BIO Test 2: Prokaryotes

Prokaryote Groups?

Bacteria and Archaea

Commonalities among all 3 domains?

• Have cell membranes and ribosomes.

• Share some metabolic pathways (e.g. glycolysis).

• Use DNA as genetic material to produce protein.

• Replicate DNA. 

• React to stimuli in their environment

All Unicellular

Can often form chains, clusters, or matrices (biofilms).   

How do they divide?

Binary Fission, producing identical daughter cells

DNA shape?

Circular, no nucleus, and they have plasmids

Haploid or Diploid?

Haploid

Do they have membrane bound organelles?

No membrane bound organelles

Cocci

Spheres

• Streptococcus (Chain) (Over 50 species)

• Staphylococcus (Cluster)

Bacili

Rods (straight) or vibrio (curved)

• Bacillus anthracis (anthrax)

• Bacillus cereus (food poisoning)

• Bubonic Plague

• Botulism

Few gram positives can produce endospores (heat resistant/dormant resting state)

Spiral

Spiral shape

• Syphilis

• Lyme disease

• Leptospirosis

• Gastric ulcers

Endospore

• Bacterium replicates its DNA

• Encapsulates one copy and some cytoplasm in a tough cell wall with extra peptidoglycans

• Can be reactivated after 1000+ years

Bacteria Cell Wall Composition

Composed of peptidoglycans

Archaea cell wall Composition

Composed of polysaccharides

Peptidoglycans

• Polysaccharide made up of amino acids and sugars, around the cell

• Maintains structural integrity, resists osmotic pressure, and determines shape

• Unique to bacteria

• Excellent for combating pathenogenic disease

Gram Positive Bacteria

• Thick peptidoglycan walls that stain purple

• More susceptible to antibiotics

Gram Positive Bacteria Picture

Gram Negative Bacteria

• Thin peptidoglycan walls

• An outer membrane

• Stain pink/red

Gram Negative Bacteria Picture

Gram Positive Cocci

• Streptococcus (strep, etc)

• Staphylococcus (staph infections)

Gram Positive Bacili

• Bacillus anthracis (anthrax)

• Clostridium (botulism, C. diff)

Gram Positive Spiral

N/A

Gram Negative Cocci

Neisseria (gonorrhea, meningitis)

Gram Negative Bacili

• Yersinia pestis (plague)

• Vibrio cholerae (cholera)

• Salmonella Typhi (Typhoid

Gram Negative Spiral

• Leptospirosis

• H. Pylori (stomach ulcers)

• Borrelia (Lyme disease)

• Treponema (syphilis)

Fimbriae

• Thin, hair-like appendages from the cell surface that help with adhesion

• Primarily found on Gram-negative bacteria

• Used to establish infection and form biofilms by binding to host tissues

Slime layer/capsule

• Loose extracellular layer

• Protective shield against the environment

• Promotes adhesion to surfaces and biofilm formation

• Type of glycocalyx

Glycocalyx

• Sticky, sugar-based outer coating of prokaryotic cells

• Increases microbe pathogenicity

Obligate Anaerobic

Oxygen is poisonous to these species. Anaerobic metabolism only.

Obligate Aerobic

Require oxygen for cellular respiration.

Facultative Anaerobic

Can switch between fermentation and cellular respiration depending on conditions.

Photoautotroph

• Get energy from light

• Get carbon from CO₂

Perform photosynthesis and carbon fixation

Chemoautotroph

• Get energy from oxidizing organic compounds

• Get carbon from CO₂

Many archaea

Photoheterotroph

• Get energy from light

• Get carbon from organic compounds from other organisms

Found where oxygen is low

Chemoheterotroph

• Get energy from Fe, S, N compounds (organic compounds)

• Get carbon from organic compounds

Need to eat other organisms

Carbon Fixation

Converting inorganic carbon into organic compounds.

Halophiles

• A type of Archaea

High salt environments. Contain carotenoid pigments

Thermophiles

• High temperatures

• Sulfolobus become inactive at 131 degrees F

• Require very high temperatures. 

A type of archaea

Methanogens

A type of archaea

• Produce CH₄ by reducing CO2

• Obligate anaerobes

• Live in the guts of ruminates (cows)

Release 2 Billion tons CH4 into the atmosphere yearly

Biofilm

Cells bind to surfaces and secrete sticky polysaccharides, become much harder to kill

• Plaque

• Can be found on contact lenses, artificial joints.

• Corrode metal pipes.

Gut-Brain Axis

Bidirectional communication network linking the central nervous system (brain/spinal cord) with the enteric nervous system (gut)

Estimated time of LUCA (Last Universal Common Ancestor)

Approximately 4.2 billion years ago

How asexual organisms maintain genetic variation?

• Transformation

• Transduction

• Conjugation

Transformation

The ability to pick up naked DNA from the environment

Transduction

Virus moves genes from one bacteria to another

Conjugation

DNA exchange using a plasmid (extra copied chromosomal DNA)