bio 205 chapter 5 powerpoint

8/14/2019 BIO 205 Chapter 5 Powerpoint

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BIO 205

Chapter 5


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Prokaryotic Growth and


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Prokaryotic ReproductionMost Prokaryotes Reproduce by Binary Fission


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A false color TEM of a cell ofBacillus licheniformis undergoing binary fission


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Prokaryotes ReproduceAsexually

The generation (ordoubling) time is theinterval of timebetween successivebinary fissions

In pathogens, ashorter doubling time

means a shorterincubation period ofdisease


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A Bacterial Growth Curve Illustrates the Dynamics of Growth

During the lag phase, no cell division occurs while bacteria

adapt to their new environment

Exponential growth of the population occurs during thelogarithmic (log) phase

Human disease symptoms usually develop during the logphase

When reproductive and death rates equalize, the population

enters the stationary phase

The accumulation of waste products and scarcity ofresources causes the population to enter the decline(exponential death) phase

Prokaryotic Growth


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When reproductive and death rates equalize, the population entersthe stationary phase

The accumulation of waste products and scarcity of resourcescauses the population to enter the decline (exponential death) phase

Prokaryotic Growth Continued


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Endospores

Endospores Are a Response to Nutrient Limitation

Endospores are a highly resistant structure formed by species ofBacillus and Clostridium when nutrient supplies are low

Core

Coat

Layers

Cortex


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The Formation ofa BacterialEndospore


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Factors Affecting Bacteria Growth:2. Temperature3. Oxygen Levels4. pH5. Hydrostatic Pressure

6. Osmotic Pressure


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Temperature

Each prokaryotic species has an optimal temperature forgrowth and about a 30 range of acceptable

temperatures

Psychrophiles grow optimally below 15C, and make upthe largest portion of all prokaryotes on Earth

Thermophiles multiply best around 60C, living incompost heaps and hot springs

Hyperthermophiles areArchaea that grow optimallyabove 80C, found in seafloor hot-water vents

Mesophiles thrive at the medium temperature range of10 to 45C, including pathogens that thrive in the humanbody


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Oxygen

Many prokaryotes are obligate aerobes, which

require oxygen to grow

Anaerobes do not or cannot use oxygen;aerotolerant species are insensitive to oxygen, butobligate anaerobes are inhibited or killed by oxygen

Facultative prokaryotes grow either with oxygen, orin reduced oxygen environments

Thioglycollate broth can be used to test an

organisms oxygen sensitivity

Carnophilic bacteria require an atmosphere low inoxygen and rich in carbon dioxide


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The effect of oxygen on prokaryotic


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pH

The majority of species grow optimally at neutral (~7.0) pH.

Acidophiles are acid-tolerant prokaryotes.

For example, those used to turn milk into buttermilk, sourcream, and yogurt

Hydrostatic and Osmotic Pressure

Barophiles can withstand incredibly high hydrostatic pressure.

For example, psychrophiles living at the bottom of the

ocean.

Halophiles are salt-tolerant prokaryotes.

They can maintain optimal osmotic pressure withoutsuffering from plasmolysis


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Culture Media and Growth


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Culture Media Are of Two Basic Types:

1. A complex mediumis a chemically unidentified

medium such as a nutrient broth or nutrient agar.

2. In a synthetic medium, the chemical composition of


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A selective medium contains ingredients to inhibitgrowth of certain species and allow the growth of others

A differential medium contains specific chemical toindicate species that possess or lack a biochemicalprocess

Some fastidious organisms require an enriched

medium containing specific nutrients

Many prokaryotes cannot be cultured in a laboratory

Culture Media Can Be Devised to Select for or Differentiatebetween Prokaryotic Species


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Bacterial Population Measurements Are Made Using PureCultures

A pure culture is apopulation consisting of onlyone species of prokaryote

The pour-plate isolationmethod allows separation ofspecies through dilution of asample


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The streak-plate isolation method spreads out individual cellsto form discrete colonies of species


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End of Chapter 5

bio 205 chapter 5 powerpoint

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