Finally, the Max Planck researchers applied conventional chemical fungicides and tried to improve the quality of the soil by adding charcoal; in the wild, young tobacco plants germinate only after wild fires which are commonly started by lightning strikes. In addition to beneficial bacteria, fungi were also selected for biocontrol applications. Neither the treatment with fungicides nor the charcoal turned out to be successful treatment options, and the combination of fungicides and charcoal, as well as a fungal biocontrol treatment, even increased the mortality of the test plants. Mortality was reduced only in plants that had been treated with a mixture of beneficial soil bacteria. The scientists then scrutinized the effect of the bacterial community and compared plants that had been treated with two, three or five different bacterial strains. Although the treatment with just two bacterial strains had virtually no effect, significantly fewer plants died after a treatment with a mix of three or five bacterial strains. Overall, both in vitro and field experiments revealed that individual bacterial strains could realize their full protective potential only when they had the chance to cooperate with other bacterial strains; these synergistic effects contributed to improved plant health and reduced mortality.