Endophytic bacteria and their role in environmental microbiology, medicine and industry

Endophytic bacteria have been known for more than 120 years. They live inside plant tissues without causing any apparent symptoms of disease or negative effects on the host. Each of the nearly 300 000 plant species that exist on the earth is host to one or more endophytes. Only a few of these plants have ever been completely studied relative to their endophytic biology. Consequently, the opportunity to find new and beneficial endophytic microorganisms among the diversity of plants in different ecosystems is considerable. During the long co-evolutionary process with their hosts, endophytes have developed many significant and novel characteristics. The relationships between plants and endophytic bacteria are very close. The endophytes which reside inside plant tissues can be classified as 'obligate' or 'facultative. The first group is strictly dependent on the host plant for their growth and survival and transmission to other plants. The second group has a stage in their life cycle in which they are able to exist outside the host plant. Recent studies have shown that endophytes accelerate the adaptation of plants to unbalanced environmental conditions such as saline soil, drought, stress caused by pesticides, heavy metals or hydrocarbons. Therefore, the exploitation of the interaction of plant endophytes for the remediation of contaminated soils is a promising area; however, role of these microorganisms is still unclear.