Bacteria and Viruses

The good, the bad, and the ugly.

Bacteria

• Prokaryotes

• Cell Wall=Peptidoglycan

• Gram-positive=thick cell wall, stains violet

• Gram-negative=thin cell wall, stains pink

Reproduction

• Binary fission=asexual

• Conjugation=when two bacteria exchange genetic material (leads to recombination of genetic material, sexual).

New Combos of DNA

Transduction

• The bacteria receives

DNA from a vector such

as a BACTERIOPHAGE

(virus) and incorporates

the viral DNA into its

own DNA.

Transformation

• The bacteria takes up

extra DNA from the

environment and

incorporates it into its

own DNA.

Shapes

• Round-Coccus

• Rod-Bacillus

• Spiral-Spirilium

Two Domains

Archaea:

Live in extreme environments

-Extremophiles

-Thermophiles (high temps)

-Halophiles (high salt)

These can live anywhere!

Eubacteria

Bacteria that live on and around us!

Examples:

Escherichia Coli

Streptococcus

A crucial part of the Nitrogen Cycle

• Nitrogen fixation=bacteria convert

atmospheric nitrogen into ammonia

so plants can absorb it.

• Denitrification=anaerobic bacteria in

the soil convert ammonia back to

nitrogen gas and return it to the

atmosphere.

Viruses!

•NON-living because they cannot reproduce

without a host.

•Viruses infect all types of cells, from bacterial

cells to human cells.

Structure

• The basic structure of a virus includes a DNA or RNA core surrounded by a

protein coat called a CAPSID.

• Many different shapes.

How does a virus attack?

• Viruses recognize the receptors on the surface of a host cell.

The proteins on the virus (the key) match with a receptor on the

surface of the host cell (the lock). When the “match” is made,

the virus then proceeds to infect the cell.

• Viruses can only infect a specific type of cell.

• Viruses can only change the type of cell they infect through

mutation.

Types of Infections

• Lytic Infection: The virus infects the host cell and immediately hijacks the

cell’s machinery to make more copies of itself. When the host cell is full of

viruses it “lyses” or bursts releasing the newly formed viruses to infect new

cells.

Types of Infections

• Lysogenic infection: The viruses sneaks its

DNA or RNA into the cell and hides inside

the host cells DNA. As the host cell grows

and divides, the viral DNA or RNA is copied

along with the host cells DNA and added to

each new cell. Eventually, the viral DNA or

RNA comes out of hiding and uses the cells

machinery to make copies of itself. When it

has filled the host cell with viruses, the host

cell “lyses” or bursts releasing the viruses.