'Ruminobacter amylophilus, Fibrobacter succinogenes and Enterococcus faecium' have characteristics that are similar to those of plant growth-promoting bacteria and can be used to promote plant development and reduce production costs. These bacteria were isolated from fistulated ruminants and are gram-negative, anaerobic or facultative anaerobic. These bacteria are frequently used to increase animal productivity through the production of many enzymes responsible for the carbon cycle and the release of other nutrients by organic matter decomposition. The bacteria 'R. amylophilus, F. succinogenes and E. faecium' have growth promotion abilities, such as phosphorus solubilization, nitrogen promotion, and indole acetic acid and siderophore production. Tests were performed under greenhouse conditions with soybean and maize crops with five treatments and six replications. The first treatment was the control (without inoculant); the other treatments included each species of bacteria, and there was a treatment with a mixture (mix) of the three bacteria. 'F. succinogenes' increased the root dry mass of maize by 21.4%, as well as the nitrogen and phosphorus contents, compared to the control. 'R. amylophilus and E. faecium' decreased the phosphorus concentration in shoots of maize, and R. amylophilus increased the soil biomass carbon by 76.39% compared to the mix under maize cultivation, while E. faecium decreased the soil biomass carbon by 56.78% compared to the mix under soybean cultivation. The present study verified that 'Ruminobacter amylophilus, Fibrobacter succinogenes and Enterococcus faecium' presented plant growth-related abilities and could be used to improve plant development, reducing the necessity of chemical fertilizers.