Chapter 20 Section 2
Cholera
E. Coli
 Prokaryote: unicellular
organism that lacks a
nucleus
 Most abundant
microorganisms on Earth
 Classified as Bacteria or
Archaea
 Two of three domains of life
 Live anywhere (fresh and
salt water, soil, bodies)
 Have cell walls made of
peptidoglycan (sugar and
amino acid polymer)
 May have flagella or pili
 Lack peptidoglycan in cell
wall
 DNA sequences of genes
more like eukaryotes
 Live in extremely harsh
environments
(hydrothermic vents, hot
springs, salty lakes)
 Prokaryotes vary in size and shape, locomotion,
nutrition, and metabolism
Rod-shaped bacilli
Sphere-shaped cocci
Spiral-shaped spirillium
 Binary fission: asexual cell
division
 End result is two identical
cells
 Endospore: thick internal wall that encloses DNA and
portion of cytoplasm
 Formed in unfavorable conditions
Endospore
 Mutations key to
prokaryotic evolution
 Can exchange genetic
material and beneficial
mutations during
conjugation.
 Plasmids that carry
resistance genes
transferred between
bacteria
 Decompose materials for reuse in the environment
 Can act as producers that are the base of every food
chain (especially aquatic environments)
 Act as nitrogen fixers so plants (and animals) can use
nitrogen to create proteins and nucleic acids (N2  NH3
 NH4+)
 Nitrogen Fixation: converting atmospheric nitrogen into
a useable form
 NH3  ammonia
 NH4+  ammonium (formed by the addition of a proton)
Root nodules formed by
Rhizobium bacteria