Here’s a little piece from the UK Centre for Ecology and Hydrology:

https://www.ceh.ac.uk/why-do-soil-microbes-matter

The challenge

Microbes are central to all life on Earth due to their huge diversity in form and function. In soils, one teaspoon of topsoil contains around 1 billion individual microscopic cells and around 10,000 different species. These organisms have many tasks, and are central to crop fertility, purifying the environment from pollutants, regulating carbon storage stocks and production/consumption of many significant green house gases, such as methane and nitrous oxides. The economic valuation of soils is in a large part due to soil microbial populations which provide key soil functions. Future climate scenarios may affect microbial populations in soil with many potential consequences, from increased losses of soil carbon due to increased respiration, changes in soil borne greenhouse gas production/consumption and changes to important plant-soil feedbacks giving rise to soil fertility.

Microbes in soil ecosystems

• They cycle most major nutrients required for plant productivity e.g. Nitrogen, Phosphorus
• They protect plants from disease and are intimately associated with plant growth and productivity
• Different types produce and consume most types of major greenhouse gases e.g. Carbon Dioxide, Methane & Nitrous oxide 
• They adapt to, and purify the environment, especially water, through degradation of pollutants e.g. removing explosives such as RDX

Microbes and climate change

• Bacteria recycle carbon in soils deposited by living and dead plants ‘The Carbon Standing Stock’
• Whilst plants are good CO2 absorbers, it is activity by soil microbes that determines whether the carbon is stored underground or release back into the atmosphere where it contributes to climate change
• More than three times the carbon is stored in soil than in the atmosphere