Download Prokaryotes - The first life forms on the planet

THE TREE OF LIFE: PART 1, The Prokaryotes … Bacteria and Archaea
Prokaryotes - (synonym = monerans) "Before the nucleus"
- All prokaryotes are unicellular, though some form colonies with specialized cells, which puts them
on the borderline of being multicellular? Cyanobacteria are an example.
- Prokaryotes lack a nucleus (that's what prokaryote means), and other sub-cellular, membrane-bound
organelles.
- Oxidative respiration in aerobic bacteria utilizes the plasma membrane to create the necessary proton
gradient. Remember, no mitochondria. Photosynthetic bacteria use their plasma membrane to create
the proton gradient of the light reactions. Remember, no chloroplasts.
Chapter 19, section 1 contains most of the information you need to know, but make sure you understand
all of the following:
Ecological roles
- Photosynthesis; cyanobacteria
- Nitrogen cycle: fixation;free- living and symbiotic in plant roots; denitrification; ammonification
- Decomosition
- Mutualistic symbiotic relations; too numerous to list
- Pathogens of animals and plants
Structural features
- cell wall; peptidiglycan (all Eubacteria); gram positive and gram negative (two variations)
- plasma membrane
- Shapes of bacteria; cocci = spherical; bacilli = rod-shaped; spirilli = corkscrew
- "chromosome" the quotes are there because it really isn't a chromosome, because bacterial DNA has
no association with histone proteins.
- Ribosomes; they do the same thing as eukaryotic ribosomes, but they are sufficiently different in
bacteria.
- Cytoplasm - also called cytosol.
Optional features include
- flagella - you should be aware that these are used for locomotion
- Pili (plural) - these are tiny hair-like projections that allow cells to stick together (aggregate), and a
specialized sex pilus (sing) is used in conjugation to transfer plasmids (small, circular DNA
molecules) from one cell to another.
- Capsule - this is a gelatinous, glycoprotein goo that is secreted by some bacteria
Mechanisms for genetic exchange - conjugation, transformation, transduction
How do they "eat" - Heterotrophic bacteria digest food outside their tiny, one-celled bodies by producing and
secreting enzymes into their food (substrate), and then absorbing the digested food by way of diffusion.
Autotrophic bacteria use sunlight or chemicals and heat to make their own food.
Respiration - All Archaea are anaerobic; Eubacteria can be aerobic, anaerobic, or switch hitters.
Relations with humans
- Bacterial diseases - there are hundreds of infectious diseases caused by Eubacteria, but most of these
are treatable with antibiotics. The nature of infection is usually parasitism, but some gut-dwelling
organisms cause disease by producing toxins while feeding on the contents of the gut.
- Mutualism - the hundreds of bacteria living on the surface, in the gut, and in all of the accessible,
moist areas of the body, serve mostly to protect us from pathogens. E. coli in the colon helps
produce vitamin K, which is involved in blood clotting.
- Commercial applications; food (yogurt, cheese, kim-chee, etc.); medicine (genetically modified
bacteria are used in production of numerous medicines, including insulin); Industrial (oil-spill
cleanup).
- Biotechnology; bacteria are commonly used as vectors for genes in genetic engineering.