Definition

Total bacteria refers to the combined amount of all phospholipid fatty acids (PLFAs) that form the membranes of bacterial cells present in a soil or organic sample. PLFA analysis is a widely used method to estimate microbial biomass and community composition because these fatty acids are essential components of living cell membranes.

Importance

Bacteria play a crucial role in soil health and nutrient cycling. They contribute to several key processes, including:

• Organic matter decomposition: Breaking down simple organic materials into usable nutrients.
• Nutrient fixation: Capturing and storing essential elements such as nitrogen.
• Nitrogen transformations: Converting ammonium into nitrate, making nitrogen available for plants.
• Soil structure improvement: Forming stable aggregates that enhance aeration and water retention.
• Disease suppression: Increasing resistance to soil-borne pathogens and producing compounds that can weaken or kill harmful organisms.

Factors influencing bacterial abundance

The abundance of bacteria in soil is strongly influenced by the availability of easily degradable organic materials. These materials typically have a low carbon-to-nitrogen (C/N) ratio, such as slurry or fresh manure. When such substrates are present, bacterial populations tend to increase rapidly due to the readily available energy source.

Role in soil ecosystem

Bacteria are fundamental to maintaining soil fertility and plant health. Their activities ensure continuous nutrient cycling, improve soil structure, and help plants resist diseases. A balanced bacterial community is therefore essential for sustainable agricultural practices.

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