Viruses

I. Viruses 1. They are Nonliving

i. Viruses are NOT cells… they carry on no life function on their own they can be stored for years and still be

viableii. Viruses do NOT replicate themselves

this happens only after invading a living Host Cell

iii. Unprecedented diversity A virus for every species RNA viruses lack any error

proofreading when being copied – leads to different forms of the same viruses that the body does not recognize

2. Named after the disease they cause or the tissue they infecti. Rabies virus & Polio virusii. Adenovirus (the Common Cold): infects the

adenoid tissue in throat and nasal cavity3. Viruses are small

i. Smaller than the smallest known cellii. about 100 times smaller than bacteria.

prokaryotics cells200-10,000 nm

eukaryotics cells10,000-100,000 nm

viruses50-200 nm

1 nanometer (nm) = one billionth of a meter

viroids5-150 nm

Rabies virus

4. Viruses are classified by a number of different characteristics:

a. Shapeb. Nucleic Acid content – DNA or RNAc. Presence or absence of an “envelope”d. Type of host it affectse. How it is transmittedf. Vectors-

i. any organism or object that carries or transmits disease causing organisms

ii. Ex. needles, worms, water, mosquitoes, etc.g. Attachment process

i. they can only attach to specific cells or cell types.

II. Types of Viruses1. DNA viruses

i. They will not change much overtime

ii. DNA tends to stay stablei. Ex.: Adenovirus (common

cold) / Poxviruses (small pox)

2. RNA virusesi. They will change often b/c

they do not proofread errors when the RNA gets copied. i. Ex. HIV (causes AIDS)/

Influenza (Swine flu)

III. Virus Structure1. Made of mainly Protein

1. Proteins on surface help viruses attach to cells

2. Has a Coat called Capsida. Contains the Nucleic acid Coreb. either DNA or RNA

i. RNA Viruses= HIV destroys white blood cells

ii. DNA Viruses= Cold sores and Smallpox

3. Some viruses have an Envelope

a. an additional coatingb. enhances the viruses’ ability to

enter an organism or host cell

capsid

DNA

tail sheath

tail fiber

V. Outbreaksi. Virology—the study of viruses (and virus-like agents) ii. Epidemic—when cases of a given disease substantially exceed

“expected” cases of that particular diseaseiii. Pandemic—occurs when an epidemic spirals out of control,

spreading across large regions (i.e. a continent or worldwide)VI. Treatments

i. Antibiotics DO NOT treat viral infections, only bacteriaii. Vaccines— are deactivated viruses that trick the immune

system into thinking there has already been an infection.i. Vaccines stimulate antibody productionii. Antibodies mark which items in the body get destroyediii. Antibodies will “remember” a virus iv. Now when the body is exposed to the harmful virus

again the antibodies will be made faster to kill the virus.

I. BacteriaA. Belong to Two Kingdoms

1. Archaebacteriai. live in extreme environmentsii. 02 free environmentiii. Extremophiles

2. Eubacteriai. The most commonii. Live in non-extreme

environmentiii. Some are parasites

B. You can find bacteria in fossils

C. Characteristics:1. Unicellular2. May live in colonies3. Prokaryotes

1. They have no nucleus2. Their DNA is floating freely in the cell

4. Autotrophs (Producers) i. Photosyntheticii. Chemosynthetic

5. Heterotrophic (consumers)1. Feed off of organic material outside of themselves

flagellumpili

plasmid

cell wall

chromosome

plasmamembrane

D. Bacterial Structure1. 3 basic shapes

i. rod (bacillus)ii. round (coccus/ cocci)iii. Spiral (spirilium)

2. 2 types of cell extensionsi. pili (pilus) –hair-like structures that helps

them stick to surfaces and each otherii. flagella –allows some bacteria to move

3. Plasmidi. small circle of DNA (a single chromosome)

4. Capsule i. is an external protective layer that keeps it

from being destroyed5. Cell walls – Similar to plants

i. Penicillin (antibiotic) stops the formation of cell walls (Helps destroy bacteria)

Spirochaeta : spiral

Enterococci: round

Lactobacilli: rod-shaped

E. Adaptations1. Bacteria live in various habitats and

have several adaptationsi. They can breakdown dead matter.

i. Prevents buildup of deceased materialii. Some can use poisonous substances

as food (ex. Oil) Bioremediationiii. They can exist in extreme hot/cold

2. High rate of Mutualismi. The relationship between two species

with both getting benefits The bacteria in your intestines help to

breakdown food faster.3. Some need an O2 environment =

aerobic (Ex. Tuberculosis – affects lungs)4. Some can’t live in O2 environment =

anaerobic (Botulism -food poisoning)

II. Bacteria Life CycleA. Asexual Reproduction

1. Binary Fissioni. Reproduce (Mitosis) by

dividing into two cellsii. Can happen very quickly

B. Sexual Reproduction1. Conjugation

i. One bacteria transfers all or part of its chromosome (DNA) to another cell through pilli that connects the two cells

ii. Results in bacteria with new genetic composition

III. DefenseA. How do Antibiotics work?

1. They stop the creation (synthesis) of bacterial cell walls or cause the cell walls to break apart.

2. Antibiotics interfere with the functions (metabolic processes) of bacterial ribosomes (i.e. protein synthesis).

3. Unlike bacteria, viruses don’t have cell walls or ribosomes, so antibiotics have no effect on them.

B. Bacteria are gaining resistance to antibiotics through: overuse underuse misusei. A bacterium may already have an gene

(DNA) for antibiotic resistance on the plasmid

ii. A copy of the plasmid is transferred through conjugation.

iii. Resistance quickly spreads through many bacteria.

IV. Good Bacteria and Bad BacteriaA. There are good and bad bacteria

1. Good bacteria are used to help fight disease/ create food (cheese)/ and deal with pollution

i. EX. Lactobacillus acidophilus, Dehalococcoides ethenogenes

2. intestinal bacteria make up approximately 95% of the total number of cells in the intestinal tract.

3. Bad bacteria cause life threatening diseasesi. Done by invading tissues or creating toxinsii. EX. E-coli and streptococci