Domain Bacteria and Archaea
Crenarcheota
includes most thermophile species Include bacteria that oxidize sulfur. Habitat example: hot springs hydrothermal vents
Nitrogen fixation by prokaryotes is
key to the nitrogen cycle and to life
Prokaryotes dominate the biosphere by
number -found in diverse habitats
Bacteria have a cell wall with
peptidoglycans Members of Archaea don't have peptidoglycans
Population Growth is linked to
resources or the accumulation of metabolic wastes
To out compete for food
some prokaryotes produce antibiotics
Many bacteria secrete a
sticky capsule layer or have surface pili
Proteobacteria (The Bad)
Animal pathogens: Rickettisas: e.g. Rocky Mountain spotted fever Salmonella, Escherichia coli, Vibrio cholerae, Helicobacter pylori
Most prokaryotes are... (as we are)
Chemoheterotrophic -saprobes -parasites
Importance of Prokaryotes: oxygen production
Cyanobacteria are key ubiquitous producers Other prokaryotes • Obligate aerobes have to use oxygen for cellular respiration. • Obligate anaerobes are poisoned by oxygen. • Facultative anaerobes can use oxygen but can also use fermentation for energy
Domain Eukarya
Eukaryotes
Gram Positive/Negative
Gram *positive* bacteria have simple walls with lots of peptidoglycans Gram *negative* bacteria have a more complex wall with less petidoglycans. Their walls contain lipopolysaccharides
Proteobacteria (The Good)
Gram-negative Mitochondria evolved from this group Rhizobium sp. : plant symbionts that live in root nodules and fix nitrogen Nitrosomonas sp. : soil bacteria that oxidize ammonium
Halophiles
Habitat examples: Great Salt Lake Dead Sea
Gram-Positive Bacteria (The Bad)
Important Examples include: Animal Pathogens: • Actinomycetes causing tuberculosis and leprosy (Gram negative) • Bacillus anthracis, Clostridium botulinum • Staphylococcus sp., Streptococcus sp. • mycoplasms (don't have a cell wall)
Gram-Positive Bacteria (The Good)
Important Examples include: Antibacterial sources: • Streptomyces
General Characteristics: Uses of Membranes
Internal membranes -Invaginated cell membrane -For respiration or photosynthesis Endospores -Highly-resistant structures -Released upon cell lysis -Can germinate back to normal cell
Domain Archaea
Korarchaeotes, Euryarchaeotes, Crenarchaeotes, Nanoarchaeotes
Taxis
Movement in response to a stimulus
Mutation
Mutations can arise spontaneously in bacteria -Also caused by radiation and chemicals Mutations (and plasmids) can spread rapidly in a population -Negative consequences for humans -For example: *-Methicillin-resistance Staphylococcus aureus (MRSA)* *-Vancomycin-resistant Staphylococcus aureus (VRSA) *
Photoautotrophic
Organisms are photosynthetic
Chemoautotrophic
Organisms use CO2 as their carbon source but H2S, NH3 or Fe+2 for energy
Photoheterotrophic
Organisms use light to generate ATP but need organic molecules as a carbon source
Chemoheterotrophic
Organisms use organic molecules for both energy and as a carbon source
Chlamydias: Beware
Parasites that live intracellularly Lack peptidoglycan Gram-negative Important example: Chlamydia trachomatis (most common STD)
Cyanobacteria
Photosynthesis, producing oxygen Enabled aerobic life (cellular respiration) Chloroplasts evolved from a cyanobacteria endosymbiont within a host. Some important in nitrogen fixation
Domain Bacteria
Proteobacteria, Chlamydias, Spirochetes, Cyanobacteria, Gram-positive bacteria
General Characteristics: External Layers
S-layer -A rigid paracrystalline layer found in some -Aids in attachment Capsule -A gelatinous layer found in some bacteria -Aids in attachment -Protects from the immune system
Exotoxin
Secreted protein
Spirochetes: The nasty
Some free-living Some pathogens, e.g. Treponema pallidum (STD syphilis) Borrelia burgdorferi (Lyme disease)
Survival in Harsh Conditions
Some prokaryotes form endospores. This is a duplicate cell wall that requires 120o C to destroy
Pathogens
commonly cause disease by the production of endotoxins or exotoxins
Endotoxin
components of the gram-neg. membrane
Importance of Prokaryotes
1. nitrogen cycling 2. as decomposers/ chemical recycling 3. symbionts 4. oxygen production *Nitrogen fixation:* converts N2 to NH4 + (among all life, only certain prokaryotes can do this) *Nitrification:* converts ammonium to nitrite and nitrate (oxidation) *Denitrification:* takes nitrite or nitrate to nitrogen gas (reduction)
First Life
3.5 Billion years ago
Prokaryote size
1-5 micrometers
Metabolic Developments
1. *ATP* 2. *Glycolysis* was probably a very early metabolic pathway 3. *Autotrophic lineages* are generally older than heterotrophic lineages 4. *Photosynthesis* 5. Photosynthesis and cellular respiration both use *electron transport chain*
Euryarchaeota
1. Methanogens: • strict anaerobes • use carbon dioxide to oxidize hydrogen gas, producing methane
Archaea- Some differences from Bacteria
*• No peptidoglycan in cell walls • Most anaerobic • Some introns present • Membrane lipids are different • Growth not inhibited by streptomycin • Histone proteins associated with DNA*
2 Domains contain Prokaryotes
-Archaea ("ancient" but not) Inhabit extreme environments -Bacteria Most known prokaryotes various nutritional types important for decomposition, oxygen production, and nitrogen fixation
Carbon Source
-Autotrophic: organisms require only carbon dioxide as a carbon source -Heterotrophic: organisms require at least one other organic nutrient
Bacteria vs. Archaea: Plasma Membrane
-Bacterial lipids are unbranched -Connected to glycerol by ester linkages -Archaeal lipids are branched -Connected to glycerol by ether linkages -Tetraethers form a monolayer
Genetic Recombination
-Conjugation -Transduction: via viruses (phages) -Transformation: with external DNA from the environment
Energy Source
-Phototrophic: organisms that use light -Chemotrophic: organisms that use chemicals
General Characteristics: Movement
-Some prokaryotes have flagella -Taxis
General Characteristics: Population Growth
-reproduce asexually by binary fission -Mutation is the major source of genetic variation
General Characteristics: Shapes
-rod (bacilli), -spherical (cocci) -helical (spirilli and spirochetes)
