Although many plant-associated bacteria have beneficial effects on their host, their importance during plant growth and development is still underestimated. A better understanding of their plant growth-promoting mechanisms could be exploited for sustainable growth of food and feed crops, biomass for biofuel production and feedstocks for industrial processes. Such plant growth-promoting mechanisms might facilitate higher production of energy crops in a more sustainable manner, even on marginal land, and thus contribute to avoiding conflicts between food and energy production. Furthermore, because many bacteria show a natural capacity to cope with contaminants, they could be exploited to improve the efficiency of phytoremediation or to protect the food chain by reducing levels of agrochemicals in food crops.