Prokaryotes and Heterotrophic Protists

Prokaryotes (success)

• Most dominant

• Most successful forms of life (can be found everywhere and are billions of years old)

General Characteristics of prokaryotic cells

• Single circular/continuous DNA molecule (non-histone proteins in nucleoid region) (may have plasmids)

• Lack membrane-bound organelles, BUT have enzyme-containing microcompartments surrounded by a protein shell.

• Granular appearance (Ribosomes and proteins)

• Some have thylakoids

• NO cytoskeleton but actin/tubulin polymers

• Many walls are rigid or flexible (some have NO walls)

• Flagella

• Fimbriae, pili

• Nanotubes

Wall components of prokaryotes

Peptidoglycans

• Capsule/slime layer (glycocalyx) mostly polysaccharides.

Diversity Prokaryotes (Simple characteristics)

• Aerobic/anaerobic

• Psychrophile (cold temp) + Thermophile (hot temp)

• Nitrogen fixation

• decomposers

• disease agents

• Commercial applications and implications

Where do you find Cyanobacteria

• Hot springs to lakes in antarctia

• On stromatolites (layers of cyanobacteria that bind calcium rich deposits)

Cyanobacteria (Forms)

Filamentous (beads on a necklace), unicellular, colonies

Cyanobacteria (pigments)

• Chlorophyll a

• Carotenoids (orange colour)

• Phycobilin

Phycobilin (is what)

Pigment of phycocyanin (blue) and phycoerythrin (red)

Mucilaginous envelope

Is a sheath on cyanobacteria that binds groups of cells/filaments (sticks to the environment)

Morphological features (cyanobacteria)

• Gas vesicles: Provide/regulate buoyancy

• Heterocyst: Cell for nitrogen fixation (specialized) with thick walls (glycolipids) to prevent oxygen diffusion in the cell (nitrogenase enzyme is sensitive to O2). Tend to join together.

• Akinetes: Resistant spore-like structure (unfavorable conditions)

Symbiosis (Cyanobacteria)

• Asian rice paddies have nitrogen-fixing cyanobacteria (aids in continuous crop growth)

• Anabaena in association with water fern Azolla.

Heterotopic Protists Oomycetes

Water molds

Oomycetes (water molds) (Cell characteristics)

• Unicellular - highly branched, coenocytic filamentous forms

Cell walls contain cellulose and cellulose like substances

Oomycetes (Water molds) (reproduction)

• Sexual reproduction: Oogamous

• Asexual reproduction: Zoospores

Oogamous

Occurs with a big egg and a sperm

Homothallic

Male/female sex organs on same individual

Heterothallic

Male/female sex organs on different individuals

Oomycetes (water molds) (aquatic forms)

Most are saprophytic (decomposers of dead organisms). Some are parasitic on fish/eggs.

Oomycetes (water molds) (terrestrial forms)

• Downy mildew in grades (Plasmopora viticola)

• Phytophthora infectants = Late blight of potatoes (type of water mold that goes after potatoes)

Oomycetes (type of life cycle)

Gametic meiosis

Heterotrophic Protists Myxomycota Plasmodial Slime molds (family)

No direct relationship to any other fungi group.

Heterotrophic Protists Myxomycota Plasmodial Slime molds (plasmodium)

• Engulfs small organic material along path

• Nuclei divide synchronously (mitosis)(close to plants)

Heterotrophic Protists Myxomycota Plasmodial Slime molds (Reproduction)

Sexual reproduction (formation of mound + sporangium)

• Spores undergo meiosis (1 out of 4 survives)

• Spores = resistant to adverse conditions

Myxomycota (Slime molds)(type of life cycle)

XXXXXXXX

Cellular Slime molds Phylum

Dictyost eliomycota

Cellular Slime molds (appearance)

• Amoeboid-like myxamoebas

• Pseudoplasmodium ‘slug’

Cellular slime mold (Aggregate)

They are aggregated by chemotaxis

• CAMP secreted by starving cells

• Fate of cell by position: stalk cells + spore-bearing

Cellular slime molds (sexual reproduction)

Macrocyst (2 myxamoebas fuse)

• An enlarged zygote undergoes meiosis and releases myxamoebas.