Molecular Aspects of Plant Growth Promotion and Protection byBacillus subtilis

Abstract

Bacillus subtilis is one of the most widely studied plant-growth promoting rhizobacteria. It is able to both promote plant growth as well as control plant pathogens through diverse mechanisms, including the improvement of nutrient availability and alteration of phytohormone homeostasis as well as the production of antimicrobials and triggering induced systemic resistance, respectively. Even though its benefits for crop production have been recognized and studied extensively under laboratory conditions, the success of its application in fields varies immensely. It is widely accepted that agricultural application of B. subtilis often fails because the bacteria are not able to persist in the rhizosphere. With this in mind, bacterial colonization of plant roots is a crucial step in the interaction between microbe and plant and seems therefore to be of great importance for its growth promotion and biocontrol effects. A successful root colonization depends thereby on both bacterial traits, including motility and biofilm formation, as well as on a signal interplay with the plant. This review addresses the current knowledge about plant-microbial interactions of the B. subtilis species, including the various mechanisms for supporting plant growth as well as the necessities for the establishment of the relationship.

Biofilm Dispersal for Spore Release in Bacillus subtilis

“…The study of B. subtilis biofilm formation was initiated about two decades ago, and has created a plethora of understanding since the first publication (3) regarding how gene expression connects to biofilm initiation and matrix production and the identity and function of the main biofilm matrix components (4,5). Interest in B. subtilis biofilms is further stimulated by the species being more than a laboratory model: biofilms are important for plant growth promotion, probiotic impact, and biotechnological applications (6,7).…”

Mutualistic interactions between B. subtilis and seeds dictate plant development

“…Bacillus subtilis and closely related species mutualistically coexist with the plants, providing a plethora of beneficial actions, such as biofertilization or protection against biotic and abiotic stresses 5 . Ecological traits contributing to bacterial fitness and bioactivity in the plants are due to polyvalent secondary metabolites, sporulation, or biofilm formation 6 .…”

Deletion of Rap-Phr systems inBacillus subtilisinfluencesin vitrobiofilm formation and plant root colonization

“…Biofilms have been widely studied since they represent a fascinating example of microbial development in response to environmental cues (O’Toole et al ., 2000). Furthermore, studying biofilms is of special interest due to their detrimental impact in clinical and industrial settings (Stewart, 2002; Di Pippo et al ., 2018) as well as their promising potential within the biotechnology industry (Singh et al ., 2006; Blake et al ., 2021). Regarding the latter, the Gram-positive bacterium Bacillus subtilis has in the last two decades gained interest due to its promising potential as a biocontrol agent within agriculture (Ongena and Jacques, 2008; Kiesewalter et al ., 2021).…”

“…In its natural habitat, the soil-dwelling bacterium colonizes plants by forming a biofilm on the root (Bais et al ., 2004; Chen et al ., 2012; Beauregard et al ., 2013). After successfully colonizing the root, B. subtilis exerts its plant-beneficial properties, including directly promoting plant growth as well as protecting the plant against diseases (Blake et al ., 2021). Furthermore, B. subtilis forms spores that are highly resistant to extreme environments (Piggot and Hilbert, 2004) facilitating easy formulation and storage of B. subtilis for application within agriculture (Ongena and Jacques, 2008).…”