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)