Post on 01-Jan-2016
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>.