Bacteria + Archaea

microbiome

community of microorganisms (bacteria, fungi, archaea) that inhibit a particular environment/organism and play a crucial role in biological processes

3 domain system

• bacteria, archaEnrichment culturesea, eukarya

• Some argue there are 2 domains (bacteria and archaea) because archaea and eukarya are more closely related and eukarya falls within archaea

Enrichment cultures + steps

• lab technique used to isolate and grow specific organisms from a mixed bacterial colony and inhibit the growth of other organisms 

• Culture an environmental sample of many types of cells

• Add some environmental condition (temperature, salt concentration, nutrient addition) 

• Isolate the cells that respond positively to the condition  

conserved + variable regions

• Conserved regions- always the same

• Variable regions- same between individuals of the same species, but different between individuals of different species

characteristics of bacteria + archaea

Feature-	Bacteria-	Archaea-
Cell type	Prokaryote	Prokaryote
Number of cells	Unicellular	Unicellular
Mode of nutrition	heterotroph/autotroph	heterotroph/autotroph
1st AA incorporated during translation	Formylmethionine	Methionine
Peptidoglycan in cell wall?	Yes	No

extremophiles

• organisms that THRIVE in extreme environments (high-salt, high/low temperature, high pressure habitats)

transformation

• form of lateral gene transfer that leads to genetic variation

• bacteria/archaea naturally take up DNA from environment  through recombination and not through sexual reproduction 

transduction

• form of lateral gene transfer that leads to genetic variation

• viruses transfer DNA from prokaryotic cell to cell to create genetic variation

conjugation

• type of horizontal gene transfer where DNA is transferred through contact between nearby cells. Not sexual reproduction because no offspring are produced 

morphological diversity of bacteria/archaea

• size

• shape (spirals, chains, rods)

• motility (swimming, gliding, non-mobile)

gram positive

• most cells

• purple in color

• peptidoglycan in cell wall

gram negative

• less cells

• pink in color

• two component cell wall 

  • thin inner layer with peptidoglycan

  • outer phospholipid layer

phototrophs

• derive energy from sunlight

chemotrophs

• derive energy from chemical compounds instead of sunlight

chemoorganotrophs

• derive energy from organic molecules

chemolithotrophs

• derive energy from inorganic molecules

heterotrophs

• take in C=C from other organisms that produce their own

autotrophs

• synthesize their own C=C from simple molecules like CO₂ and CH₄

actinobacteria

• Common in soil, freshwater, and marine environments 

• Vary in shape

• Are chemotrophs (derive E from chemical compounds, not sunlight)

spirochaetes

• Corkscrew (spiral) in shape

• Found in single cells

• Chemoheterotrophs (E from chemical compounds and C from other organisms)

crenarchaeota

• Common in extreme environments 

• Vary in shape and often have flagella

• Chemoheterotrophs & chemolithoautotrophs