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!