Answer: Actinomycetes
Explanation:
The actinomycetes are the source of more than half of all the natural antibiotics that is found today.
The soil serve as the reservoir for the discovery of many antimicrobial agents. The group of antibiotics like streptomycin, actinomycin and neomycin were also obtained from these group of bacteria.
Selman Waksman was the first to show that soil bacteria show antimicrobial properties.
