Astragalus verus, a miracle in de-desertification or a surprising niche for ecologically adaptable bacteria?

Methods to assure the health of crops owe their efficacy to the extent of which we understand the ecology and biology of environmental microorganisms, as well as the conditions under which their interactions can lead to losses in crop quality or yield. However, in the pursuit of this knowledge, notions of the ecology of plant-associated microorganisms have been reduced to an agro-centric focus. Microbial diversity is now known to be more diverse than previously thought in both environmental and host-associated habitats. This concept includes many lineages that are (or may become) host associated and can form part of pathobiomes, occasionally playing role in health condition of different plants. Surveys and samplings were conducted in natural habitats of Astragalus verus in Iran to monitor the status of prokaryotic agents associated with this herb. Two Gram-negative brownish-gray colored bacterial strains were isolated from plants, with symptoms suspected to presence of a living microorganism in two different sampling areas. The strains (namely D3 and M11) were identified as members of the genus Pseudomonas based on phenotypic features e.g., morphological characteristics, pigmentation, LOPAT scheme, etc. Precise phylogenetic position and taxonomic status of the strains were determined using the phylogeny of gyrB, rpoB and rpoD gene sequences. Accordingly, the two strains were classified within the Pseudomonas fluorescens subgroup in P. fluorescens lineage and clustered in a sister clade next to the type strain of Pseudomonas cedrina subsp. cedrina (DSM 17516). They were tested for sensitivity to copper compounds and various antibiotics with different targets and mechanisms of action. Additionally, the possibility of symptom development by these strains on some nearby and distant plants was investigated, and in many tested cases, some lesions were detected. Overall, these evidences suggest that A. verus may serve as a previously unreported ecological habitat for P. cedrina. It is hoped that this pioneering study of bacterial agents present in A. verus pathobiome will open up new horizons for investigating other existing agents associated with this herb, a plant species providing vital ecosystem functions for de-desertification, rangeland management and restoration, and yet less studied.