Bacteria



Two kingdoms of bacteria:
Eubacteria – “true” bacteria
Archaebacteria – oldest organisms on earth, live in extreme conditions
Bacteria are:
Unicellular
Prokaryotic…which means?

Fact: Each square centimeter of your skin averages about 100,000 bacteria. A single teaspoon of topsoil contains more than a billion (1,000,000,000) bacteria.  

Bacteria contain:
a singular, circular piece of DNA
tiny circular pieces of DNA called plasmids
ribosomes
Bacteria reproduce:
asexually using binary fission.
Bacteria reproduce:
sexually using conjugation.
Bacteria exchange
plasmid DNA.

This is how bacteria
become antibiotic
resistant.
Bacteria have cell walls made of:
peptidoglycan (polysaccharide linked with chains of amino acids).
this may be covered with an outer membrane of lipopolysaccharide (chain of sugar with a lipid attached).

Some bacteria:
have a gelatinous layer called a capsule surrounding the cell wall.
form thick-walled endospores around chromosomes when they are exposed to harsh conditions (drought, high temperatures) - these types cause botulism

Some bacteria have:
flagella for locomotion.
pili (short, thicker outgrowths that help cell to attach to surfaces)
¨Three bacterial shapes:

Rod shaped are called bacillus(i)
Sphere shaped are called coccus(i)
Spiral shaped are called spirillum(I)
Gram stains:
Important in medicine because provides information for treatment of bacterial disease.


Bacteria stain either gram positive (purple) or gram negative (pink).
Gram positive tend to respond to penicillin and like antibiotics.

Gram negative respond to types of antibiotics unrelated to penicillin.
Crystal violet Iodine Alcohol Safranin
Purple Decolorizes Pink counterstain

Gram Stain Process:
Gram positive = purple because of large amount of peptidoglycan in cell wall.
Gram negative = pink because¨ lipopolysaccharide membrane is removed by alcohol and thin peptidoglycan layer allows dye to escape.

work by preventing cell wall formation, breaking up cell membranes, or disrupting chemical processes.

cannot treat viral infections.
There are three types of bacteria based on how they obtain energy: heterotrophs, photosynthetic, and chemoautotrophs.

This is the anthrax bacterium.
Most are heterotrophs:

Decomposers – feed on and recycle organic material

Pathogens – parasitic, disease-causing bacteria
Either attack cells or secrete toxins

Nitrogen-fixing bacteria (Rhizobium)
Found in nodules of soybeans, peanuts, alfalfa, and clover
Convert atmospheric nitrogen (N2) into ammonia, called nitrogen fixation.
Used in crop rotation
Streptococcus
Strep throat

Staphylococcus
Nitrogen fixing bacteria
in the nodules of roots
2. Some, like Cyanobacteria, are photosynthetic.
These are autotrophs that use the sun’s energy to make food.

3. Chemoautotrophs
Obtain energy by removing electrons from inorganic molecules such as ammonia and methane to make food.

Examples: Nitrobacter and Nitrosomonas
- live in soil
- have a crucial role in nitrification (turn ammonia into nitrates, the form of nitrogen commonly used by plants).