Microbiome of Citrullus colocynthis (L.) Schrad. Reveals a Potential Association with Non-Photosynthetic Cyanobacteria.

Citrullus colocynthis grows in the sandy desert soil of the Arabian Peninsula with limited access to water, aside from occasional precipitation or dew. Understanding its ability to produce water-filled fruit and nutrient-rich seeds despite the harsh environment, can be useful for agricultural applications. However, information regarding the microbiome of C. colocynthis is lacking. We hypothesized that C. colocynthis associates with bacteria that aid its survival, like what has been observed in other desert plants. Here, we used 16S rRNA gene data to gain insight into the microbiome of C. colocynthis to identify its associated bacteria. In total, 9818 and 6983 OTUs were generated from root, soil, and leaf samples combined. Overall, bulk soils had the highest alpha diversity, followed by rhizosphere and root zone soils. Furthermore, C. colocynthis is associated with known plant-growth-promoting bacteria (including Acidobacteria, Bacterioidetes, and Actinobacteria), and interestingly a class of non-photosynthetic Cyanobacteria (Melainabacteria) that is more abundant on the inside and outside of the root surface than control samples, suggesting its involvement in the rhizophagy process. This study will provide a foundation for functional studies to further understand how C. colocynthis-microbes interactions help them grow in the desert, paving the path for possible agricultural applications.

Contrasting genome patterns of two pseudomonas strains isolated from the date palm rhizosphere to assess survival in a hot arid environment.

The plant growth-promoting rhizobacteria (PGPRs) improve plant growth and fitness by multiple direct (nitrogen fixation and phosphate solubilization) and indirect (inducing systematic resistance against phytopathogens, soil nutrient stabilization, and maintenance) mechanisms. Nevertheless, the mechanisms by which PGPRs promote plant growth in hot and arid environments remain poorly recorded. In this study, a comparative genome analysis of two phosphate solubilizing bacteria, Pseudomonas atacamensis SM1 and Pseudomonas toyotomiensis SM2, isolated from the rhizosphere of date palm was performed. The abundance of genes conferring stress tolerance (chaperones, heat shock genes, and chemotaxis) and supporting plant growth (plant growth hormone, root colonization, nitrogen fixation, and phosphate solubilization) were compared among the two isolates. This study further evaluated their functions, metabolic pathways, and evolutionary relationship. Results show that both bacterial strains have gene clusters required for plant growth promotion (phosphate solubilization and root colonization), but it is more abundant in P. atacamensis SM1 than in P. toyotomiensis SM2. Genes involved in stress tolerance (mcp, rbs, wsp, and mot), heat shock, and chaperones (hslJ and hslR) were also more common in P. atacamensis SM1. These findings suggest that P. atacamensis SM1could have better adaptability to the hot and arid environment owing to a higher abundance of chaperone genes and heat shock proteins. It may promote plant growth owing to a higher load of root colonization and phosphate solubilization genes and warrants further in vitro study.

Complete Genome Sequences of Pseudomonas atacamensis Strain SM1 and Pseudomonas toyotomiensis Strain SM2, Isolated from the Date Palm Rhizosphere.

Here, we announce the complete genome sequences of two phosphate-solubilizing rhizobacteria, Pseudomonas atacamensis strain SM1 (genome size, ∼5.9 Mb) and Pseudomonas toyotomiensis strain SM2 (genome size, ∼5.2 Mb), isolated from the rhizosphere of date palms growing in the oasis agroecosystem of the United Arab Emirates (UAE).

Complete Genome Sequence of Phytobacter diazotrophicus Strain UAEU22, a Plant Growth-Promoting Bacterium Isolated from the Date Palm Rhizosphere.

Here, we present a complete circular genome (5.4 Mb) and a plasmid (104,972 bp) of the plant growth-promoting bacterium Phytobacter diazotrophicus strain UAEU22, isolated from date palm rhizosphere in the United Arab Emirates (UAE). Annotation of the genome resulted in 5,229 predicted genes.

Complete Genome Sequence of the Plant Growth-Promoting Bacterium Pantoea agglomerans Strain UAEU18, Isolated from Date Palm Rhizosphere Soil in the United Arab Emirates.

We report the complete genome sequence of the plant growth-promoting bacterium Pantoea agglomerans strain UAEU18. Genome assembly of P. agglomerans strain UAEU18 resulted in a single gapless circular genome of 4.04 Mb, three associated plasmids (plasmid 1, 513,383 bp; plasmid 2, 86,850 bp; and plasmid 3, 184,488 bp), and a total of 4,556 gene models.