163 Prokaryotes

Cocci

Spherical

Bacilli

Rod

Spirilla

Spiral

Biofilm

Community of prokaryotes growing on a surface; example: plaque on teeth

Typical prokaryote size vs. eukaryote size

Prokaryotes are small (0.1

Nuclear envelope: prokaryotes vs. eukaryotes

Absent in prokaryotes; present in eukaryotes

DNA: prokaryotes vs. eukaryotes

Prokaryotes: a loop plus plasmids; eukaryotes: chromosomes

Membrane

bound organelles: prokaryotes vs. eukaryotes

Cytoskeleton: prokaryotes vs. eukaryotes

Absent in prokaryotes; present in eukaryotes

Ribosome size: prokaryotes vs. eukaryotes

Prokaryotes 70S; eukaryotes 80S

Asexual reproduction: prokaryotes vs. eukaryotes

Prokaryotes: fission; eukaryotes: mitosis

Sexual reproduction: prokaryotes vs. eukaryotes

Prokaryotes: apparently absent; eukaryotes: gamete fusion

Asexual reproduction (features)

One parent needed; no gametes; cell division via mitosis or fission; offspring genetically identical to parent

Sexual reproduction (features)

Two organisms needed; gametes produced via meiosis; zygote forms via fertilization; offspring are a new genetic combination of the parents

Benefits of asexual reproduction

Offspring well adapted to current conditions; fast and cheap

Benefits of sexual reproduction

Adaptation to a changing environment and evolution; but slow and expensive

Genetic recombination in prokaryotes (structure shown)

Involves a pilus connecting cells; can spread genes such as antibiotic resistance genes (ARG)

Five ecological roles of prokaryotes (lecture)

Symbiosis, disease, nitrogen fixation, photosynthesis, decomposition

Example: prokaryote disease

Staphylococcus aureus infection (e.g., MRSA)

Example: prokaryote nitrogen fixation

Rhizobium in root nodules of legumes

Example: prokaryote symbiosis

Sulfur

Example: prokaryote photosynthesis

Cyanobacteria (e.g., blooms like the one on the Potomac River)

Chemoheterotrophs

Energy: organic compounds. Carbon: organic compounds. Examples: many (saprobes)

Photoheterotrophs

Energy: light. Carbon: organic compounds. Examples: purple nonsulfur bacteria, Haloarchaea

Chemoautotrophs

Energy: inorganic substances. Carbon: carbon dioxide. Examples: sulfur bacteria, iron bacteria, many Archaea

Photoautotrophs

Energy: light. Carbon: carbon dioxide. Examples: Cyanobacteria, Prochlorobacteria, purple sulfur bacteria

Purple sulfur bacteria: reducing agent

Anaerobic; use hydrogen sulfide rather than water as the reducing agent

Purple nonsulfur bacteria: reducing agent

Usually use hydrogen

Economic importance of Class Bacteriae (lecture)

Disease, bioremediation, pest control, industrial production, food production, decomposition

Class Cyanobacteriae: pigments

Chlorophyll a, carotenoids, phycobilins (phycocyanin = blue, phycoerythrin = red)

Class Cyanobacteriae: key abilities

Produce oxygen from photosynthesis; often fix nitrogen

Heterocyst

Specialized cyanobacterial cell that is the site of nitrogen fixation

Akinete

Thick

Anabaena and Nostoc

Examples of filamentous cyanobacteria

Stromatolites

Layered structures built by cyanobacteria; evidence of early oxygen

Oldest stromatolite example (lecture)

Strelley Pool Chert, about 3.43 billion years old (bya)

Cyanobacteria roles/habitats (lecture)

Blooms, lichen symbiont, Spirulina (food supplement), soil crust, intertidal, Yellowstone hot springs (e.g., Morning Glory Pool)

Thermophilic Archaea

Live in extremely hot environments; example: Grand Prismatic Spring, Yellowstone

Halophilic Archaea

Live in extremely salty environments; example: Owens Lake, CA

Methanogenic Archaea

Produce methane; example: ruminant gut

The three domains of life

Bacteria, Archaea, Eukarya (Eukarya includes protists, plants, fungi, animals)

Origin of the nucleus and organelles

Creation of nuclear membrane and organelles, possibly in an Archaean

Origin of mitochondria

Endosymbiosis involving an aerobic proteobacterium (perhaps a purple nonsulfur bacterium)

Origin of chloroplasts

Endosymbiosis involving a cyanobacterium or Prochlorbacterium

Timing of eukaryotic cell evolution

About 1.7 to 3.0+ billion years ago