Bacteria on the point of a pin
Chapter 27:Bacteria and Archaea
Success story spanning at least 3.5 billion years
Prokaryote colonies in culture
Dominate the biosphere in terms of numbers, metabolic impact and the range of habitats they occupy!
Harmful Haemophilus influenza, the bacteria that causes pneumonia (shown on human nose cells)
27.20. Lyme disease, a bacterial disease transmitted by ticks
Bacillus anthracis. Gram stain. The cells have characteristic squared ends.The endospores are ellipsoidal shaped and located centrally in the sporangium. The spores are highly refractile to light and resistant to staining. Anthrax!
Figure 27.9 An anthrax endospore
Are all prokaryotes disease producing germs?
Without prokaryotes ecosystems would collapse!
54.13
55.4 An overview of energy and nutrient dynamics in an ecosystem.
Decomposition connects all trophic levels in an ecosystem
If all the bacteria on Earth suddenly disappeared, which of the following would be the most likely direct result?
A. Human populations would thrive in the absence of disease.
B. The Earth's total photosynthesis would decline markedly.
C. The number of organisms on Earth would decrease by 10 to 20 percent.
D. There would be little change in the Earth's ecosystems.
E. Recycling of nutrients would be catastrophically reduced.
27.15.A simplified phylogeny of prokaryotes
(see also 27.17)
Table 27.2.A comparison of the three domains of life
27.16 Some Archaea: Thermo-acidophile (“heat-acid loving”) prokaryotes
Much more common than once thought, including in non-extreme environments
Methanogens in Peat
… and the gut of cows
27.1. Pink color in the Great Salt Lake (UT) due to red membrane pigments of Archaea living in salt water with salt concentrations 10x higher than that of seawater.
Common Features of the Domain Bacteria
• May be classified according to their shape (just like Archaea)
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
27.2 The most common shapes of prokaryotes
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
Prokaryotic flagella
27.6. Prokaryotic flagellum with the basal apparatus as a ‘motor’(a system of rings embedded in the cell wall and plasma membrane (TEM)
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
27.7 Specialized membranes of prokaryotes
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
27.4. Capsule.
The cell wall of may prokaryotes is covered with a sticky layer of polysaccharides or proteins.
Streptococcus in the respiratory tract
27.5. Fimbriae.
Hair-like protein appendages that allow a prokaryote to attach itself to their substrate or to each other.
Figure 27.3 Gram-positive and gram-negative bacteria
Gram staining: Apply crystal violet dye to bacterial smear, treat with iodine, rinse with alcohol and counterstain with safranin.
Peptidoglycan
Peptidoglycan
Gram Positive
Gram Negative
Plasma membrane
Plasma membrane
Outer membrane
Lipopolysaccharide layer
Staphylococcus aureusMRSA- methicillin resistant S.aureus Streptococcus pneumoniae
Actinomycete
Gram Positive
Escherichia coli•Neisseria gonorrheae
•Yersinia pestis
Gram Negative
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
27.8. A prokaryotic chromosome and plasmids.A single ring of DNA surrounding a ruptured E. coli cell.
Plasmids: Small circular DNA molecules that replicate separately from the bacterial chromosome.
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• Asexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
Asexual reproduction:
Fission(see also Fig 12.11)
Genetic recombination in prokaryotes
No meiosis and fertilization, but
• Transformation:
• Uptake and incorporation of foreign DNA from the environment
• Conjugation:
• Direct transfer of genes from one prokaryote to another
• Transduction:
• Transfer of genes between prokaryotes by viruses
27.12. Prokaryotic conjugation.Donor cell transfers DNA to recipient.
27.13. Conjugation: Direct transfer of genes from one prokaryote to another (have only been studied in Bacteria)
The F factor (fertility) is responsible for producing the mating bridge. It can either exist as a plasmid (a small circular DNA molecule with accessory genes) or as a segment of DNA within the bacterial chromosome.
27.11. Transduction:Transfer of genes between prokaryotes by viruses.
Phages may carry pieces of bacterial chromosome from one bacterium (donor) to a recipient bacterium.
Endospores
27.9. Bacillus anthracis endospore (TEM)
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
http://www.youtube.com/watch?v=N-EYTtxsL8g
Table 27.1 Major Nutritional Modes
Figure 27.14. One of the most independent organisms on earth: Cyanobacteria (in this case Anabaena) or “blue-green algae”.
Metabolic cooperation – some cells fix nitrogen, some photosynthesize.
Algal blooms
Anabaena Microcystis
Aphanizomenon
A bloom of cyanobacteria
Heterocyst: Site of nitrogen fixation
Gas vacuoles
Table 27.1 Major Nutritional Modes
55.4 An overview of energy and nutrient dynamics in an ecosystem.
Decomposition connects all trophic levels in an ecosystem
27.18. The impact of bacteria on soil nutrient availability. Pine seedlings grown in sterile soils to which one of three strains of a bacterium was added abseorbed more potassium(K) than the control
37.9. The role of bacteria in the nitrogen cycle
Nitrogen fixing bacteria in root nodules and in cyanobacteria (mutualism)
Cyanobacteria living in the leaves of the mosquito fern (Azolla)
Common Features of the Domain Bacteria
• May be classified according to their shape
• Many are motile using flagella
• No membrane-enclosed organelles (prokaryotic!)
• Peculiar cell wall containing peptidoglycan (a combination of sugars and polypeptides)
• Smaller and simpler genome (than eukaryotes)
• A sexual or ‘sexual’ reproduction
• Diversity of nutritional modes
• Often live in close association (symbiosis) with eukaryotes
Symbiotic relationships
• Mutualism – both symbiotic organisms benefit
• Commensalism – one benefits, the other is neutral
• Parasitism – one benefits at the expense of the other
27.19. Bacterial “headlights”. Glowing oval below the eye of the flashlight fish contains bioluminescent bacteria that receive nutrients from the fish. The fish uses the light to attract prey and signal potential mates
SEM of Escherichia coli, very common in the lower intestine of warm-blooded animals where it produces a vitamin and protect against pathogenic bacteria.
Putting prokaryotes to work in sewage treatment facilities
Figure 27.21 (a) Bioremediation of an oil spill, (b) bacteria synthesizing biodegradable plastics, and (c) bacteria used to produce ethanol from plants.
In which of the following ways are prokaryotes more successful on Earth than humans?
A. Prokaryotes often parasitize humans in many ways.
B. Prokaryotes are much more numerous than humans.
C. Prokaryotes occupy more diverse habitats than humans.
D. Prokaryotes have survived on Earth for billions of years longer than humans have.
E. All of the above are true.
Chapter 27 – Review (p. 573-574)
• 27.1. Structural and functional adaptations contribute to prokaryotic success
• 27.2. Rapid reproduction, mutation, and genetic recombination promote genetic diversity
• 27.3. Prokaryotes have diverse metabolic and nutritional adaptations
• 27.4. Prokaryotic phylogeny: Bacteria and Archaea
• 27.5. Prokaryotes play crucial roles in the biosphere
• 27.6. Prokaryotes may have harmful and beneficial impacts on humans