Microorganisms In Nature

Question 1

What is Liebig’s law of the minimum?

Answer 1

Relates to resource availability

Question 2

What is Shelford’s law of intolerance?

Answer 2

Relates to the environmental impacts of life

If any condition exceeds maximum or minimum tolerance, organism will fail to thrive and die

Within the tolerance change optimal conditions exist

Question 3

What environmental factors affect microorganisms?

Answer 3

Temperature
pH
Salinity

Question 4

What are the categories of organisms based on their optimal temperatures?

Answer 4

1. Psychrophiles- optimum activity at 5-15°C, inactive above 20°C
2. Psychrotrophs- optimum activity at 25-30°C
3. Mesophiles- optimum activity 25-40°C
4. Thermophiles- optimum activity 40-60°C
5. Hyperthermophiles- optimum activity approx 85-105°C

Question 5

What are some adaptations of thermophiles and hyperthermophiles that have to survive at high temperatures?

Answer 5

High guanine-cytosine content of DNA (they have 3 H bonds, so harder to break)

High levels of proteins that stabilise DNA

High proportion of saturated fatty acids (higher melting points)

Ether-linked lipids

Isoprenoids lipids in Archaea (produce tightly packed together membranes with a high melting point)

Question 6

What’s the direct and indirect effects of pH on microorganisms?

Answer 6

Direct:

Extreme pH promote hydrolysis of biopolymers

Indirect:

Speciation of inorganic ions
Solubility
Changes in net charge

Question 7

What are the categories of organisms based on their optimal pH?

Answer 7

Acidophiles
Neutrophiles
Alkaliphiles

Question 8

What are the features of acidophiles?

Answer 8

Optimum growth at low pH, 1-5
Many fungi and yeast are acidophilic
Most acidophilic organic,s are bacteria and archaea

Examples:

Acidithiobacillus
Leptospirillum
Sulfolobus
Thermoplasma

Question 9

What are the features of neutrophiles?

Answer 9

Optimum growth around neutral pH, 6-8

Question 10

What are the features of Alkaliphiles?

Answer 10

Optimum growth at hight pH. ≥10

Examples:

Autotrophic ammonia-oxidising bacteria
Alkaliphillic cyanobacteria

Question 11

What are some acidic environments?

Answer 11

Mining regions
Volcanic areas
Forest soils

Question 12

What are some alkaline environments?

Answer 12

Soda lakes
Deserts
Soils with high levels of protein decomposition

Question 13

What are some environments with extreme hot temperatures?

Answer 13

Mining areas
Hot springs
Hydrothermal vents

Question 14

What are some saline environments?

Answer 14

Marine environments
Salt lakes
Soda lakes
Halite deposits

Question 15

What are halophiles and extreme halophiles?

Answer 15

Halophiles have an obligate salt requirement

Examples:

In salt lakes primary production dominated by the halophilic alga Dunaliella salima

Extreme halophiles require high levels of salt

Question 16

How does radiation affect microorganisms?

Answer 16

Visible light has important effects on the distribution of microorganisms, as different photosynthetic pigments absorb light of different wavelengths. For example, photosynthetic bacteria distributed in water in relation to the wavelength of light absorbed by their pigments.

Ionising radiation such as x rays and gamma rays can be lethal at high levels . They produce unstable ions and free radicals that react with living material.

UV radiation can damage DNA, as it causes adjacent Thymine in DNA to react forming thymine dimers.

Question 19

What is radiation measured in?

Answer 19

Rads or Gray