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Prokaryotes and the Origins of Metabolic
DiversityChapter 27 Part two
Prokaryotes and the Origins of Metabolic
DiversityChapter 27 Part two
By: Jonathan, Javeria & MeganBy: Jonathan, Javeria & Megan
Nutritional & Metabolic Activity
Nutritional & Metabolic Activity
Categories of Prokaryotes Based on how organism obtains energy and carbon Types: Phototrophs, Cehmoautotrophs, Photoheterotrophs, Chemoheterotrophs
Four main groups of prokaryotes
Four main groups of prokaryotes
Photoautotrophsキキ Harness light energy to drive synthesis of organic compound from carbon dioxideキキ Have internal membranes with light-harvestng pigment systemsキキ Include cyanobacteria and all photosynthetic eukaryotes
Chemoautotrophsキキ Also need CO2 as carbon source, obtains energy by oxidizing inorganic substancesキキ Extracts energy from H2S, NH3, Fe(2+)
Photoautotrophsキキ Harness light energy to drive synthesis of organic compound from carbon dioxideキキ Have internal membranes with light-harvestng pigment systemsキキ Include cyanobacteria and all photosynthetic eukaryotes
Chemoautotrophsキキ Also need CO2 as carbon source, obtains energy by oxidizing inorganic substancesキキ Extracts energy from H2S, NH3, Fe(2+)
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Prokayotic groups cont.Prokayotic groups cont.
Photoheterotrophsキ Uses light to generate ATPキ Obtains carbon in organic form
Chemoheterotrophsキ Consumes organic molecules for both
energy and carbonキ Found in prokaryotes, protests, fungi,
animals, some parasite plants
Photoheterotrophsキ Uses light to generate ATPキ Obtains carbon in organic form
Chemoheterotrophsキ Consumes organic molecules for both
energy and carbonキ Found in prokaryotes, protests, fungi,
animals, some parasite plants
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Nutritional Diversity Among
Chemoheterotrophs
Nutritional Diversity Among
Chemoheterotrophs
キキ Saprobes are decomposers that absorb nutrients from dead organic matter
キキ Specific nutrients needed for growth extremely diverse: Latobacillus requires specific medium, E. Coli has versatile needs
キキ So diverse that some bacteria can metabolize petroleum
キキ Synthetic organic compounds that can’t be broken by any chemoautotroph is nonbiodegradable
キキ Saprobes are decomposers that absorb nutrients from dead organic matter
キキ Specific nutrients needed for growth extremely diverse: Latobacillus requires specific medium, E. Coli has versatile needs
キキ So diverse that some bacteria can metabolize petroleum
キキ Synthetic organic compounds that can’t be broken by any chemoautotroph is nonbiodegradable
Nitrogen MetabolismNitrogen Metabolism
キキ Prokaryotes perform key steps in nitrogen cycle
キキ Nitrosomonas converts NH3 to NO2(+); some others perform nitrogen fixation, which is conversion of N2 to NH3
キキ Photoautotrophs that fix nitrogen only require light energy, CO2, N2, water and some minerals
キキ Prokaryotes perform key steps in nitrogen cycle
キキ Nitrosomonas converts NH3 to NO2(+); some others perform nitrogen fixation, which is conversion of N2 to NH3
キキ Photoautotrophs that fix nitrogen only require light energy, CO2, N2, water and some minerals
Metabolic Relationships to Oxygen
Metabolic Relationships to Oxygen
キキ Obligate aerobes use O2 for cellular respiration
キキ Facultative anaerobes can use either O2 or fermentation
キキ Obligate anaerobes are poisoned by O2
Either live by fermentation or anaerobic respiration, inorganic molecules other than O2 accept electrons at end of electron transport chain
キキ Obligate aerobes use O2 for cellular respiration
キキ Facultative anaerobes can use either O2 or fermentation
キキ Obligate anaerobes are poisoned by O2
Either live by fermentation or anaerobic respiration, inorganic molecules other than O2 accept electrons at end of electron transport chain
キキ All major metabolic capabilities today evolved in first billion years of life
キキ Hypotheses are from molecular systematics, comparisons between prokaryotes, and geological evidence
キキ All major metabolic capabilities today evolved in first billion years of life
キキ Hypotheses are from molecular systematics, comparisons between prokaryotes, and geological evidence
Origins of Metabolism
キキ ATP as universal source of energy points out that it was used early on
キキ Glycolysis and chemiosmotic mechanism of ATP synthesis common to nearly all organisms
キキ Traditional hypothesis is that earliest cells were chemoautotrophs, absorbing organic compounds in environment
キキ Natural selection soon favored the cells that could produce ATPキキ Favored hypothesis today is that chemoautotrophs obtained energy
from inorganic molecules, then made their own energyキキ FeS and H2S were most likely substances first used to make free
energy -Later evolution would favor cells that developed electron
transport chains
Metabolism? ……. ….. …
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The origin of photosynthesis
The origin of photosynthesis
Light absorbing pigments may have protected cells from harmful Light absorbing pigments may have protected cells from harmful excess light and then become coupled with membrane proteins to excess light and then become coupled with membrane proteins to drive ATP synthesis. drive ATP synthesis.
