33-1 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Chapter 33: Bacteria

33-2 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Prokaryotes Bacteria are prokaryotes Characteristics –single-celled –semi-rigid wall around plasma membrane –no membrane-bound organelles –genetic material free in cytoplasm

33-3 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint The first life Bacteria were the earliest forms of life on Earth –oldest fossils of bacteria are 3.5 billion years old Early forms existed under conditions hostile to most modern living organisms –anaerobic atmosphere with H 2, NH 3, H 2 S –high levels of UV radiation Descendants of early bacteria now found in hot, hypersaline or anoxic areas that resemble ancient earth

33-4 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Early photosynthetic bacteria Evolution of photosynthesis allowed bacteria to fix carbon Early photosynthetic pathways were anoxygenic (did not produce oxygen) Subsequent evolution of oxygenic photosynthesis (2.5 billion years ago) produced enough O 2 to change composition of atmosphere

33-5 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Classifying bacteria Biochemical, physiological and immunological characteristics are used as a rapid method of identifying and classifying bacteria –staining reactions –cell shape –cell grouping –presence of special structures –growth medium –antibiotic resistance –DNA sequences –immunological tests

33-6 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Super kingdoms Prokaryotes are divided into two groups on the basis of biochemical characteristics Super kingdom Bacteria –formerly called Eubacteria (‘true bacteria’) Super kingdom Archaea –formerly called Archaeobacteria (‘ancient bacteria’)

33-7 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Fig. 33.3: Evolutionary relationships

33-8 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Super kingdom Bacteria Diverse metabolic pathways have allowed Bacteria to use most materials as sources of energy –only some plastics and organochlorine compounds are resistant to bacteria Characteristics –peptidoglycan is major cell wall polymer –membrane lipids are esters –protein synthesis disrupted by streptomycin –some nitrifying and photosynthetic species

33-9 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Bacteria Cyanobacteria are also known as ‘blue-green algae’ –blue phycobilins (a water-soluble pigment) gives them the characteristic blue-green colour, which is obvious when they form dense mats or blooms in shallow waters Under poor conditions, endospores form inside bacteria (such as Clostridium and Bacillus) –endospores are resistant to high temperatures, radiation and chemicals –many species of endospore-forming bacteria are important pathogenic agents

33-10 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Archaea Many Archaea occur in extreme environments, including deep sea volcanic vents and thermal pools –halophiles (hypersaline) –acidophiles (low ph) –thermophiles (high temperatures) Characteristics –peptidoglycan is not major cell wall polymer –membrane lipids are ethers –protein synthesis disrupted by diphtheria toxin –no nitrifying or photosynthetic species

33-11 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Abundance Bacteria populations are very large and dense Human skin harbours c cells/cm -1 –clustered distribution in moist, bacteria-friendly areas –suite of species varies from person to person Human faecal material contains c cells/gm -1 –high diversity of bacteria in colon

33-12 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Metabolic diversity Energy source –phototrophs use radiant (light) energy –chemotrophs use chemical energy Carbon source –autotrophs synthesise organic compounds from inorganic carbon –heterotrophs use organic compounds as energy source Four nutritional types –chemoautotrophs –chemoheterotrophs –photoautotrophs –photoheterotrophs

33-13 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Autotrophs Photoautotrophs –photosynthetic bacteria: cyanobacteria, purple bacteria and green bacteria –use light energy to reduce CO 2 –reductant may be H 2 O, H 2 S, H 2 Chemoautotrophs –nitrifying bacteria, methanogenic bacteria, iron-oxidising bacteria and others –use chemical energy (NH 4 +, NO 2 -, H 2 S, S, Fe 3 + ) to reduce CO2 –reductant may be H 2 O, H 2

33-14 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Fig b + c: Cellular metabolic categories

33-15 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Heterotrophs Photoheterotrophs –anaerobically-growing purple bacteria and green bacteria –use light energy to reduce CH 2 O –reductant may be CH 2 O, H 2 S, S, H 2 Chemoheterotrophs –many bacteria (also animals and fungi) –CH 2 O is reductant and provides energy

33-16 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Fig d + a: Cellular metabolic categories

33-17 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Anaerobic bacteria Anaerobic pathways use compounds other than O 2 as terminal oxidants CH 2 O + NO 3 -  CO 2 + N 2 or SO 4 2-, HCO 3 -, Fe 3+ or fumarate or S, CH 4, Fe 2+ or succinate

33-18 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Nitrogen cycle Nitrogen-fixing bacteria (cyanobacteria, plant symbiotes, Clostridium, others) are the only organisms capable of fixing molecular nitrogen N 2 + 8H + + 6e -  2NH 4 + Reaction is sensitive to molecular oxygen and other oxidants, so occurs in a highly reducing or anaerobic environment Ammonium ion is used to form glutamine and glutamate (amino acids) in bacterial cell (cont.)

33-19 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Nitrogen cycle (cont.) Nitrifying bacteria oxidise ammonium to nitrite (Nitrosomonas) and nitrate (Nitrobacter) –transform fixed nitrogen from nitrogen fixers or decomposing organisms Denitrifying bacteria (Pseudomonas, anaerobic bacteria) use nitrite and nitrate as terminal electron receptors –produce gaseous nitrous oxide and molecular nitrogen –nitrogen is no longer available for other organisms, except nitrogen-fixing organisms

33-20 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Fig. 33.9a: Nitrogen cycle

33-21 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Bacterial fermentation Fermentation (anaerobic energy metabolism) produces a range of end products, many of which are used in agriculture and food and alcohol production Lactic acid –Lactobacillus, Lactococcus and other bacteria are used in the production of yoghurt and milk Ethanol –Bacteria decarboxylate pyruvate to form acetate, which is then reduced to ethanol

33-22 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Methanogens Chemoautotrophic methanogens use hydrogen and carbon dioxide to produce methane 4H 2 + CO 2  CH 4 + 2H 2 O Methanogens occur in anaerobic environments, such as animal intestines, waterlogged soils and mud or acetate or formate

33-23 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Genetic systems Bacteria reproduce asexually by fission (cell division) Genetic variation in bacteria is due to –mutation –mixing genetic material between different cells  transformation  conjugation  transduction

33-24 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Transformation Bacteria may take free DNA molecules into their cells DNA recognised as foreign may be broken down DNA similar to the bacterium’s DNA may –recombine with the chromosomal or plasmid DNA –become a plasmid This process of taking up free DNA and making it part of the cell is transformation

33-25 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Conjugation DNA may be transferred directly between bacteria via plasmids in the process of conjugation A plasmid may pass a copy of itself from one cell to another Once in a new cell, a plasmid may –establish itself as an independent plasmid in the cell –combine with another plasmid –combine with the chromosomal DNA

33-26 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Transduction Bacteriophages (viruses that live in bacterial cells) integrate their DNA into the host’s chromosomal DNA Temperate (non-virulent) phages become virulent under certain conditions, rupturing the cell and releasing virions (phage particles) A virion may inadvertently carry the original host’s DNA into another cell, where it may recombine or integrate with the new host’s DNA

33-27 Copyright  2005 McGraw-Hill Australia Pty Ltd PPTs t/a Biology: An Australian focus 3e by Knox, Ladiges, Evans and Saint Plasmids and phages Plasmids and phages are abundant in bacterial populations Gene transfer often confers new properties on host bacteria –antibiotic resistance –antibiotic synthesis –toxin synthesis –production of tissue-damaging enzymes –gall-production in plants –resistance to phage attack