Diversity and biotechnological potential of plant-associated endophytic bacteria

Endophytes are microorganisms that inhabit the interior of plant tissues without harming their hosts. This definition includes internal colonists with apparently neutral behavior, symbionts and bacteria that migrate between the surface and the inside of the plant during their endophytic phase. The utilization of endophytes for biotechnological purposes has increased recently, especially in pest and disease control and in plant growth promotion. Endophytic bacteria promote plant growth in three major ways: they synthesize particular compounds that are useful for the plants, facilitate the uptake of certain nutrients from the soil, and control or prevent diseases (biological control). Growth promotion mediated by endophytic bacteria occurs via several mechanisms: the production of vital enzymes; the production of hormones such as auxin (indoleacetic acid [IAA]); symbiotic nitrogen fixation; antagonism against phytopathogens via the production of siderophores, chitinases or antibiotics and the solubilization and mineralization of nutrients, particularly insoluble mineral phosphates. The interactions between endophytes and plants can promote plant health and play a significant role in low-input sustainable agriculture for both food and nonfood crops. An understanding of the mechanisms enabling these endophytes to interact with plants is essential for realizing the biotechnological potential of these microorganisms.