Volatile organic compounds from Lysinibacillus macroides regulating the seedling growth of Arabidopsis thaliana

Volatile organic compounds (VOCs) have the characteristics of long distance propagation, low concentration, perception, and indirect contact between organisms. In this experiment, Lysinibacillus macroides Xi9 was isolated from cassava residue, and the VOCs produced by this strain were analyzed by the SPME-GC-MS method, mainly including alcohols, esters, and alkanes. By inoculation of L. macroides Xi9, VOCs can promote the growth and change the root-system architecture of Arabidopsis seedlings. The results showed that the number of lateral roots, root density, and fresh weight of Arabidopsis seedlings were significantly higher (p ≤ 0.01), and the number of roots hair was also increased after exposure to strain Xi9. Compared with the control group, the transcriptome analysis of Arabidopsis seedlings treated with strain Xi9 for 5 days revealed a total of 508 genes differentially expressed (p < 0.05). After Gene Ontology enrichment analysis, it was found that genes encoding nitrate transport and assimilation, and the lateral root-related gene ANR1 were up-regulated. The content of NO3 - and amino acid in Arabidopsis seedlings were significantly higher from control group (p ≤ 0.01). Plant cell wall-related EXPA family genes and pectin lyase gene were up-regulated, resulting cell elongation of leaf. SAUR41 and up-regulation of its subfamily members, as well as the down-regulation of auxin efflux carrier protein PILS5 and auxin response factor 20 (ARF20) led to the accumulation of auxin. These results indicated that VOCs of strain Xi9 promote Arabidopsis seedlings growth and development by promoting nitrogen uptake, regulating auxin synthesis, and improving cell wall modification.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-022-01268-3.

Combined application of two Bacillus species enhance phytoremediation potential of Brassica napus in an industrial metal-contaminated soil

This study aimed to assess the impact of individual as well as combined application of Lysinibacillus macroides and Bacillus safensis in phytoremediation potential of Brassica napus grown in soil contaminated by industrial effluents. In response to five metals; copper, chromium, nickel, lead, and cadmium, results revealed that germination percentage, fresh and dry weights, and photosynthetic pigments of B. napus decreased under contaminated soil. On the other hand, electrolyte leakage due to cellular injury, metabolites (proline and glycine betaine), antioxidant enzymes (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase), accumulation of hydrogen peroxide and metals in plant's roots, shoots and leaves increased. Inoculation significantly reduced these effects as proved by the enhancement of germination percentage, fresh and dry biomass, and photosynthetic pigments. Simultaneously, the antioxidant enzymes, metabolites contents (proline and glycine betaine) and metal concentrations in plant's roots, shoots and leaves decreased. Combined application of both Bacilli strains was found more effective as compared to individual inoculation. It was concluded that metal resistant Bacillus species in combination had growth effects on B. napus and enhanced its phytoremediation efficiency in contaminated soil.Novelty statementBrassica napus; a hyper-accumulator of metals, loses phytoremediation potential with the passage of growth. Two Bacillus species (Lysinibacillus macroides and Bacillus safensis) having known bioremediation abilities were employed individually as well as in combination under metals contaminated soil to increase phytoremediation efficiency of B. napus. The metals containing soil used is a unique aspect in this study because selected soil, contaminated by industrial effluents, has not been evaluated or reported earlier. Combined application of Bacilli improved phytoremediation potential of B. napus more as compared to application of individual Bacillus strain which is yet another unique aspect of this investigation.

A novel protease-immobilized carbon catalyst for the effective fragmentation of proteins in high-TDS wastewater generated in tanneries: Spectral and electrochemical studies

The aim of this study was to degrade proteins in high-total dissolved solids (TDS)-containing wastewater produced during the soaking process in tanneries (tannery-TDS wastewater) using a halotolerant protease-assisted nanoporous carbon catalyst (STPNPAC). A halotolerant protease was obtained from the halophile, Lysinibacillus macroides, using animal fleshing as the substrate. The protease was immobilized using ethylene diamine (EDA)/glutaraldehyde functionalized nanoporous activated carbon (EGNPAC). The optimum conditions for the immobilization of protease were determined as time (120 min), pH (6), protease concentration (575-600 U/g), EGNPAC size, salinity, and temperature (30 °C). The immobilization was confirmed by FTIR, TGA-DSC, SEM, and XRD analyses. The adsorption kinetics was consistent with a pseudo first order rate constant of 1.43 × 10^-2 min^-1. The thermodynamic parameters (ΔG, ΔH, and ΔS) confirmed the effective immobilization of the protease onto EGNPAC. STPNAPC was found to efficiently degrade the proteins in tannery-TDS wastewater, with a complete fragmentation time of 90 min at pH 6 and 30 °C. Accordingly, the protein fragmentation was confirmed by UV-visible and UV-fluorescence spectroscopy, ESI-mass spectrometric analysis and circular dichroic studies. The formation of protein hydrolysates was confirmed by cyclic voltammetry and electrical impedance studies. BOD₅: COD value, 0.426 of treated tannery-TDS wastewater may favor sequential biological treatment processes.