Copyright © 2010 Pearson Education, Inc. The Requirements for Growth Physical requirements Temperature pH Osmotic pressure Chemical requirements Carbon Nitrogen, sulfur, and phosphorous Trace elements Oxygen Organic growth factor
Jan 13, 2016
Copyright © 2010 Pearson Education, Inc.
The Requirements for Growth
Physical requirements Temperature pH Osmotic pressure
Chemical requirements Carbon Nitrogen, sulfur, and phosphorous Trace elements Oxygen Organic growth factor
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Examples
Example: Psychrotrophs: Grow between 0°C and 20–30°C Many cause food spoilage
Extreme Thermophiles Some microbes can live at 100°C at the bottom of the
Ocean. How?
Copyright © 2010 Pearson Education, Inc. Figure 6.4
Plasmolysis
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Chemical Requirements
Carbon: The structural ‘backbone’ of organic molecules
~Half the dry weight of a typical bacterial cell is C
Carbon Sources: Chemoheterotrophs: use organic carbon sources (The
specific organic carbon source(s) that can be used are determined by an organism’s DNA)
Chemo- and Photo- Autotrophs: use CO2
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Chemical Requirements
Nitrogen Needed for amino acids (proteins), nitrogen bases (DNA,
RNA, ATP) ~ 14% of dry weight of a bacterial cell is N Most bacteria decompose proteins in the environment
from other organisms, and rearrange these amino acids to form the proteins and other N-containing molecules they need
Some bacteria use NH4+ (ammonium) or NO3–(nitrate)
Many photosynthetic bacteria use N2 in the atmosphere during nitrogen fixation. N2 is 80% of Earth’s atmosphere.
See Slide 6
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Look for common terms among the various cycles (Example: Decomposition)
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Chemical Requirements Sulfur
In amino acids, vitamins (thiamine and biotin) Most bacteria decompose proteins Some bacteria use SO4
2– or H2S for energy/e- donor/acceptor
Phosphorus In DNA, RNA, ATP, and membranes PO4
3– is a source of phosphorus, changes little
Source: Rocks, sea sediment, soil, solubilized by the acid produced by bacteria, not returned to the atmosphere like CO2, N2, SO2
Other: K, Mg, Ca, inorganic trace elements (Fe, Zn, Cu, etc.- often used as enzyme cofactors)- Found in tap water
Copyright © 2010 Pearson Education, Inc. Table 6.1
The Effect of Oxygen (O2) on Growth
Copyright © 2010 Pearson Education, Inc. Clinical Focus, p 164
Biofilms
Copyright © 2010 Pearson Education, Inc. Figure 6.12a
Binary Fission
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Time it takes for a cell to divide; therefore, the time it takes for a population to double
If a bacterium has a generation time of 2 hours, and the population begins with 10 cells, how many cells will be in the population after 10 hours?
Generation Time
Copyright © 2010 Pearson Education, Inc. Figure 6.15
Phases of GrowthBacterial Growth Curve