The Effects of Plant-Associated Bacterial Exopolysaccharides on Plant Abiotic Stress Tolerance

Abstract

Plant growth-promoting rhizobacteria (PGPR) are beneficial soil microorganisms that can stimulate plant growth and increase tolerance to biotic and abiotic stresses. Some PGPR are capable of secreting exopolysaccharides (EPS) to protect themselves and, consequently, their plant hosts against environmental fluctuations and other abiotic stresses such as drought, salinity, or heavy metal pollution. This review focuses on the enhancement of plant abiotic stress tolerance by bacterial EPS. We provide a comprehensive summary of the mechanisms through EPS to alleviate plant abiotic stress tolerance, including salinity, drought, temperature, and heavy metal toxicity. Finally, we discuss how these abiotic stresses may affect bacterial EPS production and its role during plant-microbe interactions.

Selection and Characterization of Burkholderia spp. for Their Plant-Growth Promoting Effects and Influence on Maize Seed Germination

“…The rainfall scarcity will intensify due to the global climate changes, which can promote salt accumulation in the soil (40), especially in semi-arid regions of Northeastern Brazil (45). This will become a huge challenge to be overcome (20,46,47). In this context, the bacterial isolates with high potential to express biosynthesis pathways of phytohormones and other plant-stimulating compounds under salt stress conditions can become important allies of agriculture (8,20), enabling the production of corn in these areas.…”

“…B. graminis (B9) and B. gladioli (B25 and B22) produced significantly more EPS than all other bacteria with a measured halo of 45.85, 52.77, and 54.07 mm, respectively (Table 3 and Supplementary Figure S1). The high capacity of bacteria to synthesize EPS is related to stressful environmental conditions (47,48). Under unfavorable environmental conditions, EPS production acts as a protective mechanism for bacteria, helping them to maintain the microbial community (49).…”

“…The EPS production is an important mechanism that helps in plant colonization by PGPB and increases the tolerance of plants to environmental stresses (48). Therefore, EPS production is a desired biotechnological characteristic in microbial strains that make up the bio-products used in sustainable agriculture (47). The bacteria that presented a high EPS production capacity have an advantage over the soil indigenous bacterial community (52).…”

“…Bacterial strains form dense biofilms that protect them against stressful environmental conditions such as salt stress, acidification, or drought (46,53). Furthermore, biofilms enhance the ability of bacterial colonization (47,48), which in the case of a plant growth-promoting bacterium is something very desirable (22,52).…”

The Contrivance of Plant Growth Promoting Microbes to Mitigate Climate Change Impact in Agriculture

“…EPS-coated roots are well protected from desiccation, making them less exposed to the negative effects of drought stress. In addition, bacterial EPS released into the soil can improve soil structure, retain soil water, and increase bacterial colonization on the roots [ 215 ]. EPS’s special role in drought stress alleviation has been reported by Sandhya et al [ 195 ].…”