Physiology of bacteria
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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”

Physiology of bacteria

Physiology of bacteria
pH temperature preference of bacteria?

  • Readings question four:

    Describe the pH scale.

    Acidophiles: bacteria that are remarkably tolerant of acidity

Light temperature preference of bacteria?

  • 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 temperature preference of bacteria?

  • “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

Moisture temperature preference of bacteria?

  • 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 temperature preference of bacteria?

  • Readings question two:

    Describe the differences between autotrophic bacteria and heterotrophic bacteria.

Heterotrophic bacteria
Heterotrophic Bacteria temperature preference of 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

Carbon temperature preference of bacteria?

  • 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 temperature preference of bacteria?

  • needed by microorganisms for the synthesis of cellular material

  • e.g. protein, DNA, RNA, ATP

Trace elements
Trace Elements temperature preference of bacteria?

  • iron, copper, and zinc

  • essential for the function of certain enzymes

Oxygen temperature preference of bacteria?

  • 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 temperature preference of bacteria?

  • “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 temperature preference of bacteria?

  • 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 temperature preference of bacteria?

  • can grow in the presence or absence of oxygen

    • e.g. Streptococcus pyogenes

Microbial associations
Microbial Associations temperature preference of bacteria?

  • 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

Mutualism temperature preference of bacteria?

  • “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

Commensalism temperature preference of bacteria?

  • “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

Parasitism temperature preference of bacteria?

  • “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

Physiology of bacteria

Antagonism temperature preference of bacteria?

  • “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)