Bioprospecting desert plant Bacillus endophytic strains for their potential to enhance plant stress tolerance

Abstract

Plant growth-promoting bacteria (PGPB) are known to increase plant tolerance to several abiotic stresses, specifically those from dry and salty environments. In this study, we examined the endophyte bacterial community of five plant species growing in the Thar desert of Pakistan. Among a total of 368 culturable isolates, 58 Bacillus strains were identified from which the 16 most divergent strains were characterized for salt and heat stress resilience as well as antimicrobial and plant growth-promoting (PGP) activities. When the 16 Bacillus strains were tested on the non-host plant Arabidopsis thaliana, B. cereus PK6-15, B. subtilis PK5-26 and B. circulans PK3-109 significantly enhanced plant growth under salt stress conditions, doubling fresh weight levels when compared to uninoculated plants. B. circulans PK3-15 and PK3-109 did not promote plant growth under normal conditions, but increased plant fresh weight by more than 50% when compared to uninoculated plants under salt stress conditions, suggesting that these salt tolerant Bacillus strains exhibit PGP traits only in the presence of salt. Our data indicate that the collection of 58 plant endophytic Bacillus strains represents an important genomic resource to decipher plant growth promotion at the molecular level.

Tailoring plant-associated microbial inoculants in agriculture: a roadmap for successful application

“…Jordan, Saudi Arabia, and Pakistan). Specific strains showed a great potential for desert agriculture ( Bang et al, 2018 ; de Zélicourt et al, 2018 ; Bokhari et al, 2019 ), and draft genome sequences of some of these bacterial isolates have been released ( Lafi et al, 2016a , b , c , 2017a , b , c , d ), in addition to complete genome sequence analyses ( Andrés-Barrao et al, 2017 ; Eida et al, 2020 ). We suggest that root-associated microbiota isolated from plants living in extreme conditions, possibly due to evolutionary selection, are ideal for obtaining plant growth-promoting microbes with traits for plant growth and promotion of abiotic or biotic stress tolerance.…”

Desert Microbes for Boosting Sustainable Agriculture in Extreme Environments

“…Desert PGPR are evolutionary well adapted to extreme environmental conditions such as heat and high salinity, exploiting stress response genes to promote plant growth and enhance soil fertility more than microbes found in non-arid soils (Paul and Lade, 2014;Makhalanyane et al, 2015;Eida et al, 2018;Bokhari et al, 2019;Eida et al, 2019). They grow with desert plants in intimate mutualistic interactions, helping them to thrive in the extreme conditions, providing fundamental nutrients and enhancing plant tolerance to abiotic and biotic stresses.…”

“…A number of DARWIN21 bacterial strains were genome sequenced ( Andrés-Barrao et al, 2017 ; Eida et al, 2020a , b , c ) providing a platform for genome mining and comparative genomics studies to identify the genes responsible for conferring stress tolerance and survival of desert and other plants as well explaining the PGPR activities. The potential of the plant growth promoting activities including nutrient acquisitions as well as helping the plant to grow under abiotic stress, e.g., salt and drought and fighting the plant pathogens were conducted ( Andrés-Barrao et al, 2017 ; Bokhari et al, 2019 ; Eida et al, 2020c ). Moreover, the mechanisms employed by a number of those strains were highlighted the involvement of the ethylene regulation and ions homeostasis to help plant to tolerate the salt stress ( de Zélicourt et al, 2018 ; Eida et al, 2019 ).…”

Use of Mineral Weathering Bacteria to Enhance Nutrient Availability in Crops: A Review

“…Such microorganisms reduced lipid peroxidation and increased plant cell stability under salt stress. Interestingly, Bokhari et al (2019) isolated several Bacillus strains from desert plants but these microorganisms only displayed plant growth promotion ability under salt stress, suggesting that stressful conditions might trigger the production of plant factors that ultimately stimulate yet unknown bacterial factors related to plant tolerance.…”