Bacteria and Viruses

Brought to you by Mr. Brinkman

Taxonomy

• The branch of biology dealing with the classification of life.

• 1700s 2 kingdoms: plant and animal• 1800s 3 kingdoms: plant, animal, and

protista• 1950-1990s 5 kingdoms: plant, animal,

protista, fungi, monera• Present: 6 kingdoms: eubacteria,

archaebacteria, protista, animal, plant, fungi

Prokaryotes

• Traditionally all prokaryotes

• Presently, the prokaryotes are divided into two kingdoms.– Archaecbacteria– Eubacteria

Eubacteria

• Larger of the two kingdoms• Live almost everywhere• Vital for life functions and

industry• Both helpful and harmful

Archaebacteria

• Comes from the Greek word archaio which means “ancient”

• Believed by many to be the earliest organisms to inhabit the earth

• All live in harsh environments• 3 separate phyla:

1. Methane-producing bacteria (methanogens)

• Intestinal tracts of animals

• Bottoms of swamps

• Used for sewage treatment

2. Salt-loving bacteria (Halophiles)

• Thrive in high salinity waters where no other life can exist.

• Great Salt Lake

• Dead Sea

3. Hot-acidic loving (thermoacidophiles)

• Thrive at temperatures as great as 180ºF and pHs as low as 2.

• Natural springs.• Yellowstone

National Park

Facts about bacteria:

• Found everywhere• Very small. Much smaller than any

cell in our body.• No membrane-bound structures or

nucleus. (prokaryotes)• Usually surrounded by a cell wall

and a capsule for additional protection.

General structure:

Classification according to shape.

1. Coccus (spherical)

Can be single cells

Pairs

Chains

2. Bacillus (rod)• Single cells• Pairs• Chains

• example– anthrax

3. Spirillum(spiral)

Only exist as single cells

Example:cholera, syphillis

Shapes:

Metabolic Needs

• Aerobic• The most common type• Cannot live without oxygen

• Anaerobic• Cannot live in the presence of

oxygen• Gets energy through fermentation

(CO2)

Heterotrophic bacteria

• Decomposer• Feed off the remains of dead

plants and animals. Seldom cause disease

• Parasites• Live on or in other living

organisms. Often cause disease

Autotrophic bacteria

• Photoautotroph• Use sunlight to convert carbon

dioxide into energy• Ex. cyanobacteria

• Chemoautotroph• Use inorganic chemical compounds

to convert carbon dioxide into energy.

Genetic material

• Nucleoid= a single circular chromosome containing the DNA and RNA.

• Endospore = tough protective coat that covers and protects the nuclear material.

Reproduction

• All reproduce asexually

• Usually through binary fission

• Under certain conditions, bacteria can reproduce very quickly–A small colony can double in 20

minutes.

Binary fission

• The most common type of asexual reproduction.

• A single cell splits to form two daughter cells

Exchange of DNA

Conjugation = genes move from one cell to another

Endospores

• A thick covering around the DNA that allows the bacterium to remain dormant for long periods of time. If necessary, many years.

Helpful bacteria

• Decompose food wastes• Produce vitamins• Produce antibodies• Genetic engineering• Decomposition of dead plants and

animals• Industry & agriculture

Plant roots

• Found on the roots of plants.

• Can be helpful in ‘fixing’ nitrogen for plant use.

• Rhizobium nodules on roots of soybeans

VIRUSES

• Are they living or non-living?• Contain genetic material• Lack organelles

Cannot reproduce unless inside a host cell.

• The word virus comes from the Greek word for POISON

• Cause many diseases.

How big is a virus?

• Much smaller than bacterial cells.

• Scientists have only recently, last 60 years, learned anything about viruses

• Classified according to the types of cells they attack.

Virus structure:

• A center core of DNA or RNA surrounded by a protein coat called a capsid.

2 main types of viral reproduction:

• LYTIC CYCLE1. Injects its nucleic acid (DNA or

RNA) into the cell to take over cellular activities.

• LYSOGENIC CYCLE1. Coexists with the cell without

destroying the host cell

Lytic cycle

Lysogenic cycle

RETRO-VIRUS

• Direct the production of proteins by the host cell.

• RETROVIRUS = A special type of virus that can make DNA which will produce new RNA, which, in turn, makes proteins that produce new viruses.

• Ex. AIDS VIRUS

Diseases caused by microorganisms:

• Pathogens: disease-causing agents

• BACTERIAL DISEASE:1) Damage cells and tissues

directly2) Release toxins to interfere

with normal cellular activity

Common bacterial diseases:

• LymeS disease• Tetanus• Strep throat• Tuberculosis• E. coli poisoning

Controlling bacterial disease.

• ANTIBIOTICS• 1928. Discovery

of penicillin by Sir Alexander Flemming

• Came from a mold.

Common methods of bacterial infection.

• Food & water (E. coli)

• Coughing & sneezing

• Sexually transmitted.

• Carried by insects

Food disease prevention

• Keep hands, and cooking utensils clean

• Canning and preservation techniques with food.

• Pasteurization• Freezing

How do we prevent viral diseases?

• Cannot be treated with ordinary antibiotics

• Vaccinations. The word comes from the vacca Latin for “cow”.

• A vaccine is a weakened form of a virus that is used to stimulate the immune system to produce antiviral substances.

Edward Jenner (1749-1823)

• British physician

• Developed the first vaccine in 1798 for the viral disease smallpox.

• Considered the “Father of Immunology”

Common viral diseases:

• AIDS• Measles• Chickenpox• Smallpox• Influenza• The common cold• West Nile• Polio

SMALL POX

• Viral disease that is believed to have originated in Egypt at least 2000 years ago.

• Characterized by pox lesions and boils.

• Spread to the Americas by Spanish conquistadors.

• Jenner’s vaccine was developed after observing a bovine disease: “cowpox”

Eradication of smallpox:Or is it?• In 1967 the World Health

Organization launched a global effort to eradicate smallpox.

• 1978 : Last known case of smallpox.

• 1980 : W.H.O. declares the world free of smallpox.

• Is there any smallpox virus left?

Viroids and Prions

• Viroid• Small disease causing

particle.• Affect plants

• Prion• Small disease causing particle.• Affects animals.• example:

MAD COW DISEASE