A review of bacterial endophytes in medicinal and non-medicinal plants

Most endophytic bacteria are microorganisms that spend at least one phase of their life in different partsof plants without harmful effects. Some of the identified endophytes include various species of Bacillus,Rhizobium, Bradyrhizobium, Serratia, Streptomyces, Pseudomonas, Azetobacter, Acinetobacter, andRanella. These bacteria have been isolated from various medicinal and non-medicinal plants such aswheat, cacao, thymes, asparagus, clover, soybean, peas, citrus, etc. Research shows that endophytes cangenerally increase the growth of the host plant and protect it against pathogens (parasites, viruses,bacteria, and fungi) by producing a series of metabolites, regulatory compounds, and growth stimulants.For example, most endophytic bacteria can increase root growth in some medicinal and non-medicinalplants due to their ability to produce indole-۳-acetic acid (IAA). In addition, they can produce antibiotics,hormones, potassium, a soluble phosphate, and several enzymes such as protease, lipase, cellulase, etc.Also, some endophytes, such as rhizobium species contribute significantly to the growth of their hostplant by carrying out the mechanism of biological nitrogen fixation. Researchers believe that due to thefast growth and the easy culture of bacterial endophytes compared to plants, it may have more value andbenefits for extracting effective compounds from medicinal plants. Therefore, the accurate identificationof plant endophytes and their properties can make significant progress in producing biological fertilizersand compounds of plant growth stimulating and pathogens inhibiting.Many studies have shown that to start the isolation of endophytes, the stem, leaf, or root of the plantshould be washed with distilled water and cut into pieces. Then, the plant parts should be placed in ۹۶%alcohol and ۳% to ۵% sodium hypochlorite to remove the epiphytic microorganisms on the plant surface.In the next step, after washing several times with sterile distilled water, the samples are cultured onnutrient agar and specific media and incubated in suitable conditions. To identify bacteria, in addition togram staining and biochemical methods, it is better to use molecular techniques, especially ribotyping, todetermine the sequence of rRNA۱۶s genes and the phylogenetic relationship. The Metagenomic is also anaccurate and reliable method to identify and determine the evolutionary relationships of culturable andnon-culturable symbiotic microorganisms. Therefore, considering the importance of plant bacteriasymbiotic, this review study aimed to investigate the types of bacterial endophytes, identificationmethods, production products, and their application in medicine and agriculture.

Keywords:

Applications , Bacterial endophytes , Diagnostic techniques , Microbial products