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Physiology of Bacteria. Bacterial Growth. Bacterial Colony. “a visible group of bacteria growing on a solid medium, presumably arising from a single microorganism”. Requirements for Growth. Physical: temperature, pH, light, osmotic pressure, moisture

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physiology of bacteria

Physiology of Bacteria

Bacterial Growth

bacterial colony
Bacterial Colony
  • “a visible group of bacteria growing on a solid medium, presumably arising from a single microorganism”
requirements for growth
Requirements for Growth
  • Physical: temperature, pH, light, osmotic pressure, moisture
  • Chemical: carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen
  • Readings question three:

What are psychrophiles, mesophiles, and thermophiles?

  • Desulfofrigusoceanense(Arctic and Antarctic Oceans)

E. coli


Fossilized Microbes from Yellowstone’s Hot Springs

  • Minimum: “temperature below which bacterial growth will not take place”
  • Optimum: “temperature at which organisms grow best”
  • Maximum: “temperature above which bacterial growth will not take place”
  • Readings question four:

Describe the pH scale.

Acidophiles: bacteria that are remarkably tolerant of acidity

  • Cyanobacteria: oxygen producing prokaryotes
    • thrive in the presence of light
  • Yeasts and Molds
    • prefer dark areas
  • Some bacteria are destroyed by ultraviolet light.
osmotic pressure
Osmotic Pressure
  • “pressure that develops when two solutions of different concentrations are separated by a semi-permeable membrane”
  • microorganisms require water for growth and are made up of 80-90% water
  • high osmotic pressure removes necessary water from a cell
  • plasmolysis
  • hypertonic solutions
  • maximum, optimum and minimum requirement for all microorganisms
  • Pathogenic bacteria are usually found in the body’s tissues
  • Fungal diseases are usually found on the body surface.
chemical requirements
Chemical Requirements
  • Readings question two:

Describe the differences between autotrophic bacteria and heterotrophic bacteria.

heterotrophic bacteria
Heterotrophic Bacteria
  • 3 categories:
    • 1) strict (obligate) saprophyte
    • 2) strict (obligate) parasite
    • 3) facultative bacteria:
      • Facultative saprophyte: “prefers live organic matter as a source of nutrition but can adapt to the use of dead organic matter under certain conditions”
      • Facultative parasite: capable of living and growing with the nutrients that its host provides
  • one of the most important requirements for microbial growth
  • structural backbone of living matter
  • needed for all the organic compounds that make up a living cell
  • ½ of the “dry weight” of a bacterial cell is carbon
nitrogen sulfur and phosphorus
Nitrogen, Sulfur, and Phosphorus
  • needed by microorganisms for the synthesis of cellular material
  • e.g. protein, DNA, RNA, ATP
trace elements
Trace Elements
  • iron, copper, and zinc
  • essential for the function of certain enzymes
  • Microbes that use molecular oxygen (aerobes) produce more energy from nutrients than microbes that do not use oxygen (anaerobes)
  • Reading question two:

Describe the difference between obligate aerobes and obligate anaerobes.

microaerophilic organisms
Microaerophilic Organisms
  • “a microorganism that requires very little free oxygen”
  • only grow in oxygen concentrations that are lower than those in air
  • require about 2 – 10% free oxygen
facultative organisms
Facultative Organisms
  • Facultative Aerobes: “a microorganism that prefers an environment devoid of oxygen but has adapted so that it can live and grow in the presence of oxygen”
  • Facultative Anaerobes: “a microorganism that prefers an oxygen environment but is capable of living and growing in its absence”
    • E.g. Bacillus anthracis, Corneybacteriumdiphtheriae, Escherichia coli
aerotolerant organisms
Aerotolerant Organisms
  • can grow in the presence or absence of oxygen
    • e.g. Streptococcus pyogenes
microbial associations
Microbial Associations
  • normal flora (microbiota)
  • transient microbiota
  • symbiotic relationship: “organisms live in close nutritional relationships; required by one or both members”
    • distinguished by the degree to which the host organism is harmed
  • “a symbiotic relationship in which organisms of two different species live in close association to the mutual benefit of each”
    • e.g. E. coli in the human digestive tract
  • “the symbiotic relationship of two organisms of different species in which one gains some benefit such as protection or nourishment and the other is not harmed or benefited”
    • e.g. bacteria on skin surface; microorganisms within the digestive tract
  • “an interactive relationship between two organisms in which one is harmed and the other benefits”
  • many disease-causing bacteria are parasites
  • typically the host is macroscopic and the parasite is microscopic
  • roundworms and flatworms are parasites that are large multi-cellular organisms

Readings question five:

What is the synergistic effect?

  • “mutual opposition or contrary action. The inhibition of one microorganism by another.”
  • Involves competition among microbes
  • normal microbiota protect the host against colonization by potentially pathogenic microbes
  • normal flora produce substances harmful to the invading microbes (pH, oxygen)