Download microbiology

The Good, the
Bad, and the Ugly
Bacteria and Viruses
And their Treatments
How is this different from our cells?
Microbiology
 The
study of single cell
organisms too small to see
with the unaided eye.
 Includes BACTERIA,
Archaea, Fungi, Protists, and
VIRUSES.
How Big are Bacteria compared to a
cell in your body?

A BACTERIUM is the size of a
PITCHER’S MOUND,

And, ONE CELL from your BODY
is the size of the BALLPARK!!!
BACTERIA

1. Bacteria are
independent
organisms able to
grow & reproduce
as single cells

2. Multiple
shapes: rod,
sphere, or spiral
BACTERIA, cont.
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They can be found at extreme temperatures (boiling
to freezing).
They “eat” everything from sugar to chemicals.
Classified as PROKARYOTES because they do
NOT have a nucleus.
DNA is the genetic material
Bacteria Structure and Parts


They are prokaryotes (means NO nucleus)
Characteristics of Bacteria
1. NO nucleus & NO membrane bound organelles
2. Have cell membrane
3. DNA in chromosome(s)
4. Have ribosomes but NOT the same as in our cells
5. Have a CELL WALL! (but DIFFERENT from
the
one in plants)
6. For some bacteria, capsule provides protection
How is this different from our cells?
What is the main way bacteria are
grouped?
By the way they stain:
One group is Gram Positive (+)
Second group is Gram Negative (-)
How do we treat (kill) bad bacteria?
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ANTIBIOTICS ANTIBIOTICS
ANTIBIOTICS
ANTIBIOTICS!!
The first antibiotic was discovered by
Alexander Fleming in 1928. He noticed a
mold (penicillium) inhibited growth of bacteria
he was studying.
He isolated the chemical from the mold and
named it Penicillin.
Diseases caused by Bacteria:
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Lyme Disease (Borellia)
Necrotizing Fasciitis (“Flesh eating”
bacteria; Streptococcus pyogenes)
Strep Throat (Streptococcus)
Food poisoning (Salmonella sp.,
Staphylococcus aureus)
Meningitis (Neisseria)
How do bacteria reproduce?
Primarily by Binary fission!
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The chromosome (DNA) is copied
The cell & cell wall divide in the middle to form 2
identical ‘daughter’ cells.
Under optimal conditions, bacteria divide every 20
– 30 minutes.
Bacteria occasionally use a form of sexual
reproduction called conjugation

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DNA is exchanged between cells through sex
pilus
This increases the genetic diversity of bacteria to
improve survival
If antibiotics are so effective at killing
living bacterial cells, why don’t they
hurt our cells?

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Remember the organization of bacteria- are
their cells the same as ours? NO
Cell wall (very different from plant cell wall)
Different type of ribosomes for making
proteins (different translation equipment)
Many enzymes different from the ones found
in our cells
Antibiotics are SPECIFIC for the bacteria
they can killA different type of antibiotic is
prescribed for a respiratory infection and
an urinary tract infection (UTI) because
they are caused by DIFFERENT types of
bacteria.
Problems with antibiotics:

The main difficulties with antibiotics are;
 1. Allergies
 2. Killing off the “good” bacteria in our
bodies
GOOD BACTERIA: Bacteria
aren’t all bad!
Some bacteria turns MILK into
YOGURT (Lactobacillus acidophilus)
and CHEESE.
2. Some bacteria help us digest our
FOOD and produce Vitamin K
(Escherichia coli).
3. Clean wastes from sewage water at
water treatment plants (Pseudomonas
putida).
1.
Good Bacteria, cont.
4. A natural pest killer in gardens and
on crops (Bacillus thuringiensis).
5. Clean up chemicals at hazardous
waste dumps and landfills
(Methanotrophs).
6. Make medicines, like ANTIBIOTICS
or using biotechnology, Human
Insulin.
VIRUSES- tiny parasites depending
entirely on a host to survive

Composed of:
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1. Genetic material
(DNA or RNA)
2. Protein coat (capsid)
enclosing the DNA/RNA
3. In some, a lipid
envelope surrounds the
protein
VIRUSES, cont.
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Straddle between living and not living.
Inert (not active) when outside of cells.
Thousands of different viruses in a variety of
shapes.
Viruses, cont.

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Viruses only “live”
when inside a
eukaryotic cell (one of
ours!).
They use that cell as
their own factory to
make millions of new
viruses.
VIRAL DISEASES
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AIDS (Human Immunodeficiency Virus)
Flu (Influenza virus)
Chicken Pox
“Kissing Disease” (Mononucleosis; EBV)
Hepatitis (Hepatitis A, B, C, etc)
Colds
Measles
Q. How do we treat viruses?

A. With an antiviral.
1. This is a drug that will stop a virus from
replicating in our cells.
2. There are VERY few antivirals.
3. Antivirals are more toxic to our normal cells.

If antivirals aren’t the answer, how do we
protect ourselves from viral infections?
With Vaccines!!

1. What is it?

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Part of a bacteria OR virus (or a
weakened version of the organism) is
injected into a person. To be most
protective, a person is injected multiple
times months apart.
2. How does it work?

The vaccine does NOT give the person
the disease, BUT the immune system of
the person “SEES” the bacteria or virus
as an invader and REACTS to it by
preparing the weapons to fight it off.
Vaccination, cont

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Normally, it takes our immune system several
days to a week to “see” a foreign invader
(bacteria or virus) and mount a response
against it. (that’s why we feel sick!)
If you’ve been vaccinated, your body will
immediately “see” the bacteria or virus as an
invader and it already has the weapons to
immediately fight it off. You may NEVER
know you were infected.
How does the immune response
react?

One way the immune
response reacts is to
make ANTIBODIES
specific for that virus
or bacteria. IF you
are infected with that
virus or bacteria, the
antibodies in your
body will bind to the
specific virus or
bacteria to stop it
from infecting you.
How else do we prevent disease?
Excellent Sanitation Practices!
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Wash hands frequently!
Wash foods before eating
Careful food storage and preparation
Treatment of human excrement to kill
infectious agents
Clean water supplies for drinking
Clean cuts & wounds immediately after
getting them
Sterile practices in hospitals
HOW DO BACTERIA AND VIRUSES
DIFFER?
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SIZE: Bacteria are much larger.
STRUCTURE: Bacteria are much more
complex. Bacteria have a thick cell wall, a
chromosome, & ribosomes. A virus has a
small amount of nucleic acid and a protein
coat.
Antibiotics kill bacteria. Antibiotics do NOT
kill viruses. Only antivirals kill viruses.
HOW DO BACTERIA AND VIRUSES
DIFFER?
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Bacteria are free living- they contain ALL they
need to grow and reproduce themselves.
One cell divides into 2 ‘daughter’ cells.
Viruses are moochers- they only contain
limited genetic information. They invade a
cell and hijack its machinery to turn it into a
VIRUS FACTORY!