Bacillus subtilis: A plant-growth promoting rhizobacterium that also impacts biotic stress

Abstract

Plants encounter many biotic agents, such as viruses, bacteria, nematodes, weeds, and arachnids. These entities induce biotic stress in their hosts by disrupting normal metabolism, and as a result, limit plant growth and/or are the cause of plant mortality. Some biotic agents, however, interact symbiotically or synergistically with their host plants. Some microbes can be beneficial to plants and perform the same role as chemical fertilizers and pesticides, acting as a biofertilizer and/or biopesticide. Plant growth promoting rhizobacteria (PGPR) can significantly enhance plant growth and represent a mutually helpful plant-microbe interaction. Bacillus species are a major type of rhizobacteria that can form spores that can survive in the soil for long period of time under harsh environmental conditions. Plant growth is enhanced by PGPR through the induction of systemic resistance, antibiosis, and competitive omission. Thus, the application of microbes can be used to induce systemic resistance in plants against biotic agents and enhance environmental stress tolerance. Bacillus subtilis exhibits both a direct and indirect biocontrol mechanism to suppress disease caused by pathogens. The direct mechanism includes the synthesis of many secondary metabolites, hormones, cell-wall-degrading enzymes, and antioxidants that assist the plant in its defense against pathogen attack. The indirect mechanism includes the stimulation of plant growth and the induction of acquired systemic resistance. Bacillus subtilis can also solubilize soil P, enhance nitrogen fixation, and produce siderophores that promote its growth and suppresses the growth of pathogens. Bacillus subtilis enhances stress tolerance in their plant hosts by inducing the expression of stress-response genes, phytohormones, and stress-related metabolites. The present review discusses the activity of B. subtilis in the rhizosphere, its role as a root colonizer, its biocontrol potential, the associated mechanisms of biocontrol and the ability of B. subtilis to increase crop productivity under conditions of biotic and abiotic stress.

Potential Biostimulant Effect of Clam Shells on Growth Promotion of Plantain PIF Seedlings (<i>var</i>. Big Ebanga & Batard) and Relation to Black Sigatoka Disease Susceptibility

“…Beneficial effects of clam shells treatment start from the positive modification of the soil physicochemical and biological characteristic to the interaction between the substrate, the plant and the plant microbiome. Indeed, plant roots are surrounded by a thin film of soil called the rhizosphere which represents the primary location of nutrient uptake, and is also where important physiological, chemical, and biological activities are occurring [27]. Moreover, the addition of chitin to the soil also improves microbial communities in both the abundances and structures [8].…”

“…Clam shells treatment has promoted growth and induced PIF seedlings resistance against M. fijiensis and this could be effective through his indirect role in plant as for plant-growth promoting rhizobacteria (PGPR). The direct mechanism of PGPR include the synthesis of many secondary metabolites, hormones, cell-wall-degrading enzymes, and antioxidants that assist the plant in its defense against pathogen attack, while indirectly it includes the stimulation of plant growth and the induction of acquired systemic resistance [27]. Therefore, there is a need to access the physiological mechanism involves in clam shells effect on growth promotion and protection against diseases in plantain PIF seedlings.…”

Synergisms of Microbial Consortia, N Forms, and Micronutrients Alleviate Oxidative Damage and Stimulate Hormonal Cold Stress Adaptations in Maize

“…Auxin production is considered as a central feature of Bacillus strains leading to root growth promotion via external supplementation of IAA by the inoculant (Borriss, 2015). Hence, IAA production has been reported for many Bacillus species, such as B. subtilis (Hashem et al, 2019), B. megaterium (Marulanda et al, 2009), B. licheniformis (Singh and Jha, 2016) and B. velezensis (Mpanga et al, 2019a), where IAA production was even stimulated in the presence of ammonium fertilizers. On the other hand, inactivation of genes responsible for bacterial tryptophan synthesis inhibited IAA formation and plant growth promotion (Idris et al, 2007).…”

Study on the community structure and function of symbiotic bacteria at different growth and developmental stages of Hypsizygus marmoreus

“…were the dominant species, and Bacillus bacteria promoted the growth and development of H. marmoreus by secreting antagonistic substances, lysozymes, auxin, and gibberellin [24][25][26]. At the same time, Bacillus bacteria can secrete speci c metabolites that can enhance stress tolerance of H. marmoreus [24][25][26] and could be used in the industrial production of mushrooms as a growth stimulant. The abundance of the genus Serratia of the Enterobacteriaceae family increased.…”