Chapter 27 Prokaryotes “All the world’s bacteria essentially have access to a single gene pool and hence to the adaptive mechanisms of the entire bacterial kingdom. The speed of recombination over that of mutation is superior: it could take eukaryotic organisms a million years to adjust to a change on a worldwide scale that bacteria can accommodate in a few years.” --Lynn Margulis

Characteristics of Prokaryotes  Very small--1-5  m in diameter.  Comes in a wide variety of shapes:  Bacilli  Cocci  Spirilla  Very small--1-5  m in diameter.  Comes in a wide variety of shapes:  Bacilli  Cocci  Spirilla

Characteristics of Prokaryotes  Has a cell wall, provides many functions:  Helps it maintain its shape  Provides protection  Keeps the cell from bursting in hypotonic environments.  Has a cell wall, provides many functions:  Helps it maintain its shape  Provides protection  Keeps the cell from bursting in hypotonic environments.

Prokaryotic Cell Wall  The cell wall of a prokaryotic cell is different from that of a eukaryote:  Eukaryotic cell walls are made of cellulose or chitin.  Prokaryotic cell walls contain peptidoglycan--modified sugar polymers cross-linked to short peptides.  Archean cell walls contain a variety of polysaccharides but lack peptidoglycan.  The cell wall of a prokaryotic cell is different from that of a eukaryote:  Eukaryotic cell walls are made of cellulose or chitin.  Prokaryotic cell walls contain peptidoglycan--modified sugar polymers cross-linked to short peptides.  Archean cell walls contain a variety of polysaccharides but lack peptidoglycan.

Gram Staining  Hans Christian Gram developed the Gram staining technique and it is used to classify many bacterial species into 2 categories.  Gram positive  Gram negative  Hans Christian Gram developed the Gram staining technique and it is used to classify many bacterial species into 2 categories.  Gram positive  Gram negative

Gram Positive Bacteria  Gram positive bacteria have a large amount of peptidoglycan in their cell walls.  60-90% of the entire wall.  They have very little protein (except streptococci).  Gram positive bacteria have a large amount of peptidoglycan in their cell walls.  60-90% of the entire wall.  They have very little protein (except streptococci).

7 Gram Positive Bacteria  Their thick cell walls allow them to retain the crystal-violet dye.  Yeast cells have thick walls and no peptidoglycan but still retain the stain. Wall thickness, not peptidoglycan.  Their thick cell walls allow them to retain the crystal-violet dye.  Yeast cells have thick walls and no peptidoglycan but still retain the stain. Wall thickness, not peptidoglycan. 7

Gram Negative Bacteria  Gram negative bacteria have less peptidoglycan (thin cell wall), and cell walls that are structurally more complex.  10-20% of wall is peptidoglycan.  They have an outer bilayer membrane that acts as a coarse sieve.  Gram negative bacteria have less peptidoglycan (thin cell wall), and cell walls that are structurally more complex.  10-20% of wall is peptidoglycan.  They have an outer bilayer membrane that acts as a coarse sieve.

Gram Negative Bacteria  Gram negative bacteria have less peptidoglycan (thin cell wall), and cell walls that are structurally more complex.  It has little control over the movement of substances into and out of the cell.  It does control the movement of proteins.  Gram negatives are less sensitive to penicillin because this sieve acts to keep penicillin out.  Gram negative bacteria have less peptidoglycan (thin cell wall), and cell walls that are structurally more complex.  It has little control over the movement of substances into and out of the cell.  It does control the movement of proteins.  Gram negatives are less sensitive to penicillin because this sieve acts to keep penicillin out.

Gram Negative Bacteria  Their outer membrane contains the endotoxin lipopolysaccharide.  No retention of the crystal violet-iodine stain due to the thin cell wall and large amount of lipoprotein and lipopolysaccharide.  Their outer membrane contains the endotoxin lipopolysaccharide.  No retention of the crystal violet-iodine stain due to the thin cell wall and large amount of lipoprotein and lipopolysaccharide.

