Bacteria and Viruses

Bacteria and VirusesBrought 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