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Prokaryotes
1st organisms, millions, live on and in other organisms
Anoxic
meaning that there was no molecular oxygen
anaerobic
no oxegen, able to live in ancient atmosphere
phototrophs
Autotrophic organisms that convert solar energy into chemical energy
Cyanobacteria
“blue-green algae,” evolved from these simple phototrophs at least one billion years later
Ancestral cyanobacteria
began “oxygenation” of the atmosphere
Increase in O2 concentrations allowed the evolution of other life forms
Extremophiles
Bacteria and archaea that are adapted to grow under extreme conditions (e.g. deep see vent, heat, dry, cold, radiation, etc.)
Ex. Deinococcus radiodurans - a prokaryote that can tolerate very high doses of ionizing radiation
Robert Koch: discoveries in lab
discovering the techniques for pure culture, including staining and using growth media
Culture medium:
contains all the nutrients needed by the target microorganism, can be liquid (broth) or solid After an incubation time at the right temperature, there should be evidence of microbial growth in the culture medium
Pure culture
a laboratory culture containing a single species of microorganism
Blood agar plates
used to diagnose Streptococcus infections
Growing prokaryotes in the lab
growth limited by food, moisture, crowding
Prokaryotic cell size
(0.1–5.0 μm), Bacteria and Archaea are classified as prokaryotes
4 Structures of all cells:
The plasma membrane, The cytoplasm, A double-stranded DNA genome, A double-stranded DNA genome:
Prokaryotes name
before nucleus
3 Types of Bacteria
Cocci, Bacilli, Spirilli
Prokaryote Structure
No membrane-bound organelles
• no nucleus: DNA in nucleoid
•ribosomes “free”
•No microtubules
e features of a typical prokaryotic cell
Flagella, capsules, and pili are not found in all prokaryotes
Domain Bacteria : Proteobacteria
• Gram-neg; diverse metabolism/nutrition
• includes many N-fixing bacteria •
includes common gastrointestinal pathogens (“food poisoning’)
Domain Bacteria : Chlamydias
endoparasites (live w/in animal cells)
• Ex: Chlamydia in humans causes STD
causes eye infection (conjunctivitis) or pneumonia in children of infected women
causes Pelvic Inflammatory Disease, leading to infertility
Domain Bacteria : Spirochetes
characteristic spiral shape • many free-living but include disease-causing pathogens: •
Ex: syphilis (STD)
Domain Bacteria : Spirochetes: Lyme Disease
Borrelia burgdorferi
Domain Bacteria : Cyanobacteria
• plant-like, O2-generating photosynthesis
•some are also N-fixers
cyanobacteria “blooms” can make toxins
Domain Bacteria : Gram-Positive Bacteria
•include many decomposers in soils
•include many pathogens
: • Ex: Bacillus anthracis (anthrax),
Clostridium tetani (tetanus)
• Ex: “staph” & MRSA infections
Ex: “strep” throat
Domain: Archaea
extremophiles & methanogens
• but also many live in “normal” conditions
•No human-disease-causing archaeans!
Methanogens
produce methane (CH4) as by-product of anaerobic respiration
Prokaryote Structure
• Almost all have cell wall
• lies outside plasma membrane
• protects & prevents cell lysis (rupture)
• bacteria: w/ peptidoglycan (PG)
• archaea: w/ other structural polysaccharides (do not have peptidoglycan)
Prokaryotic Plasma Membrane
Thin lipid bilayer (6 – 8 nm)
Selectively permeable:
keeps ions, proteins, and other molecules within the cell and prevents them from diffusing into the extracellular environment
Structure of membrane
phospholipid bilayer composed of two layers of lipid molecules
Bacterial membrane
fatty acids linked to glycerol
Archaeal membrane:
branched isoprene (phytanyl) chains linked to glycerol
Gram positive bacteria
•Gram-stain reflects cell wall type
•Gram + (pos.): bacteria w/ thick PG layer
•stains purple in Gram stain
Gram negative bacteria
• Gram – (neg.): bacteria w/ thinner PG layer plus outer lipid bilayer membrane
• Pink in Gram stain; outer lipopolysaccharide layer often toxic, resists drugs & immune system
Prokaryote Structure
capsule or slime layer
• sticky carbs & proteins secreted outside cell wall
• adheres (glues) cells together or to surface
• resists attack from immune system
• holds in moisture
fimbriae
e hair-like protein, • help cells stick to surfaces & each other
Flagellum
are hairlike structures that acts primarily as an organelle of locomotion (motility)
form sex pilus
pulls two bacteria cells together for DNA transfer (conjugation), mating bridge
Plasmids
• extra tiny DNA rings w/ few genes •replicate independently
• not “essential” for life, but add diversity
• e.g. drug resistance genes
Prokaryote Reproduction
Reproduction in prokaryotes is asexual
Usually takes place by binary fission
Binary fission does not provide an opportunity for genetic recombination or genetic diversity
Endospores
survive heat, drought for years
• Ex: Bacillus anthracis (causes anthrax), Clostridium tetani (causes tetanus)
Photoautotrophs
use energy from sunlight, and carbon from carbon dioxide
Chemoheterotrophs
obtain both energy and carbon from an organic chemical source
Chemolithoautotrophs:
obtain their energy from inorganic compounds, and they build their complex molecules from carbon dioxide
Photoheterotrophs
obtain their energy from light, but their carbon from organic compounds
Prokaryotes and the carbon cycle
primary producers
Symbiosis
two species living in close relationship (free-living = not living in symbiosis)
Parasitism
smaller parasite benefits at expense of other species (host)
•incl. pathogens (cause disease)
Commensalism
one sp. benefits without any impact (good or bad) on other species
Mutualism
both species benefit from each other • Ex: Rhizobium in legume roots get sugar & water; provide fixed N for plant
Pathogenic Bacteria
• exotoxins are secreted •
Produced by both gram-negative and gram-positive bacteria
• Ex: tetanus, botulism
endotoxins
are toxic outer membranes of some gram-negative bacteria • generalized toxic effect • Ex: Salmonella food poisoning
Antibiotics
kill bacteria cells but not eukaryotic cells • Ex: penicillin affects peptidoglycan cell wall •some antibiotics come from other bacteria!
bacteria becomes resistant
Due to many factors, HGT as one, the bacteria are gaining resistance faster than we can create new drugs
Prokaryotes everyday use
food products: yogurt, cheese, etc.
DNA technology & genetic engineering
• Commercial chemical & drug production