Prokaryotes and the Origins of Metabolic Diversity Chapter 27 Part two By: Jonathan, Javeria & Megan

Nutritional & Metabolic Activity

Four main groups of prokaryotes  Photoautotrophs  ｷ Harness light energy to drive synthesis of organic compound from carbon dioxide  ｷ Have internal membranes with light-harvestng pigment systems  ｷ Include cyanobacteria and all photosynthetic eukaryotes  Chemoautotrophs  ｷ Also need CO2 as carbon source, obtains energy by oxidizing inorganic substances  ｷ Extracts energy from H2S, NH3, Fe(2+)  Photoautotrophs  ｷ Harness light energy to drive synthesis of organic compound from carbon dioxide  ｷ Have internal membranes with light-harvestng pigment systems  ｷ Include cyanobacteria and all photosynthetic eukaryotes  Chemoautotrophs  ｷ Also need CO2 as carbon source, obtains energy by oxidizing inorganic substances  ｷ Extracts energy from H2S, NH3, Fe(2+)

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

Nutritional Diversity Among Chemoheterotrophs  ｷ Saprobes are decomposers that absorb nutrients from dead organic matter  ｷ Specific nutrients needed for growth extremely diverse: Latobacillus requires specific medium, E. Coli has versatile needs  ｷ So diverse that some bacteria can metabolize petroleum  ｷ Synthetic organic compounds that can’t be broken by any chemoautotroph is nonbiodegradable  ｷ Saprobes are decomposers that absorb nutrients from dead organic matter  ｷ Specific nutrients needed for growth extremely diverse: Latobacillus requires specific medium, E. Coli has versatile needs  ｷ So diverse that some bacteria can metabolize petroleum  ｷ Synthetic organic compounds that can’t be broken by any chemoautotroph is nonbiodegradable

Nitrogen Metabolism  ｷ Prokaryotes perform key steps in nitrogen cycle  ｷ Nitrosomonas converts NH3 to NO2(+); some others perform nitrogen fixation, which is conversion of N2 to NH3  ｷ Photoautotrophs that fix nitrogen only require light energy, CO2, N2, water and some minerals  ｷ Prokaryotes perform key steps in nitrogen cycle  ｷ Nitrosomonas converts NH3 to NO2(+); some others perform nitrogen fixation, which is conversion of N2 to NH3  ｷ Photoautotrophs that fix nitrogen only require light energy, CO2, N2, water and some minerals

Metabolic Relationships to Oxygen  ｷ Obligate aerobes use O2 for cellular respiration  ｷ Facultative anaerobes can use either O2 or fermentation  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 Obligate aerobes use O2 for cellular respiration  ｷ Facultative anaerobes can use either O2 or fermentation  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 All major metabolic capabilities today evolved in first billion years of life  ｷ Hypotheses are from molecular systematics, comparisons between prokaryotes, and geological evidence  ｷ All major metabolic capabilities today evolved in first billion years of life  ｷ Hypotheses are from molecular systematics, comparisons between prokaryotes, and geological evidence

Origins of Metabolism ｷ ATP as universal source of energy points out that it was used early on ｷ Glycolysis and chemiosmotic mechanism of ATP synthesis common to nearly all organisms ｷ Traditional hypothesis is that earliest cells were chemoautotrophs, absorbing organic compounds in environment ｷ Natural selection soon favored the cells that could produce ATP ｷ Favored hypothesis today is that chemoautotrophs obtained energy from inorganic molecules, then made their own energy 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? ……. ….. …

The origin of photosynthesis  Light absorbing pigments may have protected cells from harmful excess light and then become coupled with membrane proteins to drive ATP synthesis. , the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of ATP synthesis.  Bacteriorhodopsin, the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of ATP synthesis.  Components of electron transport chains that functioned in anaerobic respiration  in other prokaryotes also may have been chosen to provide reducing power.  Light absorbing pigments may have protected cells from harmful excess light and then become coupled with membrane proteins to drive ATP synthesis. , the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of ATP synthesis.  Bacteriorhodopsin, the light-energy capturing pigment in the membrane of extreme halophiles (a group of archaea), uses light energy to pump H+ out of the cell to produce a gradient of hydrogen ions. This gradient provides the power for production of ATP synthesis.  Components of electron transport chains that functioned in anaerobic respiration  in other prokaryotes also may have been chosen to provide 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 cyanobacteria The first cyanobacteria evolved a mechanism that reduced CO2 using water as a source of electrons and hydrogen. release O2 as a by-product of their photosynthesis Cyanobacteria Cyanobacteria 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 Prokaryotes  Studies of ribosomal RNA indicate the presence of signature sequences. Signature sequences  Signature sequences = Domain-specific base sequences at comparable locations in ribosomal  Cynobacteria bloom Anabaena  Studies of ribosomal RNA indicate the presence of signature sequences. Signature sequences  Signature sequences = Domain-specific base sequences at comparable locations in ribosomal  Cynobacteria bloom Anabaena

Domain Archaea 1. Domain Archaea three main groups: Methanogens1. Methanogens 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 Extreme halophiles2. Extreme 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. Extreme thermophiles3. Extreme 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: Methanogens1. Methanogens 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 Extreme halophiles2. Extreme 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. Extreme thermophiles3. Extreme 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.

2. Domain Bacteria  Bacteria comprise a majority of the prokaryotes.  Molecular systematics has helped establish about 12 groups of bacteria  Proteobacteria  Proteobacteria: 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  Spirochetes  Spirochetes: 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  Proteobacteria  Proteobacteria: 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  Spirochetes  Spirochetes: 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  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 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.

 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 & 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  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!