Transcript Bacteria
Prokaryotes Kingdoms Eubacteria & Archaebacteria Prokaryote “Before nucleus” Characteristics: • Unicellular • 1-5 μm diameter • Cell walls -Maintains shape -Provides protection -Prevents lysis in a hypotonic environment PROKARYOTES EUKARYOTES Size 1-10 microns 10-100 microns Complexity unicellular, rarely sometimes small colonies unicellular more often multicellular Membrane bound organelles none nuclei, mitochondria, chloroplasts, lysosomes, endoplasmic reticulum, golgi, & vacuoles Prokaryotes Nucleus Eukaryotes no yes Chromosomes single & circular usually several & linear Introns Rarely frequent no yes Histones Prokaryotes Eukaryotes Ploidy haploid diploid Mitosis & Meiosis absent present Sexual reproduction none, or unidirectional from donor to recipient usually, involves fusion of haploid gametes Bacteria Single-celled prokaryotes Two kingdoms of bacteria: • Archaebacteria • Eubacteria Archaebacteria • Methanogens: Anaerobic bacteria (oxygen is a poison) Produce energy by converting H2 & CO2 into methane gas. Live in swamps & marshes • Extreme Halophiles: “Salt-loving" bacteria that use salt to generate ATP for energy. • Thermoacidophiles: Live in extremely acidic environments (pH less than 2) that have extremely high temperatures (up to 110o C). e.g. geothermal springs at Yellowstone National Park. Archaebacteria Eubacteria • Contains the bacteria commonly referred to as germs. • This kingdom contains most of the world's bacteria Eubacteria are classified by: • Shape • Clustering • Respiration Eubacteria Shape • Coccus - round • Bacillus - rod-shaped • Spirillum - spiral-shaped Eubacteria Clustering • Diplo - a prefix used with the shape name to indicate pairing of cells. • Strepto - a prefix used with the shape name to indicate chains. • Staphylo - a prefix used with the shape name to indicate clusters Streptococcal (Group A) Infections Susceptibility & Resistance Eubacteria Respiration • Obligate anaerobes - cannot survive in the presence of atmospheric oxygen. • Facultative anaerobes - can live with or without atmospheric oxygen. • Obligate aerobes - cannot survive without atmospheric oxygen. MRSA Staphylococcus aureus The acronym MRSA stands for methicillinresistant Staphylococcus aureus Maggots Rid Patients Of Antibiotic-resistant Infection, MRSA — University of Manchester researchers are ridding diabetic patients of the superbug MRSA - by treating their foot ulcers with maggots. ScienceDaily (May 5, 2007) Gangrene Tetanus Necrotizing Fasciitis Leprosy Helicobacter pylori Lyme Disease Many antibiotics have no effect on gram-negative bacteria Gram Staining •Using a technique called the Gram stain –Scientists can classify many bacterial species into two groups based on cell wall composition, Gram-positive and Gram-negative Lipopolysaccharide Cell wall Peptidoglycan layer Cell wall Outer membrane Peptidoglycan layer Plasma membrane Plasma membrane Protein Protein Grampositive bacteria Gramnegative bacteria 20 m (a) Gram-positive. Gram-positive bacteria have a cell wall with a large amount of peptidoglycan that traps the violet dye in the cytoplasm. The alcohol rinse does not remove the violet dye, which masks the added red dye. Figure 27.3a, b (b) Gram-negative. Gram-negative bacteria have less peptidoglycan, and it is located in a layer between the plasma membrane and an outer membrane. The violet dye is easily rinsed from the cytoplasm, and the cell appears pink or red after the red dye is added. Bad bacteria - toxic Toxins Substances that disrupts the metabolism of other organisms. • Endotoxin - made up of lipids and carbohydrates associated with the outer membrane of gram-negative bacteria. These toxins are some of the strongest poisons known to man and cause violent reactions in host organisms. • Exotoxin - proteins produced inside gram-positive bacteria cells and secreted into the environment. These toxins usually produce fever, weakness, and capillary damage. Parts of a bacteria cell • Cell wall - some rigid and others flexible. • Cell membrane - same as other cells. • Cytoplasm - same as other cells. • DNA - a single, circular chromosome (Plasmid) located in the cytoplasm. Bacteria do not have a nucleus. • Capsule - a thick, gel-like, protective coating on some bacteria cells. • Pili - short, hairlike protein structures on the surface of some bacteria that help them stick to host cells. • Flagella - long protein structures that turn to propel some bacteria cells. •The cell wall of many prokaryotes –Is covered by a capsule, a sticky layer of polysaccharide or protein 200 nm Capsule Figure 27.4 Fimbriae and pili –allow bacteria to stick to their substrate or other individuals in a colony Fimbriae 200 nm Figure 27.5 Taxis – movement toward or away from a stimulus + chemotaxis = movement toward chemical - chemotaxis = movement away from chemical Flagellum Filament 50 nm Cell wall Hook Basal apparatus Plasma membrane Reproduction • Asexual, by binary fission - the DNA replicates and then the cell pinches inward and splits in two. • Conjugation - two cells exchange a portion of their DNA across a bridge formed between the cells. New material replaces old material in the cell. While this increases the genetic variability in the organisms, it is not true sexual reproduction. • Endospores - during adverse conditions, the DNA is encased in a protective envelope. This endospore can lie dormant for years or until favorable conditions return. Binary Fission Conjugation Endospores Can remain viable in harsh conditions for centuries Endospore 0.3 m Figure 27.9 Prokaryotic Metabolism Antibiotics Drugs that fight bacteria by interfering with their cellular functions. • PENICILLIN interferes with cell wall synthesis. • TETRACYCLINE interferes with protein synthesis. • Many antibiotics are derived from chemicals that bacteria or fungi produce. • • SULFA DRUGS - antibiotics that are synthesized in laboratories • Many Antibiotics are able to affect a wide variety of organisms; they are called BROAD SPECTRUM ANTIBIOTICS. Antibiotic Resistance When a population of bacteria is exposed to an Antibiotic, the most susceptible DIE. A Few Mutant bacteria that are resistant to the Antibiotic may continue to grow. A Resistant Population then grows from these Mutant Bacteria through reproduction and genetic recombination. These new Population are Antibiotic-Resistant. This has resulted from the Over Use of Antibiotics. Many diseases that were once easy to treat are becoming more difficult to treat. USEFUL BACTERIA • Used in Sewage Treatment, and as Decomposers, breaking down the remains of organic matter in dead plant and animal waste. Recyclers, returning nutrients back to the environment. • Food production. Bacteria help us make buttermilk, sour cream, yogurt, cottage cheese, sauerkraut and pickles. • Used in industrial chemical production. They produce organic chemicals and fuels. They’re used in the mining of minerals and their products are used as insecticides. • Used to help clean up environmental disasters caused by humans, such as chemical and oil spills. •Prokaryotes are the principal agents in bioremediation –The use of organisms to remove pollutants from the environment