View
215
Download
1
Category
Tags:
Preview:
Citation preview
34-1Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Chapter 34: Bacteria
34-2Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-3Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-4Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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 H2, NH3, H2S
– high levels of UV radiation
• Descendants of early bacteria now found in hot, hypersaline or anoxic areas that resemble ancient earth
34-5Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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 O2 to change composition of atmosphere
34-6Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-7Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-8Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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’)
34-9Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 34.3: Evolutionary relationships
34-10Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-11Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-12Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-13Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Bacterial populations• Very large and dense• Human skin harbours about 100 000 cells/cm-1
– clustered distribution in moist, bacteria-friendly areas– suite of species varies from person to person
• Human faecal material contains about100 000 000 000 cells/gm-1
– high diversity of bacteria in colon
34-14Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-15Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Autotrophs• Photoautotrophs
– photosynthetic bacteria: cyanobacteria, purple bacteria and green bacteria
– use light energy to reduce CO2
– reductant may be H2O, H2S, H2
• Chemoautotrophs– nitrifying bacteria, methanogenic bacteria, iron-oxidising
bacteria and others
– use chemical energy (NH4+, NO2
-, H2S, S, Fe3+) to reduce
CO2
– reductant may be H2O, H2
34-16Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 34.7 b + c: Cellular metabolic categories
34-17Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Heterotrophs• Photoheterotrophs
– anaerobically-growing purple bacteria and green bacteria
– use light energy to reduce CH2O
– reductant may be CH2O, H2S, S, H2
• Chemoheterotrophs– many bacteria (also animals and fungi)
– CH2O 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 CO2 as a carbon source, but obtain energy by oxidising inorganic substances
34-18Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-19Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 37.7 d + a: Cellular metabolic categories
34-20Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Anaerobic metabolism by bacteria
Anaerobic pathways use compounds other than O2 as terminal oxidants
CH2O + NO3- CO2 + N2
or SO42-, HCO3
-, Fe3+ or fumarate
or S, CH4, Fe2+ or succinate
34-21Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
N2 + 8H+ + 6e- 2NH4+
• 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
34-22Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-23Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Fig. 34.8a: Nitrogen cycle
34-24Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-25Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Methane-producing bacteria• Chemoautotrophic methanogens use hydrogen
and carbon dioxide to produce methane
4H2 + CO2 CH4 + 2H2O
• Methanogens occur in anaerobic environments, such as animal intestines, waterlogged soils and mud
or acetate or formate
34-26Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-27Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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. 34.10a: Transformation
34-28Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-29Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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. 34.10b: Conjugation
34-30Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-31Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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. 34.10c: Transduction
34-32Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
34-33Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-34Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides 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
34-35Copyright 2010 McGraw-Hill Australia Pty Ltd PowerPoint slides to accompany Biology: An Australian focus 4e by Knox, Ladiges, Evans and SaintSlides prepared by Karen Burke da Silva, Flinders University
Recommended