Protecting tobacco plants from O3 injury by Bacillus velezensis with production of acetoin

Construction of Bacillus velezensis engineering strains for producing 5-aminolevulinic acid to elicit plant resistance against abiotic stresses and tobacco bacterial wilt disease

BACKGROUND

Crops suffer from numerous biotic and abiotic stresses, leading to substantial economic losses globally. 5-Aminolevulinic acid (ALA) has been shown to stimulate plant resistance, thereby alleviating stress effects.

RESULTS

This study aimed to develop stable and multifaceted Bacillus velezensis strains with enhanced ALA production capabilities as potential biocontrol agents. To achieve this, the hemA gene sourced from Bradyrhizobium japonicum was integrated into the genomic DNA of Bacillus velezensis by sequentially replacing existing genes bdh, pgsB, and sinI with hemA, resulting in a recombinant strain, designated R9-3, harboring three copies of the hemA gene. R9-3 achieved an ALA production titer of approximately 22 mg/L. In an effort to further enhance ALA accumulation, we disrupted downstream metabolic pathways by deleting hemB, which is responsible for converting ALA into heme, and sucCD, which participates in diverting succinyl-coenzyme A, a key intermediate in ALA biosynthesis, away from succinic acid production. Unexpectedly, these genetic modifications did not result in additional increases in ALA production. R9-3 proved efficacious in mitigating the detrimental effects of salinity and drought on tobacco plants. By stimulating the activity of vital antioxidative enzymes such as catalase, peroxidase, and superoxide dismutase, and maintaining chlorophyll integrity, this strain reinforced the plants' defense against oxidative stress under harsh environmental conditions. Moreover, the resistance elicited by R9-3 effectively protected tobacco from bacterial wilt disease.

CONCLUSIONS

These findings suggest that the engineered strain has significant potential to be developed into a multi-functional biocontrol agent for future agricultural applications, offering both abiotic and biotic stress protection. © 2025 Society of Chemical Industry.

Development of a kaolin-based Bacillus velezensis BF01 composite for application in biocontrol of postharvest strawberry diseases

BACKGROUND

Biological control agents are promising alternatives to conventional fungicides for managing postharvest diseases but their practical use is hindered by variable effectiveness and by application challenges. One promising yet underexplored approach involves utilizing bacteria that produce volatile organic compounds (VOCs) with antifungal properties.

RESULTS

In this study, Bacillus velezensis BF01, a strain with significant antifungal activity, was identified and isolated. Volatile organic compounds produced by this strain inhibited the growth and conidial germination of Botrytis cinerea, Fusarium oxysporum, and Colletotrichum gloeosporioides. Gas chromatography-mass spectrometry identified 90 VOCs, with ketones, esters, nitrogen compounds, aldehydes, and alcohols as the dominant components, many of which exhibited antifungal or plant resistance-inducing properties. To enhance practical application, B. velezensis BF01 was incorporated into a kaolin-based composite, which maintained long-term viability under refrigerated conditions and inhibited fungal growth through the controlled release of volatile organic compounds. This composite significantly extended the shelf life of strawberries by reducing postharvest decay.

CONCLUSION

The development of a kaolin-based B. velezensis BF01 composite provides an effective and sustainable biocontrol strategy for postharvest disease management. By improving bacterial stability and facilitating the controlled release of antifungal volatile organic compounds, this approach offers a practical alternative to chemical fungicides, highlighting its potential in extending fruit shelf life and improving food safety. © 2025 Society of Chemical Industry.

The volatile organic compound acetoin enhances the colonization of Azorhizobium caulinodans ORS571 on Sesbania rostrata

Chemoreceptors play a crucial role in assisting bacterial sensing and response to environmental stimuli. Genome analysis of Azorhizobium caulinodans ORS571 revealed the presence of 43 putative chemoreceptors, but their biological functions remain largely unknown. In this study, we identified the chemoreceptor AmaP (methyl-accepting protein of A. caulinodans), characterized by the presence of the CHASE3 domain and exhibited a notable response to acetoin. Thus, we investigated the effect of acetoin sensing on its symbiotic association with the host. Our findings uncovered a compelling role for acetoin as a key player in enhancing various facets of A. caulinodans ORS571's performance including biofilm formation, colonization, and nodulation abilities. Notably, acetoin bolstered A. caulinodans ORS571's efficacy in promoting the growth of S. rostrata, even under moderate salt stress conditions. This study not only broadens our understanding of the AmaP protein with its distinctive CHASE3 domain but also highlights the promising potential of acetoin in fortifying the symbiotic relationship between A. caulinodans and Sesbania rostrata.

Bacillus sp. as a microbial cell factory: Advancements and future prospects

Bacillus sp. is one of the most distinctive gram-positive bacteria, able to grow efficiently using cheap carbon sources and secrete a variety of useful substances, which are widely used in food, pharmaceutical, agricultural and environmental industries. At the same time, Bacillus sp. is also recognized as a safe genus with a relatively clear genetic background, which is conducive to the industrial production of target metabolites. In this review, we discuss the reasons why Bacillus sp. has been so extensively studied and summarize its advances in systems and synthetic biology, engineering strategies to improve microbial cell properties, and industrial applications in several metabolic engineering applications. Finally, we present the current challenges and possible solutions to provide a reliable basis for Bacillus sp. as a microbial cell factory.

Adapting crop production to climate change and air pollution at different scales

Air pollution and climate change are tightly interconnected and jointly affect field crop production and agroecosystem health. Although our understanding of the individual and combined impacts of air pollution and climate change factors is improving, the adaptation of crop production to concurrent air pollution and climate change remains challenging to resolve. Here we evaluate recent advances in the adaptation of crop production to climate change and air pollution at the plant, field and ecosystem scales. The main approaches at the plant level include the integration of genetic variation, molecular breeding and phenotyping. Field-level techniques include optimizing cultivation practices, promoting mixed cropping and diversification, and applying technologies such as antiozonants, nanotechnology and robot-assisted farming. Plant- and field-level techniques would be further facilitated by enhancing soil resilience, incorporating precision agriculture and modifying the hydrology and microclimate of agricultural landscapes at the ecosystem level. Strategies and opportunities for crop production under climate change and air pollution are discussed.

Belowground plant-microbe communications via volatile compounds

Volatile compounds play important roles in rhizosphere biological communications and interactions. The emission of plant and microbial volatiles is a dynamic phenomenon that is affected by several endogenous and exogenous signals. Diffusion of volatiles can be limited by their adsorption, degradation, and dissolution under specific environmental conditions. Therefore, rhizosphere volatiles need to be investigated on a micro and spatiotemporal scale. Plant and microbial volatiles can expand and specialize the rhizobacterial niche not only by improving the root system architecture such that it serves as a nutrient-rich shelter, but also by inhibiting or promoting the growth, chemotaxis, survival, and robustness of neighboring organisms. Root volatiles play an important role in engineering the belowground microbiome by shaping the microbial community structure and recruiting beneficial microbes. Microbial volatiles are appropriate candidates for improving plant growth and health during environmental challenges and climate change. However, some technical and experimental challenges limit the non-destructive monitoring of volatile emissions in the rhizosphere in real-time. In this review, we attempt to clarify the volatile-mediated intra- and inter-kingdom communications in the rhizosphere, and propose improvements in experimental design for future research.

Genome Mining of Three Plant Growth-Promoting Bacillus Species from Maize Rhizosphere

Bacillus species genomes are rich in plant growth-promoting genetic elements. Bacillus subtilis and Bacillus velezensis are important plant growth promoters; hence, to further improve their abilities, the genetic elements responsible for these traits were characterized and reported. Genetic elements reported include those of auxin, nitrogen fixation, siderophore production, iron acquisition, volatile organic compounds, and antibiotics. Furthermore, the presence of phages and antibiotic-resistant genes in the genomes are reported. Pan-genome analysis was conducted using ten Bacillus species. From the analysis, pan-genome of Bacillus subtilis and Bacillus velezensis are still open. Ultimately, this study brings an insight into the genetic components of the plant growth-promoting abilities of these strains and shows their potential biotechnological applications in agriculture and other relevant sectors.