Characteristics of Prokaryotes:
- Small size and rapid reproduction
- High genetic variation → live in diverse environments
Bacteria Structure and Review
- Cell wall: made with peptidoglycan (carb polymer with amino acid)
- Function: protects cell, stops from bursting in hypotonic solution, structure determines rate of transformation
- Structure either gram positive and negative
- (+) = simple
- (-) = more complex, less peptidoglycan
- Capsule: layer of polysaccharides and proteins that surround cell wall
- Protect against dehydration, cell adherence, resist host organism defenses
- Endospores: resistant cells
- Plasmids: small, circular independently replicating (circular) DNA molecules
- Can be exchanged with other bacteria introducing genetic variation and promoting the transfer of antibiotic or pathogenic genes to harmless strains
- Quorum sensing: some bacteria release signalling molecule that recruits other bacteria → evaluate the local density of bacteria → bacteria respond and aggregate → form biofilms
- Biofilms: dense populations of bacteria linked by adhesive proteins
- Adhesive proteins help bacteria attach to substrates
Groups of Bacteria
- Can be categorized by how they obtain energy and carbon (include 4 modes)
- Cyanobacteria: photosynthetic
- Purple sulfur bacteria: photosynthetic but split H₂S (instead of water) to get electrons
- Nitrogen-fixing bacteria: convert/fix N2 to ammonia (NH₃) → used to make nitrogen-containing amino acids and nucleotides
- Some have mutualistic relationships with plants and bacteria
- Heterotrophic bacteria: obtain carbon and energy from organic molecules
- Ex: parasites, pathogens, decomposers, and bacteria in the digestive tract that also compete with pathogenic bacteria
Motility
- Use flagella
- Pro and eu. flagella have diff proteins, molecular composition, and method
Reproduction: Binary Fission
- Asexual→ no genetic variation
- Rapid reproduction + no proofreading enzymes → high rate of mutation = main method of creating variation for evolution (fast)
Metabolism
- Obligate aerobes require O2; obligate anaerobes are poisoned by O2; Facultative anaerobes can survive with or without
Some antibiotics disable the activity of bacterial ribosomes or break down cell wall