Serge francois physiology of bacteria
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Serge francois | Physiology of Bacteria and Genetics PowerPoint PPT Presentation

A noticeable group of viruses growing on a strong method, presumably as a result of a single microorganism

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Serge francois | Physiology of Bacteria and Genetics

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Serge francois physiology of bacteria

Serge francois | Physiology of Bacteria

Serge Francois

Bacterial colony

Bacterial Colony

  • “A noticeable group of viruses growing on a strong method, presumably as a result of a single microorganism”

Requirements for growth

Requirements for Growth

  • Physical: Temperature, pH, light, osmotic pressure, moisture

  • Chemical: Carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen



  • Desulfofrigus oceanense (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”



  • 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.

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



  • Microbes that use molecular oxygen (aerobes) produce more energy from nutrients than microbes that do not use oxygen (anaerobes)

  • Reading question four:

    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

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



  • “An entertaining connection between two creatures in which one is injured and the other benefits”

  • Many disease-causing viruses are parasites

  • Typically the variety is macroscopic and the parasite is microscopic

  • Roundworms and flatworms are harmful viruses that are huge multi-cellular organisms



  • “Mutual resistance or opposite activity. The self-consciousness of one organism by another.”

  • Involves competitors among microbes

  • Normal microbiota secure the variety against colonization by possibly pathogenic microbes

  • Normal plants generate ingredients bad for the infiltrating bacteria (pH, oxygen)

Serge francois physiology of bacteria and genetics

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