34-1 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Chapter 34: Bacteria

34-2 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Prokaryotes Bacteria are prokaryotes Characteristics –single-celled –semi-rigid wall around plasma membrane –no membrane-bound organelles –genetic material free in cytoplasm

Fig. 34.1: Relative sizes of microbes 34-3 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-4 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University The first cellular 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

34-5 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

34-6 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Classifying and identifying 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

Fig. 34.2: Examples of bacterial cells 34-7 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-8 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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’)

34-9 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig. 34.3: Evolutionary relationships

34-10 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

34-11 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Bacteria (cont.) 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

34-12 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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 the major cell wall polymer –membrane lipids are ethers –protein synthesis disrupted by diphtheria toxin –no nitrifying or photosynthetic species

34-13 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Bacterial populations Very large and dense Human skin harbours about cells/cm -1 –clustered distribution in moist, bacteria-friendly areas –suite of species varies from person to person Human faecal material contains about cells/gm -1 –high diversity of bacteria in colon

34-14 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Nutritional and metabolic diversity of bacteria 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

34-15 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

34-16 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig b + c: Cellular metabolic categories

34-17 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

Question 1 Chemoautotrophs: a) Must consume organic molecules for energy and carbon b) Harness light energy to drive the synthesis of organic compounds from carbon dioxide c) Use light to generate ATP but obtain their carbon in organic form d) Need only CO 2 as a carbon source, but obtain energy by oxidising inorganic substances Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-19 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig d + a: Cellular metabolic categories

34-20 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Anaerobic metabolism by 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

34-21 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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 + The reaction is sensitive to molecular oxygen and other oxidants, so it occurs in a highly reducing or anaerobic environment Ammonium ion is used to form glutamine and glutamate (amino acids) in bacterial cell

34-22 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

34-23 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Fig. 34.8a: Nitrogen cycle

34-24 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Commercial applications of bacterial fermentations Fermentation (anaerobic energy metabolism) produces a range of end products, many of which are used in agriculture and food and alcohol production, for example: –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

34-25 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Methane-producing bacteria 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

34-26 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Genetic systems of bacteria Bacteria reproduce asexually by fission (cell division) Genetic variation in bacteria is due to –mutation –mixing genetic material between different cells  transformation  conjugation  transduction

34-27 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Transformation: gene transfer by free molecules of DNA 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

Fig a: Transformation Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-29 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Conjugation: gene transfer by plasmids 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

Fig b: Conjugation Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-31 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University Transduction: gene transfer by bacteriophages 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

Fig c: Transduction Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

34-33 Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University 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

Fig. B34.4: Life cycle of a tailed bacteriophage Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University

Summary Prokaryotes are microscopic and unicellular Prokaryotes have evolved along two major evolutionary lineages: bacteria and archaea Bacteria are the most abundant organisms on earth, due to their remarkable range of nutritional and metabolic types Multiple genetic mechanisms have enabled remarkable adaptability and diversity Bacteria are highly complex entities, capable of performing a myriad of functions Copyright  2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and Saint Slides prepared by Karen Burke da Silva, Flinders University