bacteria and viruses

• bacteria

• : are microscopic organisms that are prokaryotes.

• prokaryotes are divided in two two domains: the domain bacteria (eubacteria) and the domain archaea (archaebacteria)

  vocabulary

  1. bacteria: are microscopic organisms that are prokaryotes.
  2. nucleoid: a large circular chromosome in a area of the cell.
  3. capsule: prevents the cell from drying out and helps the cell attach to environments surfaces.
  4. pili: are submicroscopic, hairlike structure that are made of protein.
  5. binary fission: is the division of a cell in 3 genetically identical cells.
  6. conjugation: 2 prokaryotes attach to each other and exchange genetic information.
  7. endospore: when environmental condition are harsh, some times of bacteria provide a structure.

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prokaryote structure

1. prokaryotes are microscopic, unicellular organisms.

2. they have some characteristics of all cells, such as DNA and ribosomes.

3. Lack a nuclear membrane and other membrane- bound organelles.

   identifying prokaryotes

   shape:

   1. spherical= cocci
   2. rod-shaped= bacilli
   3. spiral-shaped= spirochetes

cocci	bacilli	spirochetes

cell walls

1. eubacterial cells have peptidoglycan
2. dyes added to the bacteria identify those with those without an outer layer of lipid.

movement

a. prokaryotic flagella are made of filaments

b. flagella help prokaryotes to move toward material that they need to survive

reproduction of prokaryotes

1. binary fission: the division of a cell int 2 genetically identical cells.
2. conjugation: 2 prokaryotes attach to each other and exchange genetic information.

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phototrophs +

carry out photosynthesis in a similar manner as plants

chemoautotrophs

break down and release inorganic compounds that contain nitrogen or sulfur

aerobes and anaerobes

obligate aerobes are bacteria that require oxygen to grow

anaerobic bacteria do not use oxygen for growth or metabolism.

survival of bacteria

endospores: are resistant to harsh environments and might be able to survive extreme heat, extreme cold, dehydration, and larger amounts of ultraviolets radiation.

ecology of bacteria

nutrient cycling and nitrogen fixation

bacteria are decomposers, returning vital nutrients to the environment.

nitrogen-fixing bacteria live in a symbiotic relationship in the root nodules of plants such as soybeans, clover, and alfalfa.

normal flora: most of the bacteria that live in or on you are harmless.

disease-causing bacteria

1. a small percentage of bacteria cause disease.

2. bacteria multiply quickly at the site of infection

3. bacteria secrete a toxin.

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viruses (def + characteristics)

• a nonliving strand of genetic material within a protein coat

• no organelles to take in nutrients or use energy

• cannot make proteins

• cannot move

• cannot replicate on their own

• most viruses range in size from 5 to 300 nanometers.

  

  virus origin

  1. viruses came from parts of cells

1. genetic material of viruses are similar to cellular genes

viral infection

1. in order to replicate, a virus must enter a host cell.
2. the virus attaches to the host cell suing specific receptor on the plasma membrane.
3. many viruses cannot be transmitted between different species.

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