Bacillus: A Biological Tool for Crop Improvement through Bio-Molecular Changes in Adverse Environments

Abstract

Crop productivity is affected by environmental and genetic factors. Microbes that are beneficial to plants are used to enhance the crop yield and are alternatives to chemical fertilizers and pesticides. Pseudomonas and Bacillus species are the predominant plant growth-promoting bacteria. The spore-forming ability of Bacillus is distinguished from that of Pseudomonas. Members of this genus also survive for a long time under unfavorable environmental conditions. Bacillus spp. secrete several metabolites that trigger plant growth and prevent pathogen infection. Limited studies have been conducted to understand the physiological changes that occur in crops in response to Bacillus spp. to provide protection against adverse environmental conditions. This review describes the current understanding of Bacillus-induced physiological changes in plants as an adaptation to abiotic and biotic stresses. During water scarcity, salinity and heavy metal accumulate in soil, Bacillus spp. produce exopolysaccharides and siderophores, which prevent the movement of toxic ions and adjust the ionic balance and water transport in plant tissues while controlling the pathogenic microbial population. In addition, the synthesis of indole-3-acetic acid, gibberellic acid and1-aminocyclopropane-1-carboxylate (ACC) deaminase by Bacillus regulates the intracellular phytohormone metabolism and increases plant stress tolerance. Cell-wall-degrading substances, such as chitosanase, protease, cellulase, glucanase, lipopeptides and hydrogen cyanide from Bacillus spp. damage the pathogenic bacteria, fungi, nematodes, viruses and pests to control their populations in plants and agricultural lands. The normal plant metabolism is affected by unfavorable environmental stimuli, which suppress crop growth and yield. Abiotic and biotic stress factors that have detrimental effects on crops are mitigated by Bacillus-induced physiological changes, including the regulation of water transport, nutrient up-take and the activation of the antioxidant and defense systems. Bacillus association stimulates plant immunity against stresses by altering stress-responsive genes, proteins, phytohormones and related metabolites. This review describes the beneficial effect of Bacillus spp. on crop plants, which improves plant productivity under unfavorable climatic conditions, and the current understanding of the mitigation mechanism of Bacillus spp. in stress-tolerant and/or stress-resistant plants.

Impact of plant genotype and plant habitat in shaping bacterial pathobiome: a comparative study in olive tree

“…Cobrançosa, may give hints about their role in disease control. Among the genera associated to asymptomatic twigs (either as an epiphyte and endophyte), Bacillus have been identified as the most promising in improving plant growth and controlling plant diseases 45 . In fact, there are many studies indicating the ability of Bacillus spp.…”

Systems Biology of Plant-Microbiome Interactions

“…As a consequence of these similar requirements, in essentially all phyla of host-associated microbiomes, closely related species with pathogenic and beneficial lifestyles can be found (Figure 1). Frequently, relatives with opposite effects are found within the same genus, e.g., among the Paenibacilleae: P. azotofixans and P. amylolyticus (Grady et al, 2016), among Bacilleae: B. velezensis and B. cereus (Radhakrishnan et al, 2017), among Pseudomonas: P. simiae and P. syringae (Anderson et al, 2018) and even within the same species, e.g., Pseudomonas aeruginosa (Steindler et al, 2009;Ndeddy Aka and Babalola, 2016 Phylogenetic tree of plant growth-promoting (black) and pathogenic bacteria (red), and their corresponding phyla (in different shades of gray) mentioned in the text. The tree is supplemented with sequences from some widely applied PGPRs and closely related plant and human pathogens for comparison.…”

Alleviation of Salt Stress on Wheat (Triticum aestivum L.) by Plant Growth Promoting Bacteria strains Bacillus halotolerans MSR-H4 and Lelliottia amnigena MSR-M49

“…have been identified as the predominant communities [20] and resulted in a 40% increase in crop yield [21] and it have been commercialized for improving crop production [22,23], which is an eco-friendly approach to sustainable agriculture [13,24,25]. Exopolysaccharide (EPS) in the rhizosphere soil binds Na + and inhibits Na + transport into plant root cells [26]. Inoculating wheat seedlings with EPS producing Bacillus insolitus MAS17 and certain other Bacillus spp.…”