The most abundant prokaryotes helpful to human in making curd from milk and in production of antibiotics are the ones categorised as
Heterotrophic bacteria
Heterotrophic bacteria are the most abundant prokaryotes helpful to human in making curd form milk, e.g. Lactobacillus sp. Many of them have a significant impact on the production of antibiotics, e.g. Streptomyces sp. and fixing nitrogen in legume roots, e.g. Rhizobium sp.