Pathogens:

Agents of Disease

Microbiology is the study of microorganisms.

Microorganisms are mostly unicellular (single-

celled) organisms too small to be seen

without a microscope. They include viruses,

bacteria, protozoa, and some fungi.

Microorganisms that cause disease or harm to

living things are called pathogens.

Microbiology

All cells contain genetic material known as

DNA or RNA.

There are two major types of cells:

Prokaryotes--Prokaryotic cells have no nucleus—

their genetic material is found as coiled strands in

the cytoplasm.

Eukaryotes--Eukaryotic cells have a distinct,

membrane-bound nucleus that contains the DNA

and RNA of the organism.

Cells

Characteristics

Oldest forms of life on Earth

Unicellular (single-celled) organisms

Prokaryotic

Contain DNA (genetic material)

Can live in a variety of places (with or without

oxygen; extreme temperatures)

Bacteria

Shape

Most have rigid cell walls that give it shape

Bacteria come in one of 3 shapes rod (bacilli),

sphere (cocci), or spiral (spirilla)

Bacteria

Reproduction

Bacteria can reproduce quickly by a process

called binary fission where one bacterium

divides into two bacteria (in essence cloning

itself). *There are other forms of reproduction

Will grow in colonies (a group of many that

can be seen by the naked eye)

Their reproduction is slowed down by cold

(refrigeration or freezing), heat

(pasteurization and sterilization), and salting.

Bacteria

http://www.youtube.com/watch?v=gEwzDydci

Wc&feature=player_detailpage

Write two questions about the clip you just

saw about bacteria reproduction.

1)?

2)?

Reproduction of Bacteria Video

Role in the World Good for the Environment

Nitrogen cycle

Decomposition

Good for the People

In food…cheese, yogurt, buttermilk, sour cream, etc.

Medicines…fighting other bacteria, antibiotics, insulin

Genetic Engineering…change genes of bacteria to make insecticides, cleansers, adhesives, etc

Bacteria

Role in the World continued…

Harmful Bacteria (pathogenic—disease causing)

Infectious bacterial diseases…tuberculosis, Lyme disease, MRSA, leprosy, strep, etc. *infectious

means it can be passed from one organism to another

Bacteria

Lyme disease MRSA

leprosy

Role in the World continued…

Pathogenic (infectious disease) continued…

Can be treated with antibiotics--medicines taken by an infected person to kill the bacteria in the body (penicillin, amoxicillin, tetracycline)

Some antibiotics have been overprescribed and by natural selection, bacteria have become resistant (can’t be killed) to certain medications. This is known as antibiotic resistance. Mutant bacteria survive antibiotic treatment and a resistant population survive.

Can be prevented with vaccinations—substances that stimulate the body to produce chemicals (antibodies) that destroy familiar invaders.

Bacteria

Characteristics

Viruses are not living

They are non-cellular

Cannot reproduce on their own

Do not use energy, need food or create waste

Contain DNA or RNA (genetic material) and protein coat

Viruses are significantly smaller than bacteria (5 billion virus particles can fit in a single drop of blood)

Viruses

Shapes

Four main shapes: crystals, spheres, cylinders, and

bacteriophages (one that infects bacterial cells

only)

Viruses mutate and change their shape all the time

though

Viruses

Viruses

Reproduction Can only reproduce inside a host cell which it often

destroys

Can add their genetic material to a host cell that stays inactive for a very long time

Role in the World

Good for the Environment

Population control…limiting factor

Good for People

Can be manipulated to create medicines and treat

some diseases (very new technology)

Viruses

Role in the World continued…

Harmful Viruses (Pathogenic)

Infectious viral diseases…HIV, Chicken Pox,

Hepatitis A, B, & C, Small Pox, Ebola, Rabies, Swine

Flu, Influenza, Common Cold, etc.

Viruses

Ebola

Small Pox

Role in the World continued…

Harmful Viruses (infectious diseases) continued…

Most viral infections cannot be cured with

medications…only symptoms can be treated

Viral diseases are amongst the most widespread

illnesses in humans

Anti-viral medications are used to control and

prevent the spread of some viral diseases, but they

do not destroy the virus (they only inhibit its

development)

Many can be prevented with vaccinations (like

bacterial infections)

Viruses

Write two questions about the clip you just

saw about viruses.

1)?

2)?

Spread of Viruses video

Protozoa

Characteristics

Unicellular (single-celled) eukaryotic organisms that

are usually able to move on their own

Most are found in moist environments

Although there are over 20,000 species, very few are

pathogenic

Reproduction

The majority reproduce by binary fission but there

are a few other methods as well.

Shapes

Extremely diverse…most diverse of any kingdom

Protozoa

Role in the World

Good for the Environment

Form the foundation for food chains

Play an important role in nutrient recycling

Harmful Protozoa (pathogenic)

Infectious disease transmitted by protozoa…Malaria,

Giardia, Toxoplasmosis

http://animal.discovery.com/tv-shows/monsters-inside-

me/videos/malaria-parasite.htm

Write two questions about the clip you saw

1) ?

2) ?

Characteristics

Eukaryotic

Most are multicellular (many-celled)

Do not produce their own food (heterotrophic)

Cannot move on their own

Fungi

Reproduction

Sexual reproduction—requires two individuals and

ensures genetic diversity

Asexual reproduction—one individual produces

genetically identical organisms

Spores are dormant reproductive cells; they are thick-

walled and highly resistant so they can survive

unfavorable conditions. When conditions become

suitable they give rise to new individuals and can be

used in either form of reproduction for fungi

(depending on species)

Fungi

Role in the World

Good for Environment

Important in nutrient cycles; decomposition

Food source

Good for People

Production of medicine

Production of foods (cheese, bread, beer, etc.)

Some can convert insecticides, herbicides, etc. into CO2,

H2O, and basic elements

Fungi

Role in the World continued…

Harmful Fungi

Responsible for food spoilage

Many humans are highly allergic

Fungal infections/diseases--ringworm, yeast infections,

Athlete’s foot, fungal meningitis

Fungi

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Fungi

A parasite is an organism that lives on or in the body

of another organism—the host.

Parasites have special adaptations or body parts that

allow them to feed off their host very efficiently—get

the most they can from them.

Examples of parasites are leeches, ticks, mosquitoes,

fleas and even mistletoe in plants.

All of the above have the ability to carry or transmit

disease or eventually cause disease in the organism

they have a parasitic relationship with.

Parasites/Helminths

Some parasites that play a large role in infectious

disease are called helminths

Helminths are parasitic worms that usually live in soil

and invade human or other animals

Includes tapeworms, roundworms, pinworms, and

Trichina spiralis (causes trichinosis from eating

undercooked pork)

Symptoms often mimic that of viral and bacterial

infections in early stages of infection but eventually

lead to more serious systemic problems because

these worms can hide in intestines, bloodstream or

any tissue of the body.

Parasites/Helminths

http://health.discovery.com/videos/monsters-

inside-me-elephantitis.html

Write two questions about the clip you just

saw about parasitic worms.

1)?

2)?

Helminth Infection video