Bacteria

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Bacteria
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• Bacteria consist of only a single cell, but don't
  let their small size and seeming simplicity fool
  you. They're an amazingly complex and fascinating
  group of creatures.

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Builders of Modern Life

• Bacteria are among the earliest forms of life
  that appeared on Earth billions of years ago.
• Bacteria helped shape and change the young
  planet's environment, eventually creating
  atmospheric oxygen that enabled other, more
  complex life forms to develop.

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What are bacteria?

• Bacteria are unicellular, living things.
• Prokaryotic cells (without a nucleus).
• Obtain nutrients is different ways
• Photosynthetic autotrophs- convert inorganic
  molecules into sugar using sunlight
• Heterotrophs- consume food by growing on it
• Saprophytes- obtain food by decomposing dead
  material
• Chemotrophs- manufacture organic compounds from
  inorganic compounds such as hydrogen sulfides

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Bacteria feeding on saguaro
Cyanobacteria in a lake
Bacteria used in wastewater treatment
Chemotrophs at hydrothermal Vent
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Classification of Prokaryotes

• All prokaryotes belong to the kingdoms
• Archaea
• Eubacteria

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Archaea

• First discovered in 1970s
• Discovery made the term Moneran obsolete
• Biochemically different from eubacteria
• May have evolved in the harsh conditions of early
  Earth
• They are abundant in, but not restricted to,
  extreme environments because of their ability to
  withstand the harshest of environments
• May be the early ancestors of eubacteria

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Characteristics of Archaea

• Archaea (Formerly Archaebacteria)
• Lack an important carbohydrate (peptidoglycan)
  found in the cell wall of nearly all Eubacteria.
• Live in harsh environments
• Oxygen-free environments
• Methanogens (ex. Thick mud digestive tracts)
• Produce methane gas
• Salty environments
• Extreme Halophiles
• Great Salt Lake/Dead Sea
• Hot Springs
• Thermoacidophiles

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Characteristics of Eubacteria

• Eubacteria Modern Bacteria
• Unicellular
• Cell walls contain peptidoglycan
• Genes lack introns
• Reproduce asexually by binary fission
• Either autotrophic or heterotrophic
• Extremely diversified groups
• Certain types may be ancestors of mitochondria

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Identifying Prokaryotes

• Bacterial Shapes
• Bacillus Rod
• Coccus Round
• Sprillium Spiral

• Colony growth
• Cells arranged in particular ways
• Form long chains
• Grow in clusters
• Bacterial movement
• Flagella
• Some do not move
• Some glide

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• Shape 1 is rod shape, also known as bacillus.

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• Shape 2 is sphere shaped, also known as coccus.

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• Shape 3 is spiral shape, also known as sprillum

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Micrococcus luteus tetrad
Bacillus cereus
Vibrio
Rhodospirillum
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Bacterial Structures

• Cell Wall- support and protection
• No nucleus- Bacterial DNA is usually coil-shaped
  and not enclosed in a nuclear membrane.
• Most bacteria also have small ring-shaped pieces
  of DNA called plasmids
• Capsule- protective layer that surrounds the cell
• Some have flagellum to aide with movement
• Pilus aides in adhesion to other cells

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Bacterial growth and reproduction

• Grow and reproduce at an incredible rate when
  conditions are favorable
• Bacterial growth stays under control due to
  limiting factors such as nutrient availability
  and production of waste products.
• Reproduction methods
• Binary fission
• Conjugation

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Binary fission

• Asexual reproduction
• When a bacterium is almost double in size, it
  replicates its DNA and divides in half.
• Example E. coli

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Conjugation

• Sexual reproduction
• Long bridge of protein in between 2 bacterial
  cells connecting them.
• Genetic material from donor cell is transferred
  to the other cell.
• Recipient cell ends up with different combo of
  genes.
• Leads to genetic variation, evolution, antibiotic
  resistance

Example
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Spore formation

• Spores form when conditions become unfavorable.
• Endospore is a type of spore that forms a thick
  internal wall that protects the DNA and
  cytoplasm.
• Endospores can remain dormant for months to years
  while waiting for favorable conditions to arise.

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Why are bacteria important?

• Food production
• Yogurt, cheese, buttermilk, sour cream, pickles
• Used in industry
• Digest petroleum clean up oil spills
• Used in mining
• Used in sewage treatment plants
• Symbiosis
• Digestion
• Nitrogen-fixation and plants

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Downside of bacteria

• Pathogens
• Disease causing agents
• Small number of bacteria are pathogens
• Examples of pathogenic bacterial infections
• Syphilis, cholera, tuberculosis, bubonic plague,
  botulism, tetanus, gingivitis, strep throat
• Pathogens cause disease by
• Damaging cells and tissues for use of nutrients
• Release toxins

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Treating bacterial infections

• Antibiotics destroy bacteria by disrupting the
  structure of the cell wall
• Over prescribing of antibiotics is causing
  antibiotic resistance because bacteria mutate
  readily

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Bacterial respiration

• Energy is supplied by respiration and
  fermentation
• Respiration involves oxygen and breaks down food
  molecules to release energy
• Fermentation is energy production without oxygen
• Obligate aerobes
• Bacteria that require a constant supply of oxygen
• Obligate anaerobes
• Must live in the absence of oxygen
• Example Clostridium botulinum
• If subjected to air and allowed to grow on food,
  it will produce toxins that cause severe food
  poisoning.
• Facultative anaerobes
• Can survive with or without oxygen
• Allow facultative anaerobes to live almost
  anywhere.

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The End