Improving hybrid Pennisetum growth and cadmium phytoremediation potential by using Bacillus megaterium BM18-2 spores as biofertilizer

Abstract

Environmental pollution with heavy metals becomes an issue of serious concern worldwide. Cadmium is considered one which adversely affects living organisms. Recently, the usage of endophytic bacteria to enhance the plant growth and phytoremediation of heavy metals contaminated sites is gaining great attention. The current study focused on utilizing the spores of Bacillus megaterium BM18-2 as biofertilizer for enhancing the growth of Cd hyperaccumulator Hybrid Pennisetum and Cd tolerance of the plant. Therefore, the production of the highest proportion of BM18-2 spores in short incubation time was investigated using different culture media. The results revealed that the maximum proportion of BM18-2 spores (90%) was obtained following incubation for 48 h in Tryptone- yeast extract media (TY). Furthermore, several growth parameters of H. Pennisetum were shown to be significantly improved by inclusion of BM18-2 spores into Cd contaminated soil in contrast to non- inoculated plant. The chlorophyll concentration of the leaves rose by 5%, 13%, and 22.89% with increasing Cd concentration of soil (20, 40 and 60 mg/Kg, respectively). The percentage of total nitrogen content of the root, stem and leaf was increased due to the bacterial spores inoculation and the highest percentage was recorded in the leaf in all treatments. Moreover, Cd phytoremediation capacity of H. Pennisetum greatly enhanced with the application of BM18-2 spores into the soil. An obvious correlation was also observed between Cd accumulation and bacterial colonization where the Cd accumulation enhanced by 21.9%, 16.5%, and 94.6% and the maximum count of BM18-2 (27 × 105, 194 × 104,and 145 × 104 CFU/g) were recorded in the root system in 20, 40, and 60 mg/Kg Cd spiked soil, respectively. Consequently, the spores of BM18-2 was proven to succeed as biofertilizer to improve growth of H. pennisetum during Cd stress which subsequently improved the phytoremediation of Cd contaminated soil.