Soil microbiology is defined as the study of microorganisms in the soil that play an essential role for breaking down organic matter and are directly involved with nutrient cycling and other processes related to plants and crops.

Since 90’s this concept has increased the interested due to the technological advances that revealed the correlation of microorganisms with the soil protection. Event like the COP6 (e 6th Conference of the Parties of the International Convention on Biological Diversity celebrated in 2002), showed the important of soil microbiology in environmental sciences and agriculture. More recently, thanks to the development of molecular techniques have allowed to wide the knowledge about the microorganisms in soil, soil diversity and soil functions. In this sense, the application in this research field have experienced a quick develop.

Microorganisms are the main drivers controlling carbon flow in soils. Carbon entering the soil from plants is transformed and decomposed primarily by fungi and bacteria. In general, bacteria are more efficient at degrading easily metabolizable substrates, whereas fungi are specialists in breaking down more complex organic matter such as plant litter. The functionality of soil microbiota does not operate linearly; instead, it emerges from networks of interactions among microorganisms that occur simultaneously, creating feedback loops that sustain continuous organic matter recycling. Therefore, the collective activity of all microbial groups plays a crucial role in maintaining the balance and stability of the soil ecosystem.

Soil organic carbon (SOC) is the second largest reservoir of carbon on Earth. SOC occurs in soils as living organisms, fresh organic residues, and humus. Carbon is essential for microorganisms because it serves as their primary energy source. In the carbon cycle, microbes intervene through carbon fixation; autotrophic bacteria, such as cyanobacteria, capture atmospheric carbon dioxide and convert it into forms that other microorganisms can use for growth.

Microorganisms are also central to nutrient cycling, acting as pivotal players in maintaining soil fertility and supporting plant growth. Fungi and bacteria are the main drivers of nutrient cycling, breaking down organic matter and other complex organic compounds. As a result, their activity enhances nutrient availability, improves soil structure, and fosters a healthy soil ecosystem. 

Microbial biomass, respiration, and enzymatic activities are considered key indicators of soil health due to their ability to respond rapidly to environmental changes and management practices. Unlike physical or chemical properties that change slowly, these biological parameters offer an early warning signal of soil degradation or improvement.

Microorganisms act as the biological engine of the soil, performing vital functions for both sustainable agriculture and the long-term maintenance of soil fertility.

As previously mentioned, microbes are the main drivers of biogeochemical cycles, transforming nutrients from unavailable forms into versions that plants can assimilate. In fact, nitrogen-fixing bacteria such as Rhizobium and Azotobacter can cover up to 50% of the nitrogen requirements of some crops, reducing the need for synthetic nitrogen fertilizers. Phosphorus-solubilizing microorganisms and those specialized in mobilizing minerals, making them bioavailable, also promote soil fertility and can contribute to sustainable practices

The transition from conventional methods to molecular tools has enabled rapid advances in understanding soil health and microbial ecology. However, combining both approaches is recommended to obtain a complete picture of the soil ecosystem

SHARInG-MeD uses these indicators to evaluate overall soil health but not individually, linked with physicochemical indicators. Next table shows the microbiological indicators included in this project https://mel.cgiar.org/projects/1853

1.          Virtual lab simulations or video demonstrations  - Video of Nitrogenase activity 

2.          Discussion forums for peer interaction