Exploring the Biologically Active Metabolites Produced by Bacillus cereus for Plant Growth Promotion, Heat Stress Tolerance, and Resistance to Bacterial Soft Rot in Arabidopsis

Abstract

Eight gene clusters responsible for synthesizing bioactive metabolites associated with plant growth promotion were identified in the Bacillus cereus strain D1 (BcD1) genome using the de novo whole-genome assembly method. The two largest gene clusters were responsible for synthesizing volatile organic compounds (VOCs) and encoding extracellular serine proteases. The treatment with BcD1 resulted in an increase in leaf chlorophyll content, plant size, and fresh weight in Arabidopsis seedlings. The BcD1-treated seedlings also accumulated higher levels of lignin and secondary metabolites including glucosinolates, triterpenoids, flavonoids, and phenolic compounds. Antioxidant enzyme activity and DPPH radical scavenging activity were also found to be higher in the treated seedlings as compared with the control. Seedlings pretreated with BcD1 exhibited increased tolerance to heat stress and reduced disease incidence of bacterial soft rot. RNA-seq analysis showed that BcD1 treatment activated Arabidopsis genes for diverse metabolite synthesis, including lignin and glucosinolates, and pathogenesis-related proteins such as serine protease inhibitors and defensin/PDF family proteins. The genes responsible for synthesizing indole acetic acid (IAA), abscisic acid (ABA), and jasmonic acid (JA) were expressed at higher levels, along with WRKY transcription factors involved in stress regulation and MYB54 for secondary cell wall synthesis. This study found that BcD1, a rhizobacterium producing VOCs and serine proteases, is capable of triggering the synthesis of diverse secondary metabolites and antioxidant enzymes in plants as a defense strategy against heat stress and pathogen attack.

Examining the Transcriptomic and Biochemical Signatures of Bacillus subtilis Strains: Impacts on Plant Growth and Abiotic Stress Tolerance

“…Detecting the antifungal activity of the nonvolatile and volatile metabolites produced by bacterial strains was performed using methods described by Tsai et al [ 33 ]. In brief, to detect nonvolatile compounds, two filter paper pieces were prepared, each containing 10 µL of bacterial solutions that had been cultured overnight in LB medium at a concentration of 1 × 10 8 CFU/mL, while water was used as a control.…”

“…The protease pellets were precipitated by adding ammonium sulfate until reaching 80% saturation. Afterward, the protease pellets were collected through centrifugation, suspended in 50 mM of phosphate buffer at pH 7.0, and subsequently used for zymogram electrophoresis analysis, following the method described by Tsai et al [ 33 ].…”

“…A B. cereus strain that is capable of producing VOCs and serine proteases has been found to confer tolerance to multiple abiotic stresses in plants. This tolerance is achieved through the modulation of the auxin, ABA, and JA signaling pathways, as well as the stimulation of antioxidant enzymes and secondary metabolites that have ROS scavenging capabilities [ 33 ].…”

Employing Genomic Tools to Explore the Molecular Mechanisms behind the Enhancement of Plant Growth and Stress Resilience Facilitated by a Burkholderia Rhizobacterial Strain

“…After 4 days of culture, the formation of a yellow zone surrounding the bacterial culture was used as an indicator of nitrogen fixation. The detection of antifungal activity in the metabolites produced by the isolated bacterial strain was carried out using methods outlined by Tsai et al (2023) [140]. Briefly, two filter paper pieces, each soaked with 10 µL of bacterial solutions at a concentration of 1 × 10 8 CFU/mL, were placed 3 cm away from a mycelial plug of Fusarium oxysporum f. sp.…”

Beneficial rhizosphere bacteria provides active assistance in resisting Aphis gossypiis in Ageratina adenophora

“…The genus Bacillus can positively impact plant health through three mechanisms: (i) antagonistic activity against pests and pathogens, (ii) enhancement of host nutrition and growth, and (iii) stimulation of plant host defense ( Choudhary and Johri, 2009 ). Such as Bacillus cereus strain D1 (BcD1) induces the production of several secondary metabolites and antioxidant enzymes in plants as a protective mechanism against heat stress and pathogen attack ( Tsai et al., 2023 ). Zhang et al.…”