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Bacteria EUKARYOTES PROKARYOTES BACTERIA ARCHAEA • Bacteria are of immense importance because of their rapid growth, reproduction, and mutation rates, as well as, their ability to exist under adverse conditions. • The oldest fossils known, nearly 3.5 billion years old, are fossils of bacteria-like organisms. Classification of Bacteria • Archaebacteria: extremists • Eubacteria: –Heterotrophs –Photosynthetic autotrophs –Chemosynthetic autotrophs Archaebacteria • Methanogens – Methane producers – anaerobic • Halophiles –Halo = salt –Philia = love • Thermophiles –Thermo = heat Thermophiles These are Archaebacteria from hot springs and other high temperature environments. Some can grow above the boiling temperature of water. They are anaerobes, performing anaerobic respiration. Thermophiles are interesting because they contain genes for heat-stable enzymes that may be of great value in industry and medicine. An example is taq polymerase, the gene for which was isolated from a collection of Thermus aquaticus in a Yellowstone Park hot spring. Taq polymerase is used to make large numbers of copies of DNA sequences in a DNA sample. It is invaluable to medicine, biotechnology, and biological research. Annual sales of taq polymerase are roughly half a billion dollars. Eubacteria • Heterotrophs • Photosynthetic autotrophs • Chemosynthetic autotrophs Eubacteria - Heterotrophs • Found everywhere • Parasites: live off of other organisms • Saprobes: live off of dead organisms or waste (recyclers) • Live symbiotically in the guts of animals or elsewhere in the bodies Photosynthetic Autotrophs • Photosynthetic: make their own food from light • Cyanobacteria – blue-green • Slimy stuff in ponds, streams, moist areas • Cyanobacteria were the first organisms to do modern photosynthesis and they made the first oxygen in the earth’s atmosphere Eubacteria: Chemosynthetic Autotrophs • Get energy by breaking down inorganic substances like sulfur and nitrogen • Make nitrogen in the air usable for plants – nitrogen fixing bacteria in roots of legumes (clover, peas & beans) Most Bacteria reproduce by one of 3 means: 1. Asexually –Also known as binary fission in which the chromosome replicates and then the cell divides –This produces 2 identical cells 2. Sexually –Also known as conjugation in which genetic material is exchanged through cell-to-cell contact –This increases the genetic diversity of bacteria Sex pilus 1 m 3. Spore Formation • When living conditions become unfavorable, some bacteria can form dehydrated cells known as endospores • Endospores have thick walls and can resist heat, drought and radiation and thus they can survive harsh conditions Endospore • When conditions improve, the spore will germinate and bacteria will grow again HOW ARE BACTERIA CLASSIFIED? Structure of Bacteria • Two parts to Bacteria Structure: –Arrangement –Shape Arrangement • Paired: diplo • Grape-like clusters: staphylo • Chains: strepto Shape • Rod: bacillus • Spheres: coccus • Spirals: spirillum Shapes of Bacteria Examples • Streptococcus: chains of spheres • Staphylospirillum: Grapelike clusters of spirals • Streptobacillus: Chains of rods • The Gram stain, which divides most clinically significant bacteria into two main groups, is the first step in bacterial identification. • Bacteria stained purple are Gram + their cell walls have thick petidoglycan • Bacteria stained pink are Gram – their cell walls have thin peptidoglycan. The Gram stain has four steps: • 1. crystal violet, the primary stain: followed by • 2. iodine, which acts as a mordant by forming a crystal violet-iodine complex, then • 3. alcohol, which decolorizes, followed by • 4. safranin, the counterstain. Is this gram stain positive or negative? Identify the bacteria. Is this gram stain positive or negative? Identify the bacteria. Other ways to identify Bacteria • By their Nutrition –1. Autotroph –2. Heterotrophs • Based on Respiration –1. Aerobes- need oxygen during respiration –2. Anaerobes – do not use oxygen during respiration • Obligate aerobes - must have O2 • Obligate anaerobes – must live without O2 • Facultative anaerobes – can function without but not killed by oxygen How large are bacteria? • There are 106 µmeters in one meter, and it is these units that are used to measure the size of bacteria. • Typically, bacteria range from about 1 µm to about 5 µms. Virus Comparing the size of a virus, a bacterium, and an animal cell Bacterium Animal cell Animal cell nucleus 0.25 m Structure of Bacteria • Bacteria have cell walls made of peptidoglycan (amino acid & sugar) • Bacteria have a circular chromosome Movement • Flagella ~ Tail like structure the whips around to propel the bacterium • Cilia ~ Miniature flagella surround the cell that help to “swim” • Non motile ~ Sticky pili like structures that keep the bacterium from moving (pilus – singular) ECOLOGICAL ROLES 1. Bacteria act as decomposers, which means they break down dead organic materials 2. They also help recycle carbon, nitrogen and sulfur and other chemicals needed by living things 3.Many bacteria live with organisms of other species in a relationship called symbiosis –bacteria in your mouth (bacteria benefit & you are harmed) –bacteria in cow intestines (bacteria benefit & cow benefits) –E. coli, a bacteria found in human intestines, helps with the process of digestion DISEASES CAUSED BY BACTERIA • Some bacteria cause diseases in humans • Some examples are: –Tuberculosis, anthrax, lyme disease, strep throat, cholera • Antibiotics can kill harmful bacteria if used properly Germ Theory of Disease • Joseph Lister (1827-1912) – Aseptic Techniques • Robert Koch (1843-1910) – Germ Theory –A specific microorganism causes a specific disease HUMAN USES OF BACTERIA • Bioremediation – use of microorganisms to help restore natural environmental conditions; ex. Sewage treatment plants • Bacteria are used in the production of many foods; some examples are: cheese, yogurt, vinegar, beverages (beer & wine) • Bacteria have applications in medicine; some bacteria have been genetically engineered to produce insulin • Use plasmids – insert other genes into bacterial DNA