The soil is a complex ecosystem, and like all ecosystems there needs to be a balance of organisms, otherwise resources would run out, and one or two types of organisms would dominate. Soil microbiology is much more than bacteria and fungi – it also involves viruses to release nutrients trapped within microbes.
Even bacteria and fungi in the soil need to be kept under control, and this is done in a number of ways. The most obvious is when the soil gets very dry, as microbes will often die. Then, there are biological forms of control, for example, some nematodes are designed to feed specifically on bacteria. The mechanism which has arguably the greatest impact on soil bacterial numbers is what we call bactriophages or bacterial viruses.
When nutrients are cycled by microbes, some are in a form that the plants can take up immediately, but others become part of the bacteria and fungi themselves, so plants are unable to use them. This is one of the reasons why you actually need to destroy and break open some bacteria to get at the goodies inside.
These viruses infect and grow within the bacteria just viruses do within our own cells, and eventually the bacteria burst and release more viruses. In this process the nutrients that are trapped within a bacterial cell are released into the soil for plants to use. A great example is nitrogen drawdown, where the temporary lack of nitrogen is due to bacteria and fungi effectively trapping this nutrient in their own cells. When they die the nitrogen is released for plants to use, so we need these soil viruses just as much as we do the bacteria and fungi.
Some of these bacterial viruses live in the soil, but others live within bacteria in a manner where they do no harm. Then, when the conditions are right, they become active and kill their host and then spread to other bacteria.
Each type of virus has a very narrow range of bacteria they can infect, so diversity of these organisms is critical for good soil balance. This is why using an organic pelletised fertiliser such as Rooster Booster or Rapid Raiser, along with GOGO Juice which is populated with billions of bacteria and associated viruses are better than chemical alternatives.