Bacteria

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Bacteria
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Characteristics

• Most primitive organisms on Earth
• Microscopic
• Prokaryotic no nucleus or organelles, except for
  ribosomes
• Unicellular
• Have a single, circular molecule of DNA

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Characteristics (cont.)

• Tend to live as colonies/clusters or
  filaments/strands of cells
• Reproduce primarily asexually by binary fission
  reproduce very quickly
• No mitosis
• Most are surrounded by a cell wall, which is
  composed primarily of peptidoglycan
• Some have additional outer protective coverings
• Some have flagella

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Classification

• Archaebacteriaprimitive bacteria that inhabit
  extreme (very salty, hot, acidic, or low-oxygen)
  environments
• Cyanobacteriablue-green algae
• Eubacteriatrue bacteria

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Archaebacteria

• Methanogensthe most common type of
  archaebacteria
• Anaerobic bacteria found in sewage, swamps, and
  the digestive tracts of humans and other animals
• Produce methane gas as they decompose organic
  material

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Cyanobacteria

• Ex. Anabaena, Oscillatoria, Gleocapsa
• Found in damp or wet areas (ponds, lakes, oceans,
  pools, puddles, moist soil) and extreme
  environmental conditions
• Most are blue-green in color, but some are not
• All contain chlorophyll and can carry out
  photosynthesis (photosynthetic autotrophs) the
  chlorophyll is located within the cytoplasm or
  plasma membrane

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Cyanobacteria (cont.)

• Some go into a period of dormancy during adverse
  environmental conditions
• These cells can remain dormant until conditions
  improvesometimes for years
• Some secrete a gel-like protective coating around
  the cell wall

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Cyanobacteria (cont.)

• Many cyanobacteria fix nitrogen, or serve as
  natural fertilizers by converting nitrogen in the
  soil to a form that is usable by plants
• Some have relationships with other organisms
  (symbiosis) they may live inside another
  organism in a parasite/host relationship they
  may live with another organism in a relationship
  whereby both organisms benefit, called mutualism
  (as in lichens)

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Eubacteria

• True bacteria
• Found almost everywhere
• Classified by shape
• Coccusspherical
• Bacillusrod-shaped
• Spirillumspiral-shaped

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coccus
bacillus
spirillum
in-text, p. 313
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Eubacteria (cont.)

• Generally heterotrophs, organisms that cannot
  produce their own food by photosynthesis some
  are decomposers, which break down dead organisms
  and/or wastes others are parasites, which live
  in or on a host some live in or on another
  organism, but do not harm it
• Some bacteria carry out chemosynthesis, a
  process by which they make their own food without
  sunlight and with different chemical substances
  than in photosynthesis

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Eubacteria (cont.)

• Most bacteria are aerobic, which means that
  they require oxygen for cellular respiration
  (which occurs using the plasma membrane, since
  there are no mitochondria)
• Some bacteria are anaerobic, which means that
  they do not require oxygen for cellular
  respiration

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Eubacteria (cont.)

• Gram staina staining procedure used to
  classify bacteria based on their cell wall
  composition one of many tests used to help in
  the identification of bacteria
• Gram positive bacteriahave cell walls that
  consist of a thick layer of peptidoglycan absorb
  the stain well during the Gram staining
  procedure appear purple under the microscope
• Gram negative bacteriahave cell walls that
  consist of a thin layer of peptidoglycan and an
  outer layer of lipid do not absorb the stain
  well appear pink under the microscope

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Eubacteria (cont.)

• Antibiotics, chemical substances that can kill
  cells, are more effective against Gram positive
  bacteria than Gram negative
• Many antibiotics work by interfering with cell
  wall synthesis
• Some bacteria contain DNA that is involved with
  antibiotic resistance other bacteria can become
  dormant during times of adverse environmental
  conditions

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Discovery of Bacteria

• Leeuwenhoek was the first to see and describe
  bacteria (1600s)
• Pasteur was the first to study the relationship
  between bacteria and diseases he developed
  pasteurization, which is a process involving the
  gentle heating of a solution to kill the bacteria
  in it

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Bacteria and Disease

• Pathogensdisease-causing organisms such as
  bacteria
• Diseases/Conditions caused by bacteria
• Strep throat Ear infections
• Tetanus Tuberculosis
• Anthrax Dental Cavities
• Lyme Disease Food Poisoning
• Venereal Disease Boils
• Acne Rocky Mtn. Spotted Fever

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Bacteria and Disease (cont.)

• Examples of specific disease-causing bacteria
  include
• Streptococcusa chain of coccus bacteria
• Staphylococcusa cluster of coccus bacteria
• Escherichia colirod-shaped bacteria