In soils, which organism is associated with fast nutrient cycling?

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

Answer: (B)

Fast nutrient cycling in soils is driven by bacteria because they rapidly break down readily available organic matter and mineralize nutrients into inorganic forms like ammonium and nitrate that plants can use. Their very short generation times and ability to respond quickly to new inputs of carbon and nitrogen mean nutrients are released and made available to plants fast. Fungi tend to decompose tougher, longer-lasting compounds and contribute to slower, longer-term nutrient release, while protozoa and nematodes influence cycling mainly by grazing on microbes and releasing nutrients indirectly. The rapid, high-activity metabolism of bacteria makes them the primary drivers of quick nutrient turnover.