Answer : Nitrogen - fixing bacteria
Cellulose - degrading microbes in the rumen
Regeneration of nutrients in soil and water.
Explanation :
The impacts of presence of microbes in environment which results beneficial to the environment are the nitrogen fixation process carried out by the nitrogen fixing bacteria usually cyanobacteria.
The cellulose degrading microbes which is observed to be found in the rumen of the ruminant animals.
Also, regeneration of the nutrients in soil and water is done by micro-organisms.