Domains Archae and Bacteria What are Bacteria Bacteria
Domains: Archae and Bacteria
What are Bacteria? • Bacteria are PROKARYOTES – The smallest known living cells Most are 0. 1 -0. 5 mm in size Bacteria on head of a pin They are found everywhere! Starr, 317 Did you know? There are over 80 species of bacteria in your mouth! Bacteria in dental plaque microbeworld. org
Some cause disease We call these “pathogens” Anthrax, as seen by Koch microbeworld. org But most are beneficial Bacteria ferment cheese Schraer, 641
Structure of Bacteria Most have a cell wall Many have a capsule (jelly or slimy coating outside the cell wall, for protection) They have a single, circular chromosome. Some have plasmids (tiny rings of DNA separate from the chromosome. ) Cytoplasmic Pili help them talk to other cells. Schraer, 632
Nucleoid
Many can MOVE, or go DORMANT Some have flagella - made of rope-like proteins, not microtubules. Some slide on a slimy secretion. Many can form dormant cells called endospores to survive harsh conditions. - tetanus, anthrax
Three basic shapes • Spherical – coccus • Rod – bacillus • Coiled - spirillum Schraer, 633
Simple Colonies Staphylo = clusters Strepto = chains Staphylococcus wisc. edu Streptobacillus Diplo = double Diplococcus cat. cc. md. us
Asexual Reproduction Binary fission Normal bacterial reproduction 1) chromosome replicates 2) copies separate as cell wall lengthens 3) cell membrane pinches in 4) cells divide Bacillus dividing by fission Steps in binary fission maricopa. edu
Cell Respiration • Most are obligate aerobes • Others are facultative or obligate anaerobes. • Anaerobes make a variety of fermentation products: - acids, alcohols, methane gas - food products
See Fission in Action Did you know? In ideal conditions, some species can divide every 20 MINUTES. What stops them? They run out of food or space, or wastes build up and poison them.
Sexual Reproduction conjugation • Two bacteria connect by a cytoplasmic bridge • Donor copies & passes DNA to recipient • Recipient now has new genes Common way to transfer antibiotic resistance!!
Two more “sexual” reproductions 1. TRANSDUCTION • • virus inserts DNA into bacterium Prophage contains new genes 2. TRANSFORMATION • • Bacterium takes in plasmids or DNA fragments from environment Plasmids contain new genes
Sexual reproduction in bacteria
Two Kingdoms of Bacteria Differ in their chemistry • Kingdom Archaebacteria - “Ancient”, most primitive earliest known form of life -
Archaebacteria • Differ chemically from Eubacteria – Eubacteria have cell walls with peptidoglycan • Archaebacteria have other polysaccharides – Ribosomes, lipids, enzymes are also different • Archaebacteria are more chemically like Eukaryotes – like us! RNA polymerase enzyme
Archae are extremophiles Live in habitats like early earth Too harsh for most organisms 1) methanogens – decomposers, live in animal intestines, swamps & bogs, sewage treatment 2) Halophiles – salt 3) Thermophiles – hot 4) Acidophiles – acid pools
Archaea are Extremophiles Halophiles – Great Salt Lake, Dead Sea Thermophiles – deep sea vents Thermophiles – hot springs, geysers
Kingdom Eubacteria “Ordinary” bacteria • Many decomposers • Some autotrophs • Nitrogen suppliers • Pathogens
Heterotrophic Bacteria 1) Nitrogen-fixing bacteria a) “Fix” (change chemically) nitrogen gas from the air into a form plants can use b)need nitrogen to make proteins, nucleic acids c) live in soil and in legume plants clover, peanuts, soybeans, … Legume roots – nodules contain nitrogen-fixing bacteria
Decomposers • • Essential to nutrient cycling In soil – Return inorganic chemicals to soil – Plants take up chemicals and make food – Some bacteria return nitrogen gas to the air • Inside animals – Enterobacteria – live inside us, – break down waste, make vitamins
E. Coli (enteric bacteria)
Photosynthetic bacteria Cyanobacteria – Have chlorophyll a (green) and cyanin (blue) – Most live in fresh water – Some in salt water, soil and lichens Starr, 315
Blue-green bacteria often link together, forming “filaments”
Blue-green bacteria are major producers in aquatic ecosystems
