Question

Which bacteria help improve soil fertility?

• A. Clostridium
• B. Rhizobium
• C. Salmonella
• D. Staphylococcus

Hint:

Think about which bacteria fix nitrogen inside root nodules of legumes.

Answer 1

The Correct Option is B

Step 1: Understand what soil fertility bacteria do.
Soil fertility improves when nitrogen is added to it in a form plants can use. Air is full of nitrogen gas, but plants cannot take it up directly. Certain bacteria can pull nitrogen gas from the air and turn it into ammonia and other compounds the plant roots can absorb. This process is called biological nitrogen fixation.

Step 2: Identify the bacteria responsible.
Rhizobium is a bacterium that lives inside small swellings called root nodules on the roots of leguminous plants like peas, beans, and gram. Inside these nodules, Rhizobium fixes atmospheric nitrogen into a usable form and shares it with the plant, while the plant gives the bacteria sugars in return. This partnership adds nitrogen to the soil and raises its fertility.

Step 3: Rule out the other options.
Clostridium is a bacterium linked with diseases like tetanus and botulism, not with improving soil fertility. Salmonella causes food poisoning and typhoid like infections in humans. Staphylococcus causes skin infections and boils. None of these three fix nitrogen or help crops grow better.

Step 4: Final answer.
Rhizobium is the bacterium that helps improve soil fertility through nitrogen fixation.
\[ \boxed{\text{Rhizobium}} \]