## 5 Role of Endophytic Bacteria in _Camelia sinensis_ Metabolism  
Endophytic bacterial species, such as _Azospirillum species_, _Bacillus pumilus_, _Bacillus megaterium_, _Bacillus amyloligefaciens_, _Beijerinclia species_, _Paenibacillus polymyxa_, _Pseudomonas aeruginosa_, _Camomonas acidovorans_, and _Serratia marcescens_ have proven to promote _C. Sinensis_ growth through inducing indole-3-acetic acid (IAA), ammonia and siderophore production, phosphate solubilization, and exerting antagonism against pathogens [2; 47; 48; 49; 50; 51; 52; 53]. Endophytes-derived bioactive natural products are promising resources for medicinal, agricultural, and other related industries [54]. Different kinds of alkaloids have contributed to plant defense through endophytes action. Some of these alkaloids are growth-promoting compounds, and some have an important role in plants' resistance to environmental stress. Amines and amides are very common metabolite products from endophytes and are stated as being toxic to insects. IAA is a well-known phytohormone that can be produced by endophytes. Other bioactive compounds, such as steroids, terpenoids, and diterpenes are also generated by endophytes [55], responsible for promoting plant growth and yield, suppress pathogens growth and colonization, help in removing contaminants, solubilize phosphate, and even contribute to plant-assimilable nitrogen [56]. Thus, the proper implementation of these plant growth-promoting endophytic bacteria may be helpful in organic tea plantation [53; 57] (Table 1). [PERSON], [PERSON], and [PERSON] [53] isolated endophytic bacteria from _C. sinensis_ roots and screened it for multiple plant growth promoting activities, including phosphate solubilization and indole acetic acid, ammonia, and siderophore production. These isolates were found to be siderophore producers, phosphate solubilizers, and ammonia producers. In vivo studies revealed that _B. megaterium_ has a marked ability to promote tea plant growth [47]. _Fomes lamaoensis_ population in soil before and after _B. megaterium_ application, as determined by enzyme-linked immunosorbent assay (ELISA) and dot-blot, has risen against the pathogen, which is shown to be greatly reduced in the presence of the bacterium. _B. megaterium_ root colonization and subsequent inoculation with _F. lamaoensis_ also led to an increase in polyphenic compounds, as well as in defense-related enzymes. The analysis for _B. megaterium_ mechanism of action determination revealed that this bacterium is able to solubilize phosphate, to produce IAA, siderophore, and antifungal metabolites. _B. pumilus_, isolated from tea rhizosphere, was evaluated for its plant growth promoting and bio-control effects, both in vitro and in vivo [58]. _B. pumilus_ showed positive plant growth promoting rhizobacteria (PGPR) traits in vitro, such as phosphate solubilization, IAA secretion, and siderophore production. _B. pumilus_ inhibited the growth of tea root fungal pathogens, such as _Poria hypobrunnea, F. lamaoensis, Sphaerostilb repens, Scleorotinia scleroorum,_ and _Sclerodium rofsii_. This bacterium was also able to reduce tea root caused by _P. hypobrunnea_. Moreover, the authors found enhanced accumulation of phenolics and an improvement in defense enzymes (i.e., peroxidase, phenyl alanine ammonia lyase, beta-1,3-glucanase, and chitinase) activities, that reveals systemic-acquired resistance (SAR) activation in tea plants. Also, HPLC analysis of catechines revealed the appearance of dimers and isomers during tea fermentation [60]. [PERSON] et al. [59] explored the potential of microorganisms from _C. sinensis_ rhizosphere for the overall improvement of tea growth and productivity. _B. amyloliquefaciens, S. marcscens_, and _B. pumilus_ showed positive PGPR traits in vitro, such as phosphate solubilization and production of siderophore, IAA, and antagonism to pathogens. Then, 16S rDNA sequencing of the bacteria was done, and their phylogenetic relationships determined.