Bacteriorhodopsin, the light-energy capturing pigment in the , the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of hydrogen ions. This gradient provides the power for production of ATP synthesis. ATP synthesis.
Components of electron transport chains that functioned in Components of electron transport chains that functioned in anaerobic respirationanaerobic respiration
in other prokaryotes also may have been chosen to provide in other prokaryotes also may have been chosen to provide reducing power.reducing power.
Light absorbing pigments may have protected cells from harmful Light absorbing pigments may have protected cells from harmful excess light and then become coupled with membrane proteins to excess light and then become coupled with membrane proteins to drive ATP synthesis. drive ATP synthesis.
Bacteriorhodopsin, the light-energy capturing pigment in the , the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of hydrogen ions. This gradient provides the power for production of ATP synthesis. ATP synthesis.
Components of electron transport chains that functioned in Components of electron transport chains that functioned in anaerobic respirationanaerobic respiration
in other prokaryotes also may have been chosen to provide in other prokaryotes also may have been chosen to provide reducing power.reducing power.
Early Prokaryotes
• The nutritional modes of modern purple and green sulfur bacteria are the most similar to early prokaryotes.
• The colors of these bacteria are due to bacteriochlorophyll, which functions instead of chlorophyll a as their main photosynthetic pigment.
• These bacteria split H2S instead of H2O as a source of electrons, they produce no O2
Cyanobacteria
• The first cyanobacteriacyanobacteria evolved a mechanism that reduced CO2 using water as a source of electrons and hydrogen.
• release O2 as a by-product of their photosynthesis• CyanobacteriaCyanobacteria evolved between 2.5 and 3.4 billion years ago.• Oxygen released by photosynthesis may have first reacted with
dissolved iron ions to precipitate as iron oxide (supported by geological evidence of deposits), preventing accumulation of free O2.
• Precipitation of iron oxide would have eventually depleted the supply of dissolved iron and O2 would have accumulated in the seas.
• As seas became saturated with O2, the gas was released into the atmosphere.
Phylogeny of ProkaryotesPhylogeny of Prokaryotes
Studies of ribosomal RNA indicate the presence of signature sequences.
Signature sequencesSignature sequences = Domain-specific base sequences at comparable locations in ribosomal
Cynobacteria bloom Anabaena
Studies of ribosomal RNA indicate the presence of signature sequences.
Signature sequencesSignature sequences = Domain-specific base sequences at comparable locations in ribosomal
Cynobacteria bloom Anabaena
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1. DomainDomain ArchaeaArchaea1. DomainDomain ArchaeaArchaea• three main groups:• 1. MethanogensMethanogens are named for their unique form of energy metabolism.• They use H2 to reduce CO2 to methane (CH4) and are strict anaerobes.• live in marshes and swamps- methane that bubbles out at these sites forms marsh
gas • are used in sewage treatment and contribute to the nutrition of cattle and other
herbivores• 2. Extreme halophilesExtreme halophiles live in high salinity (15–20%) places (e.g.,Dead Sea).• Some species simply tolerate extreme salinities while others require such
conditions • This pigment is also responsible for the purple-red color of the colonies.• 3. Extreme thermophilesExtreme thermophiles live in hot environments. (60 – 80°C)• may be found oxidizing hot sulfur springs and near deep hydrothermal vents• are protkayotes which are most closely related to eukaryotes
• three main groups:• 1. MethanogensMethanogens are named for their unique form of energy metabolism.• They use H2 to reduce CO2 to methane (CH4) and are strict anaerobes.• live in marshes and swamps- methane that bubbles out at these sites forms marsh
gas • are used in sewage treatment and contribute to the nutrition of cattle and other
herbivores• 2. Extreme halophilesExtreme halophiles live in high salinity (15–20%) places (e.g.,Dead Sea).• Some species simply tolerate extreme salinities while others require such
conditions • This pigment is also responsible for the purple-red color of the colonies.• 3. Extreme thermophilesExtreme thermophiles live in hot environments. (60 – 80°C)• may be found oxidizing hot sulfur springs and near deep hydrothermal vents• are protkayotes which are most closely related to eukaryotes
Extreme halophiles. Colorful ‘salt loving’ archaea thrive in these ponds near San Francisco. Used for commercial salt production, the ponds contain water that is five to six times as salty as seawater.
Extreme halophiles. Colorful ‘salt loving’ archaea thrive in these ponds near San Francisco. Used for commercial salt production, the ponds contain water that is five to six times as salty as seawater.
