Unit 6 – Organismal BiologyPart 1: Bacteria and Viruses

Domains of Life

Archaea

• More closely related to eukaryotes than bacteria

• Extremophiles– Extreme halophiles (high saline environments;

Great Salt Lake, Dead Sea)– Extreme thermophiles (very hot environments;

special DNA/proteins adaptations; volcanic springs, deep-sea vents

Archaea

• Methanogens– Strictly anaerobic; use CO2 to oxidize H2 and release

methane as a waste product (swamps, marshes)

Bacteria – Majority of Prokaryotes

• Proteobacteria (large group, diverse)

• Chlamydias (animal cell parasites)

• Spirochetes (heterotrophs; syphilis, Lyme disease)

Bacteria – Majority of Prokaryotes

• Cyanobacteria (photoautotrophs; base of food chain in aquatic ecosystems; endosymbiosis leading to eukaryotic chloroplasts)

• Gram-positive bacteria (simple cell walls; large group, highly diverse; tuberculosis, anthrax)

Prokaryotic Cells

• Primarily unicellular • Less complex than

eukaryotic cells• No membrane-bound

organelles• Lack a nucleus

Prokaryotic Cell Structure

• Cell wall (peptidodoglycan or other proteins/carbohydrates)

– Capsule: Sticky covering of the cell wall(protection, attachment)

– Fimbriae & sex pili (pilus): Hair-like proteins (attachment, pull cells together)

Prokaryotic Cell Structure

• Flagella (motility, taxis)

• Specialized membranes (metabolic functions)

• DNA– Chromosome located in

nucleoid region– Plasmids (small rings of DNA)

Prokaryotic Cell ShapesBacilli (rods)

Cocci (spheres)

Spirals

Metabolic Diversity

• Photoautotrophs– Use sunlight energy to convert inorganic carbon

• Chemoautotrophs– Oxidize chemicals (H2S, Fe) to convert inorganic

carbon

Metabolic Diversity

• Photoheterotrophs– Use sunlight energy but need carbon in organic

form

• Chemoheterotrophs– Must consume organic molecules for energy and

carbon source

High Genetic Diversity

(1) Rapid Reproduction• Asexual • Binary fission (offspring

genetically identical to parent)• High mutation rate due to fast

reproduction – New alleles

(2) Genetic Recombination• Combining DNA from two sources, 3 ways this

happens…

High Genetic Diversity

• Transformation:– Uptake of foreign DNA from surroundings– Cell surface proteins recognize external DNA

High Genetic Diversity

High Genetic Diversity• Transduction:– Horizontal gene transfer– DNA carried by bacteriophages (viruses)

High Genetic Diversity• Conjugation:– Two cells joined by sex pilus– Mating bridge forms– Plasmid and chromosomal

DNA can be transferred

Roles in the Biosphere

• Chemical recycling (decomposers)

• Ecological interactions – Mutualism (N-fixing bacteria in

root nodules)– Commensalism (e.g. 150 species

live on your body surfaces You provide food, they don’t harm)

– Parasitism

Impacts on Humans

• Pathogenic bacteria– Cause about half of all human diseases– Produce poisons that cause illness• Exotoxins (secreted proteins)

– Cholera– Botulism

• Endotoxins (components of outer member; released when cell dies)– Salmonella

Impacts on Humans – Not all bad!!

• Research and Technology– Dairy industry (convert milk to cheese, yogurt)– Transgenic organisms Genetic engineering– Bioremediation (removing pollutants from soil,

water, air)– Used to make natural, biodegradable plastics– Produce hormones, antibiotics, vitamins