Bacteria and Archaea

Allen, Viosa, and Ali

Learning Objectives

ProkaryotesThree DomainsCharacteristicsPhylogenyEnvironmental

The Three Domains of Life:

Bacteria—prokaryotes Archaea—prokaryotes Eukarya—eukaryotes

Genetic studies clearly indicate that all three domains had a single common ancestor.

Three Common Bacteria Shapes:

Sphere—coccus (plural cocci)

Rod—bacillus (plural bacilli)

Spiral or helical—helix (plural helices)

Shapes of Archaea:• Little is known• Many have never

been seen.• Known only from

DNA samples from the environment.

Shapes and Prokaryotes

• Singly • Plates • Blocks • Clusters

The on Prokaryotes

• Locomotion is by flagella.• Reproduce asexually by binary

fission• Most successful organisms on

Earth in terms of number of individuals

• Thick cell walls• Communicate with chemical

signals

• In chains or clusters Individual cells = fully viable and

independent.• Filaments – chains of

prokaryotes• Peptidoglycan- a polymer of

amino sugars contained within the cell wall Not in Archaea

• Quorum sensing

Microbial Communities• communities contain different species,

including microscopic eukaryotes.• sometimes referred to as microbes.• perform beneficial services, (e.g., digestion

of our food, breakdown of municipal wastes). • Many form biofilms.

Biofilms• gel-like polysaccharide

matrix that traps other cells.

• Form on contact with a solid surface.

• Difficult to kill cells in a biofilm

• Biofilms form in many places: Contact lenses, artificial joint replacements, dental plaque, water pipes, etc.

• Communicate with chemical signals Ways to block the

signals are being investigated

Gram Stain Method• reveals the complexity of bacterial cell walls.

• The method uses two different stains—one violet and one red.

• Bacteria either: Gram-positive Gram-negative-Endospores: heat-resistant resting structures with tough cell wall and spore coat.

• can survive harsh conditions because it is dormant

How can we resolve prokaryote phylogeny?

• Small size hampers study.

• Much learned by using advanced microscopy techniques and from growing bacteria in pure cultures.

• Taxonomy of prokaryotes: Shape Color Motility Nutrition Antibiotic sensitivity Gram stain reaction

• Constructions of classification schemes that reflect evolution are recent.

rRNA is evolutionarily ancient

All free-living organisms have rRNA

rRNA has the same role in

translation in all organisms; lateral transfer is unlikely

rRNA has evolved slowly; sequence similarities are easily found

Prokaryotes are represented in all four categories of nutrition:

Photoheterotrophs Photoautotrophs

Chemoheterotrophs Chemolithotrophs

Evolutionary studies and Nucleotide sequencing of ribosomal RNA :

Archaea = Extremeophiles• High salinity• High Temp• High or low pH• Low O2

Archaea = Mesophiles• soil

Grouping Names• Euryarcheota, Crenarcheota,

Korarchaeota and Nanoarchaeota

• Prokaryotes are a part of all ecosystems.

• Only a small minority are human pathogens (disease-causing organisms).

• Many species play many positive roles in such diverse applications as cheese making, sewage treatment, and production of antibiotics, vitamins, and chemicals.

• Plants depend on prokaryotes for their nutrition, for processes such as nitrogen fixation and nutrient cycling.

References

• Berenbaum, May R. "Chapter 26: Bacteria and Archaea." Life: The Science of Biology, Ninth Edition. By H. Craig. Heller, David M. Hillis, and David Sadava. Sunderland, MA,: Sinauer Ass., W.H. Freeman and, 2011. N. pag. Print"HowStuffWorks

• "Science"" HowStuffWorks. N.p., n.d. Web. 10 Oct. 2012. <http://science.howstuffworks.com/>.

• "Wikipedia." Wikipedia. Wikimedia Foundation, 10 Sept. 2012. Web. 10 Oct. 2012. <http://en.wikipedia.org/wiki/Wikipedia>.