Prokaryotes and the Origin of Metabolic Diversity

Chapter 27: Bacteria and Archaea

I. General Structure of a Prokaryote

Capsule

Sticky protective layer; adhesion and protection from host defenses

Cell Wall

glucose + amino acid cross linksPeptidoglycan

1. Gram +

2. Gram -

Cell Membrane Semipermeable; may have extra folds to accommodate respiratory and photosynthetic enzymesNucleoid

Region Circular DNA; not membrane bound; not associated with protein

Ribosomes Different protein and smaller than eukaryotic ribosomes; antibiotics Pili

Adhesion to substrate or other bacteria; transfer plasmid during conjugation

Plasmid Small circular transferable DNA that contain extra genes; antibiotic resistance; metabolic enzymes; replicate independently Basal Apparatus Rotates flagella; powered by diffusion o

f H+ ions

Rigid “propeller like”(eukaryote flagella flexible); used in chemotaxis

Flagella

Thick peptidoglycan wall; stain purplePeptidoglycan imbedded in an outer and inner membrane: more pathogenic; endotoxins in membrane; antibiotic resistance; stain red

*All reproduce asexually via binary fission

Characteristic

The Domain Distinctions

1. Nuclear Envelope

2. Membrane bound

organelles3. Peptidoglycan

4. Initiator Amino Acid

5. Introns

6. Antibiotic response

(ribosome)

7. Histones

8. Chromosome

3. Present 3. Absent 3. Absent

II. Prokaryote Taxonomy

7. Absent 7. Present 7. Present

1. Absent 1. Absent 1. Present

8. Circular 8. Circular 8. Linear

6. Growth inhibited 6. No inhibition 6. No inhibition

5. Rare 5. Some genes 5. Most genes

2. Absent 2. Absent 2. Present

4. Formyl- methionine 4. Methionine 4. Methionine

(Prokarotes)(Prokarotes)

Extremophiles

Methanogens-produce methane waste; anaerobic

Halophiles

salt loving; photosynthetic bacteriorhodopsin

Thermophiles chemosynthetic sulfur metabolism

Gram Negative chemoautotrophs photoautotrophs chemoheterotrophs aerobic and anaerobic

Obligate parasites; lack peptidoglycan

Corkscrew

free living and

pathogenic

Gram Positive chemoautotrophs photoautotrophs chemoheterotrophs aerobic and anaerobic

Blue-green bacteria release O2 during photosynthesis

-conjugation: DNA (as plasmids) transferred between two temporarily joined cells via pili

1. Rapid reproduction and mutation

2. Genetic recombination

Why so many prokaryotes?

-transformation: uptake of foreign DNA

-transduction: bacteriophages carry prokaryotic genes from one host cell to another

All are forms of horizontal gene transfer

III. The Metabolic Diversity of Prokaryotes

All organism must have:

Carbon Source

Origin of carbon required to build organic molecules

Energy Source

Origin of the energy to "excite” electrons to make ATP

Possibilities

1. Carbon from CO2 (inorganic origin)

2. Carbon from pre-made organic compounds (lipids, COH’s, protein)

1. Electrons “excited” by light

2. Electrons extracted from “high energy molecules”

Name: Autotrophs

Name: Heterotrophs

Name: Photo

Name: Chemo

A. Energy and Carbon Requirements

Possibilities

Metabolism

Electron Source Carbon Source Examples

PhotoAutotroph Light CO2 Plants, Algae, Cyanobacteria

PhotoHeterotroph Light COH’s Lipids Proteins

Some Prokaryotes

ChemoAutotrophs Inorganic Chemicals (Fe++, S, NH3, NO2-, H2)

CO2 Thermophiles, Some decomposers

(Ammonifing, nitrifying, denitrifying)

ChemoHeterotrophs Organic Carbon (COH’s, Protein, Lipids)

Organic Carbon (COH’s, Protein, Lipids)

Most Prokaryotes, Protist, Fungi

Animals

B. Metabolism Possibilities

C. Oxygen Requirements:Oxygen is the most abundant and most effective electron acceptor to make ATP with an electron transport chain

1. Obligate Aerobes: Organism uses O2 as final electron acceptore-

O2H+

Electron Transport

Chain

ATP

H2O

Obligate aerobes must have O2 in order to make enough ATP for survival

a. Organism uses molecules other than O2 as final electron acceptor.

e-

S2H+

Electron Transport

Chain

ATP

H2S

2. Obligate Anaerobes:

b. Oxygen is toxic since it binds the electrons before ATP can be made

Without Oxygen Present

a. Organism uses molecules other than O2 as final electron acceptor.

e-

S2H+Electron

Transport Chain

2. Obligate Anaerobes:

b. Oxygen is toxic since it binds the electrons before ATP can be made

Oxygen Present

O2 No ATP made

Some may live exclusively by fermentation to make ATP

GlucoseFermentation

Waste Products + 2ATP

1. Ethyl Alcohol + CO2

2. Lactic Acid

3. Acetic Acid (vinegar)

Anaerobic decomposition has an acid pH due to acidic waste products

3. Facultative Aerobes/Anaerobes

1. May contain both aerobic and anaerobic ETC and rely on fermentation to make ATP

2. Some “harmless” bacteria may become pathogenic depending on the type of respiration is used determined by the environment. Example: E. coli

D. Nitrogen Requirements: Nitrogen is needed to build proteins and nucleic acids. Nitrogen can also be used as an “excited” electron source.

