In soils, which process is a major role of bacteria?

• A. Rapid nutrient cycling
• B. Slowing soil aggregation
• C. Blocking root uptake
• D. Depleting soil organic matter

Answer: (A)

Bacteria in soils are the engines of rapid nutrient cycling. They break down organic matter with their enzymes, converting complex organic compounds into simpler forms that plants can take up, such as ammonium and nitrate for nitrogen, or inorganic phosphorus and sulfur. This mineralization happens quickly, so nutrients are released into the soil solution for plant use soon after organic matter is added or residue enters the system. Bacteria respond rapidly to available carbon and nitrogen sources, driving fast turnover and keeping nutrient pools available for plant growth.

While bacteria can influence soil structure through exudates and microbial byproducts that help bind soil particles, their primary, defining role described here is making nutrients readily available through decomposition and mineralization. Blocking root uptake isn’t a general function of bacteria, and while decomposition can reduce soil organic matter over time, bacteria collectively support nutrient availability rather than simply depleting organic matter.