Bacillus spp.: Nature’s Gift to Agriculture and Humankind

Abstract

The productivity of crops is heavily depending on microbial communities present in rhizospheric soil; within the last few decades, PGPR has emerged as significant and promising tools for the sustainable agriculture practices. PGPR related to Bacillus spp. as symbiotic with plant roots or free-living in rhizosphere contribute significantly to the viability, development, and yield of plants under biotic and abiotic challenges. The Bacillus species are rod-shaped, Gram-positive, endosporic, aerobic, or facultative anaerobic and ubiquitous in nature. Many Bacillus species, e.g., B. megaterium, B. circulans, B. coagulans, B. subtilis, B. azotofixans, B. macerans, B. velezensis, etc. are extensively researched for their PGPR actions. Enhancement of nutrient uptake (N, P, K, and other vital minerals) and regulation of plant hormones are direct actions of PGPR, while promoting plant growth by inhibiting plant pathogen and induction of ISR are indirect actions of PGPR. The genus Bacillus holds largest share in microbe-based agricultural and commercial products. Due to the greater efficacy of production of metabolites and spore-forming nature of Bacillus spp., which increases the life span of cells in commercially manufactured products, Bacillus-based biofertilizers are more active than Pseudomonas-based formulations. The Bacillus species are frequently regarded as an ideal candidate for bioformulations because of their rapid growth, ease of handling, and better colonizing abilities. The Bacillus-based bioformulations for broad-spectrum application against several biotic and abiotic issues are also addressed. In this chapter we will discuss about the mechanism of Bacillus-mediated crop protection and their wide application. PGPR traits of Bacillus are discussed in terms of nutrient uptake, siderophore production, stimulation and production of phytohormone and volatile organic compounds (VOCs), antimicrobial compounds, CRY proteins, and abiotic and biotic stress tolerance. Induction of induced systemic resistance (ISR) in Bacillus inoculated plants and its molecular mechanism is also discussed in this chapter. Bacillus-mediated abiotic and biotic stress tolerance in different host, possible mechanisms, and their effects are also discussed. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.