Bacterial community dynamics with rhizosphere of Calotropis procera and Senna alexandrina desert plants in Saudi Arabia.

It is of interest to study the rhizobacteria associated with two different desert wild plants, e.g., Calotropis procera and Senna alexandrina compared with bulk soil sample in order to identify signatures of microbes in rhizospheres of the two plants and detect influence of soil microbiome in drawing soil architecture. Analysis of deep sequencing microbial dataset indicated occurrence of 296,642 sequence tags assigned 5,210 OTUs (operational taxonomic units). Species richness in control sample was higher than those of either plant's rhizosphere, while microbial abundance was lower. Principal coordinate analysis (PCoA) plot indicated complete separation of microbiome diversity among groups. Abundances of Pseudomonas stutzeri and Virgibacillus koreensis increased in the rhizosphere of C. procera compared with that of S. alexandrina, while those of Streptococcus sobrinus, Veillonella parvula and unassigned species of Sphingomonas genus increased in rhizosphere of S. alexandrina. Unassigned species of genera Marinobacter, Porticoccus and Alcanivorax only exist in rhizosphere microbiome of C. procera, while unassigned species of genus Pseudomonas only exists in rhizosphere microbiome of Senna alexandrina. High abundances of the two microbes Pseudomonas stutzeri and Virgibacillus koreensis in rhizosphere of C. procera allow the plant to grow well under both normal and saline condition. Also, Marinobacter, Porticoccus and Alcanivorax genera only exist in rhizosphere microbiome of C. procera. These microbes produce siderophores that protect plant from pathogens. Data shows that C. procera might be more protected from microbial pathogens compared with S. alexandrina. The differential abundances or exclusive presence of soil microbes reflect the ability of plant species to survive under biotic and abiotic stresses. Results imply that rhizospheric microbes can be used as biomarkers of plant growth rate and the ability to survive under harsh conditions.