Topic 3 : Prokaryotic cell

  • The term prokaryotic comes from the Greek word karyon, which refers to the nucleus of the cell. Pro- indicates before or prior to; therefore, prokaryote means before the formation of the nucleus, and refers to the lack of membrane-bound DNA found in these cells.

  • Most prokaryotic organisms are bacteria such as E.coli, Streptococcus, Salmonella, and Cyanobacteria, also known as blue-green algae.

  • Bacteria are extremely small, averaging only 0.001-0.002 mm in diameter.

  • Vast are heterotrophic, meaning they require external sources of food; but bacteria like cyanobacteria are autotrophic (phtosynthetic) and able to produce their own food.

  • Bacteria come in many shapes, such as round (cocci), rod-shaped (bacilli), and spiral-shaped (spirilla), collectively referred to as morphology

  • Gram positive retain a deep purple color will gram negative lose the color.

  • The cell wall in gram-positive bacteria is thick with containing many layers of peptidoglycan. Gram-negative bacteria have a thinner cell wall, only a few layers of peptidoglycan, which is surrounded by a protective lipid or protein layer and it appears reddish/pinkish

  • Cyanobacteria are unique prokaryotes that contain chlorohyll a, foudn in plants rather than the bacteriochlorophyll found in most prokaryotes.

  • However unlike plants chlorophyll is contained in chloroplasts whereas in cyanobacteria it is dispersed throughout the cytoplasm within thylakoid membranes.

  • Streak plate allows discrete colonies, colonies that are produced from replication of a single bacterium while the spread plate allows for quantification of bacteria present by creating an even lawn of growth.

Powerpoint

  • Archae are also called extremophiles because they are found in extreme environments such as high salt, temp, or pressure.

  • Electron microscope is used to analyzze detailed structure of tissues,cells, organelles and macromolecular complexes. (scanning and transmission are the two types)

  • Gram postive examples are staphylococci, streptococci

  • Gram negative examples are salmonella, cyanobacteria

  • Anabaena contains chlorophyll A

  • Streak plate allows for quantification of bacteria present

  • different media (liquid broth made solid with agar) can be used to grow bacteria

  • Hydrolysis makes monosaccarides

  • How would you establish a pure culture of E. coli from a mixed culture of bacteria? streak a sample on agar and isolate the colonies and pick one colony and streak it onto a fresh agar plate and than confirm it with gram staining.