Download Bacteria Section 18.2 Summary – pages 484-495

What are the two kingdoms that
contain bacteria?
Archaebacteria
Eubacteria
“The extremists”
“Found everywhere”
Bacteria
• A bacterial cell is a very small prokaryotic cell.
• Although tiny, a bacterial cell possesses
all the characteristics of life.
Ribosomes (makes proteins)
Plasma
Membrane
Inner-most
layer
Flagella (helps it move)
not all bacteria have this
Cell Wall
Middle layer
Capsule
(outer-most layer)
not all bacteria have this
Bacterium Structure
• A bacterial cell remains intact (together) as long as
its cell wall is intact.
If the cell wall is
damaged, water will
enter the cell by
osmosis, causing the
cell to burst.
• Scientists used a bacteria’s need for an intact cell
wall to develop a weapon against bacteria that cause
disease.
Antibiotics
• In 1928, Sir Alexander Fleming accidentally
discovered penicillin, the first antibiotic—a substance
that destroys bacteria.
He had been looking at bacteria under the microscope. He left the dirty slides in the
sink, and a mold began to grow on them. He later noticed that the mold was killing the
bacteria.
Antibiotics
• Later, biologists discovered that penicillin can
destroy the cell walls of bacteria.
• When bacteria are put in penicillin, holes develop in
their cell walls, water enters their cells, and they
rupture and die.
Antibiotics
Unfortunately, antibiotics kill both good and bad bacteria.
You have good bacteria that live in your intestine that help you
digest food.
Eating foods that contain these good bacteria while
you are taking an antibiotic can help keep and/or
replenish your body’s supply…yes, the above foods
contain LIVING good bacteria.
Identifying Bacteria
• One trait that helps classify bacteria is how they
react to Gram stain.
• Gram staining is a technique that stains bacteria a
certain color, which lets doctors/scientists know what
kind of cell wall the bacteria possess.
This helps doctors decide which antibiotics to use.
GRAM POSITIVE
Stain purple- thicker cell wall
GRAM NEGATIVE
Stain pink- thinner cell wall
Identifying Bacteria
Bacterial cells often grow in characteristic patterns
that provide another way of categorizing them.
• Diplo–is a prefix that refers to bacteria
that pair up.
• The prefix Staphylo–describes an
arrangement of cells that
resemble
grapes.
• Strepto–is a prefix that refers to an
arrangement of chains of cells.
Bacterium Shapes
• The three most common shapes are:
Spheres, called “coccus”
Rods, called “bacillus”
Spirals, called “spirillum”
1. The above bacteria stained a dark purple. What does that tell you about this
bacteria?
Strong/Thick cell wall
2. The above bacteria grows in chains and the cells are round. What is the
name of this bacteria?
Strepto-coccus
Bacteria Reproduction
• Bacteria reproduce asexually by a process known as
binary fission.
•Basically, it is mitosis for a
bacterial cell. The end result is
two identical bacterias.
Bacteria Reproduction
• Under ideal conditions, some bacteria can
reproduce every 20 minutes, producing
enormous numbers of bacteria quickly.
Bacteria Reproduction
• Some bacteria communicate in a process called
conjugation.
• During conjugation, one bacterium transfers all or part
of its chromosome to another bacteria through or on a
bridge-like structure called a pilus that connects the two
cells.
Survival Mechanism
• Some bacteria, when faced with unfavorable
environmental conditions, produce a tiny
“escape pod” called an endospore.
• An endospore is a tiny
structure that contains a
bacterium’s DNA and a small
amount of its cytoplasm,
encased by a tough outer
covering that resists drying out,
temperature extremes, and harsh
chemicals.
Survival Mechanism
• As an endospore, the bacterium rests
and does not reproduce.
• Endospores can survive a temperature of
100˚C, which is the boiling point of water.
GOOD BACTERIA
IN YOUR BODY
•
Trillions of “good” bacteria live in your body.
Most are found in your intestinal tract.
Write what
is in blue
and
underlined
Lactobacillus
acidophilus
• It protects intestines, helps aid in digestion,
helps build immunity to food allergies, and lowers
blood cholesterol.
GOOD BACTERIA
Makes Some Foods and Medicines
• Some foods that you eat—mellow Swiss
cheese, crispy pickles, vinegar, sauerkraut,
and tangy yogurt—would not exist without
bacteria.
GOOD BACTERIA
Makes Some Foods and Medicines
• In addition to food, some bacteria produce
important medicines.
GOOD BACTERIA
Help with Farming
• Remember, bacteria help convert
nitrogen in the soil so that plant’s can use it
and grow better!
GOOD BACTERIA
Recycle Nutrients
Life could not exist if bacteria did not break
down decomposing organisms and return the
nutrients to the environment.
Form groups of two or three
We will use an agar dish to grow bacteria.
Agar is a jelly-like polysaccharide where certain
cells can grow. It’s a “food” for the bacteria.