EUBACTERIA and ARCHAEBACTERIA pp.360-372

Classifying Prokaryotes All prokaryotes were once placed in the Kingdom Monera. Recently, biologists divided them into two different kingdoms: the Eubacteria and the Archaebacteria.

Eubacteria Archaebacteria No peptidoglycan in cell walls Live in extreme environments Thermophiles, halophiles, methanogens Peptidoglycan in cell walls Cannot survive in extreme environments Bacteria & cyanobacteria Prokaryotic No nucleus Single-celled Ribosomes No membrane-bound organelles

Archaebacteria  DNA shows a closer evolutionary relationship to eukaryotes Many archaebacteria live in extreme environments. Methanogens live in oxygen-free environments (ex. thick mud & animal digestive tracts) Halophiles live in salty environments Thermophiles live in hot environments (ex. hot springs)

2. Eubacteria Eubacteria have a cell wall that protects the cell and determines its shape. Live everywhere: in fresh and salt water on land in the human body

E. coli, a Typical Eubacterium (Peptidoglycan) A bacterium such as E. coli has the basic structure typical of most prokaryotes: cell wall, cell membrane, and cytoplasm. Some prokaryotes have flagella that they use for movement. The pili are involved in cell-to-cell contact. The cell walls of eubacteria contain peptidoglycan.

Types of Eubacteria Bacilli = rod-shaped Cocci = spherical-shaped Spirilla = spiral & corkscrew-shaped Prokaryotes can be identified by their shapes. Photo Credit: ©David Scharf/Peter Arnold, Inc.

Arrangement or Grouping Paired = diplo Filamentous (chains) = strepto Colonial (grape-like clusters) = staphylo

Identifying Prokaryotes: Two different types of cell walls are found in eubacteria. A method called gram staining tells them apart. Gram-positive bacteria have thick cell walls with large amounts of peptidoglycan. Gram-negative bacteria have thinner cell walls inside an outer lipid layer. Copyright Pearson Prentice Hall