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Transcript
Bacteria Bacteria – 2 Domains (Archaebacteria and Eubacteria) • There are more bacteria on Earth than stars in the sky! • The closest estimate is that there are 5 million trillion trillion bacteria on Earth – that’s a 5 with 30 zeroes after it. • Bacteria produce the air we breathe, clean the water we drink, and create fertile soil. • Less than one percent of bacteria cause diseases. Bacteria are prokaryotic plasmid Most bacteria die when conditions get bad: • These conditions could be a change in temperature, loss of food, exposure to specific toxic chemicals, change in pH (acid levels), etc. • Some bacteria can preserve themselves during bad times, then they can re-grow and resume their lives. They do this by producing an endospore. • Endospores can preserve the cell’s DNA until conditions get better again. They are resistant to all the bad conditions. Endospore production – preserves the cell during hard times– not a form of reproduction Endospore Bacteria that are harmful to humans and form endospores: Clostridium tetani – causes tetanus (lock jaw) Clostridium botulinum – causes food deadly poisoning Bacterial Reproduction Binary fission is an asexual reproductive process. All offspring should be genetically identical to the parent cell and to each other. Using binary fission, some bacteria can divide as often as every 20 minutes! Binary Fission DOUBLING Etc. Methods of DNA Exchange Even though bacteria reproduce asexually, they show methods of exchanging DNA pieces that increases their variability. There are 3 main methods: a) Conjugation b) Transduction c) Transformation Methods of Exchanging DNA Conjugation – two bacteria join by a cytoplasmic bridge and exchange small circles of DNA called plasmids. The cells may in this way exchange useful information. Conjugation Conjugation animation Methods of Exchanging DNA Transduction - the process by which DNA is transferred from one bacterial cell to another by infection with a virus. Viruses that infect bacteria are called bacteriophages. Bacteriophage Transduction Bacterial transduction animation Methods of Exchanging DNA Transformation- a living bacterial cell takes in the DNA from a dead bacterial cell. The DNA is then incorporated into the genome of the living cell. Transformation Bacterial transformation animation DOMAIN Archaebacteria Are EXTREMOPHILES (love extreme environments) Are usually found in harsh environments – hot, salty, acidic. Ancient – probably resemble the first bacteria and therefore the first life forms on the planet Exobiologists (biologists who are looking for life on other planets or moons) guess that they should be looking for these types of cells. WHY? Archaebacteria : Methanogens (generate methane) • produce methane – live in digestive tract of mammals, in swamps and sewage) Archaebacteria: Thermophiles • can live in extremely hot water – found in hot springs Halophiles • Live in very salty water, such as the Great Salt Lake in Utah and the Dead Sea Eubacteria – true bacteria • Many types – modern bacteria • Classification is by: – – – – Cell shape Cell wall composition Nutrition Respiration Cell Shape Coccus - round Bacillus - rod Spirillum Names can tell a lot about the bacterial growth • Some bacteria grow alone, but others stick together • Diplo…means two – Diplococcus – Diplobacillus • Strepto… means chain - as in streptococcus - and streptobacillus •Staphylo… means cluster •As in staphlyococcus or Cell Wall Composition – Gram positive or Gram negative Gram Positive Gram negative Stains blue because cell wall retains Stains pink because cell wall does not retain violet stain ( Absorbs saffrin violet stain Bacterial colonies consist of millions of bacterial cells growing together. Sample Colony Characteristics Size: 2mm diameter Shape: Circular Elevation: Convex Surface: Smooth Density: Opaque Colonies growing into each other Nutrition – Autotrophic or Heterotrophic Autotrophs –make their own food – use sun’s energy or chemical energy – E.g cyanobacteria (blue-green algae, nitrogenfixing bacteria) Most Bacteria are Heterotrophs Escherichia coli Spirillum Found in intestines Anthrax Deadly respiratory bacteria Can cause certain STD’s Types of Heterotrophic Bacteria Saprophytic - Those bacteria who live and get nutrients by digesting dead plants/animals. These bacteria are decomposing bacteria. Saprophytic colony on tree trunk Types of Heterotrophic Bacteria Parasitic – obtain food by living attached to or inside living organisms. These are harmful to the host organism, as they feed directly on the tissues of the organism. These may cause disease (in which case, they are called pathogens). Types of Heterotropic Bacteria Parasitic bacteria Staphylococcus aureus – causes pimples, boils, pneumonia, sepsis Streptococcus mutans – causes tooth decay Types of Heterotrophic Bacteria Mutualistic or Symbiotic bacteria – these bacteria feed off of other living organisms but have no harmful effect on the host organism. Types of Heterotrophic Bacteria Mutualistic or Symbiotic Bacteria E. Coli – intestinal bacteria Nitrogen fixing bacteria – plant roots Respiration – process of getting energy from food Aerobic bacteria These bacteria need oxygen to metabolize (break down) food. If a bacterium cannot live without oxygen, it is known as an obligate aerobe. » EX – TUBERCULOSIS (Tb) BACTERIUM Tb lung If a bacterium prefers to live with oxygen it is known as a facultative aerobe. Anaerobic bacteria These bacteria do not need oxygen. In some cases, these bacteria cannot survive in the presence of oxygen, in which case they are called obligate anaerobes. EX – TETANUS This baby probably got tetanus from honey – don’t give honey to a baby! Some bacteria can live in the presence of oxygen, but do not require it for survival. These are known as facultative anaerobes. E. coli How important are bacteria to the world? • Decomposition – most important function for living things. What happens to all the dead bodies? • Bacteria are important Decomposers. Food web Nitrogen cycle Bacteria recycling and incorporating nitrogen (N), for protein manufacturing. Cow Digestion Bacteria in the stomach - Help breakdown plant products for herbivores. Foods from bacteria cheese yogurt sauerkraut Uses of bacteria other than food production • Bioremediation – using microorganisms to rid environment of harmful substances – Ex – oil spill site – Hazardous waste site – Sewage treatment Antibiotics, if used cautiously, can cure bacterial infections Antibiotics are tested using Petri dishes and paper soaked in the antibiotic – anywhere the antibiotic inhibits growth, a zone of inhibition will be seen Not effective Most effective Antibiotic Resistance Antibiotics are chemicals that are selectively toxic (they are toxic to certain cells, and not others). They kill or inhibit the growth or reproduction of bacterial cells. Some prevent bacterial cells from producing parts they need, other actually break the bacterial cell wall. Antibiotic Resistance Some bacteria have evolved defenses against antibiotics. They may inactivate the antibiotic or a mutation may have changed the bacterial compound that would normally be affected by the drug. Because bacteria are able to exchange DNA (conjugation, transduction, transformation), it is easy for the resistance to be passed on to other bacteria. Antibiotic resistance animation Bacteria http://www.bozemanscience.com/bacteria • Read section 2.2 pages 59- 66 and answer questions #1, 2, 3, 5, and 7