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environmental factors ongrowth

Temperature : psychrophiles, mesophiles,thermophiles

pH: acidophiles, alkalinophiles

oxygen: aerobes : organism able to grow in the presence of atm.

oxygen anaerobes : grow in the absence of atm. oxygen anaerobes aerotolerant : ignore oxygen and grow equally

well wheather it is present or not.

Obligate anaerobes : do not tolerate oxygen at all and die inits presence.

Both the above cannot generate energy through respirationand must employ fermentation or anaerobic respirationpathways.

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Microaerophilic : damaged by the normal atm.level of oxygen (20%) and require oxygen levelsbelow the range of 2 - 10 % for growth.

Facultative anerobes : able to grow in either thepresence or the absence of oxygen. Switchbetween fermentative metabolism and aerobicrespiration depending on availability of oxygen.

Capnophiles : A microorganism that grows best at

relatively high carbon dioxide concentration (5-10%).

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Osmotic pressure : halophiles,osmophiles, xerophiles

Use of anaerobic jar : anaerobiccontainer for cultivation ofanaerobic bacteria on petri plates

Gas generator envelope; palladiumpellets; anaerobic indicator strip

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(chemical requirements)

environment

Major macronutrients; C,N,P,S,K,Mg,Ca,Na,Fe

Micronutrients (trace elements) : Co, Zn,Mo,Cu, Mn, Ni, Tu, Se.

Growth factors : organism is unable tosynthesize, must be obtained directly fromenvironment. Organic compound needed onlyin small amount and only by some cells.

Includes vitamins, a.a.

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Culture media

Types of culture media1. chemically defined media : exact composition is

known

2. complex media : contain some ingredients ofunknown chemical composition; nutritionalrequirements of a particular microorganism areunknown therefore defined medium cannot beconstructed. Eg : peptones, meat extract, yeastextract.

3. Selective media: suppress the growth of unwantedbacteria and encourage the growth of the desiredmicrobes

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4. Differential media : make it easier to distinguishcolonies of the desired organism from othercolonies growing on the same plate.

5. enrichment media : to isolate, to cultivate, mimic

many natural situation (eg. soil); usually in liquidand provides nutrients and environmentalconditions that favours growth of a particularmicrobe but not others.; also a selective medium,but design to increase very small # of the desiredtype of organism to detectable levels (fortifiedmedia).

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