Prokaryotes: Archaea & Bacteria
The Tree of Life • All living things classified in three domains: • Bacteria • Archaea • Eukarya
Amazing Living Things • Microbes indispensable to life: • Produce much of Earth’s: • Oxygen • Decomposition • Over half of Earth’s biomass • More bacterial cells than human cells in your body!
Prokaryotes • Prokaryotes have: • Circular DNA, RNA, ribosomes, cytoplasm, plasma membrane • Most prokaryotes have a cell wall, a capsule (around the cell wall) and a flagellum • Prokaryotes don’t have: • Organelles such as nucleus, chloroplasts, mitochondria.
Generalized Prokaryote Nucleoid DNA Plasmid DNA Cytosol Flagellum Capsule PlasmaMembrane Cell Wall
Prokaryotic DNA • The area that contains the genetic material is referred to as the nucleoid. • The genes are usually in one continuous circular loop of DNA. • There may be other small circles of DNA outside the nulceoid called plasmids.
Bacteria/Archaea • Habitats (name a place, and they live there!) • They are specialists • human skin, mouth, respiratory tract, large intestine, urogenital tract, etc. • salty Dead Sea • extreme pH • archea in deep sea vents: 90-106o C • Aerobes and anaerobes
Some Prokaryotes Thrive in Extreme Conditions Cyanobacteria in Yellowstone Hot Springs
Archaea • Unique lipid membranes, cell walls, and rRNA • Methanogens • Convert CO2 to methane • Swamps, hot springs, vent communities, cow stomachs • Halophiles - survive concentrated salt environment • Thermoacidophiles - thrive in hot, acidic environment • Generally in EXTREME environments
Bacteria • Evolve Rapidly • Most of the time are asexual • Classified by shape, locomotion, pigments, nutrients, colonies
Bacteria • Shape: • Cocci - round • Bacilli - rod • Spirilla - spirals
(b) (c) Three Common Bacterial Shapes (a) bacillus cocci spirillus
The Prokaryote Flagellum Flagella Bacterium
Bacteria • Reproduction • Reproduction is asexual, by simple splitting (binary fission) • Daughter cells are genetic clones of the parent cell
Binary Fission DNA
Bacteria - Reproduction • Binary fission: • Very fast, up to once every 20 minutes • One bacterium-> 1021 in 24 hours. • Conjugation: (sexual reproduction) • Used only occasionally.
Bacteria – Sexual Reproduction • Conjugation: • Genetic variation through pili (structures similar to flagella) and plasmid DNA • DNA is exchanged between bacterial cells • Occurs through a special large, hollow pilus • One bacterium acts as a donor, transferring DNA to the recipient.
Conjugation Donor Recipient Sex Pilus
Benefits of Bacteria • Symbiosis (mutualism) • Ruminants’ digestive tracts • Nitrogen fixing in soil, nodules on certain legumes • Bacteria on/in the human body: intestines and vitamin K and B12 • Biodegradation - oil • Food production - cheese, yogurt, sauerkraut • Decomposers
Bacterial Pathogens • Some cause disease = pathogenic • In humans: • Strep throat • Toxins - tetanus, botulism • Pneumonia • "Flesh-eating" bacteria • Plague • Tuberculosis • Cholera • Lyme disease ANTIBIOTICS= anti bacterial!!!
Transmission of Bacterial Pathogens • Airborne • Water • Food • Direct (skin contact, blood, and other body fluids) • Insect vectors and other hosts such as deer tick (Lyme) or mosquito.
Germ Theory of Disease • Theory that microorganisms are the cause of disease. • 1859 – Louis Pasteur • Credited with the idea that human diseases were caused by bacteria and viruses (germ theory) • Very important discovery in the field of medicine
Infectious Diseases • Average age of death, in first world countries, jumped 30+ years in last century due to antibiotics, and enhanced hygiene and nutrition. • Antibiotic-resistant infections on the rise in hospitals in the U.S. • This is due to bacterial evolution in response to widespread use of antibiotics!