Which organism is associated with fast nutrient cycling?

• A. Fungi
• B. Bacteria
• C. Protozoa
• D. Nematodes

Answer: (B)

Bacteria drive fast nutrient cycling because they mineralize organic matter quickly and respond rapidly to available substrates. They produce a wide range of extracellular enzymes that break down proteins, carbohydrates, and other organic compounds, releasing inorganic nutrients like ammonium and nitrate that plants can take up. Their small size and high reproduction rate allow rapid population growth when substrates are abundant, speeding up the turnover of nutrients through the soil.

Fungi, while essential for decomposing tougher plant litter and stabilizing soil organic matter, typically release nutrients more slowly, especially from recalcitrant carbon sources like lignin. Protozoa and nematodes influence cycling by grazing on microbes, which can boost mineralization and nutrient release, but they are not the primary drivers of the fastest turnover.