Bacillus spp. as Bioagents: Uses and Application for Sustainable Agriculture

SIMPLE SUMMARY: To fulfill the food demand of the enormously growing population, different synthetic pesticides and fertilizers are used to grow crops. These synthetic products pose ill effects on humans and the environment. In recent times, the trend has shifted towards developing and utilizing bioproducts that are eco-friendly and sustainable to use in agriculture. They enhance productivity and restore equilibrium naturally in agroecological systems. In this regard, plant growth-promoting rhizobacteria (PGPR) facilitate crop production in multiple ways. This review deals with the limitations and challenges of conventional pesticides following the different microbes used as bioproducts along with how Bacillus is one of the promising PGPR used in sustainable agriculture. Bacillus spp. improves crop growth in both direct and indirect ways through nitrogen fixation, P and K solubilization, phytohormones production, quorum quenching, biofilm formation, and lytic enzymes production. Moreover, Bacillus spp. boost plant resistance towards the notorious phytopathogens. As Bacillus spp. is eco-friendly, promotes plant growth, confers resistance against diseases, improves soil fertility, non-toxic, naturally occurring microbe, and supports sustainable agriculture, there is a need to explore the potential of native Bacillus spp. and to use them in bioproduct development to support sustainable agriculture. ABSTRACT: Food security will be a substantial issue in the near future due to the expeditiously growing global population. The current trend in the agriculture industry entails the extravagant use of synthesized pesticides and fertilizers, making sustainability a difficult challenge. Land degradation, lower production, and vulnerability to both abiotic and biotic stresses are problems caused by the usage of these pesticides and fertilizers. The major goal of sustainable agriculture is to ameliorate productivity and reduce pests and disease prevalence to such a degree that prevents large-scale damage to crops. Agriculture is a composite interrelation among plants, microbes, and soil. Plant microbes play a major role in growth promotion and improve soil fertility as well. Bacillus spp. produces an extensive range of bio-chemicals that assist in plant disease control, promote plant development, and make them suitable for agricultural uses. Bacillus spp. support plant growth by N fixation, P and K solubilization, and phytohormone synthesis, in addition to being the most propitious biocontrol agent. Moreover, Bacilli excrete extracellular metabolites, including antibiotics, lytic enzymes, and siderophores, and demonstrate antagonistic activity against phytopathogens. Bacillus spp. boosts plant resistance toward pathogens by inducing systemic resistance (ISR). The most effective microbial insecticide against insects and pests in agriculture is Bacillus thuringiensis (Bt). Additionally, the incorporation of toxin genes in genetically modified crops increases resistance to insects and pests. There is a constant increase in the identified Bacillus species as potential biocontrol agents. Moreover, they have been involved in the biosynthesis of metallic nanoparticles. The main objective of this review article is to display the uses and application of Bacillus specie as a promising biopesticide in sustainable agriculture. Bacillus spp. strains that are antagonistic and promote plant yield attributes could be valuable in developing novel formulations to lead the way toward sustainable agriculture.