Molecular Identification of Endophytic Bacteria from Silybum marianum and Their Effect on Brassica napus Growth under Heavy Metal Stress

Abstract

Silybum marianum has been used for a variety of purposes all over the world. This plant is used to treat cancer, liver disease, and inflammation. Eleven endophytic bacteria were isolated from S. marianum collected from heavy metal polluted sites and identified using 16s rRNA sequencing in the current investigation. Three isolates stood out for having many features, including heavy metal resistance, plant growth stimulation, plant hormones, heavy metal toxicity remediation, and antibacterial action. SJLC (6.06 µg/L) and SJRB (5.98 µg/L) were the greatest producers of IAA among the isolates and were identified as Bacillus sp. and Lysinibacillus sp., respectively. Root and shoot length have improved as a result of IAA production. The SJLC was found to be effective against four of the pathogens tested. The strain SJLC showed the most activity against Bacillus cereus with a 20 mm zone of inhibition, followed by the isolate SJRB, which showed a 16 mm zone of inhibition against B. cereus. The same isolates also show inhibition against X. campestris. Almost majority of the Brassica napus plants inoculated with bacterial isolates were able to translocate and degrade heavy metals like Cr. Therefore, it was concluded that these isolates are capable to grow in highly polluted environments.