Effects of Environment on Microorganisms Flashcards
Each organism has a ____ within which growth is possible, and most have well defined _____
- pH range
- pH optima
Most natural environments have pH values between ______, and most organisms have pH optima in this range.
5 to 9
Very few species can grow at pH values ____ or _____
- below 2
- above 10
The very few species that can grow at pH values below 2 or above 10.
- Acidophiles
- Alkaliphiles
As temperature rises, chemical and enzymatic reactions proceed at a _____ rate, and the growth rate ____
- faster
- increases
Above a certain temperature, _____ are irreversibly damaged.
proteins
Above a certain temperature, proteins are?
irreversibly damaged.
As temperature is increased within a certain range therefore, growth and metabolic activity increases up to a point where _____ set in
inactivation reactions
As temperature is increased within a certain range therefore, _____ and _______ increases up to a point where inactivation reactions set in
- growth
- metabolic activity
Above this temperature, cell functions fall sharply to?
zero
Above this temperature, they fall sharply to zero.
Cell functions
Temperature classes of microorganisms
- Psychrophiles
- Mesophiles
- Thermophiles
- Hyperthermophiles
They have low temperature optima.
Psychrophiles
These have midrange temperature optima.
Mesophiles
These have high temperature optima.
Thermophiles
These have very high temperature optima
Hyperthermophiles
Temperature growth rate range of Psychrophiles.
0 to 20 degrees Celsius
Temperature growth rate range of Mesophiles.
15 to 45 degrees celsius
Temperature growth rate range of Thermophiles.
40 to 70 degrees Celsius
Temperature growth rate range of Hyperthermophiles like Thermococcus celer.
65 - 95 degrees Celsius
Temperature growth rate range of Hyperthermophiles like Pyrodictium brockli.
80 to 120 degrees celsius
Example of Pyschrophile.
Flavobacterium sp.
Flavobacterium is an example of what class of microorganism based on temperature?
Psychrophiles
Example of Thermophile.
Bacillus stearothermophilus
Bacillus stearothermophilus is an example of what class of microorganism based on temperature?
Thermophiles
Examples of Hyperthermophiles
- Thermococcus celer
- Pyrodictium brockli
Classes of microbes in terms of oxygen needs and tolerance.
- Aerobes
- Microaerophiles
- Facultative organisms
- Anaerobes
They are capable of growing at full oxygen tension, and many can tolerate elevated levels of oxygen (greater than 21 %)
Aerobes
Aerobes can tolerate elevated levels of oxygen (greater than ___)
greater than 21%
They are aerobes that can use oxygen only if it is present at reduced levels in air.
Microaerophiles
They are those that under appropriate nutrient and culture conditions can grow in either aerobic or anaerobic conditions.
Facultative organisms
They are those organisms that lack respiratory systems and thus cannot use oxygen as the final electron acceptor,
Anaerobes
2 Types of Anaerobes
- Aerotolerant anaerobes
- Obligate anaerobes
They are those organisms which can tolerate oxygen and grow in its presence even though they cannot use it.
Aerotolerant anaerobes
They are types of anaerobes that are killed by oxygen
Obligate anaerobes
They are unable to detoxify some of the byproducts of oxygen metabolism.
Obligate anaerobes
They have enzymes that decompose toxic oxygen products.
Aerobes
They lack enzymes that decompose toxic oxygen products.
Anaerobes
Methods for determining oxygen need/tolerance
- Shake culture
- Paraffin-plug technique
- Thioglycollate medium thioglycollate
- O-F test
A method for isolating anaerobic bacteria by shaking a deep liquid culture of an agar or gelatin to distribute the inoculum before solidification of the medium.
Shake culture
A method of isolating anaerobic bacteria by oxygen deprivation.
Paraffin-plug technique
It is for isolation of strict anaerobes.
Thioglycollate medium thioglycollate
Its oxygen levels throughout the media is reduced, which is inversely proportional to the distance from the surface (from reaction with it)
Thioglycollate medium thioglycollate
Oxidation/ Fermentation Test
O-F test
It uses Bromothymol blue as pH indicator
O-F Test