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2. Domain Bacteria2. Domain Bacteria2. Domain Bacteria2. Domain Bacteria
Bacteria comprise a majority of the prokaryotes. Molecular systematics has helped establish about 12 groups of bacteria ProteobacteriaProteobacteria: most diverse group of bacteri and includes photoautotrophic /
photoheterotrophic purple bacteria, chemautrophic & chemoheterotrophic bacteria
Gram-Positive Bacteria:Gram-Positive Bacteria: chemoheterotrophs- form resistant endospores Cynobacteria:Cynobacteria: have plantlike photosynthesis SpirochetesSpirochetes: helical chemoheterotrophs that move in a corkscrew fashion and
cause syphilis & Lyme disease Chlamydias:Chlamydias: are obligate intracellular animal parasites. (STD)
Bacteria comprise a majority of the prokaryotes. Molecular systematics has helped establish about 12 groups of bacteria ProteobacteriaProteobacteria: most diverse group of bacteri and includes photoautotrophic /
photoheterotrophic purple bacteria, chemautrophic & chemoheterotrophic bacteria
Gram-Positive Bacteria:Gram-Positive Bacteria: chemoheterotrophs- form resistant endospores Cynobacteria:Cynobacteria: have plantlike photosynthesis SpirochetesSpirochetes: helical chemoheterotrophs that move in a corkscrew fashion and
cause syphilis & Lyme disease Chlamydias:Chlamydias: are obligate intracellular animal parasites. (STD)
Ecological Impact of Prokaryotes
Ecological Impact of Prokaryotes
Prokaryotes are indispensable links in the recycling of chemical elements between the biological and physical worlds.
As decomposers, they return carbon, nitrogen, and other elements to the environment for assimilation into new living forms.
Prokaryotes are indispensable links in the recycling of chemical elements between the biological and physical worlds.
As decomposers, they return carbon, nitrogen, and other elements to the environment for assimilation into new living forms.
Many prokaryotes are symbioticMany prokaryotes are symbiotic
• Symbiosis: an ecological relationship involving direct contact between organisms of two different species
• -probably played a major role in the evolution of prokaryotes and the origin of eukaryotes
• Organisms are called symbionts
• -if one is much larger, it is called the host.
• Mutualism: both systems benefit
• Commensalism: one symbiont benefits while the other is neither harmed nor helped
• Parasitism: the symbiont (a parasite) benefits at the expense of the host
• One half of all human diseases are caused by pathogenic prokaryotes.
• Mutualism: bacterial headlights. The glowing oval below the eye of the flashlight fish (Photoblepharon palpebratus) is an organ harboring bioluminescent bacteria. The fish uses the light to attract prey and to signal potential mates. The bacteria receive nutrients from the fish.
• Symbiosis: an ecological relationship involving direct contact between organisms of two different species
• -probably played a major role in the evolution of prokaryotes and the origin of eukaryotes
• Organisms are called symbionts
• -if one is much larger, it is called the host.
• Mutualism: both systems benefit
• Commensalism: one symbiont benefits while the other is neither harmed nor helped
• Parasitism: the symbiont (a parasite) benefits at the expense of the host
• One half of all human diseases are caused by pathogenic prokaryotes.
• Mutualism: bacterial headlights. The glowing oval below the eye of the flashlight fish (Photoblepharon palpebratus) is an organ harboring bioluminescent bacteria. The fish uses the light to attract prey and to signal potential mates. The bacteria receive nutrients from the fish.
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Koch’s postulate : four criteria for establishing a pathogen as the cause of a disease
1. find the same pathogen in each diseased individual
2. isolate and grow the pathogen in a pure culture
3. induce the disease in experimental animals
4. isolate the same pathogen from the experimental animal
Koch’s postulate : four criteria for establishing a pathogen as the cause of a disease
1. find the same pathogen in each diseased individual
2. isolate and grow the pathogen in a pure culture
3. induce the disease in experimental animals
4. isolate the same pathogen from the experimental animal
Prokaryotes & DiseaseProkaryotes & Disease
Pathogens more commonly cause disease by producing toxins
Exotoxins: proteins are secreted by prokaryotes and are very potent
Endotoxins: components of the outer membrane of certain gram-negative bacteria
Improved hygiene and sanitation and the development of antibiotics has made living better
The evolution of antibiotic-resistant strains of pathogenic bacteria poses a serous health threat
Pathogens more commonly cause disease by producing toxins
Exotoxins: proteins are secreted by prokaryotes and are very potent
Endotoxins: components of the outer membrane of certain gram-negative bacteria
Improved hygiene and sanitation and the development of antibiotics has made living better
The evolution of antibiotic-resistant strains of pathogenic bacteria poses a serous health threat
Humans use prokaryotes in research and technology
Humans use prokaryotes in research and technology
The diverse metabolic capabilities of prokaryotes have been used to digest organic wastes produce chemical products, make vitamins and antibiotics, and produced food products such as yogurt and cheese
Expanded our understanding of molecular biology and recombinant DNA techniques.
The diverse metabolic capabilities of prokaryotes have been used to digest organic wastes produce chemical products, make vitamins and antibiotics, and produced food products such as yogurt and cheese
Expanded our understanding of molecular biology and recombinant DNA techniques.
The end!The end!