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Who says science can’t be funny?. Microbial Growth and Metabolism. Chapter 7. Where are they?. Everywhere! (ubiquitous) Not all bacteria can live in every environment Important factors of growth pH Temperature Nutrient/energy sources Gas content Water Salt Radiation.

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where are they
Where are they?
  • Everywhere! (ubiquitous)
  • Not all bacteria can live in every environment
  • Important factors of growth
    • pH
    • Temperature
    • Nutrient/energy sources
    • Gas content
    • Water
    • Salt
    • Radiation
what is the cell
What is the cell?

Elements C,H,O,N,P,S make up 96% of cell

  • Products by which chemical substances (nutrients) are acquired from environment and used
  • Essential nutrients must be provided for the organism
  • Macronutrients and micronutrients exist
macro and micronutrients
Macro- and Micronutrients
  • Macronutrients are required in large amounts
    • Include lipids, carbs, and protein
    • Important for cell structure and metabolism
  • Micronutrients are needed in small amounts
    • Aka trace elements
    • Include elements like Mn and Zn
    • Help with protein structure and enzyme function
    • Microbe-specific
growth factors
Growth Factors
  • Fastidious bacteria require growth factors
    • Organic compounds that cannot be made by cell and must be provided as a nutrient
nutritional types
Nutritional Types
  • How do they get their carbon?
    • Autotroph- Inorganic molecules
    • Heterotroph- Organic molecules
  • How do they get their energy?
    • Chemotroph- Organic molecules
    • Phototroph- Light
put them together
Put them together
  • Photoautotrophs- use light for energy and use CO2 as a carbon source
    • Oxygenic PS

CO2 + H2O  (CH2O)n + O2

      • Oxygen is produced
      • Plants, algae, cyanobacteria
    • Anoxygenic PS

CO2 + H2S  (CH2O)n + Sº + H2O

      • Oxygen is not produced
      • Purple and green sulfur bacteria
put them together1
Put them Together
  • Chemoautotrophs- use inorganic molecules as a source of energy and carbon
    • Remove e- from substances and combine with CO2 and hydrogen
    • Ex: Methanogens
      • Found in hot springs, frigid ocean depths, soils, swamps

4H2 + CO2 CH4 + 2H2O

put them together2
Put them Together
  • Chemoheterotrophs- use organic molecules for both energy and a source of carbon
    • Ex: aerobic respiration

(CH2O)n + O2 CO2 +H2O + energy



    • Decomposers (rigid CW, can’t “engulf” food)
      • Release extracellular enzymes to digest
      • Can become oppotunistic pathogen—not supposed to be bad, but can under right conditions
        • Psuedomonas aeruginosa
some parasites
Some Parasites
  • Parasite
    • Infectious agents—can be small (virus) to macroscopic (worms)
    • Can be
      • On the body (ectoparasite)
      • In the body (endoparasite)
      • Inside of cells (Intracellular parasite)
water as a factor for growth
Water as a Factor for Growth

Pressure required to prevent the net flow of water across a semipermeable membrane.

Depends on the concentration of dissolved substance in solution and in the cell.

  • Isotonic – No net movement of water. [inside] = [outside]
  • Hypotonic – [inside] > [outside]
    • Net movement of water is intothe cell. Causes swelling & possible bursting –Cytolysis(cell is hypertonic)
  • Hypertonic – [inside] < [outside]
    • Net movement of water out of the cell
    • Cytoplasmic membrane shrinks-Plasmolysis (Cell is hypotonic)
    • Cell growth is inhibited
      • Why salting food and making preserves (sugar) works
philes tolerants durants and the like
Philes, Tolerants, Durants, and the like
  • “Reading to the text” activity

! = Interesting

? = I have a question—write it on the side!

*= important –summarize it

Ex = example

C = connects to something I know

Osmophile = new vocab

how does this influence us when it comes to food
How does this influence us when it comes to food?
  • Most disease causing and spoilage bacteria are Mesophiles.
    • Store at <15ºC,
    • 2 - 4ºC (35 – 38ºF) is best.
    • Psychrophiles multiply in frig so freeze the food.
temperature and disease
Temperature and Disease
  • Body isn’t evenly heated.
    • Extremities are at 30 – 35ºC and scrotum at 32ºC.
    • Cooler areas are more prone to diseases such as:
      • Hansen’s disease (Leprosy)
      • (Mycobacterium leprae) & Syphilis (Treponema pallidum).
        • Used to treat syphilis by inducing fever (with malaria) and hot springs
    • Brain, heart, GI tract, lungs at 37ºC
oxygen as a factor for growth
Oxygenas a factor for Growth
  • Oxygen is not as wonderful as we think!
  • Very destructive molecule
    • Why fruits (with antioxidants) are important
  • There are enzymes to detoxify O2
oxygen reactions
  • Superoxide dismutase
  • Catalase
how do i know who s what
How do I know who’s what?
  • Grow them on thioglycollate media!
    • Reducing media that contains a chemical that removes O2
  • Obligate Aerobe
  • Facultative aerobe
  • Aerotolerant Anaerobe
  • Strict/Obligate Anaerobe
bacterial growth
  • Bacteria grow by binary fission
    • Parent enlarges, doubles cellular content, and splits into 2
    • The time to do it is called the generation time or doubling time
      • Average is 30-60 minutes (some take up to 27 days!)
  • 1… 2… 4… 8… 16… 32… 64… 128… 256… 512…
  • 1024… 2048… 4096… in 12 hours!!! (60 min gen time)
closed systems
  • Typically, bacteria live in closed systems
    • Finite (limited number of nutrients)
    • Results in eventual die-off
bacterial growth1
  • If we to plotthe # of bacteria from start to end, we’d get thefollowing
  • Predictablepattern is called a growth curve
stages of growth
  • Lag phase
  • Log phase
    • Aka Exponential growth phase
    • Aka Logarithmic growth phase
  • Stationary growth phase
  • Death phase
lag phase
  • “flat” period at start
  • Population is either not growing or growing very slowly
    • Needs time to adjust to new environment
    • Population very small at this point
    • Cells are alive!
    • Growth > death
log phase
  • “curved” exponential period
  • Bacteria are growing at their maximum rate
    • Will continue as long as space and nutrients are good
    • Growth >> Death
stationary growth phase
  • “plateau” period in middle
  • Survival mode for bacteria
    • Nutrients and space VERY limited
    • Too many toxins present
  • Stop growing or slow down growing
  • Growth = Death
death phase
  • “Downward curve” period
  • Death occurring at an exponential rate
    • But not as fast as growth was
  • Cells can still survive for a long time at this point
  • Growth < Death
how else can we analyze growth
How else can we analyze growth?
  • Can do it quantitatively or qualitatively
    • Quantitative- involves numbers and direct counts
    • Qualitative- a “yes” or “no” answer to growth
to measure growth
To Measure growth
  • Mass of Cells

- use light scattering method or a Mass Spectrophotometer

- As there is an > in mass (# of cells), there is a < in the amount of light passing through.

- **Counts both living and dead**

    • Limited due to 1 million cells showing clear in a solution.
Plate Count

- # of colonies present represents the # of living cells in the original suspension

- Use a diluted culture to make counting easier – Serial dilutions. 1ml of culture into each successive solutions.

- **Counts living cells only (dead cells don’t multiply)**

- Difficult with strepto & staphylo forming species

Direct Microscope Count

– Count # of bacteria in an accurately measured volume of liquid on a counting chamber/ cytometer slide

- Gridded pattern - **Can’t tell living from dead**