How does microorganisms affect the quality of soil

They help decompose dead animals/plants to give nutrients to the plant(s) and soil.

this is a copy paste from the google:

Most protozoans derive their nutrition from feeding or ingesting soil bacteria and, thus, they play an important role in maintaining microbial/bacterial equilibrium in the soil. Some protozoa have been recently used as biological control agents against organisms that cause harmful diseases in plants.

Microorganisms play a crucial role in determining the quality of soil. They contribute to various important soil processes that affect nutrient cycling, fertility, and overall soil health. By decomposing organic matter, microorganisms release essential nutrients for plant growth and improve soil structure. Here's how microorganisms affect soil quality:

1. Decomposition: Microorganisms, such as bacteria and fungi, break down organic materials like dead plants, leaves, and animal remains, into simpler substances. This decomposition process releases nutrients locked within the organic matter, making them available for other plants and organisms.

2. Nutrient cycling: Microorganisms help cycle nutrients through the soil. They convert elements like nitrogen, phosphorus, and sulfur into forms that plants can absorb and use for growth. This cycling ensures a continuous supply of nutrients in the soil, promoting healthy plant growth.

3. Soil structure: Microorganisms secrete substances called exopolysaccharides, which function as a glue, binding soil particles together. This improves soil structure, enhancing its ability to retain water and resist erosion. They also create channels and pores that allow air and water to move through the soil, facilitating root growth and nutrient uptake.

4. Disease suppression: Some microorganisms have the ability to suppress plant diseases caused by harmful pathogens. These beneficial microorganisms can compete with pathogens for resources or produce antimicrobial compounds that inhibit their growth, reducing the risk of plant infections.

5. Nitrogen fixation: Certain microorganisms, like nitrogen-fixing bacteria, have the unique ability to convert atmospheric nitrogen into a form that plants can utilize. This process, called nitrogen fixation, provides plants with a vital nutrient that is typically limited in the soil. It helps maintain soil fertility and reduces the need for synthetic nitrogen fertilizers.

To assess the impact of microorganisms on soil quality, scientists often use laboratory tests and measurements. They analyze soil samples to determine microbial biomass, diversity, and activity. Additionally, DNA sequencing helps identify specific microbial species present in the soil and their functional roles. These analyses provide valuable insights into the microbial composition and their contributions to soil quality.