Bacteria on the point of a pin Chapter 27: Bacteria and Archaea Success story spanning at least 3.5 billion years

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


• May be classified according to their shape








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)










27.7 Specialized membranes of prokaryotes










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










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.







• Asexual or ‘sexual’ reproduction



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)










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)










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

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Bacteria on the point of a pin Chapter 27: Bacteria and Archaea Success story spanning at least 3.5 billion years