Kingdoms Archaebacteria & Eubacteria BACTERIA

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1 BACTERIA 3.5 billion years with our little friends. Kingdoms Archaebacteria & Eubacteria Characterized by the prokaryotic cell (no nuclear or organelle membranes). Prokaryotes outnumber all eukaryotes combined and flourish in all habitats. Exist primarily as single cells, although can form coloines. Usually 2-5 micrometers in length, onetenth the size of eukaryotic cells. Capsule: a sticky, gelatinous covering on the cell wall for protection & adherence. Bacterium with a capsule are more likely to cause disease. Cell Wall: gives the cell its shape and prevents osmosis from bursting the cell. Plasma Membrane: surrounds the cell and regulates what leaves & enters it. Flagellum: whiplike protrusion for movement. 1

2 Pilli: hairlike structures for sticking to another bacteria during conjugation. Chromosome: a single circular DNA molecule, not contained in a nucleus. Plasmids: a few genes are located in these small, circular chromosomal piece. May be several plasmids. Capitalizing on Bacterial Structure for Disease Control Sir Alexander Fleming discovered Penicillin in It is a mold that attaches to the cell walls of bacteria, creating holes. This allows water to enter and exert enough pressure so that they explode. Ribosomes: create the proteins necessary for life functions. Smaller in size than those of eukaryotes. Archaebacteria vs. Eubacteria Archabacteria : live in harsh environments and are chemically distinct from Eubacteria. Four types: 1. Methanogens: produce methane and live in oxygen free environments such as swamps, marshes, mammals. Used to purify waste water. 2. Thermoacidophiles: live in extremely hot ( C) and acidic water. Colonies glisten at the edge of boiling hot springs. 3. Chemosynthesizers: use inorganic compounds as an energy source. Flourish in deep-sea hot springs formed by volcanic vents. 4. Extreme Halophiles: live in extremely salty conditons such as Great Salt Lake in Utah and the Dead Sea in Israel. 2

3 Eubacteria Traits- Cell Walls 1. Composition: Gram-positive bacteria: walls made of protein-sugar complex, turn purple when treated with Gram stain. Gram negative bacteria: have an extra layer of lipid on outside of cell wall, turn pink from Gram stain. 2. Shape: Motility Flagella Filaments attached at either end move cell in corkscrew fashion Soil inhabiting bacteria secrete a slime upon which they glide. Many bacteria exhibit an oriented movement in response to chemical, light, magnetic, or other stimuli. Growth & Reproduction Reproduce Asexually through Binary Fission. Geometric growth Generation time from 20 minutes to 3 hours. Can form endospores: tough walled cells that can resist environments. Release antibiotics, to inhibit growth of competitors. Used by humans. Introducing Genetic Variation into Populations Despite the lack of meiosis and sexual cycles, bacteria can recombine genetic material by: 1. Transformation: uptake of genes from burst bacteria 2. Conjugation: direct transfer of genetic material from one bacterium to another. 3. Transduction: injection of genes by a virus. Example: Bacteriophage 3

4 Metabolism Heterotrophs: may be parasites (feed on live organisms) or saprophytes (feed on dead organisms or waste). Photosynthetic Autotrophs: use sunlight. Cyanobacteria contain chlorophyll, live in ponds & streams Chemosynthetic Autotrophs: break down inorganic compounds containing sulfur & nitrogen for energy and building blocks. Respiration Obligate aerobes: need oxygen for cellular respiration Facultative anaerobes: can use oxygen, but also can grow in anaerobic conditions using fermentation. Obligate anaerobes: cannot use, and are poisoned by, oxygen. Bacteria - Disease One half of all human diseases are caused by pathogenic bacteria Pathogenic bacteria commonly cause disease by producing toxins Exotoxins: potent, induces various symptoms, causes botulism & cholera Endotoxins: all produce fever aches in the host, causes typhoid fever & Salmonella poisoning. Bacteria - Uses More than half the antibiotics come from the soil bacteria genus Streptomyces. Necessary for many metabolic processes in our bodies. E. coli is needed to metabolize fecal matter in our colon in order for us to absorb minerals & Vitamin K. Prokaryotes have been used to: Digest organic wastes Produce chemical products Make vitamins & antibiotics Produce food products such as yogurt & cheese Research using Escherichia Coli has expanded our understanding of molecular biology. 4

5 Bacteria Chemical Cycles Recycle chemical elements between the biological & physical world Decompose dead organisms and the waste products of living ones Autotrophic bacteria bring carbon from CO2 into the food chain and release oxygen. Cyanobacteria fix atmospheric nitrogen and supply plants with the nitrogen they need to make proteins. 5