Some blue-green bacteria live with fungi in a symbiotic organism - lichen
Chemosynthetic Bacteria • Producers on ocean floor • Use heat and chemicals from thermal vents • Live inside giant tube worms
Human Uses for Bacteria • • Food culture (yogurt, cheeses, vinegars) Bioremediation (clean up poisons, oil spills) Gene engineering Source for antibiotics (ex. Streptomycin) Water treatment Drug development Medical, genetic research
Pathogenic Bacteria Many groups and types, but divided into two classes by GRAM STAIN Schraer 637 Gram positive Purple Respond to normal antibiotics Gram negative Pink - Cell wall resists stain Harder to treat if pathogenic
The Germ Theory of Disease 1800 s • Louis Pasteur - microscopic organisms were the cause of many human diseases • Robert Koch - devised a set of steps to identify the organism responsible for an illness “Koch’s Postulates” • Joseph Lister – sterile technique
Some Bacterial Diseases Salmonella Strep throat tetanus tuberculosis diptheria MRSA
How do bacteria make us sick? 1) some make toxins that kill cells or interfere with their function • Botulism, salmonella, cholera 2) some kill cells directly 3) some reproduce so fast their numbers interfere with organ function
How Bacteria Populations Grow!! Growth Curve (in Culture) Schraer, 634 Why do they die out? Run out of food, or wastes build up
How do we fight bacteria? Antimicrobial Agents - chemicals that inhibit bacterial growth a) antiseptics – on living tissue (skin) b) disinfectants – on nonliving surfaces c) antibiotics – inside living organisms - damage molecules needed when cells divide - cell wall (penicillin); proteins (tetracycline)
What are prions? Prions are misfolded protein molecules that can cause disease - no DNA (not a virus) - they induce normal proteins to misfold - cause loss of tissue/organ function death - ex. “Mad Cow Disease” (brain) - Creutzchfeldt-Jakob Syndrome in humans - get it from eating contaminated meat
What are viroids? • • Circular pieces of RNA No protein or membrane coat (not a virus) Can cause disease, more often in plants Only human example – hepatitis D
A misfolded protein
Little is Better!! Most prokaryotes measure 0. 5 -1. 0 mm Metabolism is FAST Bacteria can absorb nutrients and wastes rapidly because of high secrete surface-to-volume ratio Did you know? Lactose fermenters break down 10, 000 times their weight in lactose in an HOUR!
Kingdom Archaebacteria Why a separate kingdom? Archae differ chemically from other bacteria. 1) cell wall - different amino acids and sugars. Eubacteria have peptidoglycan Archaebacteria have varied polysaccharides but not peptidoglycan. 2) membrane lipids 3) ribosomes 4) enzymes - - - > 5) cytochromes RNA polymerase 6) gene sequences. . . And MORE
More photosynthetics 2) green-sulfur and purple bacteria - anaerobic - colors range from pink to black - photosynthesize without water - make no oxygen - live in pond and sea mud
Nutrition Most are heterotrophs - saprobes or parasites Some are Autotrophs -photosynthetic or chemosynthetic Did you know? Chemosynthetic bacteria are the base of the food chain at ocean floor vents.
Sources • • • Schraer and Stoltz, Biology, the Study of Life, 7 th ed. Prentice-Hall, 1999 Starr, Cecie, Biology, Concepts and Application, Wadsworth Group, 2003 Fission www. emc. maricopa. edu/faculty/farabee/BIOBK/Bio. Bookmito. html www. biology. hawaii. edu/bio 171/Notes/Bacteria/page 6. htm Archaebacteria http: //biology. com/learning/archaea/introduction. html Staphylococcus http: //www. bact. wisc. edu/Bact 330/lecturestaph Conjugation http: //tidepool. st. usm. edu/crswr/bactconjug. html Legume nodules http: //www. danieldeepak. com/bacteria. htm Salmonella http: //www. office. pref. iwate. jp/~hp 1002/eiseika/salmonella. jpg Bacteria reproducing http: //marshallteachers. sandi. net/teacher_sites/mcquillan/04. Classificatio n/Readings/Six. Kingdoms. html Dental plaque http: //www. microbeworld. org/htm/aboutmicro/microbes/types/. htm Fission time-lapse http: //www. cellsalive. com/ecoli. htm Diplococcus http: //www. cat. cc. md. us/courses/bio 141/labmanua/lab 16/diplo. html
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