Bacteria: Structure and Function

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Bacteria Structure and Function
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Bacterial Structure

• No membrane-bound organelles
• Flagella
• Pili
• Cell wall
• Gram positive vs. gram negative bacteria
• Not all bacterial have all the same structures,
  as they may have additional structures to help
  them adapt to their niche.

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Gram-Positive vs. Gram-Negative
The more peptidoglycan, the more rigid the cell
wall Why would that be important?
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Gram Positive Bacteria

• Clostridium botulinum, the bacterium that creates
  the toxin to cause botulism.

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Gram Positive Bacteria

• Bacillus anthracis causes anthrax

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Gram Positive Bacteria

• Streptococcus pnemoniae the bacteria that cause
  strep throat

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Gram Positive Bacteria

• Myobacteria cause tuberculosis

• Many species of actinomycetes - used to make
  antibiotics

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Gram Negative Bacteria

• Treponema pallidum syphillis
• STD, sores, skin rashes, lesions

Borrelia burgdorferi Lyme Disease Caused by
deer ticks, bulls-eye, fever, headache - may
spread to nervous system if left untreated
Chlamydia trachomatis chlamydia STD, can damage
womens reproductive organs
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Cell Wall

• Whats the purpose of a cell wall?
• Gives shape
• Protects
• Many bacteria have additional structures on cell
  wall that add to their disease-causing abilities

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Cell Membrane

• Selective barrier
• Metabolic functions
• cellular respiration

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DNA and Plasmids

• A single closed loop of double stranded DNA.
• Attached to cell membrane at one point
• NOT enclosed in a nucleus
• Some bacterial cells have Plasmids
• Small, circular, self-replicating loops of DNA.
• Some plasmids carry the disease-causing gene
• Some plasmids provide antibiotic resistance

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Capsules

• Outer covering that binds to cell wall and
  protects from drying or harsh chemicals
• Protects from hosts lymphocytes
• May help cell stick to host cells and tissues

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Pili

• Short, hair-like protein structures
• Help stick to each other and host cells
• Can be the bridge to pass genetic material from
  one bacteria to the next

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Endospores

• Some Gram-positive bacteria can form a
  thick-coated, resistant structure
• - Contains bacterial DNA
• Harsh conditions may destroy most of the cell,
  but the endospore may survive
• When favorable conditions return, endospore gives
  rise to a new bacterial cells

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Reproduction

• Binary Fission
• DNA is copied
• Cells divide
• Two identical daughter cells result

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Recombination

• Bacteria can exchange pieces of genetic
  information without actually having to reproduce.

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Recombination

• Genetic recombination in bacteria can occur by
  the following three ways
• transformation
• taking in DNA from the outside environment
• conjugation
• exchanging DNA with other bacteria via pili
• transduction
• transmission of bacterial DNA via viruses