ABSTRACT
Lichens are self-sustaining symbiotic organism with algae, fungi and bacteria, survives even in adverse environmental conditions. However, how these symbionts solitarily survive while subject to irradiation has not been studied yet. Here, we focused on the lichen associated bacteria possessing plant growth promoting (PGP) traits to withstand the low dose e-beam irradiation and improvement of strains for PGP traits. Lichen associated bacterial isolates (GSL-01 to 11) majorly Enterobacter cloacae and Providencia rettgeri were subjected to e-beam irradiation (2-10 Gy) and their PGP activities were evaluated. Among these, only 3 isolates of E. cloacae GSL-01, 07 and 11 and P. rettgeri GSL-09 showed the potential to withstand low dose e-beam irradiation (2-8 Gy with 10 Hz), along with isolates GSL-07 and GSL-09 resulted in enhanced PGP activity. In addition, e-beam irradiation at 10 Gy with 50 Hz adversely affected PGP properties; perhaps due to the genetic instability of bacteria by irradiation resulted in the loss of PGP properties. Contrastingly, irradiated P. rettgeri (GSL-09) and E. cloacae (GSL-07) showed elevated nitrogen fixation and IAA production compared to the non-irradiated bacterial isolates. Therefore, these potential lichenized bacterial isolates (GSL-01, 07, 09 and 11) perhaps used for plant growth promoters (after validation), especially in adverse environmental condition, as these isolates showed the tolerance to low dose e-beam irradiation. Further, this study elaborates the current knowledge of low dose e-beam irradiation effect at different doses on PGP traits of lichenized bacteria.