 Do bacteria have a nucleus??
 Do bacteria have different shapes?
 Do bacteria have a cell membrane?
A cell wall?
 How fast and how do bacteria divide?
 Are bacteria prokaryotes or eukaryotes?
 WHAT are viruses- are they cells?
Are they alive? What are they made of?

 Bacteria are both GOOD for us and our environment and BAD for our health.
 Can anyone name a GOOD purpose for bacteria?
 Can anyone name a Disease caused by bacteria?

 The study of single cell organisms too small to see with the unaided eye.
 Includes BACTERIA,
Archaea, Fungi, Protists, and VIRUSES.

 Characteristics of Monerans (& bacteria!):
 No membrane bound nucleus
 Have cell membrane, but NOT membrane bound organelles (like mitochondria)
 Most are unicellular & very small
 Ribosomes are different from ones in our cells
 Bacteria & most monerans have a cell wall!

How Big are Bacteria?
 A BACTERIUM is the size of a
PITCHER’S MOUND,
 And, ONE CELL from your BODY is the size of the BALLPARK!!!




BACTERIA, cont.


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

 Way to see almost transparent, very small bacterial cells under the microscope
 Used in laboratories as a first screening mechanism to characterize bacterial infections in people.
 Technique that differentiate bacteria into
1 of 2 groups: gram positive and gram negative .

 Purple or red stain goes with differences in the structure of the bacterial cell wall
 Gram-positive - cell wall traps the dye; stain purple
 Gram-negative - cell wall cannot trap the purple dye; counter-stained red

Photomicrograph of gram+ and gram- bacteria. A) E. coli
(common gram- rod found in colon). B) Staphylococcus epidermidis (gram + cocci found on skin C) Bacillus cereus (gram + rod in soil).

Primarily by Binary fissionSimple & FAST!
 The DNA is copied
 The cell & cell wall divide in the middle to form 2 identical ‘daughter’ cells.
Under optimal conditions, bacteria divide every 20 to 30 minutes.
 Occasionally, bacteria have sex (called conjugation) to increase genetic diversity and improve survival
 Process involves exchange of DNA between cells

Diseases caused by Bacteria:
 Lyme Disease ( Borellia )

Necrotizing Fasciitis (“Flesh eating” bacteria; Streptococcus pyogenes )
 Strep Throat (Streptococcus)
 Food poisoning (Salmonella sp.,
Staphylococcus aureus)
 Meningitis (Neisseria)

How do we treat (kill) bad bacteria?
 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.

Q. If antibiotics are so effective at killing living bacterial cells, why don’t they hurt our cells?
A. Bacteria do not have the same organization as our cells and
Antibiotics are SPECIFIC for the bacteria they can kill- they are only effective at killing certain types of bacteria

 The main difficulties with antibiotics are:
 1. Allergies
 2. Killing off the “good” bacteria in our bodies

 Bacteria turns MILK into YOGURT
(Lactobacillus acidophilus) and
CHEESE.
 Bacteria help us digest our FOOD and produce Vitamin K (Escherichia coli).
 Clean wastes from sewage water at water treatment plants (Pseudomonas putida).

 A natural pest killer in gardens and on crops (Bacillus thuringiensis).
 Clean up chemicals at hazardous waste dumps and landfills
(Methanotrophs).
 Make medicines, like ANTIBIOTICS or using biotechnology, Human
Insulin.

VIRUSES
 Tiny parasites composed of:
 Genetic material
(DNA or RNA)
 Protein
 In Some, a
Membranous
Envelope




Straddle between living and not living.
Inert when outside of cells.
Thousands of different viruses in a variety of shapes.

 Viruses exist to reproduce!
 If contacts a cell it CAN infect, the virus takes over the cell and makes lots of copies of itself!
 Viruses infect every form of life (plants, animals, fungi, bacteria)


Viruses do not “live”
UNLESS they are inside a eukaryotic cell (one of ours!).
Then, they use that cell as their own factory to make millions of new viruses.

 AIDS (Human Immunodeficiency Virus)
 Flu (Influenza virus)
 Chicken Pox (Varicella-Zoster Virus)

“Kissing Disease” or Mononucleosis (EBV)
 Hepatitis (Hepatitis A, B, C, etc)
 Colds (rhinovirus, coronavirus)
 Measles (rhabdovirus)

 A.
With an antiviral.
 1. This is a drug that will stop a virus from reproducing 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?

HOW DO BACTERIA AND
VIRUSES DIFFER?
 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 & they do NOT kill bacteria.

HOW DO BACTERIA AND
VIRUSES DIFFER, cont…
 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!



 1. What are they?
 Part of a bacteria OR virus (or a weakened version of the organism) that is injected into a person.
 To be most protective, a person is usually injected multiple times months apart.
 Vaccines must be given weeks or months BEFORE you are infected

 2. How do they 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.

 When we get sick, 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 you feel sick!

If you’ve been vaccinated, your body will immediately “see” the bacteria or virus as an invader and attack it.
 It 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 specific
ANTIBODIES against a virus or bacteria.
 Later, if you are infected with that microorganism, the antibodies in your body will bind to it and stop it from infecting you.

 Antibiotics kill ONLY bacteria.
 Vaccines can result in protection against a specific bacteria OR virus.

 Antibiotics start to kill the bacteria immediately after you take them
 Vaccines require several weeks (and possibly several shots) before they protect against the disease

How else do we prevent disease?
Excellent Sanitation Practices!
 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

Challenger Questions:
1.
2.
3.
4.
Name 2 differences between Bacteria and our cells
Name 1 difference between Bacteria and Viruses.
Do antibiotics work when you have a cold (VIRUS infection)?
Name a disease caused by a bacteria.

5.
6.
7.
8.
Name a disease caused by a virus.
Name 2 good purposes for
Bacteria.
What is one way the body fights off bacteria and viruses?
How can we PREVENT infection with bacteria OR viruses?

TO DO: What do antibiotics & vaccines have in common?
Both fight infectious agents
-antibiotics ONLY fight bacteria
- vaccines can protect against bacteria OR viruses
Antivirals= very few available; ONLY fight specific viruses

 Why do we need to be vaccinated EVERY year against Influenza?

 Working at your table, you will build an influenza virus using the dirctions & the package of supplies. Do NOT throw any of the parts away!!!
 Read the directions
 Build the virus, then answer the questions on the sheet.

 Many different strains of Flu!
 DIFFERENT types infect people each year.
 Influenza is one of the MOST changeable viruses! It makes mistakes when it copies the RNA genome.
 These result in changes (mutations) in the HA & NA protein.


Our immune response “sees” & makes antibodies to HA & NA (it’s on the outside of the virus!). These antibodies bind to
HA & NA to stop the virus from infecting our cells.
 IF HA or NA have changed, antibodies may not bind well enough to stop the virus from infecting our cells

What do we call it when the HA &
NA change from year to year?
 ANTIGENIC DRIFT: Small changes changes in HA or NA over time.
 Parts of the HA or NA are similar, but enough of it is different that antibodies to “old” version no longer protect from infection

 Antigenic Shift:
 An abrupt, major change in influenza viruses infecting humans
 People have little or no immunity to the
“new” virus- their immune response has never “seen” it
 Happens ONLY occasionally
 Like when an animal influenza virus (like
SWINE FLU or avian influenza) infects
PEOPLE!