20.2: Bacteria

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20.2 Bacteria

• Recommended reading
• pp. 462-464

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Overview

• Comparing Bacteria with Eukaryotes.
• Bacteria and the Surrounding Environment.

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Comparing Bacteria with Eukaryotes.

• Bacteria outnumber all eukaryotes combined.
• There are seven important characteristics that
  distinguish bacteria (prokaryotes) from
  eukaryotes.

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Comparing Bacteria with Eukaryotes.

• Internal compartmentalization bacteria lack a
  nucleus, unlike eukaryotes. Bacteria have no
  internal compartments or membrane systems.

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Comparing Bacteria with Eukaryotes.
Prokaryotic Cell
Eukaryotic Animal Cell
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CHECKPOINT

• What are the two major things that prokaryotic
  cells lack when compared to eukaryotic cells?
• Nucleus Internal Compartments

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Comparing Bacteria with Eukaryotes.

• Cell size Eukaryotic cells are, on average, ten
  times the size of a prokaryotic cell.

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Comparing Bacteria with Eukaryotes.

• Multicellularity Bacteria are single-celled.
  Bacteria can cluster but are not considered
  multicellular like eukaryotes. Bacteria cells are
  not specialized like eukaryotes.

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Comparing Bacteria with Eukaryotes.

• Chromosomes Bacterial chromosomes are a single
  piece of circular DNA as opposed to eukaryotic
  chromosomes, which are linear.

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Comparing Bacteria with Eukaryotes.

• Cell Division Bacteria divide by binary fission,
  however eukaryotes divide by the process of
  mitosis.

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Comparing Bacteria with Eukaryotes.

• Binary Fission
• Process by which a bacteria cells reproduce.
  Bacterial DNA molecule is replicated, separated
  and attached to the cell membrane then the cell
  splits into two identical cells, each containing
  an exact copy of the original cell's DNA.

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BINARY FISSION
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CHECKPOINT

• Before dividing into two IDENTICAL cells, the DNA
  in bacteria attaches itself to the _________
  _____________ ?
• Plasma (Cellular) Membrane

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Comparing Bacteria with Eukaryotes.

• Binary Fission (cont)
• Similar to mitosis, but binary fission is a much
  more simplified process, which allows bacteria to
  reproduce rather quickly.
• E. coli can divide as often as every 20 minutes!

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Comparing Bacteria with Eukaryotes.

• Flagella In bacteria, these are simple
  structures composed of a single fiber of protein.
  Spins in corkscrew motion to propel bacterial
  cells into motion. More sophisticated in
  eukaryotic organisms (composition and movement).

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Comparing Bacteria with Eukaryotes.

• Metabolic Diversity Bacteria can perform both
  anaerobic and aerobic respiration, whereas
  eukaryotes strictly carry out aerobic
  respiration. Some bacteria can obtain energy by
  oxidizing compounds such as sulfur or fixing
  nitrogen.

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Bacteria and the Surrounding Environment

• Bacteria can protect themselves from harsh
  environmental stress including drought, high
  temperatures, and lack of nutrients.
• When a cell encounters harsh conditions, the
  synthesis of an endospore occurs.

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Bacteria and the Surrounding Environment

• Endospore tough coating that is highly resistant
  to environmental stress.
• Process takes about eight hours from the time
  synthesis begins.

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Bacteria and the Surrounding Environment

• Endospores are resistant to most agents which
  would normally kill the cells they formed from.
• Household cleaning products generally have no
  effect.

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Bacteria and the Surrounding Environment

• Once favorable conditions resume, a rupture or
  absorption of the spore coat occurs (activation).

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CHECKPOINT

• What are factors that may cause bacteria to form
  an endospore?
• Environmental factors such as drought or extreme
  temperatures, even lack of nutrients for survival.

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Summary

• Bacteria (prokaryotes) exhibit many different
  characteristics than eukaryotes.
• Bacteria can withstand stressful environments
  through use of endospores.

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Next Day

• Bacteria and Energy