1. Ammonification Bacteria

Protein Ammonia(NH3) + (e- to make ATP)Both Aerobic or Anaerobic

2. Nitrification BacteriaNH3 Nitrite (NO2) + (e- to make ATP)

Some species

Some species

Nitrite (NO2) Nitrate (NO3) + (e- to make ATP)

Requires O2

3. Nitrogen Fixation

Atmospheric Nitrogen (N2) Nitrates (NO3)blue-green

bacteria

Some soil bacteria, legume nodule bacteria

4. Denitrification

NH3Nitrite (NO2)Nitrate (NO3) Atmospheric Nitrogen (N2)

Anaerobic denitrifying bacteria

IV. Prokaryote NichesA. Recyclers

Carbon, Oxygen, Nitrogen, Sulfur & Water

B. Symbiotic relationships

2. Interactions all involve decomposition

1. Parasitism: cause disease <1%a. Many opportunistic

b. Secrete exotoxins or membrane bound endotoxins

2. Mutualistica. Digestion (termites, herbivores) & us (Vit K, B12, thiamin, riboflavin) b. Photosynthesis (Cyanobacteria in lichens)c. Bioluminescence (deep sea fish)

1. Global cycles

d. Nitrogen fixers (legumes)

C. Industrial Processes

1. Sewage/ waste treatment/bioremediation

2. Food Products: cheese, yogurt, vinegar, butter

3. Chemicals : acetone, alcohols

4. Pharmaceuticals: antibiotics, insulin, HGH (genetic engineered)

Bacteria Cell Wall Types

Gram +

Gram -

Slide 3

Aerobic Bacteria

Note folds in membrane to accommodate electron transport chains (cristae?)

Photosynthetic Bacteria

Note folds in membranes to accommodate chlorophyll (thylakoids?)

The Extra Duties of a Prokaryote Cell Membrane

Slide 3

Pili used for adhesion A pilus used in conjugation

The Multiple Uses of the Pili

Slide 3

The Basal Apparatus: The Motor of the Flagella

Slide 3

Bacteria Flagella

Slide 3

Structure of Peptidoglycan

Slide 3

Exterme Thermophiles

Hot Springs Sulfur Metabolism

Slide 5

Cyanobacteria

NosctocGloeocapsa

Calothrix Fischerella

Slide 5

Note: The color due to bacteriorhodopsin

Extreme Halophiles in Salt Ponds

Slide 5

What do these picture have to do with methanogens?

Slide 5

Proteobacteria

Rhisobium

Chromatium

H. pyloriB. bacteriophorus

Note Yellow Sulfur globules

Myxobacteria

Slide 5

Animal Cell

Chlamydias

Chlamydias

An Animal Infected with Chlamydia

Slide 5

Spirochetes

LeptospiraB. burgdorferi

Lyme Disease Slide 5

Many Mycoplasmas on a human

fibroblast cell

Streptomyoces

Slide 5

Fermentation: Anaerobic Respiration

C6H12O6 ATP

Pyruvate With O2

Mitochondria: Oxidative

Phosphorylation

NADH H

Bucket O’ NAD

NAD

NAD

ATP

2. Fermentation allows NADH to recycle to NAD in order to continue to make ATP with out oxygen

O2

1. NADH (energy rich) can be used to convert pyruvate into another molecule

3. ATP can still be made as long as the pyruvate is “going somewhere”

NAD

1. Lactic Acid

2. Ethyl Acohol + CO2

Lactic Acid Fermentation(Muscle cells, Bacteria)

Alcoholic Fermentation (Bacteria, Yeasts)

3. Acetic Acid (vinegar) + CO2

(Bacteria)

Without O2 all that is left is NADH, Pyruvate, and Glucose with nowhere to go.

Why Cells Do “Fermentation”Types of Fermentation A

Slide 10

PILUS USED IN CONJUGATION

SLIDE 6

TRANSDUCTION

SLIDE 6

Literally translates to “division in half”

BINARY FISSION

Slide 3

MUTUALISTIC BACTERIA

HUMAN GUT BACTERIA TERMITE GUT BACTERIALICHEN

CLOVER NODULES WHERE NITROGEN FIXATION

OCCURS

BIOLUMINESCENT BACTERIA MUTUALISTS

Let’s watch it in action!

FLASHLIGHT FISH

BOBTAIL SQUIDSLIDE 14

The Nitrogen Cycle: Nitrogen Required for Making Proteins

Human Impact:1. Fertilizers2. Sewage

Eutrophication: Overgrowth in lakes

Nitrogen in atmosphere (N2)

Plants

Assimilation

Nitrates (NO3)

Denitrifying Bacteria

Decomposers (bacteria and

fungi)

Ammonification

DeathWaste

Nitrification

Nitrifying Bacteria

Nitrites (NO2)

Ammonium

(NH4+)

Bacteria soil Nitrogen

Fixing

Nitrogen-Fixing bacteria in root

nodules of legumes

Animals

Nitrifying Bacteria

Denitrification

Lightning

(N2)

Food Chains

Ammonifying Bacteria

Ammonia(NH3)

SLIDE 12