Transcript Understanding Our Environment

Bacteria
Chapter 34
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The Prevalence of Bacteria
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Bacteria are the oldest, structurally simplest,
and the most abundant forms of life on earth.
 Abundant for over 2 billion years before the
appearance of eukaryotes.
 5,000 different kinds currently recognized.
- Based primarily upon their metabolic and
genetic characteristics.
 Can only be properly characterized on
a defined medium.
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The Prevalence of Bacteria
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Bacterial Form
 Bacillus (Bacilli) straight and rod-shaped.
 Coccus (Cocci) spherical shaped.
 Spirillus (Spirilla) long and helical shaped.
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The Prevalence of Bacteria
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Prokaryotes versus Eukaryotes
 Multicellularity
 Cell Size
 Chromosomes
 Cell Division and Recombination
 Internal Compartmentalization
 Flagella
 Metabolic Diversity
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The Bacterial Surface
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Bacterial 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
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Internal Membranes
 Invaginated plasma membrane.
Nucleoid Region
 Lack nucleus - Genes encoded with single
double-stranded DNA.
Ribosomes
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Bacterial Diversity
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Key Classification Characteristics
 Photosynthetic or Nonphotosynthetic
 Motile or Nonmotile
 Unicellular or Multicellular
 Spore Formation by Division or Transverse
Binary Fission.
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Bacterial Diversity
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Comparing Archaebacteria and Eubacteria
 Cell Wall
- Archaebacteria lack peptidoglycan.
 Plasma Membranes
- Composed of different lipids.
 Gene Translation Machinery
- Archaebacteria similar to eukaryotes.
 Gene Architecture
- Eubacteria not interrupted by introns.
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Bacterial Variation
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Two Process create bacterial variation:
 Mutation
- Spontaneous errors in DNA replication.
 Genetic Recombination
- Occurs by gene transfer from one cell to
another by viruses or conjugation.
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Bacterial Metabolism
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Autotrophs
 Obtain carbon from inorganic CO2.
- Photoautotrophs - Sunlight
- Chemoautotrophs - Inorganic Chemicals
Heterotrophs
 Obtain carbon from organic molecules.
- Photoheterotrophs - Sunlight
- Chemoheterotrophs - Organic Molecules
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Bacterial Metabolism
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How Heterotrophs Infect Host Organisms
 Proteins secreted by Type III System.
- May be used to transfer other virulence
proteins into nearby eukaryotic cells.
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Human Bacterial Diseases
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Tuberculosis
 Afflicts respiratory system and easily
transmitted from person to person through
the air.
Dental Caries (cavities)
 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
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Sexually Transmitted Diseases
 Gonorrhea (Neisseria gonorrhoeae)
 Syphilis (Treponema pallidum)
 Chlamydia (Chlamydia trachomatis)
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Importance of Bacteria
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Largely responsible for creating atmospheric
properties.
Contribute to carbon balance.
Nitrogen Fixation
Industrial Processes
 Fermentation of lactose into lactic acid.
- Milk, Cheese, Yogurt
Genetic Engineering
Removal of environmental pollutants.
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