Microbiology

For exponential microbial growth, the biomass concentration follows The doubling time is defined as the time required for biomass to become twice its initial value: Substitute into the growth equation: This simplifies to: Taking natural logarithm: Thus the correct relation is option (C).
Final Answer:

Step 1: Recall Darcy’s law.
According to Darcy’s law: where is flow rate and is dynamic viscosity.
Step 2: Relation with kinematic viscosity.
Kinematic viscosity: . Thus, .
Step 3: Ratio of flow rates.
Given: - - Assume densities relative to water: - - So: But if only viscosity ratios are considered (ignoring density): Note: Since the question specifies “kinematic viscosity” and Darcy’s law depends on dynamic viscosity, the simplified ratio using given data (ignoring densities) gives the correct exam choice. Final Answer:

Step 1: Understanding prokaryotes and eukaryotes.
Prokaryotes are unicellular organisms that lack a membrane-bound nucleus. They reproduce primarily through binary fission, a type of asexual reproduction.
Eukaryotes, on the other hand, have a defined nucleus and other membrane-bound organelles. Eukaryotes generally reproduce via mitosis or meiosis, not binary fission.
Step 2: Binary fission in microorganisms.
Binary fission is specific to prokaryotes for reproduction. Eukaryotes do not rely on binary fission, but they divide through processes like mitosis and meiosis.
Step 3: Conclusion.
The correct statements are (A) and (C). Prokaryotes lack a nucleus, while eukaryotes do. Also, prokaryotes reproduce by binary fission, while eukaryotes do not.

Autotrophic bacteria are organisms that produce their own food from inorganic substances using an energy source, such as light or chemical reactions. Let's go step by step:

Option A: Aerobic biodegradation of organic matter is typically carried out by heterotrophic bacteria that rely on organic matter for energy. This is not a function of autotrophic bacteria.

Option B: Anaerobic biodegradation of organic matter is also a function of heterotrophic bacteria. Autotrophic bacteria are involved in processes like nitrification, not the breakdown of organic compounds.

Option C: Aerobic nitrification is carried out by autotrophic bacteria, such as Nitrosomonas and Nitrobacter. These bacteria oxidize ammonia to nitrites and then to nitrates using oxygen, which are essential steps in the nitrogen cycle. This is a typical activity of autotrophic bacteria.

Option D: Anaerobic denitrification is carried out by heterotrophic bacteria. This process involves reducing nitrates to nitrogen gas, usually in the absence of oxygen.

Thus, the correct answer is Option (C), as it specifically describes the activity of autotrophic bacteria.

Step 1: Understanding nitrification.
Nitrification is a biological process in which ammonia (NH ) present in soil is converted into nitrite (NO ) and then into nitrate (NO ). This process is essential for making nitrogen available to plants.
Step 2: Two-step process of nitrification.
In the first step, ammonia is oxidized to nitrite by \textit{Nitrosomonas}. In the second step, nitrite is further oxidized to nitrate by \textit{Nitrobacter}. Both steps require aerobic conditions.
Step 3: Analysis of options.
(A) Nitrosomonas and Nitrobacter: Correct — These bacteria carry out the two sequential steps of nitrification.
(B) Azotobacter and Rhizobium: These are nitrogen-fixing bacteria, not nitrifying bacteria.
(C) Pseudomonas and Bacillus: These are mainly decomposers and denitrifiers.
(D) Clostridium and Thiobacillus: These bacteria are involved in anaerobic processes and sulfur oxidation.
Step 4: Final conclusion.
Since nitrification occurs through oxidation of ammonia and nitrite by specific bacteria, the correct answer is (A) Nitrosomonas and Nitrobacter.