Phytobial remediation of arsenic-contaminated soil using Melastoma malabathricum L. and Microbacterium foliorum strain SZ1

Abstract

Arsenic (As) is an increasing threat across the globe, widely known as a threshold carcinogen, and it is reaching harmful values in several areas of the world. In this present study, the effect of Microbacterium foliorum strain SZ1, a plant growth promoting bacteria (PGPB) on inorganic As (arsenate) phytoremediation by Melastoma malabathricum L. plants were investigated through morphological, histological analysis and proteomic profiling. The experiments included a control treatment (M. malabathricum L. plants without As and bacterial inoculation) and two phytoremediation treatments, M. malabathricum L. in As contaminated soil inoculated or uninoculated with M. foliorum strain SZ1. The morphological parameter and phytoremediation potential induced by M. foliorum strain SZ1 on M. malabathricum L. were observed for 90 days. Besides, the histological and proteome analysis was conducted using Transmission Electron Microscopy (TEM) and 2-Dimensional gel electrophoresis (2-DE), respectively. The present study showed that plants did not display any noticeable signs of toxicity, but rather the root and shoot length were significantly increased in the presence of M. foliorum strain SZ1. In addition, while the Bioconcentration factor (BCF) was increased in the presence of M. foliorum strain SZ1 by 0.3 times, the Transfer factor (TF) of As in the M. malabathricum L. plants were decreased, whether in the presence or absence of PGPB. The As phytoremediation treatment with M. foliorum strain SZ1 also enhanced uptake of As in root (26%) and shoot (22%) than in the other two phytoremediation treatments (As only and control). The findings showed that M. foliorum strain SZ1 inoculation reduced As toxicity by substantially reducing the negative stress effects and increasing shoot and root fresh and dry weight. The repair of As induced structural deformities involving disintegration of cell wall and membranes were observed upon M. foliorum strain SZ1 inoculation. After PD-Quest analysis, 9 differentially expressed spots subjected to liquid chromatography-tandem mass spectrometry and 9 spots identified with a significant score. The up regulation of tubulin, nucleoside diphosphate kinase and major allergen during As with bacteria exposure confirmed the amelioration of As induced oxidative stress. The abundance of proteins involved in photosynthesis, energy metabolism, defence, signaling, protein biogenesis and nucleoside M. malabathricum L. were found higher in As with bacteria than in As alone exposure. Overall, the present study demonstrates the effectiveness of phytoremediation by M. foliorum strain SZ1 on responsive pathways including morphology, histology and proteomic of M. malabathricum L. plant.