers obtaining energy from eating other sources. Humans fall in this category.
Bacteria on your teeth (plaque) are heterotrophs scavenging your tooth enamel causing decay and cavities.
Photoautotrophs – These make their own food obtaining energy from sunlight. They are very similar to plants.
Chemoautotrophs – These share their environment with another organism and obtain energy from a chemical
reaction usually after another organism does something to it. The bacteria in your stomach are eating what you just
ate in your last meal. Thankfully, they help us digest our food.
6. Why are humans consider to be heterotrophs and not photoautotrophs? _________________________________
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Adaptation
In order to survive, bacteria must be able to adapt. This is both good and bad for humans. When bacteria adapt, we say
their chromosomes have mutated or changed. Bacteria’s ability to adapt or mutate keeps us alive. In a world without
bacteria, humans couldn’t survive since we depend on them to help us digest our food and even help return all of the
atoms we use (nitrogen, oxygen, and carbon) back to the environment. They are kind of like nature’s little recyclers.
Because they are constantly hit with different chemicals that humans create, they have to change and change quickly to
stay alive.
Mutations don’t just happen to the good bacteria though. They also happen to the dangerous bacteria. If you’ve ever
had strep throat, you are thankful that we have medicine that kills off harmful forms of bacteria. The problem is bacteria
adapts to the medicine making the medicine less effective. Unfortunately, because of all of the anti-bacterial stuff we
use in our everyday lives such as soap and medicine, some bacteria are becoming resistant to these medicines and able to
live even if we take medicine.
7. Are all bacteria adaptations bad? Why or why not? ____________________________________________________
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Pathogens
When you think of bacteria, you probably create images of all the bad things they can do to you. Most of our hand soap
comes with anti-bacterial ingredients that help kill off harmful bacteria. Keep in mind that most bacteria are not bad.
The human body carries more than 100 trillion bacteria (about 1 bacteria cell for each human cell) - up to five pounds of
the tiny single-celled organisms. The mouth alone has several hundred species of bacteria. Each tooth is its own
ecosystem.
There are a few though that makes us sick, and these are called pathogens. They make us sick because like all living
things they need food to survive and reproduce. When bacteria eat, they produce poisons (toxins) that result in fever,
headache, vomiting, diarrhea, and destroy body tissue.
A bacterial pathogen that might sound familiar is E. coli. E. coli is found in
ground beef and contaminated fruits and vegetables. It takes less than 10 E.
coli bacteria to make you sick. Although it takes millions of cells to make us
sick, another pathogen is Salmonella which is found in raw meats, poultry,
eggs, sprouts, fruits and vegetables. Unfortunately for all of those good
bacteria living in your body, these two guys get all of the attention.
8. Are you afraid of bacteria? Why or why not? _________________________________________________________
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