Chapter 20 Viruses and Prokaryotes Section 20 2

Chapter 20: Viruses and Prokaryotes Section 20 -2: Prokaryotes

Classifying Prokaryotes Unicellular organisms that lack a nucleus DNA free-floating Two groups domains: Bacteria and Archae

Bacteria Larger domain No agreement about number of phyla Live everywhere – fresh/salt water, land, within other eukaryotes, etc Usually have a cell wall for shape and protection – contains peptidoglycan Escherichia coli – found in human intestines – have extra membrane around cell wall for more protection Flagella for movement, pili to anchor bacterium

E. coli

Archae Look similar to Bacteria under a microscope Cell walls contain lipids DNA more like eukaryotes Many live in harsh/extreme environments – salt lakes, hot springs, no oxygen, etc

Structure and Function Range in size from 1 -5 micrometers Come in three shapes: Bacillus (pl. bacilli) – rod shaped Coccus (pl. cocci) – spherical Spirillum (pl. spirilla) – spiral/corkscrew shaped Also three arrangements: Diplo- (in a pair) Staphlyo (in a bunch) Strepto- (in a chain)

Shapes/Arrangements

Structure and Function Can be distinguished by how and if they move – flagella, slime Energy released during cellular respiration, fermentation, or both Vary in the way they obtain energy

Growth, Reproduction, and Recombination Binary fission occurs when a prokaryote has doubled in size – replicates its DNA and splits Asexual reproduction Can be very fast when conditions right When conditions are unfavorable, many prokaryotes form endospores Thick wall forms around DNA and part of cytoplasm Can stay dormant from many years Bacillus anthracis

Growth, Reproduction, and Recombination Mutations allow prokaryotes to evolve - inherited through binary fission Many prokaryotes also exchange genetic information through conjugation Hollow bridge forms between 2 bacterial cells and genetic information (usually plasmids) move from one cell to another Increases genetic diversity

Importance of Prokaryotes Decomposers – break down complex organic molecules into simpler ones, supplying raw materials needed Actinomycetes in soil Sewage treatment Water purification Production of fertilizers Producers – cyanobacteria responsible for photosynthesis in ponds/aquatic environments Nitrogen fixers – convert atmospheric nitrogen gas into usable forms Symbiotic relationships with plants – Rhizobium and legumes

Human Uses of Prokaryotes Foods/commercial products (yogurt produced with Lactobacillus) Digest petroleum Remove human-made wastes and poisons from water Synthesize drugs, chemicals by genetic engineering Those adapted to extreme environments may produce heat-stable enzymes