unit 6 – organismal biology part 1: bacteria and viruses
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Unit 6 – Organismal Biology Part 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) - PowerPoint PPT PresentationTRANSCRIPT
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