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Bacteria and Archaea
● Two of the three branches on the tree of life
● Most are unicellular and all are ​prokaryotic
○ Lack a membrane-bound nucleus
○ Ribosomes- protein synthesis
○ Plasmid- carry separate set of genes; has to do with antibiotic resistance
● Bacteria and archaea are distinguished by:
○ Types of molecules that make up plasma membranes and cell walls
■ Unique qualities to cell membrane
■ Ex: Phospholipids
○ Machinery they use to transcribe DNA and translate mRNA into proteins
■ Ribosomes = proteins + RNA
● Dominant life-forms (total volume)
● Live almost everywhere
● Most metabolically diverse organisms
● Microbiome
○ Personal ecosystem in which bacteria live on/in you
● Some Prokaryotes Thrive in Extreme Environments
○ Extremophiles-​ live in extreme habitats
■ Hydrothermal vents
● A fissure in a planet's surface from which geothermally heated
water issues; edge of tectonic plates
● Bacteria take hydrogen sulfide and oxygen and act as the sun and
use energy from these chemicals
■ pH < 1
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A few of them are resistant to antibiotics
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○ The resistant bacteria now have preferred conditions to grow and take over
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Bioremediation
● The use of bacteria and archaea to clean up sites polluted with organic solvents
● Water pollutants
○ Are toxic to eukaryotes
○ Do not dissolve in water
○ Accumulate in sediments
● Naturally existing populations of bacteria and archaea can grow in spills and degrade
toxins
● Fertilizing contaminated sites to encourage growth of existing bacteria and archaea
● Seeding​, or adding, specific species of bacteria and archaea to contaminated sites
○ Land mines lead TNT- some bacteria will eat it
Reproduction
● assexually - make a copy of themselves
Genetic Variation through Gene Transfer
○ Transformation​-when bacteria or archaea naturally take up DNA from the environment
that has been released by cell lysis or secreted
■ When bacteria die, dna is left in the area so other bacteria can pick it up resulting
in variation is genes

○ Transduction​- viruses pick up DNA from one prokaryotic cell and transfer it to another
cell
■ bacteriophage - have capsid on top, (DNA) and holds information from bacteria
it’s taking information from, eventually explode or inject DNA into another cell,
sometimes accidentally takes bacterium genes and transfer them from one cell to
the other instead of viral genes
○ Conjugation​-genetic information transferred by direct cell-to-cell contact
■ When a plasmid transfers from one individual to another
■ Two ways, plasmid transfer and recombination
Morphological Diversity
● Viruses are always smaller than bacteria
● Wide variety of shapes and sizes
○ Shapes- filaments, spheres, rods, and chains to spirals
● Motility
○ Some bacteria are nonmotile, but swimming and gliding are common
■ Swimming due to flagellum
■ Gliding but no idea how they do it
■ Move in response to things in their environment
Cell-Wall Composition
● Gram stain-dyeing system to examine cell walls
● Gram-positive- cells look purple under a microscope
○ Cell was has extensive amount of carbohydrate peptidoglycan
● Gram-negative- cells look pink
○ Cell wall has a thin layer containing peptidoglycan and outer phospholipid bilayer
○ Tend to be more toxic, make people more sick
Metabolic Diversity
● Bacteria have the greatest metabolic diversity
● All organisms must:
○ Acquire ​chemical energy​ that is used to make ATP
■ ATP- universal energy source
○ Obtain ​carbon compounds​ that can serve as building blocks for synthesis of
cellular components
■ We are made up of CHNOPS, mostly carbon, important for all living
organisms
● Bacteria and archaea may use of of three sources of energy for ATP production: light,
organic molecules, or inorganic molecules

Producing ATP through ​Cellular Respiration
● Eukaryotes
○ Use organic compounds with high potential energy as the original electron donor
■ Glucose
○ Use oxygen as the final electron acceptor
○ Produce CO​2​ and water as by-products
○ Aerobic metabolism (requires oxygen)
● Bacteria and Archaea
○ Exploit a wide variety of electron donors and acceptors
○ Produce by-products other than CO​2​ and water

Producing ATP via ​Fermentation
● Fermentation- make ATP without using electron transport chains
● Some bacteria and archaea use various organic compounds as starting point for
fermentation
○ Clostridium ferment complex carbohydrates, proteins, purines, or amino acids
○ Other bacteria ferment lactose
○ Bacteria in digestive tract ferment carbohydrates
○ Anaerobic (without oxygen)
● Ex of fermentation: cheese, alcohol

Producing ATP via ​Photophosphorylation
● Bacteria and archaea can undergo photophosphorylation in one of three ways:
○ Bacteriorhodopsin​ activated by light
■ Uses absorbed energy to create a proton gradient
■ The gradient drive ATP synthesis via chemiosmosis
○ One bacterium absorbs ​geothermal radiation ​for photosynthesis
■ The radiation coming from the core of the planet or any heated rock
○ Pigments absorb light- raise electrons to high-energy states (requires a source of
electrons)
■ Chlorophyll
■ Energy released as electrons move through electron transport chains
generate ATP
■ Species that use water as a source of electrons carry out ​oxygenic
photosynthesis
■ Many phototrophic bacteria use molecules other than water as the electron
donor in ​anoxygenic photosynthesis
● Carbon
○ CO​2​- Living/dead plants and animals
○ Methane
The Oxygen Revolution
● No free molecular oxygen existed for first 2
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Key Lineages of Bacteria
● Actinobacteria
○ Decomposers
○ Antibiotics

● Chlamydiae
○ Live in vertebrates
○ STD

● Cyanobacteria
○ Photoautotrophs
○ Lichens
■ Two layers of fungus with cyanobacteria on the inside
■ Fungus protects bacteria, bacteria feeds fungus

● Firmicutes
○ Help us to digest things we normally can’t
○ Disease causing
○ Used in yogurt and cheese products

● Proteobacteria
○ Food poisoning, plague, etc

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