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.

Soil heavy metal contamination and salinity constitute a major environmental problem worldwide. The affected area and impact of these problems are increasing day by day; therefore, it is imperative to restore their potential using environmentally friendly technology. Plant growth-promoting rhizobacteria (PGPR) provides a better option in this context. Thirty-seven bacteria were isolated from the rhizosphere of maize cultivated in metal- and salt-affected soils. Some selected bacterial strains grew well under a wide range of pH (4-10), salt (5-50 g/L), and Cd (50-1000 mg/L) stress. Three bacterial strains, Exiguobacterium aestuarii (UM1), Bacillus cereus (UM8), and Bacillus megaterium (UM35), were selected because of their robust growth and high tolerance to both stress conditions. The bacterial strains UM1, UM8, and UM35 showed P-solubilization, whereas UM8 and UM35 exhibited 1-aminocyclopropane-1-carboxylate deaminase activity and indole acetic acid (IAA) production, respectively. The bacterial strains were inoculated on Brassica juncea plants cultivated in Cd and salt-affected soils due to the above PGP activities and stress tolerance. Plants inoculated with the bacterial strains B. cereus and B. megaterium significantly (p < 0.05) increased shoot fresh weight (17 ± 1.17-29 ± 0.88 g/plant), shoot dry weight (2.50 ± 0.03-4.40 ± 0.32 g/plant), root fresh weight (7.30 ± 0.58-13.30 ± 0.58 g/plant), root dry weight (0.80 ± 0.04-2.00 ± 0.01 g/plant), and shoot K contents (62.76 ± 1.80-105.40 ± 1.15 mg/kg dwt) in normal and stressful conditions. The bacterial strain B. megaterium significantly (p < 0.05) decreased shoot Na⁺ and Cd⁺⁺ uptake in single and dual stress conditions. Both bacterial strains, E. aestuarii and B. cereus, efficiently reduced Cd⁺⁺ translocation and bioaccumulation in the shoot. Bacterial inoculation improved the uptake of K⁺ and Ca⁺⁺, while restricted Na⁺ and Cd⁺⁺ in B. juncea shoots indicated their potential to mitigate the dual stresses of salt and Cd in B. juncea through ion homeostasis.

The possibility of using the diseased citrus sinensis plant as a feedstock for the synthesis of biosurfactants by various species was investigated in this study. Four fungal species were identified, namely Penicillium glabrum, Alternaria alternata, Alternaria solani, and Rhizopus stolonifer. Preliminary screening of biosurfactants was carried out by dye binding assay. About 5.75cm ring was noted for Penicillium glabrum. In the blood hemolysis assay, about halo diameter of clear zone 3.85cm was noted for Rhizopus stolonifer. The highest emulsification (E24) and oil displacement ability were noted for Penicillium glabrum and Rhizopus stolonifer. Maximum drop collapsing ability was observed for Alternaria alternata. Maximum drop sliding was observed for Alternaria solani. In the Phenol- Sulfuric acid and foaming activity assay, all four fungal species showed good activity, which indicates the presence of biosurfactants. In the microplate assay, four fungal species showed small results and minor distortion. In the penetration assay, only three species, namely, Penicillium glabrum, Alternaria alternata, and Rhizopus stolonifer, showed positive results and were able to move through hydrophilic fluids to reach the oil layer, resulting in a color change from red to hazy white.