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Lecture 3

Prokaryotic Growth and Nutrition

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Growth of Bacterial Cultures

Bacteria reproduce by binary fission

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Generation Time Generation time= time required for a cell to

divide

Most bacteria have a generation time of 1-3

hours

If binary fission continues unchecked an

enormous number of cells will be produced

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Phases of growth

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Requirements for Growth

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Physical Requirements Temperature

pH

Osmotic Pressure

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Temperature Psychrophiles- below 15C

Mesophiles- 10C- 45C

Thermophiles- 40C- 70C

Hyperthermophiles- above 80C

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pH Optimal pH for growth

Acidophiles- acid-tolerant

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Osmotic Pressure

Osmotic pressure- can kill cells

Extreme halophiles- require high salt

concentration

Facultative halophiles- do not require high

salt, but can grow at high salt

concentrations

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Chemical Requirements

Carbon

Energy

Nitrogen, Sulfur, Phosphorus

Oxygen

Organic Growth Factors

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Carbon Source Heterotrophs

Autotrophs

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Energy Source

Chemoorganotrophs

Chemolithotrophs

Photoautotrophs

Photoheterotrophs

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Nitrogen, Sulfur, Phosphorus Nitrogen used to synthesize amino acids

Sulfurneeded for some amino acids, and

some vitamins

Phosphorus essential for DNA and ATP

synthesis

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Ox

ygen Obligate Aerobes- require oxygen to grow

Obligate Anaerobes- cannot tolerate oxygen

Facultative Anaerobes- can grow with orwithout oxygen

Microaerophiles- need concentration of

oxygen below what you find in atmosphere Aerotolerant- indifferent to presence of

oxygen

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Organic Growth Factors Essential organic compounds an organism is

unable to synthesize

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Media Complex media- may not know what

organism you are growing or what a

particular organisms needs

Defined Media- specific chemical

composition is known

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Media Selective Media- allows certain bacteria to

grow but will inhibit others from growing

Differential Media- contains substances that

cause some bacteria to look different then

others

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Quantification of Bacteria

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Microscopic Counts: sample diluted,

counted with microscope

Most Probable Number: # of bacteria

determined based on comparison of some

growth parameter to statistical probability

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Figure 6.20 - Overview (1 of 3)