PROKARYOTES, BACTERIA, &

VIRUSES

Eukaryotes v. Prokaryotes

Prokaryote Characteristics

Single cell

No true nucleus

Few organelles

Archaebacteria – extreme environments

Eubacteria –

“normal” bacteria

Eukaryotes v. Prokaryotes

Eukaryotes

Larger (up to 100 times!)

More complex

Nucleus

Have chromosomes

Membrane bound organelles

Ex: Animals, plants, protists

Prokaryotes

Smaller

Not as complex

No nucleus

Have single strand of DNA and plasmid

No membrane bound organelles

Ex: Bacteria

CHARACTERISTICS of Bacteria

Prokaryotes – meaning “before a nucleus”

Divided into 2 domains

Bacteria

Archaea

Archaebacteria

Dominate in extreme environments

3 types

Thermoacidophiles

Hot, acidic areas (ex: sulfur hot springs, thermal vents on ocean floor)

Halophiles

Very salty areas, usually aerobic (ex: Great Salt Lake, Dead Sea)

Methanogens

No oxygen (anaerobic) areas, take in oxygen and give off methane (ex: sewege treatment, swamps, bogs)

EUBACTERIA

Most studied organism

Found everywhere, except extreme environments

Very strong cell walls (has peptidoglycan)

Some have a second cell wall

PROKARYOTE STRUCTURE

Genetic material (DNA)

Flagella

Pili

Ribosomes

Capsule

FUNCTION of the Structure

DNA – found in nucleoid (Remember: prokaryotes DO NOT have a nucleus)

Capsule – polysaccharide layer (aka sugar), prevents dry-out, helps attach cell to surfaces, prevents WBC’s from “eating” them

Pili – made of protein, hair-like, also helps attachment, can act as a bridge between cells

Flagella – helps with locomotion (aka movement)

Ribosomes – make proteins for the chromosomes

HOW DO WE IDENTIFY BACTERIA??

Shape

Cell Walls

Movement

SHAPE of Bacteria

Cocci – spherical, round shape

Bacilli – rod-shaped

Spirilli – spiral - shaped

Strepto – long chains

Staphylo – clumps

Diplo - pairs

Let’s Practice… DRAW THE FOLLOWING BACTERIA:

1.Staphylococcus

2.Streptococcus

Now, write the types from the pictures below…

1. 2. 3.

CELL WALLS

Have peptiodglycan

(made of dissacharides & peptide fragments)

Why is it important for

bacteria to have strong cell walls?

MOVEMENT

Some are stationary

Some use flagella to move

Bacteria REPRODUCTION Sexual Reproduction – called

Conjugation

Cells attach and exchange info

Asexual Reproduction – called Binary Fission

Chromosome replicates, then separates

Can happen every 20 min.

Becomes 1 BIL. IN 10 HRS!

METABOLISM of Bacteria Photoautotrophs

Do photosynthesis need light to live

Called cyanobacteria

Release Oxygen into the environment

Chemoautotrophs

Do not require light

Break down & release inorganic compounds (Nitrogen or Sulfur) and keeps them cycling

Aerobes

Require oxygen to grow

Anaerobes

Do not require oxygen, use fermentation instead

SURVIVAL

Endospores

Dormant cell

Resistant to harsh conditions

Forms around chromosome and small part of cytoplasm

Ex: anthrax, botulism, tetanus

Mutations

Quick reproduction, so genetic mutations help survival

Leads to “antibiotic - resistant bacteria”

ECOLOGY of Bacteria

Bacteria are decomposers and return vital nutrients to the soil/environment

NORMAL FLORA – harmless bacteria in & out of your body

E.Coli in your intestines makes Vitamin K (for blood-clotting)

DIFFERENT from the food poisoning kind

FOOD & MEDICINE

Cheese, yogurt, pickles – made w/the help of bacteria

Used to make CHOCOLATE (bacteria breaks down the cocoa bean covering)

MEDICINE – some anti-biotics (ex: tetracycline) originally made by bacteria

DISEASE –CAUSING Bacteria

Only a small % of bacteria ACTUALLY cause disease

They harm in two ways…

Bacteria multiply quickly @ the infection site

Bacteria secrete a toxin that can cause harm

(ex: Botulism – paralyzes nervous system cells)

DISEASE –CAUSING Bacteria

PATHOGENS – disease-causing bacteria

ANTIBIOTICS – block the growth & reproduction of bacteria (they break down the cell wall)

How to Control “BAD” Bacteria

STERILIZATION – heat or chemically treat bacteria to kill it

Disinfect – chemical solution kills bacteria

Refrigerate – bacteria grows slower in the cold

Heat/Boil – high temps kill bacteria

VIRUSES

Why are viruses NOT ALIVE???

No organelles to take in nutrients or energy

Cannot make proteins

Cannot reproduce on their own

VIRUS STRUCTURE

Viruses contain a nucleic acid & a protein coat

Two regions: head & tail

HEAD:

Capsid – protein coat

Nucleic acid core (DNA)

TAIL:

Tail:To attach to host

Tail fibers

VIRAL INFECTION

To infect, a virus must find a host cell

The virus attaches to a specific site

Most viruses cannot transfer between species

BASIC STEPS OF

VIRAL INFECTION

1.Attachment to the host cell

2.Release of the viral genes

3.Replication

4.Assembly of viral components

5.Release of viral particles for further infection

Lytic vs. Lysogenic Cycles

Lytic Cycle

The host cell immediately makes many copies of the viral DNA or RNA

Viral genes instruct host cell to make more viral capsids before the viruses leave the cell

Lysis of host cell (or bursting when virus exits)

Common diseases: common cold, influenza

Lysogenic Cycle

Viral DNA inserts (or integrates) into a host cell and becomes part of the nucleus

This virus can be dormant for a long time in the cell’s nucleus

Infected cell will have the viral genes permanently

Common diseases: AIDS, herpes

RETROVIRUSES

Viruses that have RNA instead of DNA for their genetic material

Contains the enzyme reverse transcriptase

Retroviruses have a protein capsid

Example: HIV

PRIONS

A protein that can cause an infection

Normally exist in cells, although their function is not well know

Normal prions = coil-shaped

When mutations occur they become accordian-shaped, which can then cause disease because of their shape

Disease caused by prions – Mad Cow Disease

Types of Viruses - Bacteriophage

Bacteriophage – a virus that infects bacteria

KNOW THIS STRUCTURE! (Capsid, tail, tail fibers, DNA (or genetic material))

PATHOGENIC VIRUSES (something that causes a disease or disorder)

Ebola zaire

AIDS

Rhinovirus

Influenza

Measles, mumps, chicken pox

Polio

Rabies

Smallpox