Plants harbor a diverse community of microbes which may be beneficial or detrimental to their health. Among these microbes, plant growth promoting bacteria (PGPB) perform functions which may provide the host plant with nutrients and phytohormones or help manage environmental stress and antagonize pathogens. The use of PGPB as inoculants in agriculture is often referred to as bio-fertilization and can reduce the need for chemical fertilizers, pesticides and herbicides through the various activities provided by the bacteria. In application of PGPB, inoculation may be through the coating of seeds and treatment of furrows with a free liquid culture. It may alternatively involve the encapsulation of PGPB in biodegradable beads which reduce the loss of cells to environmental constraints and competition/predation by other soil microbes while prolonging PGPB activity and benefit to the host crop. Bio-fertilizers are currently in use but further development is needed in testing and production to make a variety of products more available for use with a wider range of crops.