Prokaryotes

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Prokaryotes

• Chapter 27

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Prevalence of Prokaryotes

• Prokaryotes are the oldest, structurally
  simplest, and most abundant forms of life on
  earth.
• abundant for over 2 billion years before the
  appearance of eukaryotes
• 5,000 different kinds currently recognized

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Prokaryotic Cell
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Prevalence of Prokaryotes

• Prokaryotic form
• bacillus (bacilli) straight and rod-shaped
• coccus (cocci) spherical shaped
• spirillum (spirilla) long and helical shaped
• Some bacterial colonies form spore producing
  structures.

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Prevalence of Prokaryotes
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Prokaryotic Diversity

• Key classification characteristics
• photosynthetic or nonphotosynthetic
• motile or nonmotile
• unicellular or colony-forming or filamentous
• Reproduction type - spore formation by division
  or transverse binary fission

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Kinds of Prokaryotes

• Very early, prokaryotes split into two lines
• Archaea and bacteria are as different in
  structure and metabolism from each other as
  either is from eukarya.
• Domain Archaea ancient bacteria (not as ancient
  as (bacteria) confined to extreme environments
  (early earth)
• Domain Bacteria nonextreme habitats and include
  nearly all of the named species of prokaryotes

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Prokaryotic Diversity

• Comparing archaebacteria and bacteria
• plasma membranes
• composed of different lipids
• cell wall
• archaebacteria lack peptidoglycan in cell wall
  mesh that strengthens
• gene translation machinery
• archaebacteria similar to eukaryotes
• gene architecture
• bacteria not interrupted by introns

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Prokaryotic Complexity

• Prokaryotic cell surface
• cell wall maintains shape and protects the cell
  from swelling and rupturing
• usually consist of peptidoglycan
• Gram-positive - thicker peptidoglycan
• Gram-negative - thinner peptidoglycan
• flagella slender protein - locomotion
• pili - hairlike structures - attachment
• endospores - resistant to environment

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Gram Stain
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The Cell Interior

• Internal membranes
• invaginated plasma membrane function in
  respiration or photosynthesis
• Nucleoid region
• lack nucleus - genes encoded with single
  double-stranded DNA
• Ribosomes
• Prokaryotic ribosomes are smaller than eukaryotic
  ribosomes, and differ in protein and RNA content.

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Prokaryotic Variation

• Two process create bacterial variation
• mutation
• spontaneous errors in DNA replication
• prokaryotic ability to mutate rapidly often has
  adverse effect on humans
• genetic recombination
• occurs by gene transfer from one cell to another
  by viruses or conjugation

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Prokaryotic Metabolism

• Autotrophs
• obtain carbon from inorganic CO2
• photoautotrophs - sunlight
• chemoautotrophs - inorganic chemicals
• Nitrifiers oxidize ammonia or nitrite producing
  nitrate (plants uptake) nitrification
• Heterotrophs
• obtain carbon from organic molecules
• photoheterotrophs - sunlight
• chemoheterotrophs decomposers - organic
  molecules

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Human Bacterial Diseases

• Tuberculosis
• afflicts respiratory system and easily
  transmitted from person to person through the air
• Dental caries
• tooth decay caused by bacteria present in plaque
• high sugar diets increase tooth decay
• lactic acid bacteria ferment sugars and reduce
  pH, thus degenerating tooth enamel

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Human Bacterial Diseases

• Sexually transmitted diseases
• Gonorrhea (Neisseria gonorrhoeae) PID
• Syphilis (Treponema pallidum)
• Chlamydia (Chlamydia trachomatis) PID

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Benefits of Prokaryotes

• Environment
• chemical cycling
• decomposition
• nitrogen fixation
• reduces N2 to NH3
• Symbiotic properties
• nitrogen-fixation
• digestive tract of animals

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Benefits of Prokaryotes

• Genetic engineering
• nonpolluting insect control
• bioremediation
• pollutant removal
• biofactories
• commercial production of antibiotics
• Bioweapons
• anthrax
• smallpox

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Bioremediation
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Summary

• Prevalence of Prokaryotes
• Prokaryotic Diversity
• Prokaryotic Complexity
• Prokaryotic Variation
• Prokaryotic Metabolism
• Human Bacterial Diseases
• Benefits of Prokaryotes