Question

1. How does pH specifically affect bacterial growth?

2. How specifically does temperature affect bacterial growth?

3. What terms are used to describe optimum temperature for bacteria?

4. Specifically, how can osmotic pressure affect growth of bacteria?

5. How can anaerobes be grown in the lab? What is the name of the broth? The indicator it contains?

6. Difference between defined and undefined media and understand how media components will support the bacterial growth or not (i.e. fastidious or not)

Answer 1

1. Bacterial growth occurs drastically in most cases around neutral pH level (7.0). But there has some exceptions like Acidophyle bacteria, they can tolerate highly acidic environment (1.0) for that reason they are termed as Acid Loving Microbe but at the same time they maintained their internal body pH closer to neutral level (7.0).

2. Specific bacterial species requires specific level of growth temperature strictly depends on temperature in which the activity of their bodily enzymes becomes best in state. Optimum Growth Temperature ranges in bacteria between -5^oC to 45^oC and in case of same exotic temperature resistant bacteria the value ranges from 70^oC to 75^oC.

3. Mainly three terms are used for optimum temperature of bacteria, these are Psychrophiles, Mesophiles and Thermophiles. In case of Psychrophiles temperature ranges from -5^oC to 20^oC, in case of Mesophiles temperature ranges from 20^oC to 45^oC and in case of Thermophiles generally temperature ranges above 45^oC.  

4. Osmotic pressure plays a very important role in bacterial growth, like Nonhalophiles - Escherichia coli (cannot tolerate osmolarity level), Halotolerant - Staphylococcus aureus (can tolerate moderate level of osmolarity), Mild-Halophiles - Pseudomonas marina (can tolerate osmolarity of 1-6% of sea water salt), Moderate-Halophiles - Vibrio costicolus (can tolerate 6-15% of salt or above in some cases), Extreme Halophiles - Pediococcus halophilus (can tolerate 15-36% of salt).

5. To cultivate anaerobic bacteria in lab firstly we have to reduce O₂ concentration (mainly used thioglycolate in thyogycolate broth) of culture medium in lab, then fill the culture medium in any bottle or test tubes and have to provide bacteria and lastly a tight fitting stopper. after certain time we can found growth of anaerobes at the bottom of test tube because O₂ cannot penetrate there.

The name of the broth in case of Thioglycolate is Thioglycolate broth.

It contains Redox indicator.

6. Main difference between defined and undefined culture medium is, in case of Defined culture medium the quantities of ingredients in it has already be known, which provide nutrients to microorganisms. on the other hand, in case of undefined culture medium the ingredients used contains unknown components (mainly mixed components) in random quantity.

Different culture medium used in lab to cultivate specific types of bacteria or microorganisms, such as Amino acid and Nitrogen nutrient media contains various compounds used to cultivate bacteria in laboratory, this is a example of Undefined Culture Medium and function of it in bacterial growth.