The invention relates to the use of microorganisms as plant growth stimulants and for the biological control of bacterium, insects, fungi and phytopathogenic nematodes. More specifically, the invention relates to the use of microorganisms of the genus Bacillus, more specifically the Bacillus methylotrophicus species, as well as to cultures thereof, compositions comprising these bacteria, different culture methods and the products comprising same, as plant growth stimulants and for the biological control of bacterium, insects, fungi and phytopathogenic nematodes.