Gram Negative Bacteria  Many pathogenic prokaryotes are Gram Negative: they usually cause illness by producing endotoxins.

Gram Negative Bacteria  Endotoxins are lipopolysaccharides released by the outer membrane of Gram negative bacteria when they die and their cell walls break down.  The bacteria that produce endotoxins are not normally found in healthy animals.  Examples: cholera, botulism, salmonella  Endotoxins are lipopolysaccharides released by the outer membrane of Gram negative bacteria when they die and their cell walls break down.  The bacteria that produce endotoxins are not normally found in healthy animals.  Examples: cholera, botulism, salmonella

Usefulness of Gram Staining  Gram staining is useful in medicine.  Gram negative bacteria are usually more pathogenic and the LPS is usually toxic and sometimes lethal.  Gram negatives are often more resistant to antibiotics due to the outer membrane.  The outer membrane of Gram negatives protect against the body’s defenses.  Some prokaryotes contain a capsule which is a sticky outer coat of polysaccharide or protein which shields the bacteria from the host’s defense system.  Gram staining is useful in medicine.  Gram negative bacteria are usually more pathogenic and the LPS is usually toxic and sometimes lethal.  Gram negatives are often more resistant to antibiotics due to the outer membrane.  The outer membrane of Gram negatives protect against the body’s defenses.  Some prokaryotes contain a capsule which is a sticky outer coat of polysaccharide or protein which shields the bacteria from the host’s defense system.

Structural Differences Between Prokaryotes and Eukaryotes  The flagella of prokaryotes are much different from those of eukaryotes.  Prokaryotic flagella are much smaller.  The flagella of prokaryotes are much different from those of eukaryotes.  Prokaryotic flagella are much smaller.

15 Structural Differences Between Prokaryotes and Eukaryotes  The flagella of prokaryotes are much different from those of eukaryotes.  Prokaryotic flagella are much smaller.  The flagella of prokaryotes are much different from those of eukaryotes.  Prokaryotic flagella are much smaller.

Structural Differences Between Prokaryotes and Eukaryotes  Although prokaryotes lack internal organization and membranous organelles, they can have internal membranes that perform certain functions--infoldings of the plasma membrane.  Some membranes similar to cristae--function in cell respiration.  Others have thylakoid membranes.  Although prokaryotes lack internal organization and membranous organelles, they can have internal membranes that perform certain functions--infoldings of the plasma membrane.  Some membranes similar to cristae--function in cell respiration.  Others have thylakoid membranes.

Structural Differences Between Prokaryotes and Eukaryotes  Eukaryotic chromosomes have about 1000 x as much DNA as do prokaryotes.  Prokaryotes’ chromosomes are circular vs. linear; there is hardly any protein associated with them.  Prokaryotic DNA is found in the nucleoid region, eukaryotic in the nucleus.  Prokaryotic DNA is often associated with plasmids.  Eukaryotic chromosomes have about 1000 x as much DNA as do prokaryotes.  Prokaryotes’ chromosomes are circular vs. linear; there is hardly any protein associated with them.  Prokaryotic DNA is found in the nucleoid region, eukaryotic in the nucleus.  Prokaryotic DNA is often associated with plasmids.

Plasmids  Recall, plasmids are small rings of DNA with a few genes that usually confer some sort of benefit to the bacterium.  Plasmids often increase a bacterium’s chance of survival in certain environments, but they are not essential to survival.  Recall, plasmids are small rings of DNA with a few genes that usually confer some sort of benefit to the bacterium.  Plasmids often increase a bacterium’s chance of survival in certain environments, but they are not essential to survival.

20 Plasmids  Plasmids generally have contingency functions:  Provide resistance to antibiotics  Direct the metabolism of rarely encountered nutrients.  Plasmids generally have contingency functions:  Provide resistance to antibiotics  Direct the metabolism of rarely encountered nutrients.

The Success of Prokaryotes  Prokaryotes are successful because they can reproduce quickly--via binary fission.  Typically a 1-3 hour generation time.  Some every 20 minutes in optimal conditions.  36 hours would cover the Earth in 18” of bacteria  3 days would exceed the mass of the Earth  They are limited by metabolic wastes, food supply and consumption by other organisms.  Prokaryotes are successful because they can reproduce quickly--via binary fission.  Typically a 1-3 hour generation time.  Some every 20 minutes in optimal conditions.  36 hours would cover the Earth in 18” of bacteria  3 days would exceed the mass of the Earth  They are limited by metabolic wastes, food supply and consumption by other organisms.

The Success of Prokaryotes  The success of prokaryotes is also due to their ability to withstand harsh environments.  Natural selection has enabled prokaryotes to adapt quickly to changing environments.  Their fast generation time allows them to propagate mutations quickly.  These mutations are often beneficial to survival.  Some bacteria form endospores when the environment becomes harsh.  The success of prokaryotes is also due to their ability to withstand harsh environments.  Natural selection has enabled prokaryotes to adapt quickly to changing environments.  Their fast generation time allows them to propagate mutations quickly.  These mutations are often beneficial to survival.  Some bacteria form endospores when the environment becomes harsh.

Endospores  Endospores are produced when the prokaryote wraps a copy of its DNA in a tough wall and then removes the water.  The metabolism inside the spore comes to a halt a picks up again when conditions improve.  Endospores are produced when the prokaryote wraps a copy of its DNA in a tough wall and then removes the water.  The metabolism inside the spore comes to a halt a picks up again when conditions improve.

Metabolism in General  Phototrophs-obtain energy from light.  Chemotrophs-obtain energy from chemicals in the environment.  Autotrophs-only need CO 2 as a carbon source, they make everything else they need themselves.  Heterotrophs-require at least one source of organic carbon to sustain themselves.  Phototrophs-obtain energy from light.  Chemotrophs-obtain energy from chemicals in the environment.  Autotrophs-only need CO 2 as a carbon source, they make everything else they need themselves.  Heterotrophs-require at least one source of organic carbon to sustain themselves.

Prokaryotic Metabolism  There are a number of different ways for organisms to obtain energy and carbon.  On the whole, prokaryotes are much more diverse than eukaryotes.  All nutrition types seen in eukaryotes are found in prokaryotes. Prokaryotes also have other means of obtaining energy and carbon.  There are a number of different ways for organisms to obtain energy and carbon.  On the whole, prokaryotes are much more diverse than eukaryotes.  All nutrition types seen in eukaryotes are found in prokaryotes. Prokaryotes also have other means of obtaining energy and carbon.

Prokaryotic Metabolism  With respect to oxygen, a prokaryote’s metabolism can vary.  Obligate aerobes require oxygen to survive.  Facultative anaerobes use O 2, but can get along without it.  Obligate anaerobes are poisoned by O 2.  Some obligate anaerobes live exclusively with fermentation. Others obtain energy from anaerobic respiration. Substances such as NO 3- and SO 4 2- accept electrons in the place of O 2 at the end of the ETC.  With respect to oxygen, a prokaryote’s metabolism can vary.  Obligate aerobes require oxygen to survive.  Facultative anaerobes use O 2, but can get along without it.  Obligate anaerobes are poisoned by O 2.  Some obligate anaerobes live exclusively with fermentation. Others obtain energy from anaerobic respiration. Substances such as NO 3- and SO 4 2- accept electrons in the place of O 2 at the end of the ETC.

Prokaryotic Metabolism  Nitrogen metabolism. Nitrogen is essential for the production of amino acids.  Eukaryotes are limited by the types of nitrogen compounds they can use.  Prokaryotes can use nitrogen from a wide variety of sources.  Nitrogen fixation is the process by which certain prokaryotes use N 2 to make NH 3. The NH 3 is then used along with CO 2 and H 2 O to create a wide variety of organic molecules.  Nitrogen metabolism. Nitrogen is essential for the production of amino acids.  Eukaryotes are limited by the types of nitrogen compounds they can use.  Prokaryotes can use nitrogen from a wide variety of sources.  Nitrogen fixation is the process by which certain prokaryotes use N 2 to make NH 3. The NH 3 is then used along with CO 2 and H 2 O to create a wide variety of organic molecules.

Prokaryotic Metabolism  There are four main modes of nutrition:  1. Photoautotrophs  2. Chemoautotrophs  3. Photoheterotrophs  4. Chemoheterotrophs  There are four main modes of nutrition:  1. Photoautotrophs  2. Chemoautotrophs  3. Photoheterotrophs  4. Chemoheterotrophs

1. Photoautotrophs  Are photosynthetic organisms that use light energy to drive the synthesis of organic compounds from CO 2.  Examples: cyanobacteria, plants, algae  Are photosynthetic organisms that use light energy to drive the synthesis of organic compounds from CO 2.  Examples: cyanobacteria, plants, algae

2. Chemoautotrophs  These oxidize inorganic substances (H 2 S, NH 3, and Fe 2+ ) and use CO 2 as a carbon source to drive the synthesis of organic compounds.  *This is unique to prokaryotes.  These oxidize inorganic substances (H 2 S, NH 3, and Fe 2+ ) and use CO 2 as a carbon source to drive the synthesis of organic compounds.  *This is unique to prokaryotes.

3. Photoheterotrophs  Use light energy and carbon from an organic source for nutrition.  *Many marine prokaryotes use this.  Use light energy and carbon from an organic source for nutrition.  *Many marine prokaryotes use this.

4. Chemoheterotrophs  Consume organic compounds for energy and carbon.  Examples: Found in prokaryotes, protists, fungi, and animals.  Consume organic compounds for energy and carbon.  Examples: Found in prokaryotes, protists, fungi, and animals.

The 2 Domains of Bacteria  1. Bacteria-the vast majority of prokaryotes of which most people are aware.  Pathogenic-cause infections  Beneficial-produce many foods  2. Archea-share traits with both prokaryotes and eukaryotes.  Extremeophiles-live in hostile environments where few other organisms can survive.  Example: extreme thermophiles, extreme halophiles, methanogens.  1. Bacteria-the vast majority of prokaryotes of which most people are aware.  Pathogenic-cause infections  Beneficial-produce many foods  2. Archea-share traits with both prokaryotes and eukaryotes.  Extremeophiles-live in hostile environments where few other organisms can survive.  Example: extreme thermophiles, extreme halophiles, methanogens.

Extreme Thremophiles  Live in very hot environments.  Sulfur-rich volcanic hot springs, 90°C+  Genus Sulfolobus.  Deep-sea hydrothermal vents, 113°C  Pycolobus fumarri.  Some grow at temperatures of 600°F+ and 265+ atm of pressure.  Live in very hot environments.  Sulfur-rich volcanic hot springs, 90°C+  Genus Sulfolobus.  Deep-sea hydrothermal vents, 113°C  Pycolobus fumarri.  Some grow at temperatures of 600°F+ and 265+ atm of pressure.

Extreme Halophiles  Live in highly saline environments. The Great Salt Lake, Dead Sea. Some tolerate the salt, others require it.

Methanogens  Methanogens are named for their mode of energy production. They use CO 2 and oxidize H 2 releasing CH 4 in the process.  These bacteria are the strictest anaerobes. They are poisoned by O 2.  Methanogens are named for their mode of energy production. They use CO 2 and oxidize H 2 releasing CH 4 in the process.  These bacteria are the strictest anaerobes. They are poisoned by O 2.

The Importance of Prokaryotes  Prokaryotes are important for the cycling of chemical elements of living and non-living components of the environment.  Decomposers break down a variety of substances.  They extract nutrients from a variety of things such as dead organisms and waste products.  These metabolites are then returned to the environment.  Prokaryotes are important for the cycling of chemical elements of living and non-living components of the environment.  Decomposers break down a variety of substances.  They extract nutrients from a variety of things such as dead organisms and waste products.  These metabolites are then returned to the environment.

The Importance of Prokaryotes  Many prokaryotes also convert usable forms of inorganic compounds into those that can be used by other organisms.  Examples: autotrophic prokaryotes use CO 2 to make organic compounds which are passed up the food chain.  Cyanobacteria produce O 2 and fix N 2 into compounds other organisms use to make proteins.  Many prokaryotes also convert usable forms of inorganic compounds into those that can be used by other organisms.  Examples: autotrophic prokaryotes use CO 2 to make organic compounds which are passed up the food chain.  Cyanobacteria produce O 2 and fix N 2 into compounds other organisms use to make proteins.

Symbiosis  Symbiosis is the ecological relationship between 2 organisms of different species.  The host is the larger organism, while the symbiont is the smaller one.  There are three types of symbiosis:  1. Mutualism  2. Commensalism  3. Parasitism  Symbiosis is the ecological relationship between 2 organisms of different species.  The host is the larger organism, while the symbiont is the smaller one.  There are three types of symbiosis:  1. Mutualism  2. Commensalism  3. Parasitism

1. Mutualism  In mutualism, both symbiotic organisms benefit.  The well being of many organisms depends on mutualistic prokaryotes.  Example: the human intestines are home to between species of bacteria that help us break down food, keep other bacteria at bay, and activate genes which stimulate our intestines to produce blood vessels and absorb food.  In mutualism, both symbiotic organisms benefit.  The well being of many organisms depends on mutualistic prokaryotes.  Example: the human intestines are home to between species of bacteria that help us break down food, keep other bacteria at bay, and activate genes which stimulate our intestines to produce blood vessels and absorb food.

2. Commensalism  Commensalism is where one organism benefits where neither of the organisms is harmed.  These are difficult to document in nature because any close association between organisms is likely to benefit both of them.  Hitchihiking species of algae is an example.  Commensalism is where one organism benefits where neither of the organisms is harmed.  These are difficult to document in nature because any close association between organisms is likely to benefit both of them.  Hitchihiking species of algae is an example.

3. Parasitism  With parasitism, the symbiont (a parasite) benefits while the host suffers.  Tapeworms.  With parasitism, the symbiont (a parasite) benefits while the host suffers.  Tapeworms.

Controlling Prokaryotes  Antibiotics have done a good job of containing disease and preventing death. However, the rapid production of bacteria enables them to propagate a mutation that confers resistance throughout the population.  Natural selection favors these mutants and allows them to survive.  Antibiotics have done a good job of containing disease and preventing death. However, the rapid production of bacteria enables them to propagate a mutation that confers resistance throughout the population.  Natural selection favors these mutants and allows them to survive.

Usefulness of Prokaryotes  For all of the harm that bacteria cause, we reap many benefits from them as well.  Can be used to produce vitamins, hormones, etc.  Bioremediation uses prokaryotes to remove pollutants from the air, soil, and water.  For all of the harm that bacteria cause, we reap many benefits from them as well.  Can be used to produce vitamins, hormones, etc.  Bioremediation uses prokaryotes to remove pollutants from the air, soil, and water.

Biomining  Prokaryotes can also be used to recover precious metals from ores in a process called biomining.  30 billion kg of Cu from copper sulfides each year.  1 million kg of gold concentrate is processed each day extracting the gold in Ghana, Africa.  Prokaryotes can also be used to recover precious metals from ores in a process called biomining.  30 billion kg of Cu from copper sulfides each year.  1 million kg of gold concentrate is processed each day extracting the gold in Ghana, Africa. The microbiology of biomining: development and optimization of mineral-oxidizing microbial consortia. Douglas E. Rawlings and D. Barrie